totm nov 2023 SpaceX Discussion Thread

[Brotoro]

6 hours ago, sevenperforce said:

To be clear, you would definitely need continuous acceleration for settling regardless of whether you used a pump. The weight of a pump that can move tens of tonnes of liquid quickly is non-negligible, and neither is the weight of a sufficient power source.

In contrast, if you're transferring by constant ullage acceleration then you're only losing gas -- gas that would have to be displaced anyway as the destination tank is filled.

If you use pressure feed to move the propellant, you don't need a heavy pump. Energy source for heating propellant to provide the pressure could be a hot-gas thruster (using the thruster output to maintain ullage).

[Meecrob]

I'm not sure Raptor is pressure-fed. I think its pump-fed.

[darthgently]

Just now, Meecrob said:

I'm not sure Raptor is pressure-fed. I think its pump-fed.

Thread is about testing tank to tank fuel xfer, iirc

[Meecrob]

Thanks! Its great to have a laugh when I totally miss the point! Ok so now that I'm up to speed, am I correct in that they are going to transfer fuel from the header tanks to the main tanks or vice versa? As in not doing a Starship to Starship transfer?

Edited December 7, 2023 by Meecrob

[darthgently]

10 minutes ago, Meecrob said:

Thanks! Its great to have a laugh when I totally miss the point! Ok so now that I'm up to speed, am I correct in that they are going to transfer fuel from the header tanks to the main tanks or vice versa? As in not doing a Starship to Starship transfer?

It seems some sources think so, lol.  Vague enough?  Will be interesting to see what is tried

[CBase]

2 hours ago, Meecrob said:

I'm not sure what your point is? Mine is that SpaceX reasonably knew they needed a deluge system, but they tried to get away without one.

My point is that they were probably right to go for IFT-1 without the deluge system. Real life testing showed a point where stage 0 simulations missed a critical point. By moving fast to IFT-1 they got the correction early.

Beyond technical issues I guess the biggest change was to adopt risk assessment to align more with goverment oversight. I do think SpaceX attitude to taking risk is beneficial to space industries. Elon did prepare SpaceX for loosing a lot of vehicles as they go. But the mishap reports seem more painful than loosing a booster.

[CBase]

1 hour ago, Meecrob said:

am I correct in that they are going to transfer fuel from the header tanks to the main tanks or vice versa?

I doubt the header tanks contain 10 metric tons of liquid hydrooxygen. According to multiple sources that is the amount to transfer. More likely something is installed inside payload area.

Edited December 7, 2023 by CBase

[RCgothic]

It won t be Hydrogen. It'll be Oxygen or Methane which is what Starship has onboard already.

[sevenperforce]

52 minutes ago, CBase said:

I doubt the header tanks contain 10 metric tons of liquid hydrogen. According to multiple sources that is the amount to transfer. More likely something is installed inside payload area.

The header tanks contain 6.25 tonnes of liquid methane and 23.75 tonnes of liquid oxygen.

[Ultimate Steve]

53 minutes ago, CBase said:

I doubt the header tanks contain 10 metric tons of liquid hydrogen. According to multiple sources that is the amount to transfer. More likely something is installed inside payload area.

Granted this is from a long time ago and is pulled off of reddit, so accuracy is dubious, but should be in the right ballpark. Non subcooled Lox is 1141 kg/m3, which comes out to 16.6 tons. Non subcooled methane is 8.63kg/m3, so about 8.63 tons.

[Meecrob]

3 hours ago, CBase said:

My point is that they were probably right to go for IFT-1 without the deluge system. Real life testing showed a point where stage 0 simulations missed a critical point. By moving fast to IFT-1 they got the correction early.

Beyond technical issues I guess the biggest change was to adopt risk assessment to align more with goverment oversight. I do think SpaceX attitude to taking risk is beneficial to space industries. Elon did prepare SpaceX for loosing a lot of vehicles as they go. But the mishap reports seem more painful than loosing a booster.

Cool, I'm glad I mis-understood you in that way, it seems we are on the same page!

[Nuke]

i wonder what the feasability of strapping a couple falcon boosters to the sides of superheavy would be (would explain why the grid fins are angled thusly). you might be able to launch a vaccum-engine only version of the tanker. 

[Ultimate Steve]

1 minute ago, Nuke said:

i wonder what the feasability of strapping a couple falcon boosters to the sides of superheavy would be (would explain why the grid fins are angled thusly). you might be able to launch a vaccum-engine only version of the tanker. 

How would it land then with just the vactors?

[Nuke]

5 minutes ago, Ultimate Steve said:

How would it land then with just the vactors?

tanker does not need to land. assuming the tanker is the one that stays in orbit and regular starships are loading it up. technically those could be called tankers to because they would be fitted with tanks. maybe i should have called it an on orbit fuel depot.

Edited December 8, 2023 by Nuke

[StrandedonEarth]

1 hour ago, Nuke said:

i wonder what the feasability of strapping a couple falcon boosters to the sides of superheavy would be (would explain why the grid fins are angled thusly). you might be able to launch a vaccum-engine only version of the tanker. 

I’ve pondered that myself; the biggest issue is that staging happens faster and farther away, making recovery of SuperHeavy more difficult. And to what end? Launching an even heavier payload? I suppose it may be one way to get a nearly-fully-fueled Starship to orbit in one launch, at the expense of a SH

[mikegarrison]

8 hours ago, Meecrob said:

There is no way SpaceX is going bankrupt. They as a single company, outpace all other launchers combined.

I am not saying SpaceX is going bankrupt.

But that being said, the size of the company is no guarantee against going bankrupt. In fact, it can mean you do so quite quickly. Bigger company means more spending means that you can rack up debts even more quickly.

