totm nov 2023 SpaceX Discussion Thread

[magnemoe]

39 minutes ago, kerbiloid said:

ICBM needs 25..30 min to make a 90..120° flight.

Standard ICBM throw high as in they have an pretty high Ap at multiple 1000 km, this because of most effective burn of 45 degree, good time to deploy warheads to widely spaced targets and short time in atmosphere on reentry minimizing the errors in trajectory because of atmosphere.  
This will not work for starship as g load will be too high. Same reason starliner centaur upper stage need two engines and facon 9 need to land on an barge even if could do RTLS with the payload, you want an shallow trajectory on manned missions because aborts and landings. 
ICBM are moving towards low Ap too but here because the long ballistic trajectory in orbit get to easy to intercept with modern ABM. 

[SOXBLOX]

1 hour ago, tater said:

FWIW, there are a couple (?) Chinese companies making F9 clones, as well as Arianespace.

^Newline-1

 

^Arianespace

 

These have rocket engines, grid fins, and overglorified unfolding table legs. None of these ideas are original. And remember, Blue Origin filed a patent for landing rockets on barges a few years before SpaceX tried it. So please, don't accuse people of cloning the Falcon.

 

1 hour ago, mikegarrison said:

We've previously discussed the many complications of commercial point-to-point travel that Elon is either overlooking or downplaying. I'm not sure it's worth going through them yet again.

Exactly. Beating conventional air travel will be tough. Elon likes to build up hype about these things; it's just his style. Hasn't hurt him yet, because if something like this doesn't pan out, he's got something else to cover with.

[cubinator]

1 minute ago, SOXBLOX said:

So please, don't accuse people of cloning the Falcon.

We'll call it "convergent evolution" then. Don't fix what ain't broke.

[kerbiloid]

9 minutes ago, magnemoe said:

Standard ICBM throw high as in they have an pretty high Ap at multiple 1000 km, this because of most effective burn of 45 degree

The most delta-V efficient trajectory, not 45°, depends on actual range.

9 minutes ago, magnemoe said:

This will not work for starship as g load will be too high.

Yes, a short-range SLBM trajectory. Requires much greater delta-V, so is several times shorter, time ~10..15 min range 1 000..2 000 km.

So, the P2P flight is either much shorter than "everywhere", or much longer than "30 min".

***

Shuttles do this longer.

https://aviation.stackexchange.com/questions/21981/how-does-the-space-shuttle-slow-down-during-re-entry-descent-and-landing

Edited June 24, 2020 by kerbiloid

[magnemoe]

3 minutes ago, kerbiloid said:

The most delta-V efficient trajectory, not 45°, depends on actual range.

Yes, a short-range SLBM trajectory. Requires much greater delta-V, so is several times shorter, time ~10..15 min range 1 000..2 000 km.

So, the P2P flight is either much shorter than "everywhere", or much longer than "30 min".

Looks like you are right ICBM stays high LEO, its the drawings who was messed up. 

[CatastrophicFailure]

Came across this:

Looks like they’re fabbing panels for the bigger VAB. 

Closer view:

 

[tater]

1 hour ago, SOXBLOX said:

These have rocket engines, grid fins, and overglorified unfolding table legs. None of these ideas are original. And remember, Blue Origin filed a patent for landing rockets on barges a few years before SpaceX tried it. So please, don't accuse people of cloning the Falcon.

Not DC-X legs. Not New Shepard legs, F9 legs. Grid fins have been a round a while, but not on VTVL rocket designs before. Before DC-X there were a lot of VTVL/VTHL designs out there. None looked like F9. https://www.pmview.com/spaceodysseytwo/spacelvs/sld001.htm has a few.

Blue Origin lost their patent dispute with SpaceX, so apparently it was not new to them, either. There were academic papers from the 90s pitching the same idea.

Bottom line is that while BO was interested in this, so certainly it was not unique to SpaceX, someone needed to do it first before others would copy it (down to the black interstage in the case of the Chinese).

