HN Theater @HNTheaterMonth

It is interesting and informative to compare SN9 to SN8.

SN8: https://youtu.be/ap-BkkrRg-o?t=6884

SN9: https://youtu.be/_zZ7fIkpBgs?t=704

With SN8, you can clearly see two engines lighting and burning properly until just before it (crash) lands.

With SN9, you can clearly see one engine lighting and burning properly, but the second engine did not light cleanly and did not stay lit.

⬐ zaroth

I don’t think that’s quite right. With SN8 they ended up with low pressure in the header tank and not enough fuel for the turbo pumps.

A so called “engine-rich” burn resulted, which is why there’s a flash of green flame.

Total thrust was much lower than spec, hence the hard landing even though both engines ignited.

I believe this is what the engines are doing during the majority of the ascent of the Starship SN8 test vehicle[0]. You can see the engines gimbaling very slightly in a circular pattern.

[0]: https://youtu.be/ap-BkkrRg-o?t=6516

⬐ aidenn0

Anything controlled by a PID can easily end up in a circular pattern, so it's not a given that this was to avoid stiction.

[edit]

1 dimensional PIDs can end up in a sinusoidal dynamic equilibrium, and a 2 dimensional sine wave is an ellipse.

⬐ HanyouHottie

It's not an ellipse if the axes have different periods: https://www.wolframalpha.com/input/?i=x%3Dsin%28t%29%2C+y%3D...

(Is there a name for this kind of curve?)

⬐ bane

The thing that is most interesting to me is that this is a major R&D program being done literally out in the open. These prototypes are being put together basically in an open field or under a tent with SpaceX sharing loads of information on the technology, price targets, mission profiles and so on. And yet nobody is coming close to matching them.

Even if another company decides to try to replicate what SpaceX is doing, they're now at least a decade behind.

Nobody has the present institutional knowledge that they have.

⬐ frakkingcylons

SpaceX has a huge lead, no doubt. But there's a handful of smaller companies which are very promising. Rocket Lab's Electron vehicle has had 13 successful launches (3 failures) to LEO. Firefly and Relativity (which are founded by former SpaceX/Blue Origin employees) are making a lot of progress as well.

⬐ mabbo

While the Electron is cool, the comparison is pretty far off.

The Electron can put 600kg into low Earth orbit.

Falcon 9 can handle 15,000 kg. Starship is expected to handle 100,000 kg.

The Falcon 1 is a good comparison to the Electron. If it had been fully developed it was expected to lift 600kg to leo by 2010 or 2011. 10 years ago, basically.

⬐ frakkingcylons

I didn't compare Electron to Falcon 9 or Starship.

⬐ temporalparts

From the parent post:

> they're now at least a decade behind.

The original claim was that competitors are a decade behind spaceX and Electron's capabilities are comparable to the technology spaceX had a decade ago. The Falcon 9 comparisons are to highlight the decade delta.

edit: grammar

⬐ Thlom

Really sad to see f.ex. Arianespace still launching with the nearly 30 year old Ariane 5. Soon EOL now, but I don't think the Ariane 6 is even close to what SpaceX is doing at the moment. And I think ESA have started muttering about both capabilities of the rocket, launch price and the slow development.

⬐ texasbigdata

What’s the Bezos one doing though? Aren’t they comparably close give or take a few years.

⬐ jiofih

Not even close. SpaceX has been launching commercial payloads for nearly a decade now, is on track to a hundred reusable rocket flights, is on the 11th or so generation, and Starship is far beyond anything BO has in their roadmap - if they manage to launch commercially one day.

⬐ someperson

For what it's worth Blue Origin's New Armstrong rocket hasn't yet been revealed (John Sheppard -> John Glenn -> Neil Armstrong) but Jeff Bezos has mentioned it. It's widely assumed to be a Saturn V class Super Heavy Lift vehicle.

⬐ jiofih

Yeah I can draw a 77 thousand ton interstellar transporter on a napkin and “announce” it too.

⬐ valuearb

BO has never launched anything into orbit.

It has plans to someday build a competitor to the 13 year old Falcon 9.

Oh and Bezos started BO before SpaceX, and has given it substantially more funding.

⬐ sq_

It's tough to tell what they're doing, as they're way less open about things than SpaceX and some of the other new commercial launchers (e.g. Rocket Lab).

Seems to me that they may be trying to pivot away from having orbital rockets being their main product with the sale of BE-4 engines to ULA for Vulcan and all of their work on lunar projects. But that could also be them trying to get more friendly with NASA or get development of the BE-4 paid for or any number of other things. They certainly are lacking in terms of actual hardware being seen.

⬐ Denvercoder9

They haven't actually put anything in orbit yet. I'd say they're at least a decade behind.

⬐ dmd

Remind me again how many times Blue Origin has put anything in orbit?

⬐ jaredmoon

No, not even close.

⬐ wongarsu

I don't think anybody knows how far Blue Origin really is. They are much more secretive and seem to do a lot less testing. New Glenn is somewhat comparable to a Falcon 9 scaled up to the size of Starship and is supposed to happen in 2021, but I don't think there's any good indication how far they are along and whether they will be able to deliver.

My gut says that if they don't test they can't deliver, and that Elon's rapid prototyping will keep SpaceX far in the lead for the foreseeable future. But only time will tell.

⬐ fastball

If you ignore payload capacity, I'd say New Glenn is much closer to Starship than it is to Falcon 9 in terms of technical development, mostly because of its novel engine, the BE-4. Like the Starship's Raptors, they are powered by a fuel that can be produced in-situ at the intended destination. Though in the case of the Raptors it's Methalox from Martian atmosphere (via Sabatier), whereas BE-4 engines are Hydrolox that they hope to get from ice on the moon.

⬐ sushibowl

Is the BE-4 design really that new? The choice of fuel is of course novel. But apart from that, it seems to be an oxygen-rich staged combustion design, which was invented by the soviets... somewhere in the 60's?

⬐ philwelch

BE-4 is methalox. BE-3 and BE-7 are hydrolox.

⬐ fastball

Thanks for the correction, you're right, I was thinking about their Blue Moon lander, which is slated to have BE-7 engines.

⬐ Denvercoder9

Payload-wise New Glenn is better comparable to Falcon Heavy than to Starship. New Glenn actually sits more or less in the middle between Falcon 9 and Falcon Heavy.

⬐ tuatoru

Expect Old Space (Boeing & co) to lobby for a law requiring SpaceX to share all their telemtry data in real time.

⬐ TheBill

They might try, but they'll still be focused on looting the .gov & first try success. SpaceX will still be 2-3 decades ahead of them.

⬐ adventured

> Even if another company decides to try to replicate what SpaceX is doing, they're now at least a decade behind.

There is one entity that can and will rapidly close that gap. In fact, they're the only one that can: China. Everyone else will continue on their slow path, more or less adopting everything SpaceX figures out a decade after the fact. The other competition operates permanently by hand-me-downs. China will invest huge sums of money and labor into doing the same thing and the difference between them and eg the Europeans, is the Chinese will and can move with ridiculous speed by comparison. The other competition won't adjust their speed, so they'll generally continue to lag SpaceX perpetually, whereas China can move at a far greater pace (aerospace, as with a few other big segments like semiconductors, is of course a core logical focus point for China, which means they will catch up no matter the cost; they'll borrow from SpaceX better than anyone else and faster than anyone else, right up to the point of copying everything). And to be clear, I don't fault China at all for that approach, it will work very well; they can leapfrog everyone not named SpaceX that way.

⬐ aardvarkr

It’s pretty damn hard to copy something that you never get to see. China can clone tech because they force companies that build products in China to essentially give away their IP. Can’t do that if the rocket is built exclusively in Hawthorne, CA and Boca China, TX with no outside contractors. They’re decades behind even the Europeans and Japanese. Chang’e5 is cool and all but Europe and Japan landed their spacecraft this year and last year on ASTEROIDS which is actually pushing the boundaries of space accomplishments and science. Hyabusa2 flew literally billions of miles (5.4bn to be exact)[0] during its mission to collect and return asteroid samples. The Chinese mission was a repeat of the 50’s just to say that they did it too. They’re not leapfrogging ANYONE, at least not until they do something novel.

http://www.hayabusa2.jaxa.jp/en/enjoy/material/factsheet/Fac...

⬐ Invictus0

All it takes is one cyber attack.

⬐ someperson

I tend to agree with you that China's space technology is not that developed -- their manned rocket and capsule is a scaled up Russian Soyuz design -- and I have doubts about their ability to catchup without major technology transfer (whether through acquisition or theft). But we should still recognize that their previous moon mission (Chang'e-4) did do something no other nation has yet done: land on the far side of the moon. That is pushing the boundaries and just repeating the accomplishments of decades ago.

⬐ aardvarkr

Is that really so impressive? The technical challenges remain the same as a near side landing except you’re in a communication blackout so signals have to bounce off a satellite in orbit. Even then that’s not novel because the Americans and Russians did the same thing, using their orbiting spacecraft to relay messages back to earth.

