totm nov 2023 SpaceX Discussion Thread

[OrdinaryKerman]

44 minutes ago, kerbiloid said:

To land, it should first survive the aerobraking.

The landing technics plays absolutely no role.

On aerobraking - definitely yes.

(Unless you want to take out 8 km/s + 400 km by engines)

Its mechanical energy should be turned into heat and dissipated by the bottom.

When you have a fusion engine and delta-V 100 km/s per flight, no problem, you even don't need a heat protection.

But while you have only chemicals , you should aerobrake.

IT DOES AEROBRAKE. There's a reason why it has large airbrakefinflaperonthings. Whether or not it has a lifting body shape doesn't really matter if it has some other way of creating large amounts of drag. And the landing method does partly inform the shape. Not entirely, but it does a bit. Parachute drop? capsule. Runway landing? plane/lifting body. There isn't any historical precedent for the 'skydiver>bellyflop>tailsitter' method, so Starship. The reasoning for the basic design has been much the same since 2017 BFR. Also its reentry profile is different than the Shuttle in that it comes in steeper and at higher AoA. And no S-turns. And it has the aforementioned 'things'.

Spoiler

'Yes, and as we all know, SpaceX has zero experience with flying long tubes at a few km/s down towards Earth, and they also have zero experience with EDL from orbit. They also own no computers, and so don't model anything.'
'They literally have no idea what they are doing, they are just welding some tubes together, and doing it Kerbal style.'

'They invented nothing, Roscosmos had even drawings of that already. SpaceX is so behind'

please put a '/s' in case Kerbiloid completely fails to notice your intent

 

Edited August 10, 2021 by OrdinaryKerman
stupid typos

[kerbiloid]

11 minutes ago, tater said:

SpaceX has zero experience with flying long tubes at a few km/s down towards Earth,

At <2 km/s speed?

8 km/s is 4 times freater.

Drag and heat flow ~16 times.

8 minutes ago, Beccab said:

They invented nothing, Roscosmos had even drawings of that already. SpaceX is so behind

Currently the only thing they have what Roscosmos doesn't is legs on the middle-sized first stage (and who knows is it worth it).

3 minutes ago, OrdinaryKerman said:

Whether or not it has a lifting body shape doesn't really matter if it has some other way of creating large amounts of drag.

The drag should be controlled. This is the main purpose of the flat-bottoms.

[OrdinaryKerman]

13 minutes ago, kerbiloid said:

At <2 km/s speed?

8 km/s is 4 times freater.

Drag and heat flow ~16 times.

Currently the only thing they have what Roscosmos doesn't is legs on the middle-sized first stage (and who knows is it worth it).

And a flight-proven reusable capsule (C206). And general will to actually develop their designs once they figure stuff out. And yes, F9 reusability is worth it.

13 minutes ago, kerbiloid said:

The drag should be controlled. This is the main purpose of the flat-bottoms.

It is  controlled. 

Edited August 10, 2021 by OrdinaryKerman

[Beccab]

4 minutes ago, kerbiloid said:

Currently the only thing they have what Roscosmos doesn't is legs on the middle-sized first stage (and who knows is it worth it).

Well, another thing they have is commercial launches that companies book on them. Unlike proton.

[tater]

13 minutes ago, kerbiloid said:

At <2 km/s speed?

8 km/s is 4 times freater.

Drag and heat flow ~16 times.

It's still experience and data. Who else has data on ~100 controlled entries even at that lower velocity?

They also have data on every Dragon, Crew Dragon, and Cargo Dragon orbital entry.

And obviously, they don't model anything, maybe they should come here, see your criticisms and abandon the project?

 

Meanwhile in Boca Chica:

 

 

Edited August 10, 2021 by tater

[OrdinaryKerman]

4 minutes ago, tater said:

It's still experience and data. Who else has data on ~100 controlled entries even at that lower velocity?

They also have data on every Dragon, Crew Dragon, and Cargo Dragon orbital entry.

And obviously, they don't model anything, maybe they should come here, see your criticisms and abandon the project?

 

Meanwhile in Boca Chica:

 

 

out of likes, so

 

[CastleKSide]

5 hours ago, mikegarrison said:

You know, it's interesting to read this SpaceX thread and see how many people laud SpaceX for learning through failures, and then compare and see how many of the same usernames lash out at the Starliner whenever it has a problem.

(Not saying you are one of them, @sevenperforce)

I would be a lot less harsh on starliner's failure if I knew they had 6 more capsules waiting in the hanger. That and if the reason for their failure wasn't "ohh  we didn't do a basic all up software test that anyone with basic engineering experience would have done."

