Predictions for Starship IFT-4

[Okie_Steve]

It will be called Flight-4

Good launch and hot staging

Improved control systems software/hardware allow booster to relight for landing burn and ship to perform propellant transfer while maintaining stability

No guarantee about booster landing

Ship will deploy something through payload door - maybe a wheel of cheese or a 2001 obelisk

Ship will peform inspace relight and then burn up later during reentry

Starlink video will be even more impressive

[uhuznaa]

I think IFT-4 will be basically a rinse-repeat of ITF-3, with (hopefully) an added first test with the dispenser and two or four dummy Starlink sats.

Reasons: They will want to launch and deploy Starlink as soon as possible with Starship and for that they need to demonstrate safe deorbiting of the second stage to not risk it being stranded in a randomly decaying orbit. They also need to test and debug the dispenser ASAP since it's a hideously complex thing with lots of moving parts, much more complex than the door (which didn't really work in IFT-3). So better start testing it now.

I guess they will be able to fix the RCS-problems, which again will give them the opportunity to try and relight the engines (or one engine). Which may or may not work. Same with reentry: With the ship in the correct orientation it should work better than last time... My guess is that when (almost) all tiles will still be there the odds of the ship coming through the hot phase of reentry should be quite good. Hypersonic control etc. may be an altogether different problem still. This is not pressing though, they will have ample opportunities to perfect this once they start to launch Starlink satellites with it and anyway there'll be a long and rocky road until they have all of this working reliably enough to go for a tower catch. For that they will need to overfly parts of the continental US and the FAA will not allow them to do this before they have demonstrated full and reliable control. I think this will be at least a dozen flights into the future.

Booster: Depending on the reasons for the loss of control and the engines not igniting getting it down in one piece may be easy or not so easy. They definitely will want to move forward here though since recovering the booster should be at least much more easy than with the ship and it's more expensive to begin with.

My prediction: The RCS will work, engine relighting will work, the dispenser test (if any) will not work, the booster will at least make it further (maybe with too few engines igniting to come to a soft landing), the Ship will make it through reentry, but then will be lost.

PS: I'm still not sure the PEZ dispenser idea will hold. It's basically the opposite of "best part is no part". It solves some structural/mass problems (due to it needing only a small door for deploying the satellites) but instead adds a myriad of things to go wrong, each of which can mean a failed mission (as far as satellite deployment is concerned). Lots of intricate moving parts, chains, rollers, pistons, pulleys... I hate it.

[Rossco]

I'd agree with the above - rinse and repeat.

I think (based on nothing but what we've seen so far): Booster: will make splashdown. Spaceship: No Payload. In-space Relight. Another Prop-Transfer Demo. Another door Demo. Break-up during re-entry having made it most of the way through.

[DanClemmensen]

Prediction based only on my possibly faulty reasoning:
   Ship: main focus will be on attitude control. It will be hard for us to know what SpaceX is doing in this regard prior to the actual flight unless they choose to tell us, although there may be some hints from the mitigation section of the mishap report. Should be obvious during the flight if it succeeds. Remainder of the flight goals same as  IFT-3, and given successful attitude control they may actually succeed.
   Booster: main focus will also be on attitude control and same comments apply. If it succeeds, landing burn may work this time.

The Starlink connection is unprecedented and underappreciated. That wealth of data multiplies the value of these test flights. We can hope that improved attitude control will improve link quality and reliability, especially during ship re-entry and descent but maybe also for booster descent and landing.

[StraumliBlight]

From today's conference:

Shotwell said the company hopes to conduct the next Starship test flight in about six weeks, though that likely won’t have satellites on board.

She specifically says:

We'll get back to flight, hopefully in about 6 weeks, Flight 4 hopefully, beginning part of May. And I don't think were going to deploy satellites on the next flight, things are still in trade but I think were really going to focus on getting re-entry right and making sure we can land these things where we want to land them, successfully.

[wannamoonbase]

From today's conference:

Shotwell said the company hopes to conduct the next Starship test flight in about six weeks, though that likely won’t have satellites on board.

It's almost like they want to get the V1's out of the way, and to get basic flying experience.  How the ship does on orbit and re-entry and collecting data on how superheavy performs in the atmosphere. 

Just fly best you can and collect data and clear out the old stock to make room for the new stuff.

I hope it is 6 weeks, but I'm expecting 8 or more.

[alugobi]

Tells me that they want to fly again, but won't have door revisions/redesigns finalized by then.

