totm nov 2023 SpaceX Discussion Thread

[magnemoe]

6 hours ago, Nuke said:

wonder if you could surf down from orbit darkstar style on one of those. 

this may be the libertarian in me talking, but this is what happens when you don't have to get approval from a dozen different government bureaucracies to get something done. though they probibly did have to apply for a building permit (otherwise they would have done this last week).

Not from orbit but if you was strapped to an fairing on the inside that suborbital flight is probably survivable with an spacesuit. Landing might be rough however.

You don't tend to need permits for repairs. Now they wanted to make sure it was not other unseen damage and I assume they make room for the metal padding at ground level and extra piping to it. Also other piping. 
 

[magnemoe]

2 hours ago, Piscator said:

As far as I undestand it, there is considerable overlap between both systems. The booster and launch infrastructure is always the same and a dedicated tanker starship would be needed for both mission types as well. At the point when people land on the moon in starship you're three quarters done with the Mars variant of the system as well.

Its an overlap in that they will use the same engines and tanks.  Else I imagine they will be very different. I imagine much smaller nose you need the cargo bay who can be pressurized and crew quarter but you don't need that much space for 4 crew maximum even with some lavish facilities as in 2-3 decks with 9 meter in diameter. 
Mars version will look much more like the reusable ship and they need to get that to work first. 

[Ultimate Steve]

3 hours ago, SunlitZelkova said:

 

I have to wonder, will Mars Starship be delayed or put on hold by Starship HLS? It just seems totally unrealistic to think both could be developed at a reasonable pace at the same time. That's just not how it works.

IMO the pacing item for a human mission to Mars is not currently the transportation system. Life support, ISRU, surface power, and countless other small but complicated systems are required.

If anything Starship HLS has probably sped up Mars Starship mission due to the increased legitimacy granted by it having won a massive NASA contract. It is easy to forget now that it has actually flown, but a few years ago many people dismissed Starship as a delusional fantasy.

Direct quotes from someone on this forum in 2018:

Quote

 

I've said it on here many times before and I'll say it again. The BFR is as real as astroturf. You might as well go looking for leprechaun colonies in the craters on the dark side of the moon. No BFR is ever going to show up and it sure as hell ain't ever flying colonist (or anyone) to Mars.  

Quote

What innovations? Unless over-promising and under-delivering massively is an innovation.  

I don't think SpaceX has any patents. They stand on the shoulders of many other great innovators.

The landing rockets shtick was done decades ago. If it saves any real money is unknown.

Quote

Starlink needs to be cancelled. 5G is fast and cell towers are almost everywhere and soon to be worldwide. No one is going to be interested in laggy expensive internet. I don't like filling up the night's sky anymore with junk for my telescope anyways. This is another of Musk's money losers.

Like that silly Mars rocket he's building. It's nothing like a real spaceship and was constructed by a company that makes water towers. It's another of this charlatans PR stunts to hustle money out of investors. 

We do know Tesla is headed to bankruptcy as soon as investors get wise. It losing billions every year. And now with such bad management Musk is putting SpaceX in bankruptcy jeopardy too.

In five years, when the dust settles on Mar's rockets and Martian colonies we'll see what's left. Everything he touches loses money.     

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My guess is SpaceX is losing money. 

The reusable booster stunt hasn't been shown to save any money. To reuse a booster you must pay a lot of money in recovery and getting it back to flight. I think SpaceX has only reused boosters up to 3 times so that can't be enough to save money.

Elon Musk is wasting so much money on that dumb "Starship" rocket to nowhere that you know investors must be getting nervous. 

Even early this year SpaceX let go 10% of its workers so you know things can't be going great. I think SpaceX will have fewer launches this year too. 

Musk is probably driving SpaceX into a ditch of bankruptcy. Just like Tesla.

Quote

 

Learned, credible, professionals don't. And they shouldn't. The BFR and its Mars/Moonbase building trips are pure, fantastical nonsense.I sit spellbound that soooo many people can believe this rot.