There is learning by failure when you are fundamentally pushing the envelope and then there is just stupidity.

[sevenperforce]

1 hour ago, kerbiloid said:

9 hours ago, sevenperforce said:

You are correct that a primitive cylinder moving with its axis at 90° to the direction of flight will have the same L/D ratio as a sphere—zero—and will descend ballistically.

You are incorrect in supposing that Starship will perform re-entry with its long axis at 90° to the direction of flight. Starship will fly with a significant angle of attack and have an L/D ratio significantly greater than a capsule like Apollo.

Any proof?

Proof?

Are you asking me for proof that a cylinder moving with its axis perpendicular to the airstream will have a L/D ratio of zero?

Or are you asking me for proof that a cylinder with a nonzero angle of attack will have an L/D ratio greater than zero?

Because Falcon 9 is a primitive circular cylinder which attains an L/D ratio of approximately 1 by flying at a high angle of attack. I mean, you can literally watch it glide.

1 hour ago, kerbiloid said:

All I can see, exactly none of spaceplane was a cylinder, even with winglets.

Yes, because neither Starship nor Superheavy nor Falcon 9 are spaceplanes.

1 hour ago, kerbiloid said:

Soyuz ~30 kg of peroxide onboard, vented out after aerobraking.

Dragon - 1+ t of MMH+NTO in the capsule on launch, they are literally sitting on the fuel barrel.

If Soyuz has a breach in its HTP tank at any point in the flight, everyone dies. What's the difference?

1 hour ago, kerbiloid said:

7 hours ago, sevenperforce said:

But this is only if there is no angle of attack (or, depending on your frame of reference, a 90° AoA). With a nonzero angle of attack, lots of things start changing. And that is what someone seems intent on ignoring.

The wings are flat for purpose.

Are you making a claim?

 

1 hour ago, kerbiloid said:

1 hour ago, tater said:

SpaceX has zero experience with flying long tubes at a few km/s down towards Earth,

At <2 km/s speed?

8 km/s is 4 times freater.

Drag and heat flow ~16 times.

It's not like anyone has ever devoted any time studying hypersonic L/D ratios in wind tunnels, right?

1 hour ago, kerbiloid said:

1 hour ago, OrdinaryKerman said:

Whether or not it has a lifting body shape doesn't really matter if it has some other way of creating large amounts of drag.

The drag should be controlled. This is the main purpose of the flat-bottoms.

No, the main purpose of the flat bottom on a capsule or the planar heat shield on a spaceplane is to increase the effective radius of curvature of the plasma sheath and produce a greater stand-off from the heat shield surface.

[RCgothic]

2 hours ago, CastleKSide said:

I would be a lot less harsh on starliner's failure if I knew they had 6 more capsules waiting in the hanger. That and if the reason for their failure wasn't "ohh  we didn't do a basic all up software test that anyone with basic engineering experience would have done."

There is learning by failure when you are fundamentally pushing the envelope and then there is just stupidity.

Elon actually touched on this in part 2 of the interview with Tim. 

Dragon can never have a failure. The development of Dragon was the polar opposite of Starship and it's worked perfectly on every flight.

Starship doesn't need to work perfectly on every flight. It just needs to work enough.

[RyanRising]

3 hours ago, RCgothic said:

Elon actually touched on this in part 2 of the interview with Tim. 

Dragon can never have a failure. The development of Dragon was the polar opposite of Starship and it's worked perfectly on every flight.

Starship doesn't need to work perfectly on every flight. It just needs to work enough.

I don’t think it’s fair to say Dragon has worked perfectly on every flight - I both remember talk of thruster heaters not functioning and higher than expected rates of ablation on the shield, as well as DM-1 perhaps having a problem similar to Starliner on its first flight but being able to recover and dock anyway. (If anyone has more info on that specific occurrence, I’d love to have it. All I’ve heard are whispers, so it may not be true at all.) However, it has always worked well enough, which is a much higher bar than working well enough is for Falcon recovery or especially Starship prototypes. 

Edited August 10, 2021 by RyanRising

[tater]

 

 

They have to pull the engines, then move the thing to that new thrust simulator contraption.

[JoeSchmuckatelli]

9 hours ago, kerbiloid said:

Currently the only thing they have what Roscosmos doesn't

Man, Putin's Soviet-style lock down on information is impressive... Because I've never seen any of Roscosmos' flights that SX is imitating. 

 

Can you smuggle out a VCR tape?

 

 

 

 

 

 

 

 

/snark

Edited August 10, 2021 by JoeSchmuckatelli

[Hannu2]

9 hours ago, kerbiloid said:

At <2 km/s speed?

