Predictions for Starship IFT-4

[alugobi]

The door is hard to do. 

So is the dispenser.

[Star-Dust]

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.

Elon aimed for the moon he landed among the stars it's ok for me

[JamesH65]

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.

Flimsy is probably no the right word, remember how big that door is, and how curved. To make it rigid would require a huge amount of reinforcement, some sort of spaceframe, and a lot of it. I suspect they can get away with some flex without causing issues. Might even be able to use cables in some places rather than rigid sections.

[yg1968]

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 ;-)

Musk has been trying to be more cautious about his predictions. But ironically that has recently gotten him in trouble when he said that crewed lunar Starship would be going to the Moon within 5 years. Of course, 2026 (the projected date for Artemis III) is within 5 years but these kind of nuances are often lost when the (main-stream/non-space specialized) media (60 minutes in this case) reports it. 

[darthguili]

I think for IFT-4, we might get into a series of flights where the perceived improvements (outside those at SpaceX with the knowledge) will be less visible/obvious.
I think :
- stability during reentry will still fail
- booster will still fail to reach velocity target prior impact
- heatshield will still fail

Maybe some marginally visible improvements on the door operations (but I don't feel those are important).

And we would enter a series of flights and tests that could be pretty long until suddenly, boom, they fix stability, they fix heatshield etc. In my predictions, they will be able to fix booster landing first, it feels the more within reach. For the other two, there are still possibilities that this design doesn't work so I'm just crossing fingers at this point. If that's the case, starship ends up a "bigger F9", kind of, instead of a vehicule that brings us to Mars and I really don't want that.

[DanClemmensen]

I think for IFT-4, we might get into a series of flights where the perceived improvements (outside those at SpaceX with the knowledge) will be less visible/obvious.
I think :
- stability during reentry will still fail
- booster will still fail to reach velocity target prior impact
- heatshield will still fail

Maybe some marginally visible improvements on the door operations (but I don't feel those are important).

And we would enter a series of flights and tests that could be pretty long until suddenly, boom, they fix stability, they fix heatshield etc. In my predictions, they will be able to fix booster landing first, it feels the more within reach. For the other two, there are still possibilities that this design doesn't work so I'm just crossing fingers at this point. If that's the case, starship ends up a "bigger F9", kind of, instead of a vehicle that brings us to Mars and I really don't want that.

However, as soon as they achieve in-space stability, they can then achieve raptor relight, and on the next flight they can actually go to orbit. That will be very obvious. Ideally, raptor relight on IFT-4 and orbit on IFT-5.

[KilroySmith]

How many times during SpaceX development flights has the same thing failed twice? 

If nothing else, SpaceX is excellent at identifying problems, and fixing them - not with duct tape and baling wire, but good solid engineering.  So my admittedly pollyanna-ish view of Flight 4 is:
0. Mission plan - identical with IFT-3.
1. Booster - I expect it to launch, separate, and rotate as neatly as it did this time.  I expect the control issues it experienced to be gone now, and I expect it to be vertical and stable when it starts it's landing burn.  I don't expect the landing burn to be completely successful, so I expect another hard impact.  In Flight 5, I expect to see a hover near the surface of the water.
2. Ship.  I expect it to separate and leave the vicinity of the booster with great haste.  I expect an engine shutdown, and a propellant transfer demo if they still need one.  I expect the stability problems to be fixed, and the ship to do a successful relight and shutdown, hit entry interface in a stable, proper attitude, and make it through re-entry.  I don't expect it to be able to successfully rotate vertical and fire engines for the landing burn.  I expect a landing burn on Flight 5, and a successful hover at the ocean's surface on Flight 6.

So, perhaps July for Flight 5, which I expect to be successful enough for the FAA to loosen the ropes a bit and let them run with only normal oversight rather than R&D ("Oh my Lord, You wanna do WHAT?") oversight. 

[Oersted]

For IFT-4 I expect them to absolutely plaster the ship with cameras, given that the Starlink download behaved in such stellar fashion on the last flight. Well-placed cameras will really inform the team about the ship's behaviour during reentry. 

[wannamoonbase]

For IFT-4 I expect them to absolutely plaster the ship with cameras, given that the Starlink download behaved in such stellar fashion on the last flight. Well-placed cameras will really inform the team about the ship's behaviour during reentry. 

Just because we didn't see more views doesn't mean that SpaceX doesn't have many more video feeds.

We know they have plenty of cameras on F9 that the public doesn't see.

They have been showing us more with each flight.  I don't blame them for holding onto information and images, there are plenty of people and entities looking forward to jump on any oppurtunity to push negative stories.  So only show things that work.

[ETurner]

How many times during SpaceX development flights has the same thing failed twice? 

Hasn't tile attachment failed every time so far?