While the industry skepticism of Starship was likely more calculated than general individuals, the sentiment that Starship lacked legitimacy was still present. Now that people are taking it more seriously, the question of what other systems are needed to get to Mars is probably being thought about more than it was before.

[Hannu2]

17 hours ago, Exoscientist said:

I also argued there should be an independent review aside from the FAA by space safety experts on the safety of the launch. If so, the inadequacy of the FTS likely also would have been picked up. I say it’s likely it would have been seen beforehand because assuming the FTS did activate there seems to be only one reason why it did not destroy the vehicle immediately: the strength of the explosives used were not sufficient to penetrate beyond the tank wall strength. This SHOULD have been seen beforehand. [/quote]

Who is independent if official state administration is not? As far as I know FAA officials will make independent detailed investigation about detected issues and will give SpaceX list of needed changes and conditions before permitting next launch attempt. I think it will take little more time than Elon expect and printed list will be so heavy that even Starship can not lift it.

I guess that they underestimated strength of stainless steel compared to common aluminium alloys. Now they detected the problem, fortunately without any collateral damage, and the next version will have strong enough FTS to break the tank. It is probable very easy thing to fix. Just buy larger explosive elements. Issues with the launch pad will be much harder.

 

[magnemoe]

4 minutes ago, Hannu2 said:

Who is independent if official state administration is not? As far as I know FAA officials will make independent detailed investigation about detected issues and will give SpaceX list of needed changes and conditions before permitting next launch attempt. I think it will take little more time than Elon expect and printed list will be so heavy that even Starship can not lift it.

I guess that they underestimated strength of stainless steel compared to common aluminium alloys. Now they detected the problem, fortunately without any collateral damage, and the next version will have strong enough FTS to break the tank. It is probable very easy thing to fix. Just buy larger explosive elements. Issues with the launch pad will be much harder.

 

How is the FTS explosives designed? is in an simple bomb outside the hull or something more advanced like an linear shape charge cutting an hole? 
If its cutting an hole I imagine the effect would be the same for steel an aluminum as long as you used an more beefy shape charge. An bomb would be much less efficient and I can imagine an simple linear cut having smaller effect as in the plated will not bend out as much. And as you say its an simple fix as in using an larger explosive charge blowing an larger hole. 
 

[tater]

19 minutes ago, magnemoe said:

How is the FTS explosives designed? is in an simple bomb outside the hull or something more advanced like an linear shape charge cutting an hole? 
If its cutting an hole I imagine the effect would be the same for steel an aluminum as long as you used an more beefy shape charge. An bomb would be much less efficient and I can imagine an simple linear cut having smaller effect as in the plated will not bend out as much. And as you say its an simple fix as in using an larger explosive charge blowing an larger hole. 
 

It's detcord.

[Hannu2]

1 hour ago, magnemoe said:

How is the FTS explosives designed? is in an simple bomb outside the hull or something more advanced like an linear shape charge cutting an hole? 
If its cutting an hole I imagine the effect would be the same for steel an aluminum as long as you used an more beefy shape charge. An bomb would be much less efficient and I can imagine an simple linear cut having smaller effect as in the plated will not bend out as much. And as you say its an simple fix as in using an larger explosive charge blowing an larger hole.

My knowledge is based on Scott Manley's video. FTS explosives are long V-shaped explosives which make long cut to tanks. In some rockets it is placed in bulkhead between tanks so that it mixes propellants anf ignite them in addition to break tanks mechanically.

I do not know how metals behave in shaped explosions but stainless steel is much more hard material to cut with normal machinig tools than ratio between tensile strengths are (in compared to aluminium alloys). I think it is easy to make an error if those devices are rarely used for stainles steel objects.

Link to Scott's video:

https://www.youtube.com/watch?v=yekMWWcpfOA

 

[Nuke]

10 hours ago, SunlitZelkova said:

Starship also resembles N1 in how it started as a Mars rocket but has become a Moon rocket.