 

 

Edited June 24, 2020 by tater

[mikegarrison]

31 minutes ago, tater said:

Not DC-X legs. Not New Shepard legs, F9 legs. Grid fins have been a round a while, but not on VTVL rocket designs before. Before DC-X there were a lot of VTVL/VTHL designs out there. None looked like F9. https://www.pmview.com/spaceodysseytwo/spacelvs/sld001.htm has a few.

Blue Origin lost their patent dispute with SpaceX, so apparently it was not new to them, either. There were academic papers from the 90s pitching the same idea.

Bottom line is that while BO was interested in this, so certainly it was not unique to SpaceX, someone needed to do it first before others would copy it (down to the black interstage in the case of the Chinese).

Based on past history, I would not at all be surprised if it turns out that China has all the manufacturing CAD data for Falcon 9. They are among the world's best at "borrowing" computer files.

Or that could just be a render that is based on seeing pictures of Falcon 9.

[tater]

It's a smaller vehicle than F9, but I think it's obvious that the success of F9 enables "fast followers" (or "not so fast followers" in the case of Arianespace). Early VTVL ideas seem to be wider and more capsule like. The Bono designs (and some of the others) with plug engines, and regenerative cooling of the whole bottom. The Boeing LEO design (always loved that) looked like a huge capsule. Anyone trying to land a booster would likely take F9 as a starting point.

 

[RCgothic]

Too little over 15y too late. The competitor isn't F9. The target is Starship.

Edited June 24, 2020 by RCgothic

[magnemoe]

22 minutes ago, tater said:

Not DC-X legs. Not New Shepard legs, F9 legs. Grid fins have been a round a while, but not on VTVL rocket designs before. Before DC-X there were a lot of VTVL/VTHL designs out there. None looked like F9. https://www.pmview.com/spaceodysseytwo/spacelvs/sld001.htm has a few.

Blue Origin lost their patent dispute with SpaceX, so apparently it was not new to them, either. There were academic papers from the 90s pitching the same idea.

Bottom line is that while BO was interested in this, so certainly it was not unique to SpaceX, someone needed to do it first before others would copy it (down to the black interstage in the case of the Chinese).

Its reusable rocket time: SpaceX has shown it work and its an winner so you copy them. 
Steam engine time is an term https://www.noahbrier.com/archives/2011/11/steam-engine-time/ however its flawed, the idea of an steam engine is old https://en.wikipedia.org/wiki/Timeline_of_steam_power
However the first commercial successful steam engine was Newcomen atmospheric engine, now all know steam engines worked so lets improve it. 
Newcomen engines main benefit was that it used vacuum not over pressure, this way it would not blow up the safety valve was not developed yet. Engine was however inefficient and could only be use close to coal mines so it was easy to improve.

History repeat itself. However Falcon 9 is an very good rocket. yes it has some weaknesses like the heavy upper stage hurt its GTO and deep space capabilities compared to 2.5 stage rockets. However FH fixes this. 
Starship, well you did not bring your ironclad into an battleship fight but an carrier fight.
In short plan for second stage reuse out you are out as commercial operator.

Yes countries like Israel and Brazil has an space program for NRO as none of them can tie up to an block for this. Brazil is easiest and less controversial. 
Brazil has interest and concerns in Central America who differ from the current US president who flip every 8 year, worse the same party might have candidates with very different view on their Central America policy as its an sideshow.
But Brazil can not alley with Russia or China as they are too linked with the US. 
An separate space program is an option. 

10 minutes ago, RCgothic said:

Too little over 15y too late. The competitor isn't F9. The target is Starship.

Yes you are an ironclad in an carrier fight

[tater]

 

Static fire!

 

[RCgothic]

9 hours ago, magnemoe said:

History repeat itself. However Falcon 9 is an very good rocket. yes it has some weaknesses like the heavy upper stage hurt its GTO and deep space capabilities compared to 2.5 stage rockets. However FH fixes this. 

Falcon's upper stage isn't a weakness. FUS is an incredible stage. It develops more DV than even Centaur for any mass of payload. It's arguably the best upper stage ever developed bar none due to its amazing mass fraction.

