Bimfred

This is why I always feel a little guilty when I'm leaving on a trip. For my cat, this house and myself are her entire world. And if I disappear, for however long, due to reasons she can't even begin to fathom, it must be confusing and stressful for her.

Which is why I give her scritches and kisses every time I go to work, and tell her that I love her. And if she wants attention when I'm home, no matter what I'm doing, she gets at least an acknowledgement that I see her, I hear her, and I care about her.

That would make things worse, because now you're carrying the extra mass of fuel, tanks, plumbing and engines for the descent. Can't run a rocket engine on two different types of fuel and oxidizer.

The rocket equation is a harsh mistress. As long as you're limited to chemical rockets, you're not gonna have enough spare propellant for a powered descent. The energy density just isn't there. We don't do direct burns to pretty much anywhere farther than Mars and a Mars Hohmann transfer (the most fuel-efficient trajectory) burn takes ~3.6km/s. Less than half of LEO velocity.

Tanking up a satellite to extend its lifetime is quite a different beast from tanking up a whole-ass second stage for a powered descent. You're looking at hundreds of tons of cryogenic liquid fuel and an enormous vehicle. For context, a Starship carrying no cargo has about 8km/s of delta-V.^1^ That's with 1500 tons of LOX and liquid methane. That's barely enough to lose the orbital velocity. Assuming that prop load doesn't include the header tanks (but it does), a fully tanked up Starship could maybe pull off a powered descent and landing from LEO. And that thing is huuuuge.

1: I ran the numbers for a block 2 Starship and came out with 11km/s of delta-V. That sounds like too much, so I'm going to assume I got the math wrong and go with the latest "official" numbers I could find.

I don't see a way to make powered descent work while we're still bringing fuel from dirtside. There's just no point, cause we can't lift enough fuel to bring down one vehicle, let alone two (the tanker and whatever it's loading up). A second stage with more than 7.8km/s of delta-V is going to be absolutely massive, as long as we're using chemical rockets. Electric engines don't work for a powered descent, they don't have enough thrust.

A capsule design will likely never be fully reusable, since it doesn't allow you to shield the second stage engine(s), propellant tanks and anything else that usually goes in the trunk section. For a fully reusable design, you need to go with either a spaceplane or whatever it is that we're calling the Starship's cylinder-with-control-surfaces design.

EDIT: Looked into Stoke's design a little more. It's a fascinating idea and I will be looking forward to test launches!

There's one more option - propulsive re-entry. You point your big engines retrograde and burn until your velocity is effectively zero, then descend on a <1g burn. Won't need heat shields if you don't have to endure re-entry heat. But this ain't happening until we develop ludicrously more efficient high thrust engines and orbital fuel production.

Preface: I'm no rocket surgeon.

Wish they weren't scribbling off SpaceX's design so hard. It's entirely possible that examining the conditions and dynamics of re-entry would lead to a very Starship-like design in the end, but there's merit in exploring the possibilities. Especially since this is supposed to be a smaller vehicle, so it won't be experiencing the same exact conditions as Starship at any stage of flight. Fingers crossed that it really is just a render for publicity and the actual design will be informed by physics, not FOMO.

But it certainly puts a smile on my face to see ESA gradually pulling its head out of its ass and realizing that reusability isn't a fad.

What power do you have when there's no one to subject to it?

ISS's radiators. It's processing data on the station that would otherwise be transmitted groundside and processed here.

BDSM dommy mommies

17cm/s seems awful low. Is that its speed relative to Didymos?

Your math ain't inherently wrong though. Without strapping a torch drive on that thing it ain't going anywhere.

There's also Santa is sick of your shit.

People can write all manner of stuff, but until someone tries, no one has a definitive answer. That's why SpaceX is doing these launches, to figure out how to build a spacecraft that can actually handle that heat. The last three flights have been such a bummer cause none of them have given actual data on the redesigned forward flaps and the various heat shields.

I wouldn't count Starship out yet. People also wrote all manner of stuff about Falcon 9's first stage reusability and at this point, it's safe to say everyone who thought it wouldn't work has been proven wrong.