I have to wonder, will Mars Starship be delayed or put on hold by Starship HLS? It just seems totally unrealistic to think both could be developed at a reasonable pace at the same time. That's just not how it works.

Overreacting much? Independent review does not imply the end of innovative spaceflight.

Speed towards space should not be pursued at the expensive of transparency and oversight. Otherwise we are asking for another Challenger disaster.

ive always been a proponent of moon before mars anyway. if we can make a 2 stage reusable we can make a 3-stage reusable. so a reusable 3-stage to the moon, with a local fuel depot might be the way to go. you can not only refuel upper stage enough to return to earth, you can also fuel ships going elsewhere. if you wanted a nuclear engine, you could operate without concern for contaminating the earth if it operates out of the moon base. if i was going on a mars mission i wouldn't mind that infrastructure existing first. you can cut significant time off of delivery of emergency supplies if its on the moon ready to go on a fast transfer trajectory.

[CatastrophicFailure]

8 hours ago, Ultimate Steve said:

Direct quotes from someone on this forum in 2018:

Ah yes, I detect the subtle bouquet of finely-aged milk. 

[sevenperforce]

8 hours ago, magnemoe said:

15 hours ago, Nuke said:

wonder if you could surf down from orbit darkstar style on one of those. 

Not from orbit but if you was strapped to an fairing on the inside that suborbital flight is probably survivable with an spacesuit. Landing might be rough however.

There's probably a decent amount of thermal radiation coming off of that plasma in the wake but yeah, as long as you have a reflective spacesuit of some kind you should be find. Probably want a good dark visor too.

Landing should be easy. You've seen how smoothly the fairing floats down to the water, right?

34 minutes ago, Nuke said:

if we can make a 2 stage reusable we can make a 3-stage reusable. so a reusable 3-stage to the moon, with a local fuel depot might be the way to go.

How so?

Two-stage reusable is the sweet spot. The lower stage can boostback to the launch site and the upper stage can loiter on orbit until it's time to initiate a re-entry that will bring it back to the launch site.

A three-stage reusable architecture, on the other hand, is extremely challenging. The second stage won't make it all the way to orbit but will be entering at such high speeds that it needs essentially a full heat shield, and it's going to come down halfway around the world, so how does it get back to the launch site?

The only thing I can think of that might work for a rapidly reusable three-stage architecture would be a RTLS booster with a second stage that brings the third stage to just shy of orbit, then re-enters about 3/4 of the way around and enjoys a hypersonic glide the rest of the way to the launch site. But then there's no real reason to make the third stage reusable.

1 hour ago, Hannu2 said:

My knowledge is based on Scott Manley's video. FTS explosives are long V-shaped explosives which make long cut to tanks. In some rockets it is placed in bulkhead between tanks so that it mixes propellants anf ignite them in addition to break tanks mechanically.

I wonder if they tried to get away with punch-out FTS instead of the detcord that ordinarily unzips the tanks, thinking that popping the tanks alone would be sufficient to destroy them.

[StrandedonEarth]

2 hours ago, Hannu2 said:

My knowledge is based on Scott Manley's video. FTS explosives are long V-shaped explosives which make long cut to tanks. In some rockets it is placed in bulkhead between tanks so that it mixes propellants anf ignite them in addition to break tanks mechanically.

I do not know how metals behave in shaped explosions but stainless steel is much more hard material to cut with normal machinig tools than ratio between tensile strengths are (in compared to aluminium alloys). I think it is easy to make an error if those devices are rarely used for stainles steel objects.

Link to Scott's video:

https://www.youtube.com/watch?v=yekMWWcpfOA

 

I know that many alloys change properties at cryogenic temperatures. Stainless steel gets stronger. A materials test in my university days showed that a steel plate that is punctured by a bullet at room temperature can stop the bullet if first cooled by liquid nitrogen. Some the energy goes into transforming the steel into a different type (into martensite IIRC, which I probably don’t)

While I’m sure SpaceX knows this, it may be tricky to get right. I still haven’t seen confirmation of if the FTS fired late, or fired earlier but didn’t do the job. You’d think they’d have tested that…

[wumpus]

50 minutes ago, sevenperforce said:

Two-stage reusable is the sweet spot. The lower stage can boostback to the launch site and the upper stage can loiter on orbit until it's time to initiate a re-entry that will bring it back to the launch site.
 

