totm nov 2023 SpaceX Discussion Thread

[ThatGuyWithALongUsername]

4 hours ago, Wjolcz said:

We will see a silo fly!

DON'T SAY THAT OUT LOUD

WHAT ARE YOU DOING

[RealKerbal3x]

2 hours ago, tater said:

 

Won't the propellant tanks have slosh baffles, or is that not an issue?

[tater]

1 minute ago, RealKerbal3x said:

Won't the propellant tanks have slosh baffles, or is that not an issue?

Yeah, it's some guy's render, I suppose he's basing it on what they have seen. Course when we see vids of rings flipping, no baffles...

[SOXBLOX]

Ugh. Starship again. What would we launch with it? Does it have any use? I mean, I'm all for colonizing space, but this isn't the way to go, in my opinion.

 

[Wjolcz]

10 minutes ago, SOXBLOX said:

What would we launch with it?

Nothing. It's impossible.

10 minutes ago, SOXBLOX said:

Does it have any use?

No.

10 minutes ago, SOXBLOX said:

I mean, I'm all for colonizing space, but this isn't the way to go, in my opinion.

You're right. What is it then?

Edited April 27, 2020 by Wjolcz

[Dirkidirk]

21 minutes ago, SOXBLOX said:

What would we launch with it?

I guess that you haven't watched their promotional vid. big thing on bottom is superheavy.

21 minutes ago, SOXBLOX said:

Does it have any use?

without superheavy, It wouldn't be able to do anything. but with superheavy It will be able to do everything another rocket could do, cheaper and bigger. 

21 minutes ago, SOXBLOX said:

I mean, I'm all for colonizing space, but this isn't the way to go, in my opinion.

ok.

Edited April 27, 2020 by Dirkidirk

[sh1pman]

17 minutes ago, Wjolcz said:

You're right. What is it then?

SLS/Orion.

 

 

 

 

 

 

[Spaceception]

38 minutes ago, SOXBLOX said:

Ugh. Starship again. What would we launch with it? Does it have any use? I mean, I'm all for colonizing space, but this isn't the way to go, in my opinion.

 

It'll tell you right here what it can do https://www.spacex.com/starship

We could launch massive payloads in excess of 100 tons, while all others can't do more than 30 (except Falcon Heavy, another SpaceX rocket), and the only other ones that can are still in development like Starship/Superheavy.

This rocket is meant to be fully reusable, and refuelable in space. Honestly, if we're to begin colonizing space in the near/mid-future, this is probably the best and cheapest option we have. And if Mars doesn't work out, they could always shift gears to early O'Neil cylinders and Lunar extraction.

Beyond their Mars ambitions, we could pull off larger probe and telescope launches (much more science and exploration) that don't really have to worry about cramming as many experiment into as little of a craft as possible. It would have the ability to send up large modules for space stations, and as mentioned, even for ones which can produce artificial gravity (which would be harder to pull off now). And they could drop off Lunar payloads for NASA or themselves which could open up the ability for a large base.

Edited April 27, 2020 by Spaceception
Laying off the snark

[sevenperforce]

The more I watch the Starship updates the more it feels like Elon is playing real-life KSP. "Oh, that part wasn't strong enough? Revert and swap it out with a stronger adapter. Did it work? Okay, now back to the VAB, add fins, and try again."

32 minutes ago, SOXBLOX said:

Ugh. Starship again. What would we launch with it? Does it have any use? I mean, I'm all for colonizing space, but this isn't the way to go, in my opinion.

Well, sending comsats to GTO is the biggest source of space-related revenue right now.

With Starship we could launch 10 tonne comsats to GTO for under $10m per launch.

And on each launch we can co-manifest five more equal-sized comsats, if we want, at no additional cost. Or not, because the cost is so low that it doesn't matter.

[tater]

I know it's a troll, but we're on lockdown, what else is there to do?

37 minutes ago, SOXBLOX said:

Ugh. Starship again. What would we launch with it?

Pretty much everything, if it works. If It flies, and cargo Starship (the second stage) is operationally reusuable (even if orbital refueling is not a thing), then it literally obviates every other launch vehicle on the planet for almost all non-human payloads.

There might still be a market for smallsat launchers if cheap enough to bespoke orbits if SS works. Except that you could skip the smallsat bit, and add props to get from whatever SS rideshare orbit was to target orbit, anyway, so it kills smallsat launchers as well I bet.

 

37 minutes ago, SOXBLOX said:

Does it have any use?

See above, huge up mass, cheaper by an order of magnitude that anything else. All other LV providers either copy it, or become weird anachronisms. IF it works.

