totm nov 2023 SpaceX Discussion Thread

[RealKerbal3x]

I found this on Google:

Of course, this assumes that Starship 2.0 keeps the same height to diameter ratio, which is unlikely, but it's kind of cool to see that an 18m diameter rocket is almost in league size-wise with the Enterprise

[tater]

https://spacenews.com/spacex-says-more-starlink-orbits-will-speed-service-reduce-launch-needs/

[tater]

 

The wiki says 330 for SL, 380 vac. Looks like it needs an edit.

With a rough minimum dv required for LEO at 9400 m/s, if SS is 85 tonnes dry, and 1300 wet, it's just shy of SSTO---assuming you use the SL I_sp to do the calculation. The first couple km/s, however is below 100km (up to ~2.1km/s).

If we use SL for that regime, and 380s for the bit above 2100m/s, we get a total dv above 10,000s.

[CatastrophicFailure]

9 minutes ago, tater said:

The wiki says 330 for SL, 380 vac. Looks like it needs an edit.

I’ll see that & raise you...

 

And also:

 

[tater]

The extra few seconds I_sp always help, but he said extremely difficult to optimize.

Still,  20s bump at SL is non-trivial.

[tater]

 

[Ultimate Steve]

Ah, so they are going poodle with Raptor.

Edit: unless dual bell means that kinked nozzle and not two bells.

Edited September 9, 2019 by Ultimate Steve

[NSEP]

Elon is on a twitter spree?

Let the infomania begin! Some juicy facts!

 

 

[tater]

18 minutes ago, Ultimate Steve said:

Edit: unless dual bell means that kinked nozzle and not two bells.

I think this means like the Merlin vacuum engine. There is a bell extension bolted on.

MVac on the right, without the extension ^^^.

 

The extension^^^.

[sevenperforce]

4 hours ago, Ultimate Steve said:

Ah, so they are going poodle with Raptor.

Edit: unless dual bell means that kinked nozzle and not two bells.

Unless Elon is using wildly imprecise terminology, dual bell means there will be a convex inflection point in the bell which produces controlled flow separation. Pioneered here:

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940018584.pdf

[tater]

18 minutes ago, sevenperforce said:

Unless Elon is using wildly imprecise terminology, dual bell means there will be a convex inflection point in the bell which produces controlled flow separation. Pioneered here:

He's been known to use imprecise terms before, but yeah, certainly possible (though never shown in previous renders of BFR/ITS/SS before).

Cool link, BTW. Seems like it makes more sense for a sustainer architecture than TSTO, however, as the Vacuum Raptors won't even fire until the thing is around 100km alt anyway.

You should ask him, maybe you'll get an Elon reply tweet

 

[CatastrophicFailure]

I shall follow this particular thread with great interest. 

[sh1pman]

Even if Raptors can be used as LES, it won’t help if Starship itself blows up.

[tater]

18 minutes ago, sh1pman said:

Even if Raptors can be used as LES, it won’t help if Starship itself blows up.

That's true for any abort system, though.

[sh1pman]

14 minutes ago, tater said:

That's true for any abort system, though.

Most abort systems detach the capsule and quickly remove it from the danger zone of exploding engines, fuel tanks or SRBs (unless it’s a Space Shuttle, no such luxury there). With Starship there’s no way to get out if something catastrophic happens to second stage engines or tanks.

(I’m not paranoid, it’s probably not important if Starship indeed reaches the airliner-level reliability)

Edited September 9, 2019 by sh1pman

[Wjolcz]

6 minutes ago, sh1pman said:

Most abort systems detach the capsule and quickly remove it from the danger zone of exploding engines, fuel tanks or SRBs (unless it’s a Space Shuttle, no such luxury there). With Starship there’s no way to get out if something catastrophic happens to second stage engines or tanks.

Just like it is with planes.

Now, I'm not saying Starship will ever be as reliable or safe as an airliner but passengers aren't handed parachutes when stepping onboard, are they?

Reusable must equal reliable.

Edited September 9, 2019 by Wjolcz

[sh1pman]

1 minute ago, Wjolcz said:

Just like it is with planes.

Now, I'm not saying Starship will ever be as reliable or safe as an airliner but passengers aren't handed parachutes when stepping onboard, are they?

Nope, that’s why I updated my post.

[tater]

Alternately, early (all?) crew versions pack the crew into the nose, and the whole nose becomes an escape pod (chutes).

I tend to think of it as a LEO/cislunar vehicle, the whole Mars thing makes little sense to me. That said, if you drink that koolaid, then launch is the least of your problems. If you could convince me to become a Mars colonist I'd be far more worried what my colleagues taste like (not raw, cooked!) when we are forced to eat each other to survive on Mars than what my chances of a quick, humane death in a launch explosion might be.

Edited September 9, 2019 by tater

[sh1pman]

22 minutes ago, tater said:

Alternately, early (all?) crew versions pack the crew into the nose, and the whole nose becomes an escape pod (chutes).

I tend to think of it as a LEO/cislunar vehicle, the whole Mars thing makes little sense to me. That said, if you drink that koolaid, then launch is the least of your problems. If you could convince me to become a Mars colonist I'd be far more worried what my colleagues taste like (not raw, cooked!) when we are forced to each each other to survive on Mars than what my chances of a quick, humane death in a launch explosion might be.

Hmm. I see how an irreparably broken hydroponic farm may be a much, MUCH worse disaster than a plain old launch failure. The latter doesn’t force you to do unthinkable things.

[tater]

 

[CatastrophicFailure]

3 hours ago, sh1pman said:

Hmm. I see how an irreparably broken hydroponic farm may be a much, MUCH worse disaster than a plain old launch failure. The latter doesn’t force you to do unthinkable things.

One reason why, as Elon recently noted, they’ll be sending two ships at once. 

Which of course I can’t find again. So here’s confirmation that Starship will also be used as a Venusian blimp. 

First one to say something about the Hindenburg gets a dirty look. 

[tater]

Dunno about the travel aspect, I just meant a group of people replicating the Martian (until they realize they need, you know, protein).

[tater]

 

 

[CatastrophicFailure]

2 hours ago, tater said:

Dunno about the travel aspect, I just meant a group of people replicating the Martian (until they realize they need, you know, protein).

Well, I mean, like, they are doing, er... fascinating things with lab-grown meat these days... 

Quote

Pd of Operation: Oct 13, 2019...

Quote

- Apr 13, 2020

...oh. Ok, but still...

My mind remains boggled that they seem to be targeting 20+km for the very first flight of this thing... 

I suppose that's a big advantage of having two prototypes in the line, and being quick and cheap to build more... they can afford to risk losing one without it being a huge blow to the program.

[tater]

2 minutes ago, CatastrophicFailure said:

I suppose that's a big advantage of having two prototypes in the line, and being quick and cheap to build more... they can afford to risk losing one without it being a huge blow to the program.

"Cheap." (for you and me, for a rocket... yeah, cheap)

I was trying to estimate costs on a Starship prototype. Say they have 100 people working at $100,000/yr (incl benis, etc) on each. Dunno what materials costs are, cheap, but non-trivial, say it costs as much as the labor. That's 20 million. When did the orbital prototypes first get noticed? Spring? FL has parts lying around for SH (and since SS/SH pretty much has to fly from FL...). I could be off by more than a factor of 2, and they could still likely build both SS prototypes, AND one SH in about a year for around 100 M$.