totm nov 2023 SpaceX Discussion Thread

[Pthigrivi]

3 hours ago, darthgently said:

a. SpaceX recently provided FAA data showing a slightly larger sonic boom area. Despite the slightly larger area, there is no new environmental impact. Nevertheless, FAA entered a new environmental consultation with FWS, which could result in a two-month delay. This is a paperwork exercise that could be swiftly addressed between agencies as a minor paperwork update.

This is the key item in the current delay, and is a direct result of them deciding to do the booster catch for IFT5 instead of waiting till IFT6 while the increased area is reviewed. And yes, if you increase the affected area there's going to be some review. Im sure SX legal team knows that. To be honest SpaceX is getting preferential treatment to be operating in this area at all but again, as a company they're given a certain amount of deference because they're important to the US's strategic goals. It's a good launch site. Its not carte blanche though. I get they want to work the ump but this a lot of whining over a 2 month delay SpaceX themselves incurred. 

Edited September 25 by Pthigrivi

[Nuke]

2 hours ago, tater said:

I don't think the Moon will ever be "colonized" as I am pretty uncertain that 1/6g is enough to make healthy humans. I'm unsure that 0.38g is healthy, actually, and if it isn't, a Mars colony is also off the table completely.

i figure moon base would be needed to get proper data on the effect of prolonged 1/6th gravity on human physiology. we have some data on living in a rotational frame of reference to go on for proper centrifuge design, but very little data on low gravity (i think there may be some data using mouse centrifuges on the iss). the use of conical centrifuges or ring trains for habitation may be desired. it may be necessary to do crew rotations in order to build such infrastructure.  but once you have it, long term habitation may continue from there.

wouldn't call something off the table if there are potential solutions. i would have accepted "prohibitively expensive" though. but even that is subject to change in a post starship world.

[GuessingEveryDay]

3 hours ago, Nuke said:

i figure moon base would be needed to get proper data on the effect of prolonged 1/6th gravity on human physiology. we have some data on living in a rotational frame of reference to go on for proper centrifuge design, but very little data on low gravity (i think there may be some data using mouse centrifuges on the iss). the use of conical centrifuges or ring trains for habitation may be desired. it may be necessary to do crew rotations in order to build such infrastructure.  but once you have it, long term habitation may continue from there.

We don't really need to do that much, they already have a simulation set up at the Huntsville Space Center. It was a lot of fun to ride.

[tater]

One area of possible use for SpaceX on the Moon would be IRSU for O2 I suppose (slightly more on topic than lunar colonization). By mass, O2 is ~78% of Starship props. There might be a use case for O₂ extraction (loads of it on the Moon), where they simply bring the CH₄ with them.

CH4 (full) for SS v2 is ~330t.

CH4 (full) for SS v3 is ~506t.

V2 has ~10.28 km/s dv (full, no payload, 100t dry). It can get 425t of props to LLO, enough to make a CH4 tanker that could 100% fill another V2 with CH4, with enough dv to get back to Earth (direct entry, or aerobrake—assuming the residuals are methalox, not just CH4).

V3 has ~11.14 km/s dv (full, no payload, 120t dry). It can get 680t of props to LLO. Enough to refill a v3 with CH4, or 2 V2s (has about half what it needs leftover for TEI in the latter case). Note that if the tanker variants in this thought experiment were lighter we still might get better round trip margins—or even 100% propulsive returns. V3 needs ~250t of total props for a propulsive return to LEO at 120t dry, cut dry mass to just 98t, and it gets home with 200t of props.

Of course if the residuals are just CH4, then the lunar SS brings excess O2 as cargo. In the V3 case if a lunar ISRU tanker brought up 617t, then our V3 would have a total of 790t of props (after donating the 506t of CH4 to top off a V3 in LLO)—7.5 km/s of dv. Alternately, our V3 keeps 506t of CH4, donates 174t of CH4 to the lunar vehicle, and accepts 1794t of LOX—which looks like it could be done with 2 trips of a tanker for LOX from the lunar surface. Our full V3 in LLO has that 11.14 km/s to play with now. ~2.9km/s will get our V3 to Mars orbit, another 1.4 km/s to LMO, looks like more nominal might be a total of ~4.7 km/s from LLO to LMO (propulsively). Our V3 gets to LMO with 560t of props as a tanker for other Starships there. Better with aerobraking.