The Chinese literally haven’t done anything novel in their space program. Even the words they said upon landing on that mission were a copy of the Americans. ‘"It's a small step for the rover, but one giant leap for the Chinese nation," Wu Weiren, the chief designer of the Lunar Exploration Project, told state broadcaster CCTV.’ The Chinese literally can’t do anything but copy and it’s embarrassing.

https://phys.org/news/2019-01-chinese-rover-exploring-dark-s...

⬐ someperson

Well I think landing a rover on the far side of the moon is impressive. It's definitely a first for humanity and the scientists and engineers behind that mission deserve praise for that, even if in the achievement isn't pushing forward space technology at all.

⬐ valuearb

Chinas launchers improvements have been moving at a slow pace. Lots of obsolete solid rockets and dangerous propellant.

⬐ ansible

It would be nice for the environment and the Chinese people if they pursued reuse more. Landing the 1st stage is a lot better than dropping it on top of a village and exploding... as part of a normal and successful launch.

No, I'm not kidding.

https://arstechnica.com/science/2019/11/china-keeps-dropping...

⬐ nickik

Easy to claim. So far China human space program has been very slow. And they have not gone full power into even a Falcon 9 clone. China is in the same space as everybody else outside of the US, with a slow moving bureaucracy leading it, wanting to switch into more commercial companies.

China has not yet itself produced an engine anywhere close to a Raptor and they have been trying for quite a while.

China can not spend gigantic amounts of money on everything at once, and even if they do, it by far doesn't work all of the time.

When you are copying SpaceX you are always cooping something that is already outdated and SpaceX will not stop innovating.

⬐ babesh

https://en.wikipedia.org/wiki/2020_in_spaceflight

In 2020, China has launched more rockets to space than any other nation.

https://en.wikipedia.org/wiki/Chang%27e_5

It has a mission to bring lunar rock back to earth for the first time since the 70s.

So I would say that China has put quite a bit of energy in this area and is moving faster than other nations but not as fast as SpaceX.

⬐ nickik

Go look at how much payload by weight was launched by China. Or how many different payloads.

> It has a mission to bring lunar rock back to earth for the first time since the 70s.

Yes its a fine mission, but its a mission that is not outside of the capability of others. There are simply many space missions that could be done.

Yes, China is doing things and the are moving fast, but your prediction and text were still over the top.

⬐ babesh

That wasn’t my prediction. It was from another poster.

⬐ babesh

Opps. US passed China with the last few flights. Counting SpaceX and Electron in the US stats.

⬐ oska

And SpaceX has another 3 launches planned for December (SXM-7, NROL-108 & Turksat 5A). Although the last one is on Dec 31, so could easily slip into next year.

⬐ NikolaeVarius

Why do the US numbers include electron?

⬐ skissane

Because the statistics are based on the nationality of company/agency that designs and builds the launch vehicle, not the launch site. So even though Soyuz launches from Kazakhstan and French Guiana, it is counted as a Russian launch since a Russian company (Energia) designed and built the rocket. Similarly, even though a lot of Electron launches are from New Zealand, the company that builds Electron is ultimately US-headquartered/US-controlled. (Rocket Lab was originally founded in New Zealand, but they moved their HQ and parent company to the US so are now considered a US company rather than a New Zealand one.)

⬐ valuearb

China launches a bunch of obsolete rockets with relatively small capacities. Long march 3 has half the capacity of a Falcon 9, Long March 2 is about one seventh the payload capacity.

They should be justly proud of their robotic lunar missions though.

⬐ djaychela

I wasn't sure if the ascent looked OK - no idea if it was supposed to be running on two, then one engine. But that was a moment that I'll remember for the rest of my life. Amazing stuff, even with what obviously meant the complete demise of SN8.

I'm sure they'll learn an immense amount from it, and it was amazing to see it nearly pull off the landing. Given the way that Falcon 9 early landing attempts went, it'll go the same way with Starship, and it'll be landing soon.

⬐ grishka

> no idea if it was supposed to be running on two, then one engine

Yeah and then something caught fire near the engines. I expected it to explode that very moment.

⬐ AnimalMuppet

Delayed gratification by a few minutes, but we got the pretty fireball in the end...

⬐ Filligree

I think that was the ignition system; the green flame matches. Which makes sense if they lost an engine, of course.

⬐ grishka

No, not that, I meant the moment when one of the three engines shut off mid air and then moved away a bit so the remaining ones point straight down.

⬐ remarkEon

What's the reason that the flame produced by the ignition system is green?

Edit: ah, it's answered here https://news.ycombinator.com/item?id=25366736

⬐ elteto

That’s incorrect. Raptor does not use a TEA/TEB igniter like Falcon. It uses a spark igniter.

The green flame here is unintended engine ablation :) The chamber was melting.

⬐ ArPDent

specifically it's copper being vaporized i believe

⬐ remarkEon

Nice. Flashbacks to highschool chemistry. I'm assuming this isn't something you want to have happen ...

⬐ SAI_Peregrinus

No, engine-rich combustion cycles are definitely not something you usually want. Especially not on a re-usable craft.

⬐ Gwypaas

The merlin engine uses TEA-TEB which causes the green flame seen on Falcon 9. The raptor uses electric spark ignition, which is harder but doesn't require any awfully poisonous chemicals and you can't run out.

https://en.wikipedia.org/wiki/SpaceX_Raptor

⬐ oska

> Yeah and then something caught fire near the engines.

This is an artifact of air flow vortices around the base of the rocket and its skirt and is completely normal. This video [1] explains it well.

[1] https://www.youtube.com/watch?v=yJceyvBKxc0&t=15m14s

⬐ enraged_camel

>>I wasn't sure if the ascent looked OK - no idea if it was supposed to be running on two, then one engine.

I realized that this may have been done to slow down the acceleration to make sure it doesn't go past the 12 km limit. I may be wrong though.

⬐ codeulike

I think it was hovering for a while at the top of the ascent.

⬐ endymi0n

I also wasn't entirely sure whether the engine shutoffs were fully intended... at least the sideways acceleration of the Raptors at shutoff looked scary.

⬐ Kye

We don't usually see rocket engines cut off in that much atmosphere, but it's probably normal.

⬐ apendleton

As engines shut off, the remaining ones that were still going had to rapidly re-center to keep the direction of thrust aligned with the center of mass of the vehicle, and the ones that had shut off had to move out of their way to make room.

⬐ codeulike

I'm wondering if the engine shutoffs on the way up were deliberate, so they could get data on running on 3,2 and then 1 engine.

⬐ qayxc

They looked planned. I think they tested the full array of required operations: shutdown, gimbal, throttling, re-ignition.

⬐ wongarsu

Even in normal operation it might have been useful to throttle down the engines in order to ascend a bit slower (less drag). If you have multiple engines, shutting some of them down is a convinient way to throttle.

⬐ seg_lol

It was a wonderfully designed test. I'd love to hear a presentation on test design, the mission profile and what data they were looking at with each one.

I assume SpaceX has the same video feed with superimposed telemetry. I'd love to know turbo pump pressure and rpm during landing.

⬐ smiley1437

If you look at the timer, it's almost certainly planned

Engine 1 cuts off 1m45s after launch

Engine 2 cuts off 1m28s after engine 1

Engine 3 cuts off 1m28s after engine 2 and then SN8 goes into glide testing.

The extra time on all 3 engines is probably to gain sufficient height?

⬐ betwixthewires

I laughed loudly at that ending. The explosion seems so comical.

The test was great, it proved the concepts in principle do work in practice, and proved that the design fundamentally works. Launch, high altitude, belly flop and flip and burn landing. I'm excited to see the coming tests, design improvements, and to watch the thing land without blowing up.

⬐ cma

To fundamentally work it needs to handle reentry speeds with that same geometry.

⬐ aardvarkr

Next one should have heat shields for them to try for a real re-entry attempt but the terminal velocity was surprisingly slow with that geometry so I’m not sure it’s really going to change much.

⬐ sq_

Kinda hoping that we get an updated "How Not to Land an Orbital Rocket Booster" video [0] covering Starship development eventually...

[0] https://www.youtube.com/watch?v=bvim4rsNHkQ

⬐ CobrastanJorji

I remember Musk giving a big presentation showing off the model of this rocket when he announced the Mars plan, and I laughed because it was obviously a very rough, ugly aluminum grain silo that was vaguely rocket-shaped and not any sort of real rocket.

Well...that thing looks exactly the same. Shows what I know.

⬐ mulcahey

They are using much bigger panels for raw material now, & have iterated on their welding process.

Here is Mark 1:

https://www.spacex.com/static/images/starship/STR_9.webp

Here is Serial Number 8:

https://www.spacex.com/static/images/crew-1/SN8.webp

⬐ intotheabyss

It's actually an ugly steel grain silo

⬐ the_duke

To be fair to you, that prototype (called MK1) indeed was extremely shoddy and could never have survived today s flight. It probably only existed for the presentation and as a production pathfinder, and indeed failed shortly after during a simple pressurisation test.

