totm nov 2023 SpaceX Discussion Thread

[CBase]

25 minutes ago, PakledHostage said:

That's hard to find reasonable... Starship hasn't reached orbit yet, and it seemingly hasn't maintained attitude control in zero-g, either. Who would put a non-expendable payload on it before it's been proven more capable?

My guess is that they will put a dummy payload about the size and weight of starlink 2 into IFT-4 while still staying in a suborbital trajectory. That way they can test payload dispensing during coast, improve attitude control and engine relight while staying inside a flight envelop that keeps FAA happy. Depending on the result they might go for orbital trajectory and actual starlink payload in IFT-5.

[CatastrophicFailure]

1 hour ago, darthgently said:

While it would add complexity, they could circulate heat from engine components into a sink and use that to deice the cold gas thrusters.  Maybe

There’s big ol’ Tesla batteries on board to power the grid find, TVC, etc. Tesla butt warmers work pretty good. Just sayin… 

 

1 hour ago, Codraroll said:

Quite aside from the whole re-entry thing, what Starship just did was to bring more mass to orbit than SLS ever could, at a vastly lower cost than even the side boosters of SLS, and there's a mass production line of these already up and running. It wouldn't take much adaptation of the already proven concepts of Starship to far outperform everything SLS dreams of doing. Even when treated as an expendable two-stage rocket, with all the waste it implies, Starship still does more than SLS does, for less.

I get into this on that other platform all the time. Artemis needs Starship to work. But the moment Starship does work, even partially, SLS becomes obsolete. 

[tater]

Yeah, I don't see an operational payload on 4.

[Brotoro]

But an operational payload DISPENSER would be nice. And as long as you're going to pop out a test mass, it might as well have a camera on it to send back images of Starship.

[tater]

1 minute ago, CatastrophicFailure said:

I get into this on that other platform all the time. Artemis needs Starship to work. But the moment Starship does work, even partially, SLS becomes obsolete. 

Yes.

Today completely obviated SLS.

As an expendable, lower "ship" mass (think ship 26 with lower steel thickness), separate fairings after sep, payload can be moon ship parts.

Just now, Brotoro said:

But an operational payload DISPENSER would be nice. And as long as you're going to pop out a test mass, it might as well have a camera on it to send back images of Starship.

Yeah (no likes, lol)

[Spaceception]

Today's flight almost made them ready to pursue orbital testing.  So I think that'll be their main goals for the 4th flight - fix attitude control, make sure the pez dispenser works, relight the Raptor engine(s). Recovery and reentry will still be more stretch goals, but I feel like the booster will have a good shot to make a soft landing at least. B11 can avenge SN11!

[zolotiyeruki]

1 hour ago, sevenperforce said:

See where this is going?

I'll bet we can pretty reliably predict Exoscientist's next dozen concern trolling posts.  Can I try a few?

"SpaceX have got it to space, but they haven't demonstrated they can control SS enough to safely deploy satellites!"

"SpaceX is successfully deploying satellites, but they haven't demonstrated SS controllability through reentry!"

"SpaceX solved the controllability issue, but they shouldn't be launching until they can reliably demonstrate (with some sort of ground test) that the heat shield tiles won't fall off!"

"SpaceX have solved the landing burn relight problem, but they haven't demonstrated sufficient accuracy for the chopsticks!"

"SpaceX have captured the booster safely, but they haven't demonstrated reliable Raptor reuse!"

 

 

 

[Codraroll]

2 hours ago, PakledHostage said:

That's hard to find reasonable... Starship hasn't reached orbit yet, and it seemingly hasn't maintained attitude control in zero-g, either. Who would put a non-expendable payload on it before it's been proven more capable? (Maybe some Star Trek red shirted crew want to go for a ride?)

On the other hand, we are talking about Starlink satellites, which are approximately as expendable as non-expendable payloads get. They've launched almost six thousand of the little fellas by now, about a thousand per year. They reported building six Starlink satellites per day back in 2020. It would not be a bank-breaking gamble to put a few on the next Starship flight, if only to test how well Starship can carry and dispense them. If it works, hey, bonus Starlinks in orbit! And if not, well, they can probably afford to lose a few.

Edited March 14 by Codraroll

[Meecrob]

On 3/13/2024 at 7:24 AM, Meecrob said:

 

Scratch above

 

stop trying to snipe at me re: Elon Musk

Scratch that. Please be my partner in crime, continue sniping at me, in your trademark snarky self, and we can educate the kids together!