 

[Nuke]

2 hours ago, GuessingEveryDay said:

We don't really need to do that much, they already have a simulation set up at the Huntsville Space Center. It was a lot of fun to ride.

ah yes, the gravitron. in the '80s it was all fake gravity and heavy metal, a good combination imho. in the '90s i saw a carny do the humpty hump on the wall. there seems to have been several attempts to rebrand the ride, but it will always be the gravitron to me. scale it up and you can supplement weak surface gravity. coriolis is less of a problem when the thing doesnt need to produce a full g. if 0.5g is suffiecient then you only need a third of a g out of the centrifuge, so you can reduce the radius. ring trains seem like they would be easier to build though, but requires a tbm, or really precise blasting. i suppose you could build it on the surface put semicircular panels over it and cover it with regolith. you could all but eliminate coriolis effects if your loop is a few km in circumference. maglev tracks would give you the smoothest ride (i for one cant sleep on anything with a running motor in it, i once stayed awake on a ferry for 3+ days), but iron wheels seem like something you can make in situ.

[tater]

12 hours ago, Nuke said:

i figure moon base would be needed to get proper data on the effect of prolonged 1/6th gravity on human physiology. we have some data on living in a rotational frame of reference to go on for proper centrifuge design, but very little data on low gravity (i think there may be some data using mouse centrifuges on the iss). the use of conical centrifuges or ring trains for habitation may be desired. it may be necessary to do crew rotations in order to build such infrastructure.  but once you have it, long term habitation may continue from there.

wouldn't call something off the table if there are potential solutions. i would have accepted "prohibitively expensive" though. but even that is subject to change in a post starship world.

I missed this somehow. Yeah, they actually talked about this decades ago as a possible solution during the Lunar Bases and Space Activities in the 21st Century conference, and again at a civil engineering in space conference that was here in NM. I think it's a work-around for a base, but I don't think it's acceptable for a true colony. We definitely need some work on how gravity impacts long term health (and embryology).

[tater]

 

They intentionally left a couple tiles off the last flight in the skirt area, so I wonder if those 2 are intentional as well.

[darthgently]

8 hours ago, Nuke said:

ah yes, the gravitron. in the '80s it was all fake gravity and heavy metal, a good combination imho. in the '90s i saw a carny do the humpty hump on the wall. there seems to have been several attempts to rebrand the ride, but it will always be the gravitron to me. scale it up and you can supplement weak surface gravity. coriolis is less of a problem when the thing doesnt need to produce a full g. if 0.5g is suffiecient then you only need a third of a g out of the centrifuge, so you can reduce the radius. ring trains seem like they would be easier to build though, but requires a tbm, or really precise blasting. i suppose you could build it on the surface put semicircular panels over it and cover it with regolith. you could all but eliminate coriolis effects if your loop is a few km in circumference. maglev tracks would give you the smoothest ride (i for one cant sleep on anything with a running motor in it, i once stayed awake on a ferry for 3+ days), but iron wheels seem like something you can make in situ.

My issue with surface based centrifuges is that rotation is far simpler in orbit.  

Once on a surface one gets into regolith dust combined angrily with moving parts.  

Sure there are obvious cases for surface bases, mostly for ISRU, mining, industry, sheltered storage, and locale-oriented science.  But I really see the bulk of lunar citizens and families being in 1G rotating habs in lunar orbit or Lagrange,  with many having work stints (n days/weeks on, m days/weeks off) in the surface facilities

[Ultimate Steve]

They've certainly come a long way since:

 

[Nuke]

7 hours ago, tater said:

I missed this somehow. Yeah, they actually talked about this decades ago as a possible solution during the Lunar Bases and Space Activities in the 21st Century conference, and again at a civil engineering in space conference that was here in NM. I think it's a work-around for a base, but I don't think it's acceptable for a true colony. We definitely need some work on how gravity impacts long term health (and embryology).

thats another reason im for a moon base as opposed to a mars colony. its the perfect testbed for not terrestrial colonization. and if something goes wrong, a hospital is a mere 3 days away instead of 2 years+transit time. i dont think were at the trl necessary for a colony and that a lot more research need be done. were probibly going to need some irsu, but not at an industrial scale. use it as a small scale testbed for colonization tech. then by the time we are ready we will have much better propulsion technology and perhaps some infrastructure.

6 hours ago, darthgently said:

My issue with surface based centrifuges is that rotation is far simpler in orbit.  

Once on a surface one gets into regolith dust combined angrily with moving parts.  

Sure there are obvious cases for surface bases, mostly for ISRU, mining, industry, sheltered storage, and locale-oriented science.  But I really see the bulk of lunar citizens and families being in 1G rotating habs in lunar orbit or Lagrange,  with many having work stints (n days/weeks on, m days/weeks off) in the surface facilities

yea but you dont get the rad shielding from an orbital hab. unless you have enough power to put up a magnetic shield. but that only covers charged particles. and the bulk needed to cover all the radiation hazzards would require substantial surface industry.  even if you are just sintering regolith bricks and launching them. bringing that from earth will cost a fortune. the belt is probibly a better place for big centrifuge stations as you can just get the material from asteroids and not have to worry about launching anything out of a gravity well.