That's only clear without full reuse.  With full reuse, launch costs will be dominated by fuel costs and integration costs, with integration costs hopefully becoming automated.  I've mentioned my "Starship followup" a few times, but why not again.

I'd expect that 3 stages would be considered for a Starship 2.0.  It would have been silly for the first model, especially with a limited budget, but not necessarily for a follow on.  Ideally, the first stage would be air-augmented (reducing fuel is nearly the entire goal).  This should also have a relatively easy return to launch trajectory, with few losses in the "boostback".  The second stage depends a lot on information from Starship.  I'd assume that return to launch is clear off the table (less fuel needed to ship it back by boat, although this adds to integration costs).  Generally speaking, the second stage has a bunch of potentially conflicting criteria:

use vacuum optimized engines, but retroland.   Current thinking assumes merlin engines for return
add 4-6km/s delta-v (roughly half what's left after the first stage), obviously this is likely to change a lot
no heat tiles (probably, depends on the cost of applying/maintaining starship's tiles and their safety).  Expect this to  be what really limits the amount of delta-v

I'd also expect the second stage to look a lot more like a squashed cylinder (with an extended radius to keep the heat away) that more or less resembles starship (and does a similar bellyflop re-entry).

The whole point of all this extra mass (presumably only the extra engines needed for stage 2, plus a little needed for an extra set of landing fins is that it should lead to overall lower mass of fuel burned, primarily by using air augmentation for the critical ultra-thirsty early burn (most of the gains) followed by dropping a second chunk of the mass halfway through the main burn.

Most of the justification of 3 stages assumes that Starship (needing full reentry capacity) will be significantly more massive than your typical single use fuel tank (and why it has been hard to design).  Splitting the orbital (and beyond) part into two parts, a significantly larger part that has to re-enter at a significantly slower speed) will require less overall mass.  It is much like the original trick for Falcon 1 (recover the massive low-delta-v part), only iterated a second time.

 

[sevenperforce]

9 hours ago, Ultimate Steve said:

12 hours ago, SunlitZelkova said:

I have to wonder, will Mars Starship be delayed or put on hold by Starship HLS? It just seems totally unrealistic to think both could be developed at a reasonable pace at the same time. That's just not how it works.

IMO the pacing item for a human mission to Mars is not currently the transportation system. Life support, ISRU, surface power, and countless other small but complicated systems are required.

Agreed.

Also, the most important parts of the Mars Starship program -- Superheavy and the rapidly reusable tanker -- are also the most important part of the HLS program.

[wumpus]

3 minutes ago, StrandedonEarth said:

While I’m sure SpaceX knows this, it may be tricky to get right. I still haven’t seen confirmation of if the FTS fired late, or fired earlier but didn’t do the job. You’d think they’d have tested that…

You'd also assume that Musk would have tested throwing a ball at cybertruck's glass...

Spacex also loves changing things.  I wouldn't be surprised if there's no alert to redo the self destruction tests everytime there is an ECO in the outer stainless steel hull/fuel tank design.  That type of thing would probably ruin spacex's entire design methodology.

[sevenperforce]

5 minutes ago, StrandedonEarth said:

I know that many alloys change properties at cryogenic temperatures. Stainless steel gets stronger. A materials test in my university days showed that a steel plate that is punctured by a bullet at room temperature can stop the bullet if first cooled by liquid nitrogen. Some the energy goes into transforming the steel into a different type (into martensite IIRC, which I probably don’t)

While I’m sure SpaceX knows this, it may be tricky to get right. I still haven’t seen confirmation of if the FTS fired late, or fired earlier but didn’t do the job. You’d think they’d have tested that…

Yeah, I am surprised that they didn't do a cryo proof FTS test, especially given how cheap the tanks are.

