Jump to content

SpaceX Discussion Thread


Recommended Posts

 

For early cislunar plans, and before Starship is something that NASA would send crew on...

Link to post
Share on other sites

If they lofted a SS where the nose mostly came off, and the SS was NOT for reuse on Earth, so it had no wings/legs, they could send a large cargo in the fairing. The front of the cargo has a docking port, and the cargo includes an upper stage in the 100t mass. Refilling happens, and other cargos are launched which dock to the ferry SS cargo. It sends the whole mass to TLI, and the upper stage component does the LOI.

The abbreviated SS has just enough of the belly fairing that stays with it that it is capable of aerobraking back into LEO.

Link to post
Share on other sites

What are the logistics of double orbital refuel? With SS and SH using (superchilled) LOX, they need to launch all three rockets roughly at the same time to minimize LOX boiling away (or is that negligible in vacuum?). How long does the orbital fuel transfer take? Can all three rockets be hooked up at the same time? Do they need to perform it at slight acceleration? Can I have a cookie? What sort of ullage motors do they have on SH? How much would the orbit change due to prolonged ullage acceleration during fuel transfer?

Link to post
Share on other sites

From 100km LEO, SS/SH can send 30 to 50 tonnes to TLI with a hypergolic kick stage.

Apropos of nothing:

Starship-Apollo-CSM.png

The Apollo CSM/LM fits inside a Starship shroud. With a little bit of LM leg optimization it fits the other way up without needing the 22m version.

Not that this is a sensible architecture. But drop the capsule, enlarge the service module with +110t of propellant and rendezvous with a Dragon 2 launched on a falcon 9...

Edited by RCgothic
Link to post
Share on other sites
1 hour ago, Shpaget said:

What are the logistics of double orbital refuel? With SS and SH using (superchilled) LOX, they need to launch all three rockets roughly at the same time to minimize LOX boiling away (or is that negligible in vacuum?). How long does the orbital fuel transfer take? Can all three rockets be hooked up at the same time? Do they need to perform it at slight acceleration? Can I have a cookie? What sort of ullage motors do they have on SH? How much would the orbit change due to prolonged ullage acceleration during fuel transfer?

no, the orbital refuelling is not that hard, at least not the part of the boiloff, in the vacuum is not that big of a problem, especially when your propellent is highly pressurized. Orbital refuelling should happen butts-to-butts, only a pair at the time. They will do it with little poof of trust, but we don't know how much time it will be needed. The centre raptor, who can steer, have from what i have seen some stupid amount of vector control ( 15-19° if i'm not mistaken)

Link to post
Share on other sites
4 hours ago, Wjolcz said:

Wasn't ACES supposed to basically be this except with hydrogen instead of methane? 

ACES is a great idea, but it still sits on top of an expendable launch vehicle, and some of the ACES is used to achieve LEO. So you launch ACES, then refill ACES with another ACES, which is then disposed of. You now have a full ACES in LEO, which can act as a tug to do all kids of cool things, but it literally cost 2X getting ACES to LEO (including 2X hardware) to get it there. The payload is a third launch. Assume they get launches really cheap for ULA, like 80M$ a pop.

So for $240,000,000 you can send something like a B330 to lunar orbit (ULA/Bigelow proposed just that, but the total cost was a couple billion, so maybe I'm lowballing launch costs).

The first SS gets to LEO with a much bigger cargo than a B330, more like the B2100 (an SLS-sized expandable hab). Let's say the same B330 hab. The SS with 1 refilling can easily take the B330 not just to TLI, but can deliver it, and come back given the 77t of residual props. So for well under the cost of the single ACES launch, the thing is already delivered to the Moon (possibly multiple times cheaper than a single ACES launch).

Refilling is everything, but the "tanker" needs to be 100% reusable, or ridiculously cheap.

Link to post
Share on other sites
7 hours ago, Flavio hc16 said:

no, the orbital refuelling is not that hard, at least not the part of the boiloff, in the vacuum is not that big of a problem, especially when your propellent is highly pressurized.

Still no cryo orbital refueling ever happened irl.
Even no significant hypergolic one.
1-2 t of UDMH/NTO, nothing more.

Redistribution of mass can cause problems, redistribution of heat also can. And all that under +100 / -100 °C variation every 1.5 hours due to the absence of air thermal capacity.

Link to post
Share on other sites
On 4/12/2020 at 7:57 PM, tater said:

Refilling is everything, but the "tanker" needs to be 100% reusable, or ridiculously cheap.

Yes, even in KSP this becomes obvious. Refueling (even with KSP magic physics) is almost never worth the cost of launching the tanker, unless you can recover the tanker with very little cost. Disposable tankers are only good for when you launch some ridiculous interplanetary ship and you use the ship's own engines to achieve orbit (so you then need to refill their tanks before burning for another planet).

Link to post
Share on other sites
6 minutes ago, mikegarrison said:

Yes, even in KSP this becomes obvious. Refueling (even with KSP magic physics) is almost never worth the cost of launching the tanker, unless you can recover the tanker with very little cost. Disposable tankers are only good for when you launch some ridiculous interplanetary ship and you use the ship's own engines to achieve orbit (so you then need to refill their tanks before burning for another planet).

I suppose the only caveat is that for some missions you might need a ship bigger than you can launch (in a world with no refilling), and refilling, even if not really cost effective might possibly give you capabilities you wouldn't otherwise have. Of course you could also make the payload of the expendable LVs just full tanks of whatever size, and "fill" the larger spacecraft via docking tanks.

Regardless, this really needs to be a thing, be it Starship, or even something much smaller like Skylon.

Link to post
Share on other sites
Quote

SN26

21 more skipped?

***
"Spaceballs", the final countdown. (from memory)

"9... 8... 6..."
"Where's 7?!"
"Just joking. 5... 4..."

Edited by kerbiloid
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...