B9 + S25 IFT/General Discussion

[Starmang10]

My own poll:

1: B9 explodes on pad before liftoff

2: B9 makes it off the pad but falls back, causing total devistation of the OLT, OLM, and OTF

3: B9 makes it off the pad, Astra-Powerslides into the ocean

4: B9 makes it off the pad, gets towards Max-Q but explodes/crumples

5: B9 makes it off the pad, passes Max-Q, but pulls a B7 moment and doesn't release S25

6: B9 makes it off the pad, passes Max-Q, releases S25 but it fails to ignite its engines, throwing itself off B9 during the boostback maneuver

7:B9 makes it off the pad, passes Max-Q, releases S25, S25 ignites its engines, but then pulls a Terran 1 second stage moment

8:B9 makes it off the pad, passes Max-Q, releases S25, S25 ignites its engines, gets into orbit, B9 is unable to reignite its engines and slams into the Gulf of Mexico

9:B9 makes it off the pad, passes Max-Q, releases S25, S25 ignites its engines, gets into orbit, B9 re-ignites its engines for a soft touchdown into the Gulf of Mexico

10: B9 makes it off the pad, passes Max-Q, releases S25, S25 ignites its engines, gets into orbit, B9 re-ignites its engines for a soft touchdown into the Gulf of Mexico, S25's engines die in some way, shape, or form, and is unable to deorbit manually, leaving it to burn up in the atmosphere.

11:B9 makes it off the pad, passes Max-Q, releases S25, S25 ignites its engines, gets into orbit, B9 re-ignites its engines for a soft touchdown into the Gulf of Mexico, S25 is able to reignite its engines to deorbit.

12: B9 makes it off the pad, passes Max-Q, releases S25, S25 ignites its engines, gets into orbit, B9 re-ignites its engines for a soft touchdown into the Gulf of Mexico, S25 is able to reignite its engines to deorbit, it burns up in the atmosphere.

13:B9 makes it off the pad, passes Max-Q, releases S25, S25 ignites its engines, gets into orbit, B9 re-ignites its engines for a soft touchdown into the Gulf of Mexico, S25 is able to reignite its engines to deorbit, it burns up in the atmosphere.

14: B9 makes it off the pad, passes Max-Q, releases S25, S25 ignites its engines, gets into orbit, B9 re-ignites its engines for a soft touchdown into the Gulf of Mexico, S25 is able to reignite its engines to deorbit,  it reenters successfully, does an SN11.

15: B9 makes it off the pad, passes Max-Q, releases S25, S25 ignites its engines, gets into orbit, B9 re-ignites its engines for a soft touchdown into the Gulf of Mexico, S25 is able to reignite its engines to deorbit, it reenters successfully, crashes into the ocean as planned.

Cast your votes, yall!

[alugobi]

So, basically, it's just a guess at what will happen? 

[gaballard]

I’m split between 8 and 10 - I think they’ll get SS into orbit, B9 won’t relight enough engines to soft land, and it’s a total toss up whether SS fails.

[TomH]

So many F-9 boosters have landed successfully, that I think SH will correctly simulate a landing on water (Can you legitimately call it a landing if you come down in water?) I think tiles will be an issue for SS and it will RUD during entry

Aren't 12 and 13 the same scenario?.

[JaimeZX]

Recommend adding a poll as these threads often do, along the lines of:
How far will 25-9 make it?
* Off the pad
* Max Q
* Staging
* B9 landing issue but S25 Full suborbital trajectory
* B9 and S25 complete flight profile as planned
-----------------------

Also... WRT Max Q... I've always wondered if that's something calculated based on velocity & altitude/air density, or does the ship have like... a pitot tube?

You left out B9 successful landing, but S25 RUD upon reentry.

  Wasn't meant to be a comprehensive list of possibilities, just a starter list for the OP; hence the "along the lines of..."

[sebk]

There's not deorbit in the flight test so the points about failing to deorbit can't happen.

What could happen but is missed is that S25 loses reaction control and can't position itself properly for reentry. Then its either aerodynamically stable and will self orient and would continue reentry but with large positional error, or it's not stable, so it will tumble and disintegrate.

[Herb Schaltegger]

So many F-9 boosters have landed successfully, that I think SH will correctly simulate a landing on water

If SH was just a giant kerolox stage with lots of Merlins I would agree with you. But relighting Raptors on flight vehicles has been hit-or-miss on just about every test vehicle. Hell, just getting them all to light ONCE still hasn’t happened yet.

I sincerely hope they don’t rush to OFT-2  and instead spend some time taking advantage of the newly rebuilt OLM + water-cooled steel blast plate and get engine start down to 100% reliability.

[abaddon]

So many F-9 boosters have landed successfully, that I think SH will correctly simulate a landing on water

If SH was just a giant kerolox stage with lots of Merlins I would agree with you. But relighting Raptors on flight vehicles has been hit-or-miss on just about every test vehicle. Hell, just getting them all to light ONCE still hasn’t happened yet.