Then again, perhaps there's some difference with blowing the tanks at altitude vs at sea level.

I actually have a reasonably significant amount of experience with brittle vs ductile fractures in steel, although typically with much higher pressures and much thicker vessels. I wonder if they were expecting a ductile fracture propagation from the FTS point but ended up with a brittle fracture surface that didn't propagate.

[sevenperforce]

12 minutes ago, wumpus said:

I'd expect that 3 stages would be considered for a Starship 2.0.  It would have been silly for the first model, especially with a limited budget, but not necessarily for a follow on.  Ideally, the first stage would be air-augmented (reducing fuel is nearly the entire goal).  This should also have a relatively easy return to launch trajectory, with few losses in the "boostback".  The second stage depends a lot on information from Starship.  I'd assume that return to launch is clear off the table (less fuel needed to ship it back by boat, although this adds to integration costs).  Generally speaking, the second stage has a bunch of potentially conflicting criteria:

use vacuum optimized engines, but retroland.   Current thinking assumes merlin engines for return
add 4-6km/s delta-v (roughly half what's left after the first stage), obviously this is likely to change a lot
no heat tiles (probably, depends on the cost of applying/maintaining starship's tiles and their safety).  Expect this to  be what really limits the amount of delta-v

I'd also expect the second stage to look a lot more like a squashed cylinder (with an extended radius to keep the heat away) that more or less resembles starship (and does a similar bellyflop re-entry).

The whole point of all this extra mass (presumably only the extra engines needed for stage 2, plus a little needed for an extra set of landing fins is that it should lead to overall lower mass of fuel burned, primarily by using air augmentation for the critical ultra-thirsty early burn (most of the gains) followed by dropping a second chunk of the mass halfway through the main burn.

What overall OML are you thinking about for the air-augmented vehicle? That's always a challenging approach because the aerodynamics become non-trivial.

I've always liked the idea of a crossfed air-augumented booster with all the intakes located on the parallel booster that provides the crossfeed.

[Exoscientist]

12 hours ago, CatastrophicFailure said:

The FAA IS the independent reviewing authority. 
 

Once again, we don’t have all the data. They do. 

 I’m suggesting they are being lax to appease SpaceX since SpaceX is currently the only provider of military launches, the only provider for launches to the ISS, and the only provider for a lunar lander for the Artemis missions.

 So there need to be reviewers independent of both SpaceX and the FAA.

Something just occurred to me. If SpaceX previously said the Starship launchpad would be located 20 miles off-shore because of the noise from sonic booms, wouldn’t the same issue apply to the residents of South Padre Island and Port Isabel only 5 to 6 miles away?

ELON MUSK: NOISY STARSHIP SPACEPORTS WILL BE 20 MILES OFFSHORE. https://futurism.com/the-byte/elon-musk-starship-spaceports-offshore

  Bob Clark

 

Edited May 3, 2023 by Exoscientist

[wumpus]

6 minutes ago, sevenperforce said:

What overall OML are you thinking about for the air-augmented vehicle? That's always a challenging approach because the aerodynamics become non-trivial.

I've always liked the idea of a crossfed air-augumented booster with all the intakes located on the parallel booster that provides the crossfeed.

To be honest, I'm not even sure air-augmenting methane gives much boost in the way of Isp.  I know adding air to kerolox should beat hydrolox (without air), but it isn't clear if methane gets similar boosts.

Originally I assumed some sort of side boosters (more air), but expect that wouldn't be worth it and vertical stacking/staging would vastly easier.  Ideally it would be more of a nearly straight rocket (aerodynamically), possibly with a larger radius at the base sucking up all the air.

Scott Manley's analysis of how Starship .001 was doomed harped back on having the center of lift over the center of mass.  Two re-entry vehicles would play havok on the center of lift, but hopefully an air-sucking base could provide the necessary stability.  I hadn't thought of that until watching his video.