8 km/s is 4 times freater.

Drag and heat flow ~16 times.

What is the point of all this complaining? We know that you do not like SpaceX and do not believe they could achieve success. But they will absolutely surely not cancel their projects if someone in Internet do not like or believe them. Let them try whatever they want.

9 hours ago, kerbiloid said:

Currently the only thing they have what Roscosmos doesn't is legs on the middle-sized first stage (and who knows is it worth it).

I would mention also lion's share of global satellite markets and real attitude to try some real development instead of empty talks like national space organizations (except Chinese who also attempt to develop their space operations). I would not give applauds for Nasa, Esa or Roscosmos (or governments funding them) for activities in last 2 decades.

 

9 hours ago, kerbiloid said:

The drag should be controlled. This is the main purpose of the flat-bottoms.

Drag can also be controlled by orientation of craft. There is no need for large corrections in pinpoint landing. Controlled drag is needed for last minute change of landing area which is not needed in civilian space applications. Even spacecraft could do it and there would be another landing rig nearby such a major change of flight profile would need bureaucratic paperwork of months in normal conditions and be practically illegal.

[JoeSchmuckatelli]

9 hours ago, tater said:

It's still experience and data. Who else has data on ~100 controlled entries even at that lower velocity?

They also have data on every Dragon, Crew Dragon, and Cargo Dragon orbital entry.

And obviously, they don't model anything, maybe they should come here, see your criticisms and abandon the project?

 

Meanwhile in Boca Chica:

 

 

@sevenperforce - looks like the actuators are on the inner ring.

If you recall the pic from tater's earlier post 

 

The actuators were evident but not obvious 

On 8/7/2021 at 11:59 AM, sevenperforce said:

The actuators are inside

 

Edited August 10, 2021 by JoeSchmuckatelli

[kerbiloid]

As expected, the lack of counter-arguments resulted in festival of political insinuations.

[JoeSchmuckatelli]

3 minutes ago, kerbiloid said:

As expected, the lack of counter-arguments resulted in festival of political insinuations.

Grin - not political, just snark! 

(low hanging fruit) 

Edited August 10, 2021 by JoeSchmuckatelli

[tater]

8 minutes ago, kerbiloid said:

As expected, the lack of counter-arguments resulted in festival of political insinuations.

There is zero need for counter arguments here. The counter argument is literally being worked on as we speak in Boca Chica.

They have done the math, they have done the simulations, they have a plan, and they are willing to adjust the design quickly if actual testing doesn't validate their models.

They will hit some milestone, then the complaints will slightly change, and they will persist in moving forward, addressing the problems they think need addressing regardless of what internet randos think. They will alter their models to better conform to test results, iterate the design, and test again. All this in front of us while we watch.

Edited August 10, 2021 by tater

[Beccab]

10 minutes ago, kerbiloid said:

As expected, the lack of counter-arguments resulted in festival of political insinuations.

As expected, the lack of answers to the dozens of comments results in focusing on a single "political" comment

Edited August 10, 2021 by Beccab

[SOXBLOX]

Ah, @kerbiloid, I think we've gone over this before...

Tell me if I'm right or wrong, but as I read it, your argument is that 1) Starship is not like other reentry vehicles. It's not like the Shuttle or the Soviet rip-off of the Shuttle; it's not like a capsule, and it's not like anything else ever tried.

Therefore, 2) it's a bad idea because no aerospace engineers have tried it before. There's clearly a reason the other vehicles were built the way they were.

The thing is, you're right. Well, almost. There is a reason those vehicles are built the way they are. The reason is they were designed to complete a certain flight profile. The thing is, Starship flies a completely different flight profile.

Your entire argument is beside the point. It's invalid. Irrelevant.

Now please reconsider your position before you lose all credibility. 

Edited August 10, 2021 by SOXBLOX
I speekee Englis!

[Beccab]

8 hours ago, sevenperforce said:

Proof?

Are you asking me for proof that a cylinder moving with its axis perpendicular to the airstream will have a L/D ratio of zero?

Or are you asking me for proof that a cylinder with a nonzero angle of attack will have an L/D ratio greater than zero?

Because Falcon 9 is a primitive circular cylinder which attains an L/D ratio of approximately 1 by flying at a high angle of attack. I mean, you can literally watch it glide.

Yes, because neither Starship nor Superheavy nor Falcon 9 are spaceplanes.

If Soyuz has a breach in its HTP tank at any point in the flight, everyone dies. What's the difference?

Are you making a claim?

 

It's not like anyone has ever devoted any time studying hypersonic L/D ratios in wind tunnels, right?