 

37 minutes ago, SOXBLOX said:

I mean, I'm all for colonizing space, but this isn't the way to go, in my opinion.

By all means, what's the way to go that is different?

[RCgothic]

Indeed.

Without refuelling and *expending* the second stage, Starship Superheavy is twice SLS's payload for less cost than a Falcon 9.

With a reusable second stage you might as well call it Dreadnought because every other booster just became completely obsolete outside extremely niche applications.

Even for those: Smallsat to weird orbit? Add more propellant to your sat and rideshare from somewhere more popular. Probe to high C3? Lift an entire fully fuelled Super-Centaur kick stage and watch your probe overtake Voyager2.

With in-flight refuelling? There's nowhere in this solar system it can't go.

Edited April 27, 2020 by RCgothic

[Flavio hc16]

50 minutes ago, RCgothic said:

With a reusable second stage you might as well call it Dreadnought because every other booster just became completely obsolete outside extremely niche applications.

this is probably the best "one liner " explanation about starship i have ever seen.

It simply makes every other rocket irrelevant

[tater]

 

[Wjolcz]

3 minutes ago, tater said:

 

Such telescopes could probably be cheaper too since they could have solid mirrors like Hubble and be overbuilt in general.

Edited April 27, 2020 by Wjolcz

[Nightside]

2 hours ago, sevenperforce said:

The more I watch the Starship updates the more it feels like Elon is playing real-life KSP. "Oh, that part wasn't strong enough? Revert and swap it out with a stronger adapter. Did it work? Okay, now back to the VAB, add fins, and try again."

Maybe he couldn't get RO to work on his computer. If it was easier to install we might not have SpaceX.

 

What % of SpaceX revenue comes from YouTube ads?

Edited April 27, 2020 by Nightside

[RCgothic]

14 hours ago, RCgothic said:

Lift an entire 149t kick stage and watch your probe overtake Voyager2.

I stated this a bit flippantly, but:

Voyager 2 has ~15km/s. Escape velocity from its current position is ~4km/s. Velocity at infinity is therefore ~11km/s.

Earth has 30km/s. In LEO you have roughly 8km/s. A 149t Raptor-powered kick stage with a similar tank fraction to Falcon9US could give ~11km/s to an 825kg Voyager replica. Solar escape velocity from earth orbit is ~42km/s, so you'd end up with 7km/s at infinity, just 4km/s short.

You can easily pick up 4km/s with a single gas giant flyby. Pick up 6km/s and you can overhaul Voyager 1!

And with orbital refuelling to get into an extreme elliptical you may not even need the flyby!

Edited April 28, 2020 by RCgothic

[magnemoe]

1 hour ago, RCgothic said:

Indeed.

Without refuelling and *expending* the second stage, Starship Superheavy is twice SLS's payload for less cost than a Falcon 9.

With a reusable second stage you might as well call it Dreadnought because every other booster just became completely obsolete outside extremely niche applications.

Even for those: Smallsat to weird orbit? Add more propellant to your sat and rideshare from somewhere more popular. Probe to high C3? Lift an entire fully fuelled Super-Centaur kick stage and watch your probe overtake Voyager2.

With in-flight refuelling? There's nowhere in this solar system it can't go.

Think Rocketlab thinking about this, they are combining the kick stage into an satellite buss who will also control the rocket, standard second stage has their own flight system, saw an interview with him, and he found it wasteful that second stage is in practice an satellite, carrying an second smaller satellite who is the payload. As their pumps is electrical powered the engines are cheap. 

And yes Dreadnought might be a bit to week an therm. yes it was an good ship but put three good pre-dreadnoughts against her and she would loose, yes she could also run but might give the enemy an victory. 
Ironclad might be an better analogy, you brought an gun to an sword fight, see the action of Merrimack until it was countered the other Ironclad, monitor. 

And yes starship would change everything about space launches. And yes Musk is obviously playing RL KSP, that is the other mad thing here, this thing is not only reusable but also cheap to build. 
I say its only weakness is that second stage high weight make it less suitable for GEO or farther missions without refueling .
However an idea of mine is an reusable 3rd stage / tug, something like an centaur vacuum only stage who go from LEO into GEO or other orbits including lunar injection, add an disposable version for deep space missions. 
But you can top this up with flagship, launch an starship with two extra stages, an empty 3rd stage with an single raptor and a 4rd probably hypergolic braking and insertion stage, You fuel up the starship and 3rd stage in orbit, starship does it burn, it can not however raise Ap very high as its now carry around 500 ton payload, but it then release 3rd stage who do the rest of the burn. 
Start planning you mission around this  Europa ocean sample return is a hint. Oumuamua intercept is another one, that thing is weird. 