[RCgothic]

I think the biggest concern is lack of attitude control. If you can't control attitude you can't control re-entry burns, and for the largest single object ever placed into space that would be a problem. I can see a repeat of IFT-3 for IFT-4. Don't want to go orbital until you can demonstrate ability to bring it down again, or it could come down anywhere.

The amount of shed debris in video was also a bit concerning.

[.50calBMG]

Starting to think that the crew dragon test that exploded a few years ago may be raptors fault. Also that falcon heavy center core curse... And crs 7...

[RCgothic]

Scott Manley points out around 8 mins into his video recap, vapours in the payload bay, then getting vented as the payload door opens. Very cool!

[Exoscientist]

2 hours ago, zolotiyeruki said:

I'll bet we can pretty reliably predict Exoscientist's next dozen concern trolling posts.  Can I try a few?

"SpaceX have got it to space, but they haven't demonstrated they can control SS enough to safely deploy satellites!"

"SpaceX is successfully deploying satellites, but they haven't demonstrated SS controllability through reentry!"

"SpaceX solved the controllability issue, but they shouldn't be launching until they can reliably demonstrate (with some sort of ground test) that the heat shield tiles won't fall off!"

"SpaceX have solved the landing burn relight problem, but they haven't demonstrated sufficient accuracy for the chopsticks!"

"SpaceX have captured the booster safely, but they haven't demonstrated reliable Raptor reuse!"

 

 

 

 

 That would be a lot of failures before getting to operational status. I hope it doesn’t take that many.

  Bob Clark

[Pthigrivi]

1 hour ago, RCgothic said:

I think the biggest concern is lack of attitude control. If you can't control attitude you can't control re-entry burns, and for the largest single object ever placed into space that would be a problem. I can see a repeat of IFT-3 for IFT-4. Don't want to go orbital until you can demonstrate ability to bring it down again, or it could come down anywhere.

The amount of shed debris in video was also a bit concerning.

Ice or heat tiles? I feel like  heat elements around hot gas ports could be mass-cheaper than a full hypergolic RCS system, if thats even the actual issue. After reaching pre-orbital altitude you've got a few minutes to melt or prevent frozen LOX that would impact thruster vectors and retain attitude control above atmosphere. It looked from the video that they were venting almost throughout the coast phase which *should* cancel out if the ports are oppositional. All of the weird roll and tumble action seemed to induce in coast phase.

Edited March 15 by Pthigrivi

[CatastrophicFailure]

2 hours ago, Codraroll said:

On the other hand, we are talking about Starlink satellites, which are approximately as expendable as non-expendable payloads get. They've launched almost six thousand of the little fellas by now, about a thousand per year. They reported building six Starlink satellites per day back in 2020. It would not be a bank-breaking gamble to put a few on the next Starship flight, if only to test how well Starship can carry and dispense them. If it works, hey, bonus Starlinks in orbit! And if not, well, they can probably afford to lose a few.

First Starlinks deployed NEED to have cameras tho. Just to make this a thing:

Spoiler

 

[SunlitZelkova]

9 hours ago, Minmus Taster said:

Rewatching the feed from the booster it looks like it was intact up until the end and smacked into the water at over 1100 KM an hour, yikes.

7 hours ago, JoeSchmuckatelli said:

Very late to the party - just watched with my students. 

Why was Booster so much above terminal so deep into the atmosphere? 

It was supersonic at 5km

They said on the SpaceX stream they were deliberately not going to soft land it. There were no recovery assets out there, after all.

6 hours ago, Exoscientist said:

So SpaceX still has not demonstrated the Raptor can relight reliably in flight. In fact, all the Starship landing tests and actual flight tests have shown it is not reliable after relight in flight.

 Bob Clark

What is your point?

The answer is that problem, if it exists, is just to do more testing.

I imagine your solution to this would be to build a single stack SLS based lunar landing architecture, but that is not going to solve the problem any faster than further testing of Raptor- it will just take longer.

If you want to get to the Moon fast, we need to have faith in Starship and continue testing it. Not drop it and start on a new design.

Starting a second design when something is already in testing is what helped kill the Soviet N1 lunar landing program, and it is often speculated that if NASA had elected to build any of the Lunar Gemini concepts that were touted as a “faster” way to the Moon- that coincidentally are not unlike your SLS based frankenrocket proposals- it probably would have delayed a Moon landing past Kennedy’s 1969 goal.