Their welding technique has come a long way since then!

Here is a comparison shot: https://www.reddit.com/r/SpaceXLounge/comments/j7g07d/compar...

Video of the failure: https://youtu.be/3nTSubYzQOM?t=14

⬐ _Microft

Crash landing not withstanding but as any other rocket launch provider or space-faring nation, I'd be scared shitless now. SpaceX is in a league by itself.

⬐ tuatoru

The crash is valuable by itself.

Examining the wreckage will tell SpaceX lots about structural defects/overbuilt areas.

Edit: SpaceX has invented a vastly better process for innovation. That's what should be scaring the others.

⬐ texasbigdata

What is that? Iteration?

⬐ tnli

Fast iteration. Not aware of anyone else doing that with 50m tall 9m wide rockets.

⬐ kitsunesoba

Furthermore, fast iteration that isn't averse to failure. While they do what they can to make each test a success, they don't let it turn into a black hole of time, money, and manpower. They're willing to say, "yeah, that's good enough", test, and make the most of every aspect of the test.

Where a more traditional aerospace company would go out of their way to avoid failures at any step, SpaceX embraces them so long as nobody is endangered in the process.

⬐ trhway

>as any other rocket launch provider or space-faring nation, I'd be scared shitless now.

Russian Space agency "Roskosmos" strikes back - it plans to produce alcohol, perfume, clothes, etc. under the trade mark "Poehali" ("let's go") - the word famously uttered by Gagarin when the rocket started to ascent.

(in Russian) https://lenta.ru/news/2020/11/13/poehali/

Also comes to mind the "Souz vs. Crew Dragon" tweet couple months back by a Russian cosmonaut which brought the Roskosmos CEO and the other top bureaucrats there into boiling publicly with rage https://twitter.com/Msuraev/status/1313945340039528448/photo...

⬐ avmich

Russian space program is in a pretty low state these days. It will take significant changes in Russia to come back to space exploration comparable to peers.

⬐ trhway

>It will take significant changes in Russia to come back

As Russian joke about road building and everything else that requires any concerted effort goes - "There are 2 possible alternatives, a realistic one and a fantasy one. The realistic one is when aliens come to Earth and accomplish it for us. The fantasy one is when we accomplish it ourselves."

For example Russia has been for several years trying to build a new spaceport in the Far East. After the first years of tremendous corruption discovered and prosecuted, the total control, audit and surveillance there have been unparalleled, yet despite it there have already changed several waves of the top/mid management - they get assigned there, steal a lot, get arrested, and new people get assigned, ...

⬐ philwelch

Also, the only road to the new launch facility goes through an extremely narrow Tsarist-era tunnel that severely limits rocket size.

⬐ avmich

> they get assigned there, steal a lot, get arrested, and new people get assigned, ...

This is just an illustration of what the state of things currently is around Russian space efforts. To change that requires changes above that in government operations.

There are still a lot of capable engineers and even managers in space industry. But being capital and material heavy, space industry can't hide from corruption, which isn't going anywhere while Kremlin is as it is today.

Soyuz spacecraft is a wonderful machine, but lately it more and more served as largely a cash cow and political facade. With Crew Dragon flying, that role diminishes. Given that Proton doesn't provide either, Russian space is left with just a few venues for development. It's hard to see bright sides there until incentives would change.

⬐ ninjamayo

By far the most amazing launch and rocket I've ever seen. This is history in the making!

⬐ Nas808

The test flight of Falcon Heavy (when they sent the Tesla Roadster to space) is still the most memorable launch for me. Watching those 2 boosters land side-by-side simultaneously looked like magic.

⬐ johncalvinyoung

Yes. The whole office broke what they were doing and watched that launch and landing together, on one of our big displays. A cheer went up when they landed, side by side--a moment I'll remember for the rest of my life. Goosebumps then, and goosebumps now. Felt like the most significant thing for manned space since maybe Apollo (well, definitely since early days of the Shuttle!)

⬐ ansible

We had just finished a code review, and I put the launch / landing up on the TV in the meeting room. Good times.

⬐ Diederich

Yes! https://www.youtube.com/watch?v=A0FZIwabctw

⬐ mrlala

Ok thanks for making me cry, haven't seen that since it was live. How has it been two years already.. damn.

⬐ Rebelgecko

Unfortunately, if you were watching the livestream it was actually just 2 shots of the same booster (although later videos fixed that mixup)

⬐ ninjamayo

I rewatch that launch every time I am low and always makes me happy. But this feels different. It feels like it is the beginning of the space age.

⬐ chasd00

I do this too. I watch when I need inspiration and I watch when I start thinking I'm hotshit and need some humbling.

⬐ nsxwolf

Honestly, I'd have been a little disappointed if it hadn't ended the way it did. SpaceX seems to be all about an iterative process of showing us cool new capabilities ending in awesome explosions.

⬐ jonplackett

New company mantra to be had right there.

⬐ buu700

SpaceX's new mascot: https://youtu.be/jar1LTxxAeM?t=14

⬐ sq_

Eventually we're gonna run out of funny three letter acronyms to describe the different explosion types. We've already got RUD for rapid unscheduled disassembly and SRD for scheduled rapid disassembly (Crew Dragon In-Flight Abort test).

⬐ modeless

Looked perfect right until the end, appeared to lose an engine, hit the landing pad and exploded. Instant replay: https://www.youtube.com/watch?v=gBELXjq_X-M&t=17585

Incredible test! The "bellyflop" maneuver was the main test objective I think, and it appeared to work. They need to figure out the causes of the engine failures now.

⬐ _ph_

Elon tweeted it wasn't an engine failure but the fuel pressure was too low.

⬐ rst

They were attempting to switch to a separate set of tanks, ultimately meant to sequester fuel used for landing. It was pressure in the landing-fuel tanks that was low after the switch.

⬐ mulcahey

More info about Starship

https://www.spacex.com/vehicles/starship/

> As early as Wednesday, December 9, the SpaceX team will attempt a high-altitude suborbital flight test of Starship serial number 8 (SN8) from our site in Cameron County, Texas. The schedule is dynamic and likely to change, as is the case with all development testing.

> This suborbital flight is designed to test a number of objectives, from how the vehicle’s three Raptor engines perform to the overall aerodynamic entry capabilities of the vehicle (including its body flaps) to how the vehicle manages propellant transition. SN8 will also attempt to perform a landing flip maneuver, which would be a first for a vehicle of this size.

> With a test such as this, success is not measured by completion of specific objectives but rather how much we can learn, which will inform and improve the probability of success in the future as SpaceX rapidly advances development of Starship.

> This past year alone, SpaceX has completed two low-altitude flight tests with Starship SN5 and SN6 and accumulated over 16,000 seconds of run time during 330 ground engine starts, including multiple Starship static fires and four flight tests of the reusable methalox full-flow staged combustion Raptor engine. Additionally, with production accelerating and fidelity increasing, SpaceX has built 10 Starship prototypes. SN9 is almost ready to move to the pad, which now has two active stands for rapid development testing.

> SN8’s flight test is an exciting next step in the development of a fully reusable transportation system capable of carrying both crew and cargo to Earth orbit, the Moon, Mars, and beyond. As we venture into new territory, we continue to appreciate all of the support and encouragement we have received.

> There will be a live feed of the flight test available here that will start a few minutes prior to liftoff. Given the uncertainty of the schedule, stay tuned to our social media channels for updates as we move toward our first high-altitude flight test of Starship!

⬐ lxe

At around 1:49:46 (https://youtu.be/ap-BkkrRg-o?t=6586) (T+1:34) one of the engines shuts off, and things seems to move a bunch. Some equipment covered in some kind of tarp really close to the engines ends up burning up. What is behind these loose coverings? Why are these things so close to the engines?

⬐ nickik

They have tanks for nitrogen thrusters there and maybe some other things. These will eventually be removed and replaced with hot methane gas thrusters that are feed directly from the main fuel tank.

⬐ grecy

Elon Tweets since the RUD

1: Successful ascent, switchover to header tanks & precise flap control to landing point!

2: Fuel header tank pressure was low during landing burn, causing touchdown velocity to be high & RUD, but we got all the data we needed! Congrats SpaceX team hell yeah!!

3: Mars, here we come!!

1 - https://twitter.com/elonmusk/status/1336808486022258688

2 - https://twitter.com/elonmusk/status/1336809767574982658

3- https://twitter.com/elonmusk/status/1336810077555019779

⬐ oska

Good analysis of the flight from a knowledgeable commenter on r/spacex:

https://www.reddit.com/r/spacex/comments/ka34n6/elon_musk_fu...

And an analysis video from Scott Manley:

https://www.youtube.com/watch?v=egHxiX40eJY

⬐ dwd

Engine rich exhaust seems to be the current consensus.

The footage SpaceX got with this launch, particularly that pad view Manley had of it falling directly towards the camera and then flipping was insane.

