totm nov 2023 SpaceX Discussion Thread

[RCgothic]

 

I think it's increasingly likely that BN2.1 isn't a thing. Just a prototype intertank bulkhead and nothing more.

SN17 also seems decently close to completion. There's a real question mark over whether it will fly though. It'll probably depend on how the schedule works out. If 16 is delayed or 15 can be made ready for flight again, then the probability of a flight for 17 goes down.

I'd expect we'll start seeing parts for SN21 shortly.

Edited May 8, 2021 by RCgothic

[tater]

[Beccab]

SN16 doesn't have Raptors yet, right?

[tater]

Interesting thread at NSF raises a good point regarding (near) future SS testing.

When they launch an orbital SS, they need to make sure it's not like the CZ-5B core stage. Maybe early tests are intentionally suborbital—Pacific perigee for "disposal," but with a controlled reentry and soft water landing?

Redundant systems to deorbit it? Early vehicles will certainly have mass margin for redundancy.

[YNM]

13 minutes ago, tater said:

When they launch an orbital SS, they need to make sure it's not like the CZ-5B core stage. Maybe early tests are intentionally suborbital—Pacific perigee for "disposal," but with a controlled reentry and soft water landing?

Redundant systems to deorbit it? Early vehicles will certainly have mass margin for redundancy.

Betting on a suborbital test first to the middle of the Atlantic, then I guess you can intentionally make the orbit of the first orbital test low enough so it's guaranteed to re-enter after certain number of orbits a la Atlas-Mercury or have the range-safety detonation available on orbit (so you can detonate it when you detect it's going to re-enter soon, avoiding large debris).

Edited May 8, 2021 by YNM

[RCgothic]

Starship is intended to be a controlled vehicle. It'll be able to deorbit with Raptors, or RCS if necessary, or even orient for maximum drag. It'd take a major failure for it to be an uncontrolled object.

And the initial orbit could indeed be low to decay within a few orbits 

That's quite different from launching something to orbit with no control at all.

[tater]

10 minutes ago, RCgothic said:

Starship is intended to be a controlled vehicle. It'll be able to deorbit with Raptors, or RCS if necessary, or even orient for maximum drag. It'd take a major failure for it to be an uncontrolled object.

And the initial orbit could indeed be low to decay within a few orbits 

That's quite different from launching something to orbit with no control at all.

I understand that, but failures are not impossible, and this is not a normal stage 2.

For F9 stage 2, a major failure of control ends up with a light show over the Pacific NW (recent event). Large portions of SS would impact the ground, even if shredded I think. Seems to me they will likely at least consider this, just as they have to consider where a test reentry and landing occurs (likely soft water landings at first?). Disposal perigee, then under control, raise it for an orbit (so if a control failure there, it's disposed of)?

Then as you say, deorbit burn with Raptors or RCS (so some redundancy). Presumably all preset onboard, so comms failures are not a concern (though comms can override I'm sure).

[SOXBLOX]

What comes in between these 10km hops and orbital flight? Anything? Do you think they'd do a hop to somewhere besides Boca Chica?

[RealKerbal3x]

19 minutes ago, SOXBLOX said:

What comes in between these 10km hops and orbital flight? Anything? Do you think they'd do a hop to somewhere besides Boca Chica?

They might do some higher-altitude hops to test supersonic descent, but seeing as very few components for SN18 and 19 have been spotted (compared to most of the tank section for SN20), it's more likely that they focus attention on booster testing and then head straight for orbit. That way they can start actually delivering payloads while continuing to test EDL.

[JoeSchmuckatelli]

43 minutes ago, SOXBLOX said:

What comes in between these 10km hops and orbital flight? Anything? Do you think they'd do a hop to somewhere besides Boca Chica?

I would think they'd have to... But none of the oil rig platforms are landing capable as yet... 

What was falcon's testing like just before they went full orbital? 

[YNM]

3 hours ago, JoeSchmuckatelli said:

What was falcon's testing like just before they went full orbital? 

They went straight to the orbital phase. Initially the recovery method was going to be with parachutes, more in line with Shuttle SRBs or Electron's 1st stage, but that was abandoned.

Then... you know the story how they managed to do things. First stage is completely suborbital so they started guiding the booster on re-entry, then over-the-sea hovering, over-barge hovering (then crashing on the barge), and then the first land back to the LZ. Also Grashopper.

Starship testing is akin to try to land back the 2nd stage of F9 but the stage itself is much larger than three F9/FH 1st stages (or cores) combined. This is why it's a lot more risky.

Edited May 8, 2021 by YNM

[tater]

I think they do some more 10km tests, then space.

I would assume they do what I suggest above.