[darthgently]

4 hours ago, Terwin said:

It seems reasonable that SpaceX may include starlinks as payload on attempts 4+

They may wait until 5, but loading 4 seems plausible 

Take heart and don't listen to the naysayers here, you are in good company wrt your opinion

Also, Codaroll makes some excellent arguments down-thread on how this makes sense

 

Edited March 15 by darthgently

[AckSed]

There's an interesting comment about how Starlink could/should have transmitted all through the descent:

Quote

 @holyknight51: Hey Scott, A note on the hypersonic communication blackout problem. The frequencies that are cutoff is a function of the density of the plasma, so the more dense the plasma, the higher the cutoff frequency, for reentry vehicles this can go as high as 40 GHz depending on several other factors. However, about a month or two ago, SpaceX placed a starlink terminal on a dragon capsule in order to experiment with using starlink as a bent pipe similar to how the space shuttle handled the problem. So with starlink using higher frequencies to go above the cutoff frequencies and being placed on the backside of starship where the plasma is less dense and thus a lower cutoff frequency, I would have expected them to be able to maintain communications through the descentl My credentials are a masters in engineering physics, having studied Ionospheric scintillation in college and currently work as an RF test engineer.

So 1: when it cut out would have been when the airframe couldn't take it any more; 2: next test we should see it stream its reentry all the way to the ground. Ocean.

Edited March 15 by AckSed

[Nuke]

6 hours ago, Terwin said:

It seems reasonable that SpaceX may include starlinks as payload on attempts 4+

They may wait until 5, but loading 4 seems plausible 

i suspect they will want to test relight in space capability before they do that. also the attitude hold issues and any other problems would need to be fixed first. you would want to fully orbit the vehicle to deploy satellites (thrust on the sats is too low to orbit them in time). and still be able to re-enter the atmosphere at this early stage of development. all orbital trajectories have been intentionally high for a passive re-entry. but you might see that on ift5 at the earliest if it works on ift4. of course thats the lower threshold. they might want more than one successful test first.

Edited March 15 by Nuke

[tater]

 

[PakledHostage]

2 hours ago, darthgently said:

Take heart and don't listen to the naysayers here, you are in good company wrt your opinion

Whale, oil, beef, hooked...

[magnemoe]

2 hours ago, Nuke said:

i suspect they will want to test relight in space capability before they do that. also the attitude hold issues and any other problems would need to be fixed first. you would want to fully orbit the vehicle to deploy satellites (thrust on the sats is too low to orbit them in time). and still be able to re-enter the atmosphere at this early stage of development. all orbital trajectories have been intentionally high for a passive re-entry. but you might see that on ift5 at the earliest if it works on ift4. of course thats the lower threshold. they might want more than one successful test first.

Agree, starlink boilerplates, probably but real ones will just burn up unless they reach orbit, and I don't think they go orbital on the next as they lost control this time and its not something you want happening in orbit. 

[mikegarrison]

11 hours ago, AckSed said:

Can you make a staged combustion engine more reliable? Peter Beck of Rocket Lab says you can: by building it to withstand and run at extremes, then under-driving it, you end up in the same level of reliability as a gas-generator rocket engine. Neutron's Archimedes is ox-rich, not full-flow, but building to run at max, then under-running at a more comfortable level is a solid path to good reliability.

That's just standard engineering. You always have to balance margins of performance between the risk that you unexpectedly exceed the limits versus the risk that you overdesign and fail for cost, weight, etc.

The skill and experience is in knowing how close to the edge you should get. Race car engineer Carroll Smith wrote in one of his books: "An engineer is someone who can do for a dime what any fool can do for a dollar."

Edited March 15 by mikegarrison

[kerbiloid]

12 hours ago, AckSed said:

Will they, or is Elon cowboying ahead with demands for, "More pressure! MORE thrust! More payload! Stuff blowing up! Boom!" and laughing maniacally?

He's provided with money and time. The money is unlimited, the time isn't. As he's enough young, probably some deadline is coming.

***

Btw, how many SH/SS successful launches ( * 40 successful ignitions for one-way flight) is required for one lunar expedition?..

Edited March 15 by kerbiloid

[Superluminal Gremlin]

I would like to propose the possibility of the sem-failure of the final booster relight. The tanks were not fully loaded, even at launch, so there may not have been enough fuel to create a nice, clean, no-gas relight. Of course, those oscillations didn't help.