Starship flight N5 in 57minutes and they try to Catch the Booster

[paulca]

Holy crap, they actually bloody did it.  They caught a booster.  First time attempt!  Incredible engineering.  Small fire but that can be resolved right? 

Me and my brother were discussing this.  In order to run a rocket motor you need a turbo pump.  Turbo pumps burn either fuel rich or oxydizer rich.  Looking at the footage I believe the raptors in use during 'landing' share a turbo pump or a turbo pump exhaust.  You can see when the engines back off the turbo pump is spewing unburnt fuel everywhere in a big plume of yellow flame (O2 starved gas burn).

In order to light, extinguish, relight, throttle etc those engines the turbo pump must be kept running, no?  You won't see it on the way up as (apparently) they are normally "closed cycle" and the turbo pump exhaust is reinjected and not vented.

I may have to go and rewatch all the techie detail videos on the raptors again.

[paulca]

Somewhere in SpaceX there are a room full of engineers all picking from a cup of straws.

He who draws the shortest is the one who walks up to it first.

Note.  The condensation rings top and bottom suggest it's still got fuel and oxydizer onboard.  It could very well still go boomksi.

[paulca]

It was awesome

Now observe all the news organizations. They will totally ignore the successful and awesome booster catch and instead focus on the negative. "SpaceX rocket explodes on landing", when it actually landed, and then exploded.

I'm not too sure if they terminated the ship on purpose after landing was over to sink it, or if the ship falling over ruptured a tank. Probably the former.

Speculation, but it looked like some of the rocketry stuff was still running when it landed.

I think we got to find out what happens if you run a raptor engine under water.

[tom66]

Holy crap, they actually bloody did it.  They caught a booster.  First time attempt!  Incredible engineering.  Small fire but that can be resolved right? 

Me and my brother were discussing this.  In order to run a rocket motor you need a turbo pump.  Turbo pumps burn either fuel rich or oxydizer rich.  Looking at the footage I believe the raptors in use during 'landing' share a turbo pump or a turbo pump exhaust.  You can see when the engines back off the turbo pump is spewing unburnt fuel everywhere in a big plume of yellow flame (O2 starved gas burn).

In order to light, extinguish, relight, throttle etc those engines the turbo pump must be kept running, no?  You won't see it on the way up as (apparently) they are normally "closed cycle" and the turbo pump exhaust is reinjected and not vented.

I may have to go and rewatch all the techie detail videos on the raptors again.

I don't think that's strictly required.

The fuel pumps are probably electrically started and then run on combustion energy.  These run on partially burned fuel - oxygen-rich methane or methane-rich oxygen gas output.  This partially combusted fuel is then sent to the main combustion chamber where it is fully combusted to provide thrust.

The ignition is via spark ignition so does not require any pump to operate.

So turn electric fuel/LOX pump on, engage igniters, igniters cause fuel combustion which causes turbos to spool.   All it would need is the minimum amount of fuel/LOX to get the reaction going. Some very rapid control electronics and software will be monitoring the fuel/LOX rates to ensure that the engine starts up quickly as I am sure it is possible to put it into very dangerous and failure-prone operating modes. 

Shutdown would be by isolating fuel/LOX which will result in engine running fuel rich as methane is denser than oxygen.  This results in the visible dark orange flames of poor combustion before shutdown.  They might keep methane going for a tad longer to avoid overheating the nozzle, as that is fuel cooled, but just a guess on my part.

As can be seen here, the startup and shutdown are pretty rapid.



SpaceX relies on this since the three Raptors aren't enough to slow down until the terminal phase of the flight so they have to alternate between 13 and 3 raptors on at various stages.  On Falcon 9 a single Merlin engine is actually sufficient to allow the empty Falcon 9 to lift off again so the descent profile is based on very careful timing of the single engine relight.  Merlin uses a consumable liquid ignition fuel and takes longer to ignite than Raptor, but not exactly sure on why.

[Psi]

I'm not too sure if they terminated the ship on purpose after landing was over to sink it, or if the ship falling over ruptured a tank. Probably the former.

Speculation, but it looked like some of the rocketry stuff was still running when it landed.

Possible. Something definitely detonated violently though, you can see the exploded shock and many parts flew up in the air and rained back down.  It's possible it was something other than a tank explosion. Like an engine, or a COPV or something.
But the flight termination system does make a lot of sense based on what we saw. 
Also you wouldn't want to leave the explosives in the flight termination system intact. Otherwise they might wash up on some beach somewhere. So setting them off after landing is complete would make a lot of sense if you don't plan to recover it intact.

[Psi]

Me and my brother were discussing this.  In order to run a rocket motor you need a turbo pump.  Turbo pumps burn either fuel rich or oxydizer rich.  Looking at the footage I believe the raptors in use during 'landing' share a turbo pump or a turbo pump exhaust.  You can see when the engines back off the turbo pump is spewing unburnt fuel everywhere in a big plume of yellow flame (O2 starved gas burn).