No, the main purpose of the flat bottom on a capsule or the planar heat shield on a spaceplane is to increase the effective radius of curvature of the plasma sheath and produce a greater stand-off from the heat shield surface.

I'd really love to hear what kind of "political arguments" or "lack of counter arguments" kerbloid finds in this comment

[MKI]

I've been watching Everyday Astronaut's tour of Starbase with Elon. Elon mentions that all early launches of Starship+Super-Heavy will probably be used/worked until their destruction. The primary reason for this is they don't have the space to store these versions.

 

So more explosions confirmed 

 

Also Elon confirms he is aware of is "optimistic schedules", and the fact "he is often wrong" when addressing some aspects he apparently isn't clear on. This also brings up the fact he is very aware of a lot of the process, which is honestly incredible. 

Edited August 10, 2021 by MKI

[tater]

It's beyond flight profile. Musk points out the goal in the interview/tour vid (one of them at least, anyway) that the goal is an operationally reusable spacecraft. Aircraft-like reuse.

This has not worked for capsules, obviously, that's a non-starter.

Shuttle was reused but at huge cost, and not with aircraft-like cadence (though I think a flyback booster version as was proposed in the 60s/70s might be able to accomplish that). They are trying something different. Mars is always there for SpaceX as well, so that's part of the equation, anyone wanting just a LEO craft with difference design constraints should just build one.

[JoeSchmuckatelli]

1 hour ago, tater said:

Mars is always there for SpaceX

I've noticed a slight change in rhetoric from Musk lately.  He's more often talking about shifting the industry to 'aircraft like' reuse & cadence than Mars. 

Personally I perceive this as a recognition of what SX actually sees as feasible in the short term.  Like a reasonable goal that run-of-the-mill SX employees can see as attainable during their employment. 

Mars has always seemed like 'crazy space billionaire' talk to me - whereas this new tone is 'we are on the cusp of a new commercial capability' and 'we sense a market is primed for our products'. 

Mars can sit out there as an aspirational 'wouldn't it be cool if/when we can do it' as well as a 'design our ship to be a (pickup truck) capable craft with the ability to do anything from LEO to Lunar to Mars' design philosophy. 

IOW - they started off with this crazy idea and set out for the hills, only to discover a vista of possibilities that became evident only after the journey was commenced.  So it looks like they are likely to explore the new possibilities for a while... Because Mars isn't going anywhere 

Edited August 10, 2021 by JoeSchmuckatelli

[cubinator]

17 minutes ago, JoeSchmuckatelli said:

I've noticed a slight change in rhetoric from Musk lately.  He's more often talking about shifting the industry to 'aircraft like' reuse & cadence than Mars. 

Personally I perceive this as a recognition of what SX actually sees as feasible in the short term.  Like a reasonable goal that run-of-the-mill SX employees can see as attainable during their employment. 

Mars has always seemed like 'crazy space billionaire' talk to me - whereas this new tone is 'we are on the cusp of a new commercial capability' and 'we sense a market is primed for our products'. 

Mars can sit out there as an aspirational 'wouldn't it be cool if/when we can do it' as well as a 'design our ship to be a (pickup truck) capable craft with the ability to do anything from LEO to Lunar to Mars' design philosophy. 

IOW - they started off with this crazy idea and set out for the hills, only to discover a vista of possibilities that became evident only after the journey was commenced.  So it looks like they are likely to explore the new possibilities for a while... Because Mars isn't going anywhere 

I think they are confident that an aircraft-like level of reusability is the tool that is necessary to send people to Mars. They are still absolutely aiming for Mars, but they are taking one step at a time and making sure to do each step right. I think that once they get orbital refueling working they will immediately start trying to land test articles on Mars.

[tater]

39 minutes ago, JoeSchmuckatelli said:

Mars has always seemed like 'crazy space billionaire' talk to me - whereas this new tone is 'we are on the cusp of a new commercial capability' and 'we sense a market is primed for our products'. 

There's not really any market, however (unless you count P2P travel, which I don't, because it's astoundingly unlikely IMHO).

NASA will not get a huge budget increase, that's not a thing.

Commercial launches in total is on the order of the NASA annual budget—at current launch prices. So even if SpaceX hoped to magically capture ALL of the NASA budget (not even remotely plausible), the total launch market is noise.

There is no economic case for colonizing Mars (sorry Mars fans). There's no economic case for cislunar except to capture some of the NASA budget (great f you are a tiny company, sorta meaningless for a large company). All of this work is spending money, it's not for making money. If they manage to get enough in business that it offsets costs? That helps their goal, nothing more.