1. Nominal insertion with low perigee (disposal if failure on #2).

2. Relight, and circularize.

3. Deorbit, test EDL (entire hazard area at sea).

[Lukaszenko]

On 5/7/2021 at 6:58 PM, SpaceFace545 said:

Like spaceman said, spacex's goal is to leave earth. Starship isn't being built to be a launcher, it is to go to mars. Even dragon was developed initially as a mars lander. Spacex is run by a man obsessed with mars and he could care less about earth. They haven't done anything for this planet and its people and I doubt they ever will.

What about that whole Tesla "sustainable transport and energy" thing?

And the solar energy thing? They certainly don't seem like the "screw earth" types of ventures.

[tater]

Dragon was not developed as a Mars lander, that's absurd.

They said they could send one to Mars, not that it was supposed to be used for that (going to the Moon in a few cubic meters with 4 people is absurd enough (<cough>Orion</cough>), much less Mars).

[Spaceman.Spiff]

17 minutes ago, tater said:

I think they do some more 10km tests, then space.

I bet they’ll try to refly a few times. 

[magnemoe]

1 hour ago, RealKerbal3x said:

They might do some higher-altitude hops to test supersonic descent, but seeing as very few components for SN18 and 19 have been spotted (compared to most of the tank section for SN20), it's more likely that they focus attention on booster testing and then head straight for orbit. That way they can start actually delivering payloads while continuing to test EDL.

Now SN15 used did an 4:30 minutes burn reaching 10 km, that is an average velocity of 133 km/h who is car speeds not even propeller planes, driving at 120 km/h you do 2 km / minute. 
Why so slow?  MaxQ Structural? doubt it forces on forward fins coming down is pretty large and sideways, TWR? well Wikipedia list over 200 ton trust. 
Safety?  I say doing an shorter burn is safer as the engines run for an shorter time so less time for something going wrong. 
What is  I missing. 

[Beccab]

3 minutes ago, magnemoe said:

Now SN15 used did an 4:30 minutes burn reaching 10 km, that is an average velocity of 133 km/h who is car speeds not even propeller planes, driving at 120 km/h you do 2 km / minute.

remember that a good part of the flight was done with less than all engines as they are turned off in sequence, ending with Starship doing a hover

[Spica]

1 hour ago, magnemoe said:

What is  I missing. 

Starship is not designed to ascend at supersonic speeds under it's own power. I assume it is both unstable and insufficiently controllable in that flight regime without being attached to the superheavy booster.

[RCgothic]

14 hours ago, magnemoe said:

Now SN15 used did an 4:30 minutes burn reaching 10 km, that is an average velocity of 133 km/h who is car speeds not even propeller planes, driving at 120 km/h you do 2 km / minute. 
Why so slow?  MaxQ Structural? doubt it forces on forward fins coming down is pretty large and sideways, TWR? well Wikipedia list over 200 ton trust. 
Safety?  I say doing an shorter burn is safer as the engines run for an shorter time so less time for something going wrong. 
What is  I missing. 

We think that in order to go from up to belly down in a controlled manner a kick from the raptors is required. Therefore they can't just coast to apogee, which means they have to keep the speed down so as not to exceed the altitude limit.

Edited May 9, 2021 by RCgothic

[grawl]

On 5/7/2021 at 5:28 AM, SpaceFace545 said:

Yep, I don't like starship but I do enjoy looking at every design.

I do have a question about the big fat window they want to put on it. So in space big windows are a big no The biggest windows on the space station is covered most of the time when not in use so it doesn't get hit. But the windows on starship will be much much bigger. You have to agree with me that these windows aren't feasible so how do you think they'll get around that?

Big 8k "holographic" screens inside the habitat should do the trick.

[tater]

8 hours.

[JoeSchmuckatelli]

4 hours ago, magnemoe said:

Now SN15 used did an 4:30 minutes burn reaching 10 km, that is an average velocity of 133 km/h who is car speeds not even propeller planes, driving at 120 km/h you do 2 km / minute. 
Why so slow?  MaxQ Structural? doubt it forces on forward fins coming down is pretty large and sideways, TWR? well Wikipedia list over 200 ton trust. 
Safety?  I say doing an shorter burn is safer as the engines run for an shorter time so less time for something going wrong. 
What is  I missing. 

The 10km limit?  They're not trying to get to orbital speed - rather an altitude they can limit, hover and then flop from to test landing.  Get distracted, go too fast and whoops, you miss the earth entirely.

 

(Don't you know your Adams?)

[tater]

 

[Xd the great]

1 hour ago, tater said:

 

Which thruster is that? Starship RCS?

Edited May 9, 2021 by Xd the great

[tater]

The assumption is hot gas rcs for starship.