In order to light, extinguish, relight, throttle etc those engines the turbo pump must be kept running, no?  You won't see it on the way up as (apparently) they are normally "closed cycle" and the turbo pump exhaust is reinjected and not vented.

I may have to go and rewatch all the techie detail videos on the raptors again.

I'm 99% sure each raptor engine has its own dedicated turbo pumps, and that they only have to spin them up a few seconds before they want to start the engine. So the pumps are fully off if the engine is off.

The outer ring of raptors doesn't have the plumbing needed to spin up the turbo pumps with pressured gas from the tanks. So those ones require the pressure feeds from the launch pad to start them. They can never be relit in flight.

All the center engines, including the 3 they use for landing, can relight by spinning the pumps up with gas a few sec before starting the engine

[paulca]

So the plume of yellow "rich" flame up the side?

Maybe it's not the turbo pumps "running", but just spinning down?  Maybe there is venting required and it just happens to get lit due to the rage under it?

[paulca]

The best bit, was when the footage from the tower itself appears, you can see the booster does not get "caught" at all.

The booster "lands" exactly 1 foot over the rails, lowers itself onto them and then lifts its own weight back off again and settles finally.

It's not like it threw itself into the arms, it deliberately settled itself and made sure.  Amazing.

[tom66]

The best bit, was when the footage from the tower itself appears, you can see the booster does not get "caught" at all.

The booster "lands" exactly 1 foot over the rails, lowers itself onto them and then lifts its own weight back off again and settles finally.

It's not like it threw itself into the arms, it deliberately settled itself and made sure.  Amazing.

It's very similar to Falcon 9, but obviously on a much larger scale.  F9 intercepts the landing pad at, hopefully 0m/s.  Though realistically it is going some small velocity into the ground surface when it impacts and the sea undulating below means that the springs inside the landing legs (which are also designed to break safely if the load is too much) have to absorb some energy.  Since Starship Heavy can hover (for a short period of time) they can keep the time spent close to 0m/s longer to allow for a more precise docking. F9 will just go up in a parabola on one engine until it crashes so timing with the engine there is critical.  In some senses you could argue the F9 landing is more impressive because of this interception speed at zero... though obviously landing a ~twenty-storey building-sized rocket is something else altogether.

[paulca]

.... and they absolutely have to have the gantry make a loud

"KaKlunk!    PSSSSSSSsssss."  Noises just like sci-fi would.

[Psi]

So the plume of yellow "rich" flame up the side?

Maybe it's not the turbo pumps "running", but just spinning down?  Maybe there is venting required and it just happens to get lit due to the rage under it?

Pretty sure the fire from the side was an unintended leak or vent of some sort.
One of the raceway panels (that cover up the plumbing that runs up the side of the booster)  exploded off for some reason when the engines were lit, which is probably related.
There was also some fire coming out of the 'quick disconnect' used to load fuel into the rocket. Perhaps what was sitting in the fueling pipes.

As far as i'm aware, anything coming from the turbo pumps can only vent out the nozzle.

There are a few vents for various other things on the rocket, like bleed off vents to keep the tanks at the right pressure, and vents used to quickly detank all fuel from the rocket in an emergency. It's possible one of those got damaged by atmospheric heating and started leaking.

Just rewatched the video, you can see gas leaking out the side, and then flames from the engine reach that and ignites it. After that there's a fire on the side of the rocket.

[coppice]

The best bit, was when the footage from the tower itself appears, you can see the booster does not get "caught" at all.

The booster "lands" exactly 1 foot over the rails, lowers itself onto them and then lifts its own weight back off again and settles finally.

It's not like it threw itself into the arms, it deliberately settled itself and made sure.  Amazing.

Of course. If you are going to hold a massive heavy and rather fragile structure by 2 small lugs you've got to settle gently onto the supports. The real operation is a combination of catching and fine control by the thrusters. The arms move in AND the thrusters settle the ship into place. What I found interesting is the way the booster descended over the water, and only at the last moment nudged itself over to the land and the tower. Some people seem to think that path showed a lack of control, but it was clearly an intentional path to avoid risk to the tower and other facilities until the last moment.

[paulca]

Yep and you can guarantee that the ABORT button would cause it to point out to sea, fire fully away and then blow up.

[Andy Chee]

Yep and you can guarantee that the ABORT button would cause it to point out to sea, fire fully away and then blow up.

That plan requires a functioning attitude control system. 

I always envisaged an ABORT system being activated in the event attitude control was completely lost.

[tom66]

I imagine ABORT for this case was the landing pad area was completely evacuated and they accepted that in the event of close FTS activation they'd have to rebuild the pad.  They would be carefully monitoring its descent the whole way and if it went outside of nominal trajectory then 'boom'.

How that works when SpaceX imagines these craft being used as Earth point to Earth point passenger transport is unknown to me. That itself presents some very interesting challenges and I think those will ultimately prevent it from being a commercially feasible operation.  At least if an aircraft crashes, it usually leaves the airport intact, damaging at most the runway and hardware nearby.  (There are of course exceptions but they are rare.)