⬐ huhnmonster

At around 1:54:50, upon full landing thrust, the exhaust flames turn green. I know colored flames from chemistry classes, but I always assumed that was caused by certain salts.

Rocket fuel, to my knowledge, does not contain any of those ingredients. Can someone explain what happened there? Was this planned?

⬐ tw04

I believe it was burning through the copper liner due to fuel starvation (oxygen rich which makes it SUPER hot)

http://photos1.blogger.com/blogger/1613/496/1600/Merlin1C_Ch...

Seriously getting downvoted? That's what caused the issue.... Elon already tweeted they had low fuel pressure...

⬐ mulmen

You may be right but Starship uses Raptor engines, not Merlins.

⬐ tw04

I'm aware, the picture was to show what the liner looks like (approximately), the engines are of similar design. I apologize if anyone thought that was literally the liner in question.

⬐ mulmen

Ah yeah, lots of confusion re: TEB in other comments. Seems like a lot of people have the Raptor and Merlin mixed up so at least in this context probably have to be explicit.

⬐ fabian2k

I really don't know enough about this, but this might be "engine-rich combustion". Which would also explain why the landing part didn't work.

⬐ luizfzs

"engine-rich combustion" has become my favorite expression

⬐ aazaa

Copper and boron, according to Wikipedia, will give green flame:

https://en.wikipedia.org/wiki/Colored_fire

But given the extreme conditions, a number of other factors could be at work.

⬐ Diederich

I think that was caused by the out engine trying to re-start itself using TEA-TEB.

EDIT: Correction: Raptor doesn't use TEA-TEB.

⬐ modeless

There were supposed to be two engines burning, but one shut down prematurely. I suspect the other one was burning up inside. Probably some burning metal made the green flames.

⬐ rajup

Most likely the chemical used to (re)start the engine, triethylborane (TEB)

https://en.wikipedia.org/wiki/Triethylborane.

⬐ handol

I thought the raptor was going to use a spark plug.

⬐ NikolaeVarius

Which it does not use

⬐ orost

Copper burns green, and the engine contains a lot of copper, so I think we saw a malfunctioning Raptor burning itself up.

Other answers mention TEB starter fluid but I don't think that's right, because as far as I know Raptor has spark ignition only.

edit: Elon Musk just tweeted that the immediate cause of the crash was low pressure in the fuel tank, so that would make sense, as running oxygen-rich would overheat and melt the engines.

⬐ dgritsko

The bellyflop and subsequent RUD is one of the most spectacular things I think I've ever seen.

⬐ grecy

Oh my god. I was genuinely pumping my fists and screaming at my screen. THIS is the start of a new space age.

I will remember this as long as I live.

EDIT: ... and they just posted a new road closure. How many days before SN9 flies?

⬐ sxarose

You know, we're hiring software engineers over here! :)

If that was your (or anyone else's) reaction and you'd be interested in learning more about what we're doing and how you might fit it, I'd be happy to chat! I'm a manager for one of the software teams here - we're always looking for great engineers who care about the mission!

⬐ grecy

My god I would love to. Absolute dream. I am actually a Software Engineer, and even your reply gets me excited.

I'm not American.

⬐ ColinWright

> ... we're hiring software engineers over here ...

...provided they are US citizens.

⬐ throwawaybutwhy

Well, if all you want is going to Mars ASAP, this is less of a hurdle than it seems.

⬐ dev_tty01

Getting back is the harder part.

⬐ sxarose

Yes, or green-card holders.

⬐ scarygliders

Congrats on the successful SN8 test!

Being born on the 4th July 1969, I always had a fondness for Apollo and rocketry in general. Always wanted to move to the USA as well, but my life's route took me elsewhere :) (although I /did/ once launch a rocket with the MARS team in Black Rock desert in 2001 in an attempt to break the UK amateur rocketry record! [http://www.mars.org.uk/phoboseav.html])

That SN8 flight was beautiful. The Belly Flop manoeuvre... wowsers!

I'm content now at 51 to watch you and the rest of the SpaceX team make history.

Do awesome stuff!

⬐ reducesuffering

Could you add your email to your profile? Is the location just in Hawthorne/LA?

⬐ sxarose

I just added it (thanks for pointing that out) but for anyone that wants to get in touch it is anthony.rose [at] spacex.com.

Edit: and there are other locations too, including Redmond, WA.

⬐ ColinWright

Your email address is still not on your profile. Did you add it to the window only visible to the HN mods? Or have you removed it again?

Regardless, as I type this, there are no contact details in your profile.

⬐ nynx

I suppose you're not looking for any more interns?

⬐ sxarose

We're still discussing the plans for 2021 given the challenges w/ CV19, but feel free to ping me (email in profile) and I can send you more info.

⬐ nynx

Sent! Subject line contains my hn username.

⬐ ninjamayo

Unfortunately for a lot of us outside the US, this is just a dream.

⬐ robotresearcher

Elon started outside the US, and I'm sure many of the team did too.

⬐ sxarose

Yep - I'm from the UK :)

⬐ ninjamayo

I am partially from the UK but I imagine you need citizenship to work for a rocket company like SpaceX.

⬐ None

None

⬐ nojvek

Very interested. How do I reach out?

⬐ throwawaybutwhy

Hi Anthony! Congrats on the mostly successful test, and a huge thank you to your colleagues.

⬐ fabian2k

That was about as awesome as a failed attempt could be. I assume that there were real engine failures on ascent, but it still all seemed to work like it was supposed to until the landing. And the scariest part, the belly flop maneuver looked like it worked just as it should.

⬐ aardvarkr

The first may have been unintentional on ascent but the second wasn’t. On the descent however both active engines failed due to fuel pressure, sadly, though it was awesome to watch.

⬐ mlindner

Timestamp for the flight: https://youtu.be/ap-BkkrRg-o?t=6480

⬐ ninjamayo

From Elon: Successful ascent, switchover to header tanks & precise flap control to landing point!

⬐ throwawaybutwhy

Amazing stuff for a rocket that had two of the Raptors replaced. I'd guess the engines will have to be perfected. Those are some finicky beasts.

A big thank you to all the engineers and technicians at SpaceX.

⬐ lpellis

That was epic, it felt like an eternity before engine shutdown, and then the freefall took just as long.

⬐ jonplackett

I just posted a gif of the landing on reddit and people are convinced it's edited and fake because they switch the camera almost exactly on impact. I kinda see their point!

⬐ soneil

I think my brain was screaming that it was fake because rockets simply don’t do this. Absolutely mindbending to watch, I can totally understand if anyone’s gut reaction that if it looks unreal, it might just be unreal.

(To be explicit; I don't believe it was faked. There was far too many people watching. But I can understand why the gut reaction may not agree.)

But in all seriousness, I suspect they were prepared for it to hit the ground. Once it left the ground, that part was guaranteed.

⬐ jonplackett

The world these days, when you have to explain yourself so much to make sure you aren't accidentally lumped in with people who really are that crazy.

⬐ agar

Maybe the scene was switched because two of the three cameras in that view had...just blown up?

⬐ Diederich

Link please?

⬐ nickik

On every single video about Space these idiots comment this garage. Don't waste your time with reading it.

⬐ jonplackett

I HATE it when people talk garage about SpaceX

⬐ imladyboy

Just look up any of the other footage. https://www.youtube.com/watch?v=gBELXjq_X-M

⬐ jonplackett

Yeah, I mean I don't actually think it's fake. I just see why someone might think it was from the Official Live Stream™

⬐ lmilcin

I know it might be a stupid idea, but would it be possible to have liquid propellant/oxidizer tanks perform double duty and serve as living space while underway?

The fuel here is methane and oxygen, nothing problematic. I know the shell is very thin and only maintains integrity due to pressure but it would still have to be pressurized to 1 atm for the trip and wouldn't be subjected to forces once in space..

⬐ jstsch

Fantastic, bullseye. What an event, beautiful! If it managed to slow down a tiny bit more it'd be still standing... Phenomenal.

⬐ boznz

Roll on SN9 :-)

⬐ grecy

In a sense the RUD might make it easier - now they just sweep up the debris and test SN9. If it hadn't RUDed, they would have to somehow dispose of SN8.

⬐ comfydragon

I actually think SN9 is going to be at least launching from a different stand. Perhaps also landing on a different pad.

⬐ Diederich

That's the main thing to remember: the main thrust of their iteration and innovation is to build the machine that makes the machine. To pump out Starships (and Raptors and Super Heavies) very rapidly, repeatably and cheaply.

⬐ tus88

That was awesome. I really thought it was going to blow when it started going sideways...then realized that was all part of the plan. Even the landing explosion was a fitting end to a first flight.

⬐ mlindner

That was amazing. History in the making.

⬐ lambda_obrien

When I saw the flaps bent at the seam, not twisting, I knew immediately that I've played too much KSP. It reminded me of a parachutist using their arms and legs to manage their decent.