The Booster doesn’t have the crazy flip maneuver.  F9 has never had to do anything like that, so we have no idea what Merlin would do in those circumstances.  A “normal” landing profile should be much simpler for Raptor to handle in comparison.

[chopsticks]

So many F-9 boosters have landed successfully, that I think SH will correctly simulate a landing on water

If SH was just a giant kerolox stage with lots of Merlins I would agree with you. But relighting Raptors on flight vehicles has been hit-or-miss on just about every test vehicle. Hell, just getting them all to light ONCE still hasn’t happened yet.

The Booster doesn’t have the crazy flip maneuver.  F9 has never had to do anything like that, so we have no idea what Merlin would do in those circumstances.  A “normal” landing profile should be much simpler for Raptor to handle in comparison.

That makes no difference to the point Herb made that they often don't even start up on the first try.

Every single flight test has had engine issues, whether on the way up or on the way down. Getting them to work reliably should be at the top of the list, IMO.

[steveleach]

So many F-9 boosters have landed successfully, that I think SH will correctly simulate a landing on water

If SH was just a giant kerolox stage with lots of Merlins I would agree with you. But relighting Raptors on flight vehicles has been hit-or-miss on just about every test vehicle. Hell, just getting them all to light ONCE still hasn’t happened yet.

I sincerely hope they don’t rush to OFT-2  and instead spend some time taking advantage of the newly rebuilt OLM + water-cooled steel blast plate and get engine start down to 100% reliability.

I suspect that they have good enough (maybe not quite 100%) reliability on the test stand, and what they need now is to find all the edge cases that drop the start reliability down when 33 of them fire up at the same time, from the same tanks.

I don't think they really know how to do that without getting more data, and they could well have concluded that the best way to get that data is to simply to launch a bunch of times.

[alugobi]

They're more significant than edge cases given that the failures are consistently repeated, from how many causes we don't know.

[rpapo]

They're more significant than edge cases given that the failures are consistently repeated, from how many causes we don't know.

Edge cases that simply don't happen on the test stand.  Perhaps they could be replicated on the test stand, if they only knew the trigger.

[abaddon]

That makes no difference to the point Herb made that they often don't even start up on the first try.

Every single flight test has had engine issues, whether on the way up or on the way down. Getting them to work reliably should be at the top of the list, IMO.

Disagree, the vast majority (all?) of engines that lit successfully and failed to relight were after the flip maneuver and it seemed like those were mostly (not all) due to the engine not being supplied fuel and/or oxidizer as expected (i.e. ingesting gas bubbles due to insufficient pressurization or purging of the lines).  They were also REALLY old Raptors at this point.  The Raptors on the test stand have progressively gotten better and better with a lot of test hours behind them and seem to be advanced by some amount beyond the B8 engines in reliability.

It's really more about the vehicle the Raptors are attached to and the flight profile they have to execute at this point than Raptor start reliability, IMO.  We'll see how things go on the next flight attempt.  If B9 makes it to the boostback and/or soft water landing stage I expect IF it fails, it will be something other than Raptor relight that causes the operation to fail - pick any number of failure cases in early F9 landings as examples.

[StarshipTrooper]

They're more significant than edge cases given that the failures are consistently repeated, from how many causes we don't know.

Edge cases that simply don't happen on the test stand.  Perhaps they could be replicated on the test stand, if they only knew the trigger.

Of course you could replicate this by building a test stand that approximates the OLM and holds 33 Raptor engines, with the plumbing used by the Super Heavy and the OLM. This would retire almost all the risk of engine performance during liftoff.

But it's quicker to just blow up a few prototypes. This is the SpaceX way.

And you can test the Flight Termination System at the same time. 

[chopsticks]

That makes no difference to the point Herb made that they often don't even start up on the first try.

Every single flight test has had engine issues, whether on the way up or on the way down. Getting them to work reliably should be at the top of the list, IMO.

Disagree, the vast majority (all?) of engines that lit successfully and failed to relight were after the flip maneuver and it seemed like those were mostly (not all) due to the engine not being supplied fuel and/or oxidizer as expected (i.e. ingesting gas bubbles due to insufficient pressurization or purging of the lines).  They were also REALLY old Raptors at this point.  The Raptors on the test stand have progressively gotten better and better with a lot of test hours behind them and seem to be advanced by some amount beyond the B8 engines in reliability.

It's really more about the vehicle the Raptors are attached to and the flight profile they have to execute at this point than Raptor start reliability, IMO.  We'll see how things go on the next flight attempt.  If B9 makes it to the boostback and/or soft water landing stage I expect IF it fails, it will be something other than Raptor relight that causes the operation to fail - pick any number of failure cases in early F9 landings as examples.

You can disagree if you want, but it doesn't change the facts. I said "every flight test has had engine issues, whether on the way up or on the way down". That is not controversial. SN15 lost an engine on the way up (which didn't relight), and there were some engine bay fires on some other suborbital flights IIRC, and there were fires on the last integrated flight test. Anyway, as you said, the engines used on the suborbital tests are quite old by now, but in the end it doesn't seem that reliability has improved all that much looking at B7's flight.