[coppice]

I imagine ABORT for this case was the landing pad area was completely evacuated and they accepted that in the event of FTS activation they'd have to rebuild the pad.

Obviously everyone has to be cleared from a big enough area that a disastrous failed catch won't kill people. That's a bit beyond abort. I assume the last abort point was just before they steered the descending craft from over water to over land. After that any failure is going to be pretty costly, and will cause a long outage. I'm surprised how close the 2 towers are. I assume that spacing is considered adequate for a failed landing taking out one tower to not affect the other. I find it hard to imagine that a major failure on the way up is not going to take out both towers.

[paulca]

The rising issue they are increasingly having to consider is simply put as:

The global public are now starting to state they would like "that which rains down from space" to be regulated.

Not all of it breaks up.

Texas, the FAA etc had a spat with them recently about the ablative tiles (silicon dioxide?) cause particulates which can be termed "toxic".

They have had many a spat with the FAA because the flight rules for these "exceptional flights" as they are filed, do NOT permit deliberate failures.  Sending up a rocket (or anything) with the complete expectation it will fail is illegal.  The FAA can not permit you otherwise.  The military might help though.

China unfortunately has been giving the hand-wringers the ammunition by dropping half fuelled, orange smoke spewing hypergolic(sp?) rockets on villages with no more than an "Oops".

[iMo]

Some new video footage from the splashdown..

[Brumby]

Lots of great stuff in this trip. All of it progress. However, they are really struggling with the Starship heat shield. NASA did. Everyone has. If they had recovered that Starship it would clearly have required a massive refurbishment of the heat shield, just like the Space Shuttle required after every flight. That isn't going to bring Space X to the kind of cheap, fast turnaround reuse they are aiming for. Could this be an insurmountable problem that will wreck the Starship program? I hope not.

I wouldn't be too concerned at this point.  Yes, there are some stiff challenges, but then SpaceX has addressed quite a few already ... and they're still not done.  Remember, this is still a DEVELOPMENT program!

[Brumby]

As insanely impressive that catch was, somehow I feel a rocket landing on the ground balanced like a pencil dropped on it's eraser staying standing vertical is just more difficult and impressive.

I think landing a rocket on the crane that's going to put it back on the launch pad is impressive enough for me.

Yes, yes, I know there is the concept of landing directly back onto the launch pad, but I think that is impractical for several reasons.  Besides, the chopstick "catch" manoeuvre makes for excellent theatre.

[RJSV]

   I've only been paying casual attention,  but can somebody answer:   Isn't that about the same as the previous Booster landing in almost backwards running video ?
Booster would come down, powered, and land.
How, is this new, then ?
...(just curious, thanks).

[CatalinaWOW]

   I've only been paying casual attention,  but can somebody answer:   Isn't that about the same as the previous Booster landing in almost backwards running video ?
Booster would come down, powered, and land.
How, is this new, then ?
...(just curious, thanks).

In the same sense that a small business jet and an Airbus 380 are the same.  Both put wheels and flaps down, slow down and land.

[CatalinaWOW]

Lots of great stuff in this trip. All of it progress. However, they are really struggling with the Starship heat shield. NASA did. Everyone has. If they had recovered that Starship it would clearly have required a massive refurbishment of the heat shield, just like the Space Shuttle required after every flight. That isn't going to bring Space X to the kind of cheap, fast turnaround reuse they are aiming for. Could this be an insurmountable problem that will wreck the Starship program? I hope not.

Another thought on this subject.  While refurbishment after each flight won't lead to the incredible price reduction they want, there are things about the Starship design that will still dramatically reduce costs.  On of the cost drivers on the shuttle was that most, perhaps all of the tiles were a custom design, specifically shaped for their location.  On Starship the vast majority of the tiles are one of two different varieties.  The savings from just having to stock a handful of replacement part numbers is enormous.

[Andy Chee]

   I've only been paying casual attention,  but can somebody answer:   Isn't that about the same as the previous Booster landing in almost backwards running video ?
Booster would come down, powered, and land.
How, is this new, then ?
...(just curious, thanks).

The "new" thing is that; instead of the booster landing on land, the booster is now landing on the tower structure.

Landing on a tower structure requires greater precision in both attitude control, and thrust control.

Returning to the launch structure could potentially see a massive time saving between successive launches, assuming that the rocket can be refueled and payload assembled at the tower.  OTOH, if transport to the vehicale assembly buiilding is still required, then the "chopsticks" landing doesn't gain much advantage.

Successive launches is an important requirement for launching Starlink and other low earth orbit cube sats.  Cube sats by their nature, will deorbit rapidly compared to geosynchronous satellites, hence the cube sats need to be constantly replaced.

[Psi]

Some people for scale, since its easy to miss just how huge starship and the booster actually are.