⬐ rkagerer

At about T+1:40, the three engine bells appeared to shake and diverge away from each other slightly, and one appeared to flame out, spewing flame around the compartment, with one side of the chamber (and maybe craft) catching fire. https://i.imgur.com/KER9nqc.png

Is that what happened, or was it perfectly normal?

⬐ rkagerer

Nevermind, found the answer and shared it here: https://space.stackexchange.com/a/49066/21328

⬐ CarVac

That was absolutely incredible.

It looked like most of the flight went just as planned except for the engine relight at the end.

⬐ enraged_camel

Yeah, a few seconds too late to re-ignite is what it looked like. Great test though!

⬐ endymi0n

Flame looked very green very late, looks like they might have burned through quite a lot of TEA-TEB trying to get that candle lighted but it didn't react as expected...

⬐ CarVac

The Raptor doesn't use TEA-TEB, it uses an augmented spark igniter.

⬐ Gwypaas

Maybe some metal in the engine burning, you could see some green streaks at the edge right at the relight. Engine rich combustion?

⬐ CarVac

Yeah.

https://twitter.com/elonmusk/status/1336809767574982658

The fuel flow must have dropped, leading to oxygen-rich, and then engine-rich combustion.

⬐ CarVac

From Everyday Astronaut's slow-mo replay, it looks like two engines both relit properly, and then one shut down (intentionally), and then the final engine throttled down and turned green.

⬐ grishka

It landed, just not in one piece.

⬐ rkagerer

KABOOM!

<giant fireball, smoke, bits of rocket>

"Incredible work team, nice work!"

That cracked me up.

⬐ JshWright

The point of the test was the ascent and "belly flop" descent, which all seemed to work very well.

Landing was a secondary objective, and even there they seem to know exactly what went wrong (which means it was a very good test).

⬐ rkagerer

Yep, just the apparent juxtaposition make me feel exactly like I was watching one of my KSP simulations ;-). Must be a fun place to work.

⬐ dang

The story is also being discussed here: https://news.ycombinator.com/item?id=25366719.

⬐ tnli

Bloody Hell, that was the best thing since the Falcon Heavy!

Amazing, flying wheat silo!

⬐ shireboy

I watched this with my kids, and it really was surreal. My 11 yo said “it looks like something from Star Wars”. Exciting times for space. Hope we can keep this momentum

⬐ sneak

I think this counts as a rapid scheduled disassembly.

⬐ blackrock

The Starship floated down like a feather. I counted about 30 seconds when it was still higher than the cloud it passed through.

How many G’s is it pulling?

⬐ elihu

With three raptor engines, probably not very many. Though if I remember right from the Starship user manual posted here a couple days ago, a launch could experience up to about six Gs (and about 2 Gs or so sideways or backwards). That would be with the super-heavy booster. I'm not sure if the landing and belly-flop maneuver were included in those figures.

⬐ blackrock

How will the flaps handle the heat from re-entry speeds? Especially from the Moon or Mars.

Those crevices between the flaps, seems like great places for the atmospheric re-entry heat to punch through and destroy the Starship.

I would assume that during the initial re-entrant speed, the flaps would be locked, to minimize errant heat from entering the inner mechanisms. Then after it’s bled off most of its speed, at the last few kilometers off the ground, would the flaps begin to actuate and adjust to the air speed of terminal velocity.

I wonder if atmospheric re-entry is the bigger test, should they succeed with SN9.

⬐ grecy

They're working on heat tiles and how to attach them now - and I agree, somewhere around SN12 (my guess) we're going to start seeing tests of the heat tiles and more energetic reentries.

⬐ irrational

At one point it looked like one wall of the engine chamber caught on fire. Is that accurate?

⬐ elihu

I wondered about that too. After watching a couple of times, I think what happened is that they used some sort of tarp or plastic to cover a bunch of things, and part of it caught fire and burned. So, it was probably unplanned, but if everything else in the vicinity of the engine is fireproof, probably not a big deal.

⬐ lovetocode

I wish I was smart enough to understand anything being said here.

⬐ ColinWright

It's not a question of being smart, it's a question of reading about these things, reading what people have previously said, thinking hard, asking questions, and getting engaged and involved.

Some of this stuff is hard,and you're not expected to understand it without work. So don't just flip it off and say "I'm not smart enough" ... recognise that with work you can understand it, and if you choose not to put in the effort, that's your choice.

⬐ lovetocode

Thank you for this wonderful advice!

⬐ ColinWright

That's a great reaction ... I was hoping you'd take it as positive and encouraging, that's certainly how it's intended.

There's a lot in this world that takes time to work on, and time to come up to speed with. If you have seventeen lifetimes then you can do a lot, but otherwise you need to make choices. There's a lot you can appreciate from the sidelines, and agree is amazing, without necessarily understanding it all.

But other things you will want to get stuck into and get your hands dirty with, and it takes time and effort.

Smart isn't where it's at ... persistence and resilience are the critical components, combined with a desire to make progress. Absolutely you can look at something and choose not to engage with it, but if you're interested,have a go! Be methodical, be persistent, read around, ask questions, and go for it.

By the way ... I certainly don't know everything ... far from it ... very, very far from it, but if ever there's something you think I might be able to help with, just let me know. If I can't help, I'll say so. If I can, I'd be happy to do so.

⬐ lovetocode

Thank you Colin! I think what spurred my comment was that I feel like I have hit a brick wall and just feel exhausted. I am not getting younger, got a wife, two kids and a demanding career as a principal engineer. I want to desperately build my own start up again and learn something new. As you said, persistence and resilience are the critical components to getting through that barrier. Like many others here I assume, it can be exhausting wanting to learn about everything :).

⬐ Geee

That was incredible. Great job SpaceX!

⬐ DarmokJalad1701

That was an epic flight!

⬐ camilomaiden

https://onezero.medium.com/survival-of-the-richest-9ef6cddd0...

⬐ areoform

For my online presence, I make efforts to add to discussions instead of subtracting with negativity.

Recently, I've broken my rule quite a few times, fretting over the future of general compute. I'd vowed to not break it again, but this discussion lacks a vital perspective.

I don't understand the hype behind Starship. It's confusing to me. It is touching and nice; it's great to see people excited about space. However, the expectations and projections seem misaligned with reality.

At some level, people are assuming that this is the vehicle itself. In some ways, SpaceX is feeding into it. This isn't anywhere close to the finished vehicle and several key technological problems remain. Yet, they've explicitly shaped it like the final version, and hyped it.

Beyond GNC, SpaceX's most impressive achievement is a high performant, stable Liquid-Methane engine. Prior investigations and projects found notable instability during ignition as well as low frequency instability. Another historical issue has been the need for a high pre-burner chamber pressure for a LCH4 engine.

These issues were mapped out via prior research. For e.g., in 2014, there was a NASA project that shares some heritage with Raptor, https://en.wikipedia.org/wiki/Project_Morpheus

> During the rest of March 2014 the ALHAT hardware was inserted again permitting a successful tethered test of the assembly on March 27, 2014. Tether Test 34 flight trajectory was similar to TT33 and TT29 with two hovers and a 3 m (9.8 ft) translation during a 3.25 m (10.7 ft) ascent.[97] Free Flight 10 (FF10) took place on April 2, 2014 with the ALHAT in open loop mode. The ALHAT imaged the Hazard Field and calculating navigation solutions in real time. Morpheus ascended to a maximum altitude of about 804 feet (245 m), then flew forward and downward initially at a 30-degree glideslope, then levelling out, covering a total of about 1334 feet (406.5 m) horizontally in 50 seconds while diverting to a landing site location 78 feet (23.8 m) from its initial target, before descending and landing on a dedicated landing pad at the front (south) of the ALHAT Hazard Field. The total flight time was ~96 sec, the longest flight to date.[98] Free Flight 11 on April 24, 2014 was a repeat of Free Flight 10 with some changes to the ALHAT.[99] April 30, 2014 Free Flight 12 was a repeat of FF10 but with the ALHAT choosing the landing location.[100]

The engine was designed for moon operation, and demonstrated dynamic hazard avoidance and translation to a previously unknown "safe" landing area. The technology has found its way to the Nova-C lander which is slated for 2021. https://en.wikipedia.org/wiki/Nova-C

NASA also has some fairly detailed technical reports on the subjects from earlier experimentation,

https://ntrs.nasa.gov/search.jsp?R=20100034924

and a comparative analysis of LCH4 and RP-1 for reusable boosters,

https://www.researchgate.net/profile/Holger_Burkhardt/public...

The key impressive element over here is a reusable, throttleable, stable LCH4/LOX engine that seems to be capable of reignition (at least in the atmosphere). This is a significant achievement and one that SpaceX should be lauded for. However, an engine does not a starship make.

A proper comparison would be the Space Transportation System, or the Shuttle. As Starship has Raptor, the Shuttle had the RS-25, a high efficiency, highly manoeuvrable and performant marvel of engineering. It is perhaps the only engine that could be re-used over a dozen times. A claim unmatched until the development of the past few blocks of Merlin engines. The STS also had superior GNC, for its time, and could autonomously land in flying brick mode all the way from orbit.