Edited September 25 by Nuke

[Nuke]

7 hours ago, tater said:

 

They intentionally left a couple tiles off the last flight in the skirt area, so I wonder if those 2 are intentional as well.

have they done anything to remediate melty flaps?

[tater]

38 minutes ago, Nuke said:

thats another reason im for a moon base as opposed to a mars colony. its the perfect testbed for not terrestrial colonization. and if something goes wrong, a hospital is a mere 3 days away instead of 2 years+transit time. i dont think were at the trl necessary for a colony and that a lot more research need be done. were probibly going to need some irsu, but not at an industrial scale. use it as a small scale testbed for colonization tech. then by the time we are ready we will have much better propulsion technology and perhaps some infrastructure.

I think there are many good reasons to up some TRLs on the Moon for exactly this reason. I don't think colonization is right in either case unless we know more, though—ie: sending people to actually live either place full time, including having kids.

4 minutes ago, Nuke said:

have they done anything to remediate melty flaps?

They might have changed the tiles to the new ones. The real change is the next ship with them moved leeward out of harm's way.

[darthgently]

20 minutes ago, Nuke said:

have they done anything to remediate melty flaps?

As Tater mentioned they moved them leeward but iirc they also have better coverage of the seam/hinge area wrt backup ablative layer beneath reworked tile coverage

[zolotiyeruki]

On 9/24/2024 at 3:31 PM, Pthigrivi said:

The question is whether they lose thrust due to engine failure during the landing burn. One of the engines in IFT4 failed to light during this maneuver just a km from the target and in the surface camera view you can see flames billowing out of the side of rocket the even as its going 150kph right over the LZ. I know they've done a lot to mitigate the ice contamination issue and maybe they have it nailed. Why not just do one more test to make sure? The risk/reward of the catch vs waiting till IFT6 seems out of wack to me as an outside observer. Same with doing IFT1 before getting the deluge system fully ready. I get "move fast and break things" but there is a point where you are breaking things you don't have to and it becomes counterproductive. 

So here's my take on it:

Short version:  SpaceX have the most to lose here, and I'm inclined to think that they're confident in their fixes to the earlier problems.  Given SpaceX's rapid pace of development and iteration, and that regulatory approval seems to consistently stand on the critical path, it makes sense to test as many things as possible with each launch.  In other words, if the FAA/EPA/FWS are going to drag their feet for months for every launch, you'd want to maximize the amount of test data you get with each launch.

Longer version:

A successful chopsticks-catch relies on all the various bits working correctly--engine relight, flaps, engine gimbals, control system, radar altimeter, GPS, etc.    And all of that is moot unless the launch, separation, and boostback are nominal.  Rather than take an overly-simplified perspective on it ("they haven't had a flawless soft ocean landing yet"), it's important to get into the details.  First, you have to define the actual Bad Thing that could happen. Let's call it "damage to the tower."  Second, you have to figure out what failures on the booster could cause that. Third, you have to eliminate (or accept the reduced risk from) those failures which have mitigations in place.  For example, several of those failures (failed relight, GPS, a few others) are mitigated by having an initial trajectory that sends it offshore.  Several others may be mitigated by FTS.  Fourth, you look at the ask-yet-unmitigated failure modes.

It appears that SpaceX have already proven out most of the systems--the aerodynamics, engine gimbals, control systems and GPS/altimeter stuff is fine, based on the previous launch.  The propulsion systems appear to be the last piece (at least for the booster) that haven't had a perfect performance.  SpaceX have surely addressed (or attempted to address) the issues that caused the engine fire on the last SuperHeavy, which means that the last known unmitigated failure modes have been addressed.  Besides, you could make the argument that the successful water landing proved that the existing mitigations (e.g. throttling the other engines up to compensate) already work.

And lastly, you have to evaluate the consequences of a failure.  At this point the Bad Things that are left are some sort of failure in the chopsticks, and a fuel leak and fire at the engine end of the booster, with a potential structural failure and spectacular-but-brief fire.  SpaceX have to test the chopsticks at some point, and I'd be willing to bet that SpaceX have a solution to the engine fire thing. 

So yes, they could do one more soft water landing to prove that all the systems work.  At that point, however, they'd be chasing unknown unknowns, i.e. now-we're-just-guessing-what-might-go-wrong.

[tater]

33 minutes ago, zolotiyeruki said:

Short version:  SpaceX have the most to lose here, and I'm inclined to think that they're confident in their fixes to the earlier problems.  Given SpaceX's rapid pace of development and iteration, and that regulatory approval seems to consistently stand on the critical path, it makes sense to test as many things as possible with each launch.  In other words, if the FAA/EPA/FWS are going to drag their feet for months for every launch, you'd want to maximize the amount of test data you get with each launch.