[tater]

3 minutes ago, Exoscientist said:

 I’m suggesting they are being lax to appease SpaceX since SpaceX is currently the only provider of military launches, the only provider for launches to the ISS, and the only provider for a lunar lander for the Artemis missions.

 So there need to be reviewers independent of both SpaceX and the FAA.

LOL. Independent review not by the government.

For a problem they now know exists and will promptly be fixed.

 

3 minutes ago, Exoscientist said:

Something just occurred to me. If SpaceX previously said the Starship launchpad would be located 20 miles off-shore because of the noise from sonic booms, wouldn’t the same issue apply to the residents of South Padre Island and Port Isabel only 5 to 6 miles away?

ELON MUSK: NOISY STARSHIP SPACEPORTS WILL BE 20 MILES OFFSHORE. https://futurism.com/the-byte/elon-musk-starship-spaceports-offshore

This is talking about point to point. Wake me up when that is a thing.

[Terwin]

Falcon 9 hits Max Q after roughly 70 seconds, this is also shortly after it passes Mock 1

Wikipedia says the fastest air-breathing  aircraft is the SR-71 blackbird that hit 2,193.2mph/mock 2.81  in 1976

The falcon 9 first stage only burns for 162 seconds.

For a first stage air-breathing engine to work, it would, at best, replace less than half of the first stage.  This would cost the use of an extra set of engines, an extra recovery, and lots of extra development.

I just cannot see a sufficient increase in efficiency during the first minute of flight to warrant splitting up a less than 3 minute burn across 2 stages.

[sevenperforce]

7 minutes ago, Exoscientist said:

I’m suggesting they are being lax to appease SpaceX

Conspiracy theories require more evidence than a bare recitation of possibility.

6 minutes ago, wumpus said:

I'm not even sure air-augmenting methane gives much boost in the way of Isp.  I know adding air to kerolox should beat hydrolox (without air), but it isn't clear if methane gets similar boosts.

As a rule, increasing the specific impulse of your underlying engine ultimately improves air augmentation because you have a higher burnout velocity. However, the liftoff thrust boost isn't as high, because you have less mass to mix with the air.

[tater]

The best "reusable third stage" would be using the 2-stage model to make a tug. Stage off the nose cone (using the same mechanism on the SH interstage), and have added batteries and some deployable solar arrays.

Make this Stage 2 (left in space forever, reused there) as light as possible consistent with the loads of pushing other starships as a tug.

[CatastrophicFailure]

1 hour ago, wumpus said:

You'd also assume that Musk would have tested throwing a ball at cybertruck's glass...

They did. What they did not test, apparently, was hitting the door with a sledgehammer then throwing a ball at the window… 

30 minutes ago, Exoscientist said:

I’m suggesting they are being lax to appease SpaceX since SpaceX is currently the only provider of military launches, the only provider for launches to the ISS, and the only provider for a lunar lander for the Artemis missions.

 So there need to be reviewers independent of both SpaceX and the FAA.

That’s absurd. Tho it’s amusing we’ve now come full-circle from “the FAA is conspiring against SpaceX!” to “the FAA is conspiring with SpaceX!” 

The FAA is the authority, and they, in turn, had sign-offs from various other authorities (F&W, etc) beforehand too. 
 

Also ULA is still a thing, still has more military contracts than SpaceX IIRC, and they fly north cargo and (eventually) people to the ISS too. 

[sevenperforce]

15 hours ago, kerbiloid said:

Will they investigate, why the engine failure indicator failed?

Look, six engines are off (two wide gaps), but the indicator shows just 5?

Egads!

Whatever will we do?

While we're at it, let's investigate ALL the inaccurate depictions of vehicles in ALL purely promotional or webcast material!

/s

[Exoscientist]

44 minutes ago, tater said:

 

This is talking about point to point. Wake me up when that is a thing.

 Launch and landing is by same vehicle.  SpaceX is still talking about rapid reuse out of Boca Chica, so same issues arise.

   Bob Clark