However, that wasn't enough. The real issue turned out to be the thermal protection system, operational temperature ranges and the cost of refurbishing these machines.

The STS may look like a bad bet right now, but if you were sitting in the 1970s, watching the RS-25 perform, seeing the GNC work, and watching NASA nail the first test flight with two humans on top in a single go, it would have seemed like the future.

However, much of what makes rocket science hard is in the details. And those details simply haven't been filled in yet for Starship. These hops are excellent tests, but once again, an engine and GNC do not a starship make.

In light of this, I am unable to understand the excitement for this vehicle. Several people assume that they're close to sending an orbital vehicle. Perhaps, but it wouldn't be reusable. And it would be quite mass inefficient for a one-way trip due to the construction techniques used.

Starship isn't anywhere close to the primetime. It's at least half-a-decade to a decade away from initial reusable testflights, and perhaps more given the under funding of the Artemis program. This perception is mixed with a more dangerous one that the Starship is in a league of its own. It's not. Blue Origin's work and approach may be superior in the long run, as they're designing mission specific vehicles that are optimised to their context.

I am worried about a rocketry winter, as Musk is playing a dangerous game with the public's attention. People are far more fickle than politicians. It is worth remembering that early on in SpaceX's history, Musk made a dummy rocket and took it to DC to convince politicians to help allocate COTS & CRS funding to SpaceX. His gambit succeeded. My personal perception and worry is that SpaceX is repeating the tactic at scale, creating a sense that they're further along than they are.

It is hard to convey to the public what realistic milestones look like in rocketry, but for context Raptor has been in development since 2009. The LCH4/LOX variant since 2012. It has taken nearly a decade to near the (limited) flight readiness stage. It is likely that the other components will take longer. Will the public's attention sour?

⬐ guardiangod

https://twitter.com/elonmusk/status/1336808486022258688

Successful ascent, switchover to header tanks & precise flap control to landing point!

Fuel header tank pressure was low during landing burn, causing touchdown velocity to be high & RUD, but we got all the data we needed! Congrats SpaceX team hell yeah!!

It seems that the Raptor engines didn't failed due to defects at the end of the landing. The fuel pressure from the header tank wasn't high enough and the engines became fuel starved. It is obvious in the video as the engine exhaust became bright green at the end, a sign that the engine was restarting by TEB.

Edit:

https://twitter.com/elonmusk/status/1336810077555019779

Mars, here we come!!

Indeed

⬐ jonplackett

Just amazing to watch.

The flip down to gliding just looked so bizarre and futuristic.

It's the big WTF I got from first seeing Grasshopper stop and hover in mid air and land again. That's not what rockets are meant to do!

Except of course they are meant to do it!

⬐ sytse

And they had enough confidence that it might work that they attempted to land the first attempt on solid ground instead of in the water.

⬐ mulmen

The F9 water landing attempts were just because it was so far downrange though right? Not because a water landing would have been somehow better for the vehicle?

⬐ chasd00

iirc when spacex asked permission to land a falcon9 on the ground it was a firm "are you crazy? no." So lots of water practice.

⬐ mulmen

Hmm yeah you may be right. I definitely remember some failures that stopped above the water then tipped over but I don’t remember the circumstances.

⬐ wolfram74

If they'd decided for a water "landing" with SN8, I'd have assumed it was because they wanted any failures to happen further away from their test infrastructure, not necessarily because it was easier.

⬐ jonplackett

Yeah I thought they might do the same kind of 'pretend to land' hover over the water the first time, but no!

Maybe because they want to be able to keep it for posterity if it makes it - or launch it again!

⬐ bob33212

It is the flight back that they need data for, not landing.

⬐ rst

Not much different from early work on Falcon 9 landings -- the Grasshopper test rig and F9R-dev-1 prototype both did a bunch of land-to-land hops (the last being the crash that destroyed F9R-dev-1 after an engine failure) before they transitioned to attempted water landings from orbital flights

⬐ oska

> (the last being the crash that destroyed F9R-dev-1 after an engine failure)

From memory I think it blew itself up in the air when something went wrong, rather than crashing.

⬐ fnord77

this sort of thing existed before spacex

https://www.youtube.com/watch?v=o2sHf-udJI8

⬐ mulmen

It really didn't though. I'm not aware of any vehicle that does the belly flop flip to vertical landing maneuver, or has even attempted it.

⬐ valuearb

Why I love me some DC-X footage, and bemoan what we lost when NASA killed the project for their own boondoggle that failed, talk about missing the point.

• 45,000 feet is a lot farther that 450 feet. • Falling and using movable aerodynamic surfaces to descend in reentry position, then rotating into landing position is kind of hard.

• Running rocket engines for over four minutes straight is hard, BO has barely run their engines more than 4 minutes total in years of ground tests, without the realism of actual flight and its associated vibrations and accelerations.

• Restarting rocket engines is hard.

Lastly DC-X cracked up its last landing too.

⬐ seg_lol

Retractable leg failed to extend and it tipped over when the engines were throttled down.

The real issue is why did it have retractable legs in the first place, esp on a test vehicle. Sounds like a great to start writing a post mortem is in the design phase.

⬐ valuearb

It was a super cheap program as well. The post mortem should have been let’s build a bigger, better version with a similar budget, but instead NASA killed it to go all in on the 10X+ more expensive X-33 and killed that well before first flight.

⬐ jvzr

I've been following SpaceX for years, and this is exactly my reaction today! Watching the belly flop and the (relatively) slow descent, it felt completely alien, surreal. I'm in utter awe. Congrats to the teams involved, can't wait for SN9 and the rest of Starship!

⬐ fnord77

the apollo lunar lander did pretty much the same thing.

⬐ NikolaeVarius

Are you seriously comparing the Lunar Lander to this?

The Lunar Lander was piloted since the computers couldn't do everything, but at the same time a human was good enough at piloting to be able to take over for what the computer couldn't do.

This is the result of modern day CFD that that would take humans millions of years to do by hand

⬐ davegauer

Aside: the book Digital Apollo[0] gave me the impression that the computer might well have been able to land, but we'll never know since the astronauts didn't trust it enough to find out.

[0] https://mitpress.mit.edu/books/digital-apollo

⬐ serf

>This is the result of modern day CFD that that would take humans millions of years to do by hand

the package as a whole, yes.

belly reorientation for flight has been a thing since the early American arms' race. It's a useful missile trait.

Gimbaled vector rockets have existed since the 1940s.[0]

Yes, restart is very important -- it's not a requirement for atmospheric belly flight, though.

[0]: https://en.wikipedia.org/wiki/RTV-A-2_Hiroc

⬐ HPsquared

Nailing the transition to and from belly flight is the hard part, especially so when it's so close to the ground with little margin for error.

⬐ ddalex

Military have been doing the belly flop for years

https://www.youtube.com/watch?v=o9vljzfywJI

⬐ Gravityloss

Alpha Draco was testing body lift in the fifties https://en.wikipedia.org/wiki/Alpha_Draco

Robert Brulle has a fascinating memoir https://www.airuniversity.af.edu/Portals/10/AUPress/Books/B_...

⬐ galacticaactual

The Apollo lunar lander objectively did not belly flop through atmosphere at 1G while having to deal with aerodynamic control surfaces.

⬐ augusto-moura

RUD = Rapid Unscheduled Disassemble

For the people not familiarized

⬐ diimdeep

> With liquid propellants (but not gaseous), failure to ignite within milliseconds usually causes too much liquid propellant to be inside the chamber, and if/when ignition occurs the amount of hot gas created can exceed the maximum design pressure of the chamber, causing a catastrophic failure of the pressure vessel. This is sometimes called a hard start or a rapid unscheduled disassembly (RUD).

https://en.wikipedia.org/wiki/Rocket_engine#Ignition

⬐ NikolaeVarius

Raptor doesnt use TEB. It uses spark ignition

⬐ guardiangod

It must be the engine burning its internal alloys then. Probably the turbopumps' due to the fuel running rich?

⬐ Denvercoder9

It's probably the engine bells, since they are known to contain copper, and copper burns green.

Source: https://mobile.twitter.com/elonmusk/status/11773871411160023...

⬐ chasd00

copper gets used because it conducts heat very well and so assists in cooling. In one of the first test stand videos of a raptor run you can see a little bit of green and I think Musk even tweeted it was running "a little engine rich". the first time I watched a night flight of a falcon9 there was a green glow right at ignition which caused me to hold my breath but that was the hypergolic ignition fluids which also burn green. Raptor uses a torch ignition so any green from a Raptor is very bad news.

⬐ NikolaeVarius

Probably oxygen, since the fuel tank had low pressure

⬐ guardiangod

That's my suspicion as well. If it's methane rich then the exhaust would have a lot of soot due to incomplete combustion. If it's oxygen rich then the burn temperature would be much higher than designed, and every internal metal surface would get oxidize in a hurry.

⬐ amluto

Why would oxygen rich combustion be hotter than stoichiometric combustion?