It's important to note that SpaceX has pointed out that none of the issues withthe current 2 month paperwork period are safety related at all. The 2 month FWS is related to the slightly changed size of the sonic boom profile—not that the impact is any larger (it's "no impact" per the previous EPA findings, just "no impact" over a slightly larger area).

Also:

and:

 

 

[Pthigrivi]

23 minutes ago, tater said:

It's important to note that SpaceX has pointed out that none of the issues withthe current 2 month paperwork period are safety related at all. The 2 month FWS is related to the slightly changed size of the sonic boom profile—not that the impact is any larger (it's "no impact" per the previous EPA findings, just "no impact" over a slightly larger area).

I think this is probably right, but being somewhat entangled with state regulation in the course of my day job (you all would lose your minds if you knew about VT Act 250) technically speaking, just because the sonic boom doesn't affect species within X radius doesn't mean it wont affect species within Y radius because there may be a wider range of biology in the wider area. If there's a nesting site for something endangered just outside the X radius boundary it might affect species recovery. I have to deal with these kinds of questions for basic housing and commercial projects with 2-20m budgets. Honestly the fact that they're able to build a rocket factory and launch site in an active wetland is kind of mindboggling to me so whining about "Oh you've increased your impact area but we'll review and get back in 60 days" seems like wildly generous deference to me. 

[tater]

It's not like there's some other biome just outside the previous area. The creatures under scrutiny are in the current boom footprint. My guess is it's a 2 month wait so that some people at FWS who know bupkis about sonic boom impacts on animals* look at what the EPA already decided and sign off on it.

*I say this because probably no one knows much of anything about sonic boom impacts on these particular animals, there are not many places at all where supersonic aircraft fly.

[Terwin]

'Nearby thunder usually has a sound pressure of 165-180db and sometimes more than 200db'

'A sonic boom is typically around 110db'. 'Sonic booms can be particularly loud and startling from large supersonic aircraft'

'Technically thunder is a sonic boom'

Boca chica, TX averages 78 days of rainfall per year.

Sounds like regulatory paperwork requirements more than a specific identified need to me.

[tater]

They never get any lightning, way more sonic booms

[Codraroll]

On 9/25/2024 at 5:25 AM, GuessingEveryDay said:

We don't really need to do that much, they already have a simulation set up at the Huntsville Space Center. It was a lot of fun to ride.

You don't get low gravity in a Gravitron on Earth, though. You get the regular 1G gravity downwards, plus the centrifugal component of rotation, for a total >1G, no matter what you do. If you want to test partial gravity in a centrifuge, it must be stationed in space or on the Moon.

Edited September 26 by Codraroll

[PakledHostage]

Aren't you lot presuming to know what the bureaucrats are thinking, with all this criticism of the regulatoty process and related talk of the  relative impacts of thunder vs. sonic booms? Or is it open knowledge what's behind the delays? Don't get me wrong. That's what internet forums are for (i.e. presuming to know what others are thinking and responding accordingly), but I feel the need to point it out in light of some of the discussion up thread.

[darthgently]

20 minutes ago, PakledHostage said:

Aren't you lot presuming to know what the bureaucrats are thinking, with all this criticism of the regulatoty process and related talk of the  relative impacts of thunder vs. sonic booms? Or is it open knowledge what's behind the delays? Don't get me wrong. That's what internet forums are for (i.e. presuming to know what others are thinking and responding accordingly), but I feel the need to point it out in light of some of the discussion up thread.

Whitaker at the FAA has stated what he thinks the issues are, no mind reading required.  The fact that the FAA has approved basically the same processes and differences are minimal would naturally lead to a rational questioning of Whitaker’s curiously timed delay and the length of the delay.  
Strangely, the analysis of a slightly different sonic boom footprint, of the same magnitude and still mostly over water in a keep out zone, could not possibly occur prior to a very large civic event, according to Whitaker, an appointee, while the FAA apparatus seemed to be naturally moving toward a timely approval prior to Whitaker’s suddenly inspired divergence

Edited September 26 by darthgently

[Pthigrivi]

21 hours ago, tater said:

It's not like there's some other biome just outside the previous area. The creatures under scrutiny are in the current boom footprint. My guess is it's a 2 month wait so that some people at FWS who know bupkis about sonic boom impacts on animals* look at what the EPA already decided and sign off on it.

*I say this because probably no one knows much of anything about sonic boom impacts on these particular animals, there are not many places at all where supersonic aircraft fly.

Yeah this is why I say it probably doesn't matter and will indeed be approved.  SpaceX has anticipated at some point having a daily launch cadence which may matter for things like bird nesting. Again it probably isn't different given the extended area but Im not shocked that some review is necessary. Id personally expect more like 4 weeks than 8 weeks but I mostly deal with state agencies. 

Edited September 26 by Pthigrivi

[tater]

[tater]

This is pretty cool