[tater]

14 minutes ago, magnemoe said:

I say its only weakness is that second stage high weight make it less suitable for GEO or farther missions without refueling .

It still gets like 20t to GEO with no refilling, for some fraction of a F9 launch in costs.

[RCgothic]

Interestingly - for a 150t kick stage with very low payload, there's almost nothing to choose between Centaur hydrolox and Raptor methalox. Centaurs's ISP advantage is almost exactly balanced by worse mass fraction. Both manage about 10.5km/s.

But Raptor would be smaller, have a higher structural rigidity, and generally be less finicky. Plus no replumbing the pad for hydrolox!

[tater]

If SS/SH works (is reusable), then the only LVs that have any utility at all will be those launching crew vehicles. If SS ever gets crew capability (this is a long, long pole, IMHO), then there's no reason for anything else unless someone comes up with another 100% reusable LV that is equally capable per dollar of cost (or better).

All of the existing launch providers need a Plan B, and soon. They can count on SS/SH failing, which is literally betting their companies on their competitor failing. The competitor that is already beating them.

NG is Blue's entry, and per Bezos the smallest orbital rocket they will ever build. If SS works, NA will have to be either like SS, or designed for full orbital reuse. Orbital depots make the most sense if the supply vehicle (Earth—>LEO) is 100% reusable, though. A world with functional SS makes that a reality—assuming your delivery vehicle is SS. If that's not something Blue wants to pay SpaceX for... not so much.

If I was an extant launch provider that isn't SpaceX, I'd seriously consider leveraging SpaceX as a Plan B. Forget launch, and work on spacecraft, instead. ULA simply can't compete, no way to innovate fast enough. They could instead make giant ACES tugs, and refill via Starship (have a hydrolox tank as cargo). Maybe one of the other players could work with NASA on NTP.

Arianespace? Guess they can launch the payloads their governments will mandate use their expensive, legacy vehicles.

Roscosmos? Ditto Arianespace, plus Soyuz crew vehicles.

China? They will likely copy SS as soon as it demonstrates itself. And I mean immediately after it works, or even shows it's likely to work.

[magnemoe]

5 minutes ago, RCgothic said:

Interestingly - for a 150t kick stage with very low payload, there's almost nothing to choose between Centaur hydrolox and Raptor methalox. Centaurs's ISP advantage is almost exactly balanced by worse mass fraction. Both manage about 10.5km/s.

But Raptor would be smaller, have a higher structural rigidity, and generally be less finicky. Plus no replumbing the pad for hydrolox!

Thought Centaur had better mass faction, as raptor was a bit overkill for this note an kick stage would be centaur design.
However methalox would not only give an less fuel lines. You have the option to drain the tanks for an RTLS abort option if you loose engines. 
Yes starship even on caro missions has far more abort modes than the shuttle. Not very happy with it having no abort system for manned missions but for unmanned this is very nice. 

[RCgothic]

Centaur has rubbish mass fraction due to its tank insulation. About 9% dry.

Taking F9 US (4t), removing the MVac gives a tank structure of 3.5t. Scale up 111t propellant to 148t means 32% more tank. Methalox 900kg/m3 vs kerolox 1085kg/m3 means 20% extra tank. So 5.6t for tanks, plus 1.2t for Raptor is 6.8t. 4.6% dry.

Actually I'd forgotten to remove the Merlin before factoring earlier. So that pops the Raptor stage ahead to 11km/s with a 1t payload vs 10.7km/s for Super-Centaur.

Much shorter burn time too due to higher TWR.

Edited April 27, 2020 by RCgothic

[magnemoe]

2 minutes ago, tater said:

If SS/SH works (is reusable), then the only LVs that have any utility at all will be those launching crew vehicles. If SS ever gets crew capability (this is a long, long pole, IMHO), then there's no reason for anything else unless someone comes up with another 100% reusable LV that is equally capable per dollar of cost (or better).

All of the existing launch providers need a Plan B, and soon. They can count on SS/SH failing, which is literally betting their companies on their competitor failing. The competitor that is already beating them.

NG is Blue's entry, and per Bezos the smallest orbital rocket they will ever build. If SS works, NA will have to be either like SS, or designed for full orbital reuse. Orbital depots make the most sense if the supply vehicle (Earth—>LEO) is 100% reusable, though. A world with functional SS makes that a reality—assuming your delivery vehicle is SS. If that's not something Blue wants to pay SpaceX for... not so much.