I know very little about rocket engines, but I would imagine that the fuel pre-burner, which appears to be intended to run extremely fuel rich, might have some serious problems if it didn’t have enough fuel coming in. Aside from just generally not working, it could internally burn much less fuel rich and therefore much hotter than intended, resulting in any number of failure modes.

⬐ sitharus

Running fuel-rich is cool since the fuel won’t find extra oxidiser to burn.

Excess hot oxidiser on the other hand can often fuel. Like the combustion chamber wall.

⬐ dotancohen

This is the answer that the GP was looking for, but it's phrased funny.

sitharus means that the excess oxygen will oxidize (burn) things other than methane if there is enough oxygen present at the temperatures and pressures found in a rocket engine combustion chamber. It will oxidize (burn) things that you wouldn't normally think of as "fuel", such as the copper in the metal alloys.

⬐ kortex

The adiabatic temperature peak is stochiometric. However dynamics can shift the peak temperature lean or rich.

However, SpaceX is also tuning for engine temperature control and specific impulse. Raptor runs ~3.55 lox/methane (very rich), 4.0 is stoich.

https://www.researchgate.net/publication/255632584_On_the_Of...

⬐ xcskier56

This line of thought is very reasonable for normal engines, but I wonder if it’s not quite right for the raptor.

I’m not 100% on this, but I think the raptor actually runs really oxygen rich. According to Elon’s tweet and Wikipedia, it runs 3.5-1 O2-CH4. It runs so lean that the unburnt o2 cools things.

If it were running closer to 1-1 (low ch4) then it would run much hotter and burn things like we saw.

Edit: reading more I’m not positive they run O2 rich anymore

⬐ tdy721

You were probably thinking for the turbo pump? There is a lox rich condition somewhere to get full flow. Just not the overall ratio

⬐ dotancohen

To clarify this point. The Raptor uses two turbopumps. One turbopump hangs off the side and runs fuel rich, and this fuel-rich exhaust is the fuel input for the combustion chamber.

The second turbopump, to which tdy721 is referring, sits right above the injectors and runs oxygen rich. This oxygen rich exhaust is the oxidizer input for the combustion chamber.

⬐ kortex

Minor correction: 4.0 lox/methane is stoichiometric. 3.8 is rich. 3.55 is very rich. It runs fuel rich to keep cool and possibly increase specific impulse.

⬐ yholio

Once you hit a propellant bubble, the combustion temperatures are the least of your worries. The turbines are designed to ramp up gently, work fully loaded and transfer the energy from the hot side to the liquid propellants; the power density is enormous, 100.000 horsepower in the space of a truck engine 100 less powerful. Without an energy sink this immense power is directed at the turbine itself, which spins out of control and will dismantle or shatter when hitting liquid again.

Your engine is now full of solid projectiles that take out other parts, fuel lines and injectors, damage film cooling nozzles and coolant canals, and in general transform your precision machine into a smoldering pile of gunk.

⬐ chasd00

heh describing the ramp up of a turbo pump on a rocket engine as "gentle" seems funny. zero to 100k HP in about 500ms or so right?

also, from the pictures I've seen, the turbopumps are about the size of a propane tank, even smaller than a truck engine.

⬐ yholio

Well, half a second is quite gentle compared to ramming a fluid with a speed in the tens of m/s into a surging turbopump, especially one that is designed to minimize mass and exactly handle normal operating load and not more.

⬐ highenergystar

The exhaust was engine rich :)

⬐ nickik

> It is obvious in the video as the engine exhaust became bright green at the end, a sign that the engine was restarting by TEB.

The Raptor doesn't use TEB. It uses spark ignition.

The green is most likely 'engine rich' exhaust. Meaning the cooper cladding of the engine bell started to burn away.

⬐ ChuckMcM

Wow, thanks for that link, clarifies what happened. I never thought I'd see a "flash gordon" shaped space ship actually fly, and no here we are.

⬐ Gravityloss

I think once the aerodynamics are tried a little bit more, it can be refined to a lifting body. Strakes and deltaish wing, something a bit like the space shuttle or X-37.

Having completely cylindrical body and two sets wings now for the prototype phase makes control authority good and iterating changes very easy (you can change either wing shape easily), even if it's not optimal mass wise.

⬐ TigeriusKirk

What would cause the fuel pressure to be too low?

⬐ sq_

Aside from what a sibling comment mentioned about fuel sloshing from the flip maneuver, Raptor/Starship use autogenous pressurization (i.e. some of the gas produced by the engines is tapped off to pressurize the tanks), so there could have been an issue with that, too.

⬐ LeSaucy

Centrifugal forces of doing the belly flop maneuver. Ever try to flip a spinning object sepaofrom the axis it’s spinning on? Imagine a fuel pump or turbine full of liquid oxygen. The engineering to get this to work is astounding.

⬐ aardvarkr

Can you explain this more? I’m intrigued to learn about it

⬐ bigyikes

Fill a bucket with water and swing it upside down over your head. The water stays in the bucket because centrifugal forces apparently push the water outwards.

The same may have happened for the fuel, I guess lowering the pressure? I know nothing about rockets.

⬐ bigyikes

Not sure, but they might be talking about this: fill a bucket with water and swing it upside down over your head. The water stays in the bucket because centrifugal forces apparently push the water outwards.

The same may have happened for the fuel, I guess lowering the pressure? I know nothing about rockets.

⬐ CodeGlitch

"Fail fast, fail often"

Seems to be working for SpaceX. Makes for impressive videos too.

Congratulations to all involved.

⬐ strangemonad

Raptors don’t use teb or hypergols. This is some other fuel mix reaction

⬐ pbreit

Were all the engine outages planned?

⬐ TrueDuality

I believe some were. The plan was to switch over to two engines on ascent, and use two engines during the rapid deceleration. The full shut down was intentional. It looks like they might have briefly went to one engine during ascent but it wasn't entirely clear. The flame out of the first shut off was probably not intentional as well. It's really hard to tell.

None of that information was official though so take it with a grain of salt, it's all come from personal knowledge and analysis by some people watching.

⬐ handol

I think all the shutdowns on ascent were planned, but not the shutdown that happened during the landing burn.

⬐ dpifke

According to Musk, yes: https://twitter.com/elonmusk/status/1336818987389181952

The orientation change just prior to shutoff is also a clue: https://twitter.com/joebarnard/status/1336820348071849986

⬐ potiuper

This test of lossless convexification showed good results with the stochastic control problem, but the fluid dynamics model could use some work before:

> Mars, here we come!!

⬐ mlindner

https://www.youtube.com/watch?v=RXJKdh1KZ0w

⬐ nikolay

A nice try to make an explosion sound like a success - reminds me of the Soviet times when the Party was never wrong!

⬐ jryle70

Since you're are such impressively unimpressed, maybe you could tell us what the objectives of this test were and how SpaceX failed to achieve them?

⬐ nikolay

No, I'm commenting on Elon Musk's comment. I would have taken a humble: "Sorry, we blew up this (literally), but we're gonna get better after learning from our mistake." You blow things up, you fail. No excuses, sorry! Don't start a test knowing it most certainly will fail! Start a test when you're a lot more confident!

⬐ mkl

The purpose of a test is to gather the data you need to improve. Scientists and engineers constantly start tests knowing it will most likely "fail". Actual failure would be a test that didn't produce any data.

⬐ nikolay

No, an explosion and destruction of equipment is a failure. Why do you keep dancing around this truth? It is a failure everywhere else in the world! You should've listened to the commentary of foreign anchors! They don't look at it as a success!

⬐ fastball

They are currently building like 10 other Starship prototypes.

Even if this model had worked perfectly, it's unlikely they ever would've flown it again. Remember, SpaceX's goal is to mass produce these.

Much better to fail hard now and in many different ways, as the more problems you can find with your expendable prototypes the better (before your manufacturing process starts to ossify).

⬐ mkl

Things are successfully tested to destruction every day. That is the truth. Some of the most successful tests involve explosions and loss of equipment; it's the only way to be sure where the limits are.

News anchors? They're often pretty clueless about technical things, so their mistakes don't mean much.

⬐ JshWright

I'm very confused by your take here... SpaceX made it clear beforehand that the primary objectives of this test were the ascent and descent, not the landing. The "belly flop" horizontal descent is entirely new, and something they have only modeled so far.

The primary objectives of the test were completed without any issues. If that doesn't meet your definition of success, I don't know what to tell you...

⬐ sitharus

But it didn’t fail, landing wasn’t a test objective.

⬐ restalis

Landing may not have been one of the primary objectives, but it clearly was an objective, since they didn't just let it crash at will after having completed the flight maneuvers.

⬐ DarmokJalad1701

> Don't start a test knowing it most certainly will fail! Start a test when you're a lot more confident!

Good thing you aren't the one designing these things.

⬐ jessriedel

It's a test flight. Musk gave only a 1/3 chance of mission success before the flight.

⬐ nikolay

Yes, but a 1/3 success chance doesn't not mean a 2/3 one of an explosion.