Edited December 8, 2023 by mikegarrison

[Nuke]

giants have tanked before. 

3 hours ago, StrandedonEarth said:

I’ve pondered that myself; the biggest issue is that staging happens faster and farther away, making recovery of SuperHeavy more difficult. And to what end? Launching an even heavier payload? I suppose it may be one way to get a nearly-fully-fueled Starship to orbit in one launch, at the expense of a SH

i was thinking a much larger fuel depo than a standard starship. what you are delivering to orbit is essentially a mostly empty tank with a smaller than usual number of engines, all vacuum rated. a bit more space in the main tanks, maybe some auxiliary pressure fed tankage for stable fuels for sat refueling. whole thing built extremely robust for long term endurance. put them at orbits of interest, leo, near geo, lunar orbit. launch it, send other ships to refuel it, and move it to its final destination under its own power. think of it as a space infrastructure starter kit. 

[Meecrob]

4 hours ago, mikegarrison said:

I am not saying SpaceX is going bankrupt.

But that being said, the size of the company is no guarantee against going bankrupt. In fact, it can mean you do so quite quickly. Bigger company means more spending means that you can rack up debts even more quickly.

Fair enough, I'll concede that you can make any company go bankrupt if you try.  The previous trajectory of SpaceX does not mean their future trajectory will be the same. They could drop the ball at any time hypothetically.

Thanks for keeping me honest, lol. We have enough SpaceX fanboys up in here hahahaha!

Edited December 8, 2023 by Meecrob

[tomf]

2 hours ago, Meecrob said:

Fair enough, I'll concede that you can make any company go bankrupt if you try.  The previous trajectory of SpaceX does not mean their future trajectory will be the same. They could drop the ball at any time hypothetically.

Thanks for keeping me honest, lol. We have enough SpaceX fanboys up in here hahahaha!

A paywalled article on Bloomberg suggests that spacex employees are going to be offered a deal to sell their shares at a total company valuation of 175 billion, so going bankrupt imminently seems unlikely.

[Hannu2]

18 hours ago, Ricktoberfest said:

I think if SpaceX went bankrupt to that extent there’s someone out there willing to buy the rights to falcon 9, at least for the foreseeable future until they all get on the reusable bandwagon. 

Probably. But if some capital investor bought Falcon 9 business, the price of launch would triple immediately and most of benefits of reasonable prices to industry would be lost for several years or even decades. Blue Origin seems to be maximizing profits instead of developing space tech and they would be happy if they could keep prices higher than SpaceX. Other companies need many years to develop large rockets.

[tater]

2 hours ago, tomf said:

A paywalled article on Bloomberg suggests that spacex employees are going to be offered a deal to sell their shares at a total company valuation of 175 billion, so going bankrupt imminently seems unlikely.

https://archive.ph/wasEr

(site that you paste a link and it finds or makes an archive of it: https://archive.ph/)

My 2¢: Any company can fail financially. That said, SpaceX is not about making money to make money, so as long as Musk (and/or like-minded people) are willing to throw money at it for whatever (or no) return it can progress. Their Mars goals are offset by customer revenue clearly, so it only burns cash at whatever the difference is between revenue and dev cost. I recall seeing Starbase costs ~$2B/year, so Musk will run out of money for it in maybe 100 years assuming Tesla completely stalls and ceases growth, and there is no SpaceX revenue above cost for F9 launches. BO has been all-burn for many years, though they have only been spending money in earnest since SpaceX started reuse I think (around the "Welcome to the club" tweet stuff I think). It's a really different dynamic than a, well, "real business" in both cases.

Edited December 8, 2023 by tater

[Ricktoberfest]

1 hour ago, Hannu2 said:

Probably. But if some capital investor bought Falcon 9 business, the price of launch would triple immediately and most of benefits of reasonable prices to industry would be lost for several years or even decades. Blue Origin seems to be maximizing profits instead of developing space tech and they would be happy if they could keep prices higher than SpaceX. Other companies need many years to develop large rockets.

The way I see it going would be for Blue or somebody to buy the rights to Falcon simply as a shortcut for their own rocket. It’s more about the information they’ve learned landing 250 rockets than about the design of it. Im pretty sure that info would be worth a few million. And yes- they would most definitely not keep prices as low. 

[tater]

Falcon 9 being sold off is less likely than SLS being transformed a useful, cost-effective rocket.

[Terwin]

11 hours ago, Nuke said:

i was thinking a much larger fuel depo than a standard starship. what you are delivering to orbit is essentially a mostly empty tank with a smaller than usual number of engines, all vacuum rated. a bit more space in the main tanks, maybe some auxiliary pressure fed tankage for stable fuels for sat refueling. whole thing built extremely robust for long term endurance. put them at orbits of interest, leo, near geo, lunar orbit. launch it, send other ships to refuel it, and move it to its final destination under its own power. think of it as a space infrastructure starter kit. 

Unfortunately, boiloff is not a solved problem.

At the current time, any fuel you take to orbit that is not already allocated to a specific mission with a near-future departure, is basically gone.

Hypergolics are shelf-stable, but do not offer a lot in the way of isp. 

Everything you want to use for interplanetary missions is cryogenic and will be lost if not used quickly.

Just putting a container up there is not terribly useful if you do not yet have a plan for it because it just limits future options(need a special connector or fuel type/ratio?  too bad your pre-launched container does not support that)

[tater]

1 hour ago, Terwin said:

Unfortunately, boiloff is not a solved problem.

Yeah, a shame depots were not tested for years now (thanks, Shelby).

That said there has been a lot of work on them from a theoretical standpoint over the years, so I think it's not impossible to have a solution that works for slightly longer than "quickly." Mitigate boiloff for some number of weeks anyway.