If I was an extant launch provider that isn't SpaceX, I'd seriously consider leveraging SpaceX as a Plan B. Forget launch, and work on spacecraft, instead. ULA simply can't compete, no way to innovate fast enough. They could instead make giant ACES tugs, and refill via Starship (have a hydrolox tank as cargo). Maybe one of the other players could work with NASA on NTP.

Arianespace? Guess they can launch the payloads their governments will mandate use their expensive, legacy vehicles.

Roscosmos? Ditto Arianespace, plus Soyuz crew vehicles.

China? They will likely copy SS as soon as it demonstrates itself. And I mean immediately after it works, or even shows it's likely to work.

NG should be able to do second stage reuse, it has enough payload to sacrifice some for this on most missions. Falcon 9 was too small for this outside smallsats. 
Rocketlab might manage to get out out of this, they are already focusing on satellite buses who also run the rocket. 
China having an sputnik moment and like the US did back then uses turbopumps to pump in enough money to catch up. 
This has an ripple effect even if starship fails. 

For the others either you adapt or you get used to be an 3rd rate launch provider like Israel or Brazil. Both want NRO capabilities without reeling on others as in who president is in the white house and how much they like you. 
No its not economical viable but warships has lost money  before the end of piracy and at an time warships start evolving fast both in capability and cost. 
 

[sevenperforce]

Something y'all might like...

Over in the "Build a Better Saturn V" thread, I just posted a link to a spreadsheet I created that will let you play rocket legos with a three-stage moon rocket. It also holds a wealth of information about mass fractions, engine weights and performance, different kinds of drag, and the like. Here it is. It led me to some interesting discoveries about Raptor vs hydrolox for high-energy launches...

47 minutes ago, magnemoe said:

Thought Centaur had better mass faction, as raptor was a bit overkill for this note an kick stage would be centaur design.

Hydrolox for a first-stage engine has a bulk density of up to 363 kg/m^3. On an upper-stage engine you want it to run more fuel-rich so it is more like 344 kg/m^3 (that's the RL-10C-2 with its otherwise-impressive 466 s of isp). Compare to subcooled methalox at 903 kg/m^3 and dramatically higher T/W.

24 minutes ago, RCgothic said:

Centaur has rubbish mass fraction due to its tank insulation. About 9% dry.

Taking F9 US (4t), removing the MVac gives a tank structure of 3.5t. Scale up 111t propellant to 148t means 32% more tank. Methalox 900kg/m3 vs kerolox 1085kg/m3 means 20% extra tank. So 5.6t for tanks, plus 1.2t for Raptor is 6.8t. 4.6% dry.

Actually I'd forgotten to remove the Merlin before factoring earlier. So that pops the Raptor stage ahead to 11km/s with a 1t payload vs 10.7km/s for Super-Centaur.

Much shorter burn time too due to higher TWR.

What he said.

50 minutes ago, tater said:

If SS/SH works (is reusable), then the only LVs that have any utility at all will be those launching crew vehicles. If SS ever gets crew capability (this is a long, long pole, IMHO), then there's no reason for anything else unless someone comes up with another 100% reusable LV that is equally capable per dollar of cost (or better).

If SS/SH works well enough that crewed orbital destinations are cheap, I think we might have a good business case for a small, rapidly reusable crew SSTO shuttle (or perhaps one that uses drop tanks) with fractions for full-envelope launch abort. That would be delightful. 

EDIT: Re that spreadsheet...

...iIf anyone has suggestions for other engines to add, let me know. I limited it to large engines that are currently (or will soon be) in use on American launch vehicles, but I can go back and add the F-1 for reference or others for comparison.

Edited April 27, 2020 by sevenperforce
question

[RCgothic]

8 minutes ago, sevenperforce said:

Something y'all might like...

Over in the "Build a Better Saturn V" thread, I just posted a link to a spreadsheet I created that will let you play rocket legos with a three-stage moon rocket. It also holds a wealth of information about mass fractions, engine weights and performance, different kinds of drag, and the like. Here it is. It led me to some interesting discoveries about Raptor vs hydrolox for high-energy launches...

Hydrolox for a first-stage engine has a bulk density of up to 363 kg/m^3. On an upper-stage engine you want it to run more fuel-rich so it is more like 344 kg/m^3 (that's the RL-10C-2 with its otherwise-impressive 466 s of isp). Compare to subcooled methalox at 903 kg/m^3 and dramatically higher T/W.

What he said.

I used some of your numbers as a reference. ;-)