⬐ robotresearcher

After engine ignition, isn't it pretty much that success or massive explosion are the only outcomes?

⬐ NikolaeVarius

Nah engines are able to turn off after ignition. Thats what the Raptor safety is. Usually the blow or moment is when it lifts off the tower with one notable exception that I know of.

https://en.wikipedia.org/wiki/Mercury-Redstone_1

Technically the Shuttle go or blow moment is when the SRBs are turned on.

But yes, otherwise in the spirit, it will either blow up or be generally sucessful.

⬐ aardvarkr

So you’re saying that if the engines had been off the starship wouldn’t have exploded? Try again bud. That’s still an object full of compressed methane and liquid oxygen falling at terminal velocity.

⬐ NikolaeVarius

This is such a straw man that I don't even know where to begin to answer.

⬐ valuearb

So you are admitting that what Musk meant was they had a 2/3s chance of an explosion.

⬐ restalis

You're right that the destruction of equipment and loss of material resources in general is a failure that could have been prevented with a more cautious approach, but that's not the entire picture. Another resource, one that Mr. Musk cares more about, is time. He both affords to and is willing to throw material resources at the technology development problem, even at a loss (i.e. the stated "1/3 chance of success"), just so he could "move fast and break things" (from time to time, if it comes to that). In this context, even with that prodigious blow at the end, having at least some of the testing goals met can be a genuine success in Musk's own eyes, not just a sell for the rest of us. The political actors, on the other hand, had to play the perception image game because that's the world they reside in. The politicians' primary objective in that space program has always been the prestige that comes attached from bearing it to fruits. Sure, in a race they went on in a similar fashion and threw copious amounts of material resources, but for them the cost of technical failures were not so much about loosing material as were about loosing face, hence the propaganda that had to handle/mitigate that. Same rocket science development game, different rules for the actors involved.

⬐ pertymcpert

Was it a complete failure?

⬐ nikolay

Well, nothing is a complete failure ever from your point then - you always learn from mistakes.

⬐ sirk390

Yes, but if it explodes during launch you learn only a little(you don't have any data for flight and landing) Here it went almost perfect because they have the data for everything to be able to fix issues

⬐ pertymcpert

What point was that? I just asked you a question.

⬐ mulmen

You have identified the purpose of test flights.

⬐ mlyle

We have launch, controlled flight through the desired test regime, and a botched landing.

And as others have said, it's either complete success-or-explosion that's expected in this area.

⬐ ChrisFoster

No, I'd say it was an almost-complete success. The point of this was to test several things which they've never tested before and gather data to drive design improvements. They successfully tested: ascent under three engines, flap-controlled aerodynamic descent to the landing site, the landing flip maneuver - including drawing propellant from the header tanks - and final landing burn.

They didn't stick the landing, but it looks like they got test data from all the planned test activities. The explosion will prevent gathering some data from post-flight inspection, but other than that I doubt it has much affect on future development.

To look back on SN5/SN6 testing, they stuck the landings with those prototypes, but the prototypes themselves are now obsoleted by the new prototypes in production (up to SN16?!)

⬐ sq_

It sounds like they've got SN9 just about ready to go, too, so they should be able to put the data that they gathered to good use quite soon.

Seems to be a great benefit of this method that SpaceX is following with Starship: if you build hardware fast and cheap enough, you can afford some partial failures since you just put the lessons learned into the next flight in a few weeks.

⬐ elihu

They had to get a lot of things right on the first try for a successful landing. They got a lot of them right, but had trouble with fuel pressure at the end and landed too hard because there wasn't enough thrust.

As problems go, that's a relatively simple one that they ought to be able to address. The ascent appears to have been successful (though for a few moments it looked like something caught on fire and I'm not sure if that was planned or expected). The glide worked. The rocket was able to navigate to the landing pad.

Next time they'll be working with a lot more information. This seems like overall it was a success, even though they're down one rocket and three engines. A failure would have been the rocket blowing up on the pad during launch or other similar mishap from which they wouldn't have learned much aside from "make sure that doesn't happen again".

⬐ fastball

The fire after first engine cutoff was just extra gases from the cutoff engine getting trapped and burning off.

⬐ sitharus

> It is obvious in the video as the engine exhaust became bright green at the end, a sign that the engine was restarting by TEB.

They wouldn't carry enough TEA/TEB to make that much flame - it's likely the engine itself burning. Also I don't think Raptor uses TEA/TEB as that would put a cap on the number of restarts - not something you want for an interplanetary mission!

⬐ rst

It uses electric spark igniters.

⬐ sq_

If I remember correctly, green from Raptors has always been the result of “engine-rich combustion” of copper in the combustion chamber/nozzle.

⬐ lapitopi

Looks like a success! Almost nailed the landing as well!

May have ran out of fuel towards the end.. but amazing to watch.

⬐ aeternum

Green flame might mean something copper burning that shouldn't be. Based on the size of the explosion it looks like there was still a decent amount of fuel.

⬐ gizmo385

Is it necessarily copper? There are other compounds that can produce green flames (like https://en.wikipedia.org/wiki/Triethylborane)

Edit: There are some other comments talking about "engine rich exhaust" that are burning parts of the engine. Still incredible they got it this far.

⬐ marsokod

The inside of the nozzle uses copper for heat dissipation. There were previous cases of green flames with the Raptor, and Elon said it was copper. The big question is why it was low on methane - bad calculation in the planned consumption, too methane rich during the ascent?

⬐ diimdeep

> This suborbital flight is designed to test a number of objectives, from how the vehicle’s three Raptor engines perform, and the overall aerodynamic entry capabilities of the vehicle, including its body flaps, to how the vehicle manages propellant transition. SN8 will also attempt to perform a landing flip maneuver, which would be a first for a vehicle of this size.

> With a test such as this, success is not measured by completion of specific objectives but rather how much we can learn as a whole, which will inform and improve the probability of success in the future as SpaceX rapidly advances development of Starship.

⬐ Dirak

That was spectacular! I'm completely blown away by how audacious and bold the Starship project is. Sending a rocket that massive into space and then attempting to land it back on earth, with the intention of using it to eventually send people to Mars and back. Just thinking about how much force those thrusters must have been exerting to propel the ship and pull off that flip maneuver gives me chills. I can't wait to see how fast they'll take to build and send up the next one. Props to the people at SpaceX for getting this far!

⬐ robodale

That flip at the end was fun to watch. Getting 15 stories of rocket back to vertical like it ain't no thing. An engine was out earlier in the flight (intentional or not?), so I wonder if more fuel was onboard than planned and came down heavier than expected? I am only speculating...their engineers are smarter than me.

They came down vertical, right where they wanted...just a little hot. The next Starship iterations are gonna be awesome.

⬐ zaroth

> Fuel header tank pressure was low during landing burn, causing touchdown velocity to be high & RUD, but we got all the data we needed! Congrats SpaceX team hell yeah!!

https://twitter.com/elonmusk/status/1336809767574982658?s=21

⬐ klohto

Awesome! The landing was almost there but the test was most definitely a success. Great work SpaceX.

⬐ _Microft

Tentative time for launch is when this comment is 6 minutes old.

That's 21:40 UTC or 3:40 p.m. local time there.

⬐ rswail

Task failed successfully :)

⬐ jonplackett

R2D2, watching on from the sidelines...

⬐ the-dude

Delayed to 22:40 UTC / 4:40PM CST

⬐ igravious

Ka-boom! Spectacular fail!

⬐ handol

It completed the high altitude flight test

⬐ _fs

Unfortunately people are going to focus on the explosive ending. But the high altitude test went well.

⬐ angelbar

The belly cruise and the final flap too...

⬐ igravious

I know that. I watched the entire thing live: climb, stall, belly flop, tail stand, landing, rapid disassembly. I understand the significance.

Still a cool explosion though. :)

⬐ floatingatoll

That was amazing. I don't normally watch SpaceX launches but I'm glad I watched this one. They did all their orientations perfectly. I've never seen a rocket take fall damage while vertical before. Thanks for the heads up, HN.

⬐ nickik

That was the literal bomb. So awesome.

Not understanding yet why it was green at the end. Raptor shouldn't really use TEA-TEB.

Seems like an engine busted on the way up. Or maybe one of the nitrogen tanks in the skirt.

Scott Manley will do a rundown on all of these soon I would assume. Tim Dodd will do an interview with Elon.

Great community making content about this.

⬐ JamesCoyne

The green flame might indicate my new favorite term: Engine-rich exhaust.

⬐ arijun

> Not understanding yet why it was green at the end

I think they call it engine rich exhaust; some of the copper from the engine being burned

⬐ adrian_b

Yes, Elon Musk explained what happened.

The pressure of the fuel was too low during landing, which had 2 effects:

1. the exhaust gases contained mostly oxygen, which burned the copper linings, giving a green flame

2. the decceleration was insufficient, causing the impact with the ground which resulted in an explosion

⬐ paulmendoza

It also didn’t help that the legs didn’t deploy