[uhuznaa]

I think for IFT-4, we might get into a series of flights where the perceived improvements (outside those at SpaceX with the knowledge) will be less visible/obvious.
I think :
- stability during reentry will still fail
- booster will still fail to reach velocity target prior impact
- heatshield will still fail

Maybe some marginally visible improvements on the door operations (but I don't feel those are important).

And we would enter a series of flights and tests that could be pretty long until suddenly, boom, they fix stability, they fix heatshield etc. In my predictions, they will be able to fix booster landing first, it feels the more within reach. For the other two, there are still possibilities that this design doesn't work so I'm just crossing fingers at this point. If that's the case, starship ends up a "bigger F9", kind of, instead of a vehicle that brings us to Mars and I really don't want that.

However, as soon as they achieve in-space stability, they can then achieve raptor relight, and on the next flight they can actually go to orbit. That will be very obvious. Ideally, raptor relight on IFT-4 and orbit on IFT-5.

I think if their RCS wouldn't have failed the outcome would have been very different. They would have at least have been able to try and relight the Raptors and reentry would have looked very different, and longer.

Nobody knows how it would have ended but it definitely would not have ended there and then. In fact I think the immediate reentry interface isn't the real problem at all, hypersonic control and keeping the ship on the planned trajectory until final descent is the problem that needs some more experimentation. And the sooner they get to this stage the better.

I think with the next launch they will solve the problems they faced this time and get to log and hopefully debug the problems they will run into after that. Step after step.

[uhuznaa]

How many times during SpaceX development flights has the same thing failed twice? 

Hasn't tile attachment failed every time so far?

Looked quite good this time. And I doubt it will get worse next time. This is small stuff being very conductive to small changes and mitigations. If 100 of your 18000 tiles detach you can try to look at what happened and make sure that next time more of those 100 keep stuck.

Mitigation is like magic once you prove that it works principally, it's just more of the same.

[KilroySmith]

How many times during SpaceX development flights has the same thing failed twice? 

Hasn't tile attachment failed every time so far?

Well, you got me on that one.  But I will argue that, so far, tiles falling off haven't endangered any missions.  Flight 4 will be interesting in that regard - can the ship make it through re-entry with missing tiles?  Inquiring minds want to know!

[JaimeZX]

I don't think anyone will know since even if it makes it through the ED part of EDL it's going to explode on impact with the Great Southern Ocean.

[Kspbutitscursed]

I don't think anyone will know since even if it makes it through the ED part of EDL it's going to explode on impact with the Great Southern Ocean.

You mean the Indian Ocean?

[KilroySmith]

I don't think anyone will know since even if it makes it through the ED part of EDL it's going to explode on impact with the Great Southern Ocean.

That seems a bit dismissive of SpaceX's communications platform.  Do you really believe that they won't be able to re-establish communications after re-entry but before the RSD (that would be a "Rapid Scheduled Disassembly")?

[litton4]

For me, the most important will not just be Raptor re-light in orbit, but RELIABLE Raptor re-light.
I'd expect them to have to demonstrate this more than once, or have a contingency system to provide a controlled re-entry.

Aside from that, I'd expect mods to the payload bay door (HAL), which clearly didn't work. (I wonder if they named the computer that controlled it?)
On the next flight, though they could include some dummy or disposable Starlinks, so if the door opens, they can test the dispenser.

Booster, get it under control and re-light engines for landing.
It looked like it was doing engine chill as it came down, but couldn't re-light in time for whatever reason.
I'm sure SpaceX will be closer to nailing this on IFT4

I would say that medium term goal MUST be to progress Booster landing/Recovery.
That's where the most cost is - 4/5ths of the engines for a start, so as in F9, most benefit.

[wannamoonbase]

For me, the most important will not just be Raptor re-light in orbit, but RELIABLE Raptor re-light.
I'd expect them to have to demonstrate this more than once, or have a contingency system to provide a controlled re-entry.

They have 6 opportunities to demonstrate Raptor relight on orbit.  I have assumed from the information given that it was a 1 engine relight. 

Doing all 6, just long enough to prove startup would give them 6 data points instead of one.

[DanClemmensen]

For me, the most important will not just be Raptor re-light in orbit, but RELIABLE Raptor re-light.
I'd expect them to have to demonstrate this more than once, or have a contingency system to provide a controlled re-entry.

My guess: a single successful re-light will suffice, IF the system is heavily instrumented and the data shows that the system worked as designed instead of working by coincidence. The redundancy happens because they only need one of the engines to work.

The risk is that a huge SS becomes derelict and stranded in orbit. If there are multiple opportunities to retry the de-orbit, then that risk is reduced.

[alugobi]

As long as they're flying a profile that will bring the ship down without an engine light, the priority should be fixing whatever didn't happen on the previous flight such that they had no thruster control.  They'll never get a landed vehicle if it's rolling and flipping until it breaks up.