If Falcon 9 has a weakness it's that the first stage stages low and slow which means the second stage is starting from a handicapped position. FUS really needs a larger 1st stage. But it's staging low and slow that enables its killer capability of reuse, so it's not easy to fix without losing that.

The partially expendable and expendable FH modes do largely fix that, you're right, at the cost of losing the core stage.

Edited June 25, 2020 by RCgothic

[RealKerbal3x]

Figured out how to embed tweets! Apparently you have to paste it as plain text.

[RCgothic]

I love how the high bay is suddenly being called the mid bay because there's a higher bay under construction!

[RealKerbal3x]

Just now, RCgothic said:

I love how the high bay is suddenly being called the mid bay because there's a higher bay under construction!

They need to build a helipad on top of the new high bay and land Starship on it

[RCgothic]

SpaceX haven't tweeted out confirmation of a successful static fire, which is worrying for today's mission. It's usually done quite quickly after the test.

Edited June 25, 2020 by RCgothic

[RealKerbal3x]

4 minutes ago, RCgothic said:

SpaceX haven't tweeted out confirmation of a successful static fire, which is worrying for today's mission. It's usually done quite quickly after the test.

Huh. Elon hasn't tweeted any info on SN7's pressure test either.

[RCgothic]

5 minutes ago, RealKerbal3x said:

Huh. Elon hasn't tweeted any info on SN7's pressure test either.

I would have thought it must have improved on last time, as it failed in a different place?

But yup, no confirmation there yet either.

[SOXBLOX]

4 hours ago, RCgothic said:

Falcon's upper stage isn't a weakness. FUS is an incredible stage. It develops more DV than even Centaur for any mass of payload. It's arguably the best upper stage ever developed bar none due to its amazing mass fraction.

If Falcon 9 has a weakness it's that the first stage stages low and slow which means the second stage is starting from a handicapped position. FUS really needs a larger 1st stage. But it's staging low and slow that enables its killer capability of reuse, so it's not easy to fix without losing that.

The partially expendable and expendable FH modes do largely fix that, you're right, at the cost of losing the core stage.

Uhhhhh, pretty sure Centaur beats it on high orbits and escape trajectories. SpaceX won't touch hydrolox, it's too difficult for them.

And yes, if China can hack the F35 program, then yes, they have the plans for Falcon. They probably have the Merlin schematics, too, but they can't build it. It is a well -known fact that the US possesses more advanced metallurgical techniques than China.

Another reason for the success of SpaceX. They don't spend on security.

[tater]

59 minutes ago, SOXBLOX said:

Uhhhhh, pretty sure Centaur beats it on high orbits and escape trajectories. SpaceX won't touch hydrolox, it's too difficult for them.

So you have to throw the FH away to beat most DIVH launches—which throws the DIVH away, too. For >2X the cost.

https://elvperf.ksc.nasa.gov/Pages/Default.aspx

The trouble for F9/FH at the site above is that recovery is all cores I think on FH, and I presume downrange for F9. The lack of 3 stages downrange as an option probably lowballs the payload mass for "recovery." Course it's cheaper even expended.

[tater]

 

[RCgothic]

1 hour ago, SOXBLOX said:

Uhhhhh, pretty sure Centaur beats it on high orbits and escape trajectories. SpaceX won't touch hydrolox, it's too difficult for them.

Yes, but not thanks to Centaur or DCSS being better than FUS. Centaur and DCSS light higher and faster than F9US so they don't have to do as much work. That's thanks to DIVH and AtlasV.

F9US has at least 4.4km/s more DV than DCSS and Centaur for any mass of payload between 0t and 16t. F9US does more work than the second stage of any other operational rocket.

 

SpaceX don't have any reason to do hydrolox.

Would their first stage be improved by hydrolox? No. It couldn't get off the pad without boosters.

Would the second stage be improved? No. The extra insulation would reduce the mass fraction more than the ISP gains.

Edited June 25, 2020 by RCgothic

[tater]

 

[RCgothic]

Sure is busy at the Cape!

At first I thought this was a retest of yesterday, but no, different mission.

Edited June 25, 2020 by RCgothic