totm nov 2023 SpaceX Discussion Thread

[mikegarrison]

4 hours ago, tater said:

Huge rockets are nothing new at all:

*Real* huge rockets, on the other hand....

(And no, this thing we are talking about is not yet real either.)

Edited August 30, 2019 by mikegarrison

[CatastrophicFailure]

5 hours ago, tater said:

Huge rockets are nothing new at all:

What’s that thing above the C-5, left of the shuttle? RHOMBUS? Looks like a great big aerospike... uses it as a heat shield on reentry? Then stubby wings for some control to a vertical landing? MOAR BOOSTERS! optional?

[tater]

56 minutes ago, mikegarrison said:

*Real* huge rockets, on the other hand....

Well, yeah, obviously not REAL, but certainly seriously considered by people who knew their business well enough (or just Nova, had LoR not become the route to the moon).

Yeah, that's ROMBUS (no h in the rocket name). 450 tons to LEO.

Plug engine.

 

[magnemoe]

Why will they not do more testing with the hopper but jump to starship? 
After all they don't mind loosing the hopper much while loosing any of the starships will set them back quite a bit. 

Yes the hopper is set up for the old engine layout while statship has its 3 surface engines in an triangle around center so engine handling will be different. 

[CatastrophicFailure]

1 minute ago, magnemoe said:

Why will they not do more testing with the hopper but jump to starship? 
After all they don't mind loosing the hopper much while loosing any of the starships will set them back quite a bit. 

Yes the hopper is set up for the old engine layout while statship has its 3 surface engines in an triangle around center so engine handling will be different. 

SpaceX already has the whole VTVL thing down pretty good, they arguably have a better understanding of it than anyone else in the industry right now. What they don’t have is flight data on reentry and descent on their unprecedented plan of doing so. There’s probably not a whole lot more they could learn from Hoppy, that’s why the first Starship test will be all the way to the edge of space and back— that remains the big unknown. Once Starship is back down low and going butt-first on a pillar of fire, that’s actually the easy part. 

[kerbiloid]

7 hours ago, tater said:

Huge rockets are nothing new at all:

The rightmost in the middle row even existed.

[tater]

No matter where this hurricane hits it's gonna be messy, but the track now shows it pretty far South, which for this forum is good news after a fashion (less impact on KSC, and the various launch providers).

[MinimumSky5]

It might still be quite bad. Winds and storm surges tend are worst on the northern edge of hurricanes, as the hurricanes motion adds to the local wind velocity. 

[Nothalogh]

3 hours ago, CatastrophicFailure said:

Once Starship is back down low and going butt-first on a pillar of fire, that’s actually the easy part.

I just remembered, there was an abortively developed SSTO project of the DARPA and Company, that was actually going to EDL more or less how Starship is supposed to.

https://en.wikipedia.org/wiki/McDonnell_Douglas_DC-X

[Wjolcz]

3 hours ago, Nothalogh said:

I just remembered, there was an abortively developed SSTO project of the DARPA and Company, that was actually going to EDL more or less how Starship is supposed to.

https://en.wikipedia.org/wiki/McDonnell_Douglas_DC-X

I've heard somewhere that people from that project work with SpaceX now. Delta Clipper was pretty cool. It's a shame it had one minor failure that got it cancelled. Also, it was designed to be SSTO from the start, so wasn't going to happen anyway.

Edited August 30, 2019 by Wjolcz

[tater]

https://www.spacex.com/smallsat

Quote

Dedicated ESPA Class Missions as low as $1M

SpaceX’s SmallSat Rideshare Program will provide small satellite operators with regularly scheduled, dedicated Falcon 9 rideshare missions to sun synchronous orbit (SSO) for ESPA class payloads for as low as $1M per mission, which includes up to 200 kg of payload mass.

Monthly now, price to 1M for 200kg. Price also dropped.

 

[Nothalogh]

9 hours ago, Wjolcz said:

one minor failure that got it cancelled

It was politics that got it cancelled.

DC-X was DARPA and McDonnel-Douglas, VentureStar was NASA and Lockmart

9 hours ago, Wjolcz said:

I've heard somewhere that people from that project work with SpaceX now.

That would not surprise me

[tater]

 

[Aegolius13]

The ignition issue with Starhopper on Monday got me wondering - how does ignition on a preburner vs. combustion chamber work?  Do they separately ignite them both?  In a certain order?  I would have thought that in a closed-cycle engine, if the preburner was going,  the hot exhaust might be able to light the main chamber without a separate ignition source.  Though perhaps not in a FFSC design where the exhausts are getting mixed in with all the extra fuel/oxidizer, and presumably getting cooled substantially.

[sh1pman]

42 minutes ago, Aegolius13 said:

The ignition issue with Starhopper on Monday got me wondering - how does ignition on a preburner vs. combustion chamber work?  Do they separately ignite them both?  In a certain order?  I would have thought that in a closed-cycle engine, if the preburner was going,  the hot exhaust might be able to light the main chamber without a separate ignition source.  Though perhaps not in a FFSC design where the exhausts are getting mixed in with all the extra fuel/oxidizer, and presumably getting cooled substantially.