[jmsanman]

Vehicles: Booster 11 / Ship 29

Launch Date: 18th May 2024 (Note: this would be the same percentage improvement of IFT-2 to IFT-3 over IFT-1 to IFT-2)

Booster RUD Chance: 20% during landing burn

Ship RUD Chance: 50% chance of surviving the re-entry plasma phase.

Flight Success Chance: 80%

What Would I Consider As A Success: SpaceX a) has no repeat issues, b) demonstrates resolution of all IFT-3 issues and c) gets enough information from IFT-4 to fix newly discovered issues. For the Booster, this means successfully maintaining attitude through Raptor landing burn relight and getting much closer to a controlled splashdown. For the Starship, this means successful (sub-)orbital insertion, completion of all missed IFT-3 tests, and maintaining attitude from orbital insertion through most (if not all) of the plasma part of re-entry.

Bonus points: no FAA incident report needed.

Extra-special bonus points: quiet discussions within NASA about SLS vs. fully expendable SS/SH become less quiet. Yes, I know, ‘politics’. That’s why the points are extra-special.

[FinalFrontier]

Flight 4 in May.
Nominal performance to orbit insertion.
50% chance of booster landing burn ignition.
50/50 on controlled attitude for re-entry by starship.
I still have doubts about the design and capability of the RCS on starship in its current form. On flight three it would seem it never even got a chance to work, however, didn't seem it ever activated.
So we still need to actually see how that does when it properly activates.

[uhuznaa]

Tells me that they want to fly again, but won't have door revisions/redesigns finalized by then.

Depending on what exactly failed with the door they may not need a real redesign.

But the door problem just shows that having moving parts that need to work after all the vibrations and acceleration loads during launch and then in a vacuum isn't exactly easy. Lubrication isn't straight forward and no lubrication may lead to cold-welding in vacuum. And any play anywhere is a bad thing to have with the vibrations.

Or maybe the door was sealed too well against the residual pressure inside and opening it against this pressure bent or broke something. Would be easily solved with fully venting the payload bay though before opening the door.

But that they couldn't make such a comparatively dead-simple mechanism work at first try makes me wary about their PEZ dispenser contraption. I mean, look at that:

https://ringwatchers.com/article/ship-pez-dispenser

They really would need to test and debug this on the ground, with load and vibration tests, maybe even in a vacuum chamber, and it's not exactly a small thing to deal with. Most of it is bigger than the door and it has so many more moving parts, and it will have to carry dozens of tons of satellites amplified by the acceleration during launch without anything bending out of shape or seizing up or shaking loose. And it's full of motors, rollers, chains, long cables with pulleys, piston-driven latches... Easily two orders of magnitude more complex than that simple door.

If they don't have one dispenser ready to test with a few dummy satellites to push out for the next launch it will just mean that they're still working on it and don't even dare to launch and test what they have yet.

At first I thought the dispenser was a good idea since it meant they won't have to deal with huge payload bay doors but this thing is just so incredibly complex mechanically. Sometimes it's easier to deal with one or two big problems than with dozens of smaller ones, each one different and with it's own failure modes. Maybe two huge load-bearing doors with load-bearing hinges and latches and then just kicking the full satellite stack over the doorstep would be the better solution. This though would mean some serious redesign. But at least this also would open the door (lol) to deploy other things than just flatpack Starlink satellites. Sooner or later they will have to have this capability anyway.

Well, we will see.

[alugobi]

Tells me that they want to fly again, but won't have door revisions/redesigns finalized by then.

If they don't have one dispenser ready to test with a few dummy satellites to push out for the next launch it will just mean that they're still working on it and don't even dare to launch and test what they have yet.

Shotwell has already announced that they're not carrying a payload next launch.

Vid from flight 3 showed that door panel shaking and wobbling.  Not what you'd expect from a component in a system that is supposed to be designed for many and and frequent uses.  I'm leaning towards them redoing it with a different panel and/or mechanism.

[FutureSpaceTourist]

Re 6 weeks to flight 4:

https://twitter.com/elonmusk/status/1770173270366499013

That’s if everything goes right, but certainly possible

[mordroberon]

Oh boy, another one of these

Vehicles: Booster 11/Ship 29 (B11-S29)

Launch Date: First half June 2024 (Around 6/9 because its Elon)

What Will Happen:
- Successful launch, all booster engines light [100%]
- Successful hotstaging, all ship engines light, successful stage separation [100%]
- Nominal Boostback burn [90%]
- More successful landing burn than IFT-3 [75%]
- Hard splashdown in the ocean (no explosion before impact) [90%]
- Ship reaches target trajectory [100%]
- trajectory is same as IFT-3 [75%]
- Starship will complete engine relight and entry burn [90%]
- Starship will have a controlled reentry through the atmosphere [75%]
- Starship will either burn up in the atmosphere, or hard-land in the ocean [90%]

[wannamoonbase]

Bonus points: no FAA incident report needed.