I agree about the test stand tests getting better, but we really don't have any insight into how those tests are conducted, what the startup or run parameters are, or any number of things that are different from being installed on the actual vehicle.

With B9 using the steel cooled plate, I hope that they will be able to conduct a full power static fire will all 33 engines - hopefully multiple static fires - nominally.

Once we stop seeing raptors eat themselves and blow up, I will have a lot more confidence in the vehicle. If they are able to use the OLM as an engine test stand, that will hopefully be able to prevent engine issues before actually launching and seeing what happens (since right now that is the only way to test all booster engines at full thrust). 

[lykos]

Test the Raptors and test the OLM!

[meekGee]

That makes no difference to the point Herb made that they often don't even start up on the first try.

Every single flight test has had engine issues, whether on the way up or on the way down. Getting them to work reliably should be at the top of the list, IMO.

Disagree, the vast majority (all?) of engines that lit successfully and failed to relight were after the flip maneuver and it seemed like those were mostly (not all) due to the engine not being supplied fuel and/or oxidizer as expected (i.e. ingesting gas bubbles due to insufficient pressurization or purging of the lines).  They were also REALLY old Raptors at this point.  The Raptors on the test stand have progressively gotten better and better with a lot of test hours behind them and seem to be advanced by some amount beyond the B8 engines in reliability.

It's really more about the vehicle the Raptors are attached to and the flight profile they have to execute at this point than Raptor start reliability, IMO.  We'll see how things go on the next flight attempt.  If B9 makes it to the boostback and/or soft water landing stage I expect IF it fails, it will be something other than Raptor relight that causes the operation to fail - pick any number of failure cases in early F9 landings as examples.

You can disagree if you want, but it doesn't change the facts. I said "every flight test has had engine issues, whether on the way up or on the way down". That is not controversial. SN15 lost an engine on the way up (which didn't relight), and there were some engine bay fires on some other suborbital flights IIRC, and there were fires on the last integrated flight test. Anyway, as you said, the engines used on the suborbital tests are quite old by now, but in the end it doesn't seem that reliability has improved all that much looking at B7's flight.

I agree about the test stand tests getting better, but we really don't have any insight into how those tests are conducted, what the startup or run parameters are, or any number of things that are different from being installed on the actual vehicle.

With B9 using the steel cooled plate, I hope that they will be able to conduct a full power static fire will all 33 engines - hopefully multiple static fires - nominally.

Once we stop seeing raptors eat themselves and blow up, I will have a lot more confidence in the vehicle. If they are able to use the OLM as an engine test stand, that will hopefully be able to prevent engine issues before actually launching and seeing what happens (since right now that is the only way to test all booster engines at full thrust).

It's not controversial that they had them, but it's very arguable what you can take from that.

Relight failures, as observed, were during a maneuver that's not applicable to SH, and using very old hardware.

On-launch failures are often a result of start box conditions, which are not applied during landing relights.

[Kspbutitscursed]

My opinion is that Ship 25 will seperate and light up 5 of its engines i thing that only 2 of the RC engine will light
Booster 9 will lose 1 engine upon boostback and have 12 engines to complete the boostback burn and then the 3 engine will light for the final landing burn
For the ships reentry iit will inevitably fail on reentry
Thoughts

[Herb Schaltegger]

Relight failures, as observed, were during a maneuver that's not applicable to SH, and using very old hardware.

On-launch failures are often a result of start box conditions, which are not applied during landing relights.

Assuming the stack gets to and survives separation on the next flight (or the next or however many it takes ...), then sure. That booster will simply orient ass-forward and fall toward the water. Once at terminal velocity and effectively 1G, restart should be as close to "nominal" as it will ever be. Assuming the right number of engines restart and don't start consuming themselves, great. Huzzah. There will be much rejoicing as it settles into the water.

However ... at some point they want recover these things, which means two things - first, a relight for boostback, which will require a pretty substantial attitude change while effectively in free-fall - there's your "crazy flip maneuver, folks); second, another attitude change in free-fall back to bass-ackward - less "crazy" but still going to roil up the prop and create the potential for the same restart issues we saw during Starship's test hops.

These are not insurmountable issues, but they ARE going to be issues that need to be addressed.

[CameronD]

Relight failures, as observed, were during a maneuver that's not applicable to SH, and using very old hardware.

On-launch failures are often a result of start box conditions, which are not applied during landing relights.

Assuming the stack gets to and survives separation on the next flight (or the next or however many it takes ...), then sure. That booster will simply orient ass-forward and fall toward the water. Once at terminal velocity and effectively 1G, restart should be as close to "nominal" as it will ever be. Assuming the right number of engines restart and don't start consuming themselves, great. Huzzah. There will be much rejoicing as it settles into the water.

The big question then is: Will video of that event be as significant, or more so, than that historic F9 water landing so many short years ago?!?

I, for one, hope so.