Raptor engine has 3 igniters, one for each preburner and one for the main combustion chamber. Every igniter is also double-redundant. I’m not sure about the order, but it makes sense to first ignite the preburners, and then the combustion chamber.

 

[satnet]

1 hour ago, Aegolius13 said:

The ignition issue with Starhopper on Monday got me wondering - how does ignition on a preburner vs. combustion chamber work?  Do they separately ignite them both?  In a certain order?  I would have thought that in a closed-cycle engine, if the preburner was going,  the hot exhaust might be able to light the main chamber without a separate ignition source.  Though perhaps not in a FFSC design where the exhausts are getting mixed in with all the extra fuel/oxidizer, and presumably getting cooled substantially.

I know this isn't the Raptor, but Scott Manley did a detailed video on the F-1 engine startup procedure that was pretty interesting.

 

 

[tater]

Guess I was right...

 

[Brotoro]

That tent thingie is really hurricane-proof?

i guess we'll see.

[Ultimate Steve]

3 minutes ago, Brotoro said:

That tent thingie is really hurricane-proof?

i guess we'll see.

I really hope we don't lose more starship hardware to wind...

[kerbiloid]

9 hours ago, Nothalogh said:

19 hours ago, Wjolcz said:

I've heard somewhere that people from that project work with SpaceX now.

That would not surprise me

That had surprised me. 2019-1970s = 40+ years, and these people obviously were not students in that time.
So, probably they are 70..80 years old now, and it has grown 2 generations of engineers since then (40/20).

Edited August 31, 2019 by kerbiloid

[tater]

55 minutes ago, kerbiloid said:

That had surprised me. 2019-1970s = 40+ years, and these people obviously were not students in that time.
So, probably they are 70..80 years old now, and it has grown 2 generations of engineers since then (40/20).

DC-X was in the 1990s.

[kerbiloid]

Oops, then OK.

[Aegolius13]

13 hours ago, sh1pman said:

Raptor engine has 3 igniters, one for each preburner and one for the main combustion chamber. Every igniter is also double-redundant. I’m not sure about the order, but it makes sense to first ignite the preburners, and then the combustion chamber.

 

Thanks.  Makes sense they'd have to also light the preburners.  Guess this is one of the (probably many) reasons FFSC is tricky enough no one's flown one before. 

 

Not that this is probably ever going to happen, but the Hopper success makes me wonder -- if, hypothetically, SpaceX decided to make an expendable version of SH and a simplified Raptor-based second stage, how much more time / money would that take?  Seems like we more or less know Raptor works, assuming (1) that orange flame was not a major problem, (2) the interaction of multiple of Raptors won't pose new problems, N-1 style, and (3) they can air-start the upper stage.  Making structures and tanks out of steel seems almost trivial based on what's happened to date.  The big challenges remaining with the official program seem like propulsive landing and heat shielding, but those wouldn't apply to a hypothetical expendable system.

As far as cost, I think Everyday Astronaut estimated that Raptors cost $2 million each, with the price hopefully coming down due to mass manufacture.  The steel stuff is very cheap per Elon. The fuel is very cheap.  So even if you threw the whole thing away, a simplified version of the whole thing should cost, maybe, one or two hundred million dollars?  

The nub of my question is, as you might expect, how much more would SpaceX have to do to have a working rocket that matches or beats SLS in performance at a far lower cost?  (Putting aside political issues, of course).  

Final thought - in the spirit of Bridenstein Kerballing Orion on top of Falcon Heavy, if you were able to put an RL10 or BE-3 powered third stage on top of this hypothetical rocket, that seems like an awful lot of delta-v for something like Europa Clipper.

[linuxgurugamer]

1 hour ago, Aegolius13 said:

) that orange flame was not a major problem

According to @EJ_SA, it was a major problem.  I dont remenber the details, but something broke and it fell the last 5 feet to the ground.

[sevenperforce]

18 hours ago, Aegolius13 said:

The ignition issue with Starhopper on Monday got me wondering - how does ignition on a preburner vs. combustion chamber work?  Do they separately ignite them both?  In a certain order?  I would have thought that in a closed-cycle engine, if the preburner was going,  the hot exhaust might be able to light the main chamber without a separate ignition source.  Though perhaps not in a FFSC design where the exhausts are getting mixed in with all the extra fuel/oxidizer, and presumably getting cooled substantially.

There's no extra fuel/oxidizer; that's why it's a Full Flow Staged Combustion cycle. Something like 90% of the LOX and 10% of the CH4 runs into the oxidizer preburner; something like 10% of the LOX and 90% of the CH4 runs into the fuel preburner. Then 100% of both exhaust flows is routed into the combustion chamber, so you have a purely gas-gas reaction in the chamber, leading to very high efficiency. All of the propellant goes through either one preburner or the other.

Now, they may do film cooling injection with a very small amount of still-liquid fuel, but as far as I know the cooling is purely regenerative, by looping the propellant through the engine nozzle and chamber walls.

Despite the high preburner temperatures, you don't reliably reach autoignition temperatures for the mixed exhaust flows, and so you use a separate igniter. The dual-redundant igniters are not purely spark igniters; rather, they are spark plugs used to ignite a gas-gas torch fed from the autogenous pressurization tapoff. The mixed preburner exhaust hits the torch flame and, well, kablooey.