Extra-special bonus points: quiet discussions within NASA about SLS vs. fully expendable SS/SH become less quiet. Yes, I know, ‘politics’. That’s why the points are extra-special.

No FAA incident report would help a lot.

Regarding replacing SLS, Starship just needs to keep going it's thing successfully.  When it's flying often and successfully the SLS discussion will solve it's self without much of a fight.

[uhuznaa]

Tells me that they want to fly again, but won't have door revisions/redesigns finalized by then.

If they don't have one dispenser ready to test with a few dummy satellites to push out for the next launch it will just mean that they're still working on it and don't even dare to launch and test what they have yet.

Shotwell has already announced that they're not carrying a payload next launch.

Vid from flight 3 showed that door panel shaking and wobbling.  Not what you'd expect from a component in a system that is supposed to be designed for many and and frequent uses.  I'm leaning towards them redoing it with a different panel and/or mechanism.

Well, technically she said that they won't deploy satellites and if they would deploy some dummies these wouldn't be satellites since they would follow the same trajectory as the ship and reenter with the ship, so they're not satellites ;-)

Well, and that wide, thin door panel shaking and wobbling when just hanging on a few (two?) hinges is just to be expected. Doesn't have to be a bad thing in itself. It may well be that there was just some fixture that shook loose during launch, or the motors opening the door inwards against the pressure inside bent or broke some lever. Could have been any small thing that failed and that can be easily fixed. I mean, that door is by far the smallest challenge with the PEZ dispenser method to get right and work reliably.

I hope they have some better insight into this than we have.

By the way, I'm really wondering how many engineering cams they have. I mean, they don't even need to stream them for such things that aren't really time-critical, just record from dozens of cameras and download only the recordings of things that didn't work right then. I would fully expect them to have a close-up wide-angle camera looking at the door mechanisms. There was ample time to download this then.

[DanClemmensen]

Well, technically she said that they won't deploy satellites and if they would deploy some dummies these wouldn't be satellites since they would follow the same trajectory as the ship and reenter with the ship, so they're not satellites ;-)

If it were my decision, I would not want satellites re-entering near the SS while the re-entry test is underway. Even if the risk of interference or collision is small, it's not zero.

[uhuznaa]

Well, technically she said that they won't deploy satellites and if they would deploy some dummies these wouldn't be satellites since they would follow the same trajectory as the ship and reenter with the ship, so they're not satellites ;-)

If it were my decision, I would not want satellites re-entering near the SS while the re-entry test is underway. Even if the risk of interference or collision is small, it's not zero.

They wouldn't be exactly "near" the ship when you push them out half an hour before entry. The risk of collision would be close enough to zero. Very different densities too, the satellite dummies would overtake the ship immediately at entry and never would come closer to it again.

And it would be a test anyway, if you can push out the satellites successfully them colliding with the ship later (which won't survive no matter what) would be meaningless. But knowing that the dispenser works would retire some massive risks for what the ship is actually there for thoroughly.

[uhuznaa]

Re 6 weeks to flight 4:

https://twitter.com/elonmusk/status/1770173270366499013

That’s if everything goes right, but certainly possible

Musk sounding cautious is almost frightening ;-)

[alugobi]

I mean, that door is by far the smallest challenge with the PEZ dispenser method to get right and work reliably.

I don't agree.  It moves, it seals, it requires self-alignment, and it has to do this repeatably.  What we saw in flight 3 was pretty flimsy.  Does not inspire confidence.

[uhuznaa]

I mean, that door is by far the smallest challenge with the PEZ dispenser method to get right and work reliably.

I don't agree.  It moves, it seals, it requires self-alignment, and it has to do this repeatably.  What we saw in flight 3 was pretty flimsy.  Does not inspire confidence.

Still comparatively dead-simple. Have you looked at the actual dispenser?

https://ringwatchers.com/article/ship-pez-dispenser

Read this article from top to bottom and then say again the door is hard to do. This door is the easiest thing of all this.