totm nov 2023 SpaceX Discussion Thread

[JoeSchmuckatelli]

1 hour ago, tater said:

NSF posted this (bocachicagal):

Looks like these renders are pretty close:

 

Okay - excuse my ignorance please - but clearly there are tiles applied to the body - but when I reenter in KSP, the stuff sticking out from the body seems to get hotter than the main body (and blow off) - so why do we not see (or apparently need) tiles on the control surfaces? 

[magnemoe]

1 hour ago, tater said:

NSF posted this (bocachicagal):

Looks like these renders are pretty close:

 

It looks like they have dropped the raceways between lower and upper fin mount, I thought it was needed for piping for return lines and gas for pressurization. 
You need this even for the top header tank. 
They should also help with making the LOX tank more rigid and probably help by creating an clear cutoff for the area needing heat tiles. 

10 minutes ago, JoeSchmuckatelli said:

Okay - excuse my ignorance please - but clearly there are tiles applied to the body - but when I reenter in KSP, the stuff sticking out from the body seems to get hotter than the main body (and blow off) - so why do we not see (or apparently need) tiles on the control surfaces? 

They will have tiles on the flaps, its just not added to the 3d model yet, this is not an official model by the way. 

[Meecrob]

1 hour ago, JoeSchmuckatelli said:

Okay - excuse my ignorance please - but clearly there are tiles applied to the body - but when I reenter in KSP, the stuff sticking out from the body seems to get hotter than the main body (and blow off) - so why do we not see (or apparently need) tiles on the control surfaces? 

The flaps will get hot, but that's ok, similar to Falcon 9's grid fins. Its the main body that is critical for temperature control as it contains all the pressure vessels, sensitive electronics, etc. When comparing with KSP, remember that parts in KSP are some random "space-grade" pseudo material probably similar to aluminum or CFRP, and Starship is steel. I forget which STS mission it was, perhaps the first flight after Challenger, where some tiles came off similar to Columbia. The orbiter made it back in one piece because the tiles just happened to be protecting a bit of steel structure. The steel was able to absorb the re-entry heat and maintain strength. Having said that, I'm sure everybody collectively crapped their pants when they did the post flight inspection.

Additionally, I recall the re-entry profile for Starship will be shallower such that it spends more time at high temperature, but the peak temperature will be much lower than more conventional re-entries.

Edited to add: I'm not saying there will not be tiles on the flaps - I have no info on that. I was trying to explain why KSP behaves differently

Edited October 12, 2020 by Meecrob

[RCgothic]

There will definitely be tiles on the hot side of the flaps.

 

 

[RCgothic]

 

 

[cubinator]

Would SN8 be capable of a 100 km hop?

[Cuky]

 

Edited October 12, 2020 by Cuky

[RCgothic]

20 minutes ago, cubinator said:

Would SN8 be capable of a 100 km hop?

I think so. Once you've got engine relight and the landing manoeuvre sorted the limiting factor becomes thermal protection.

You'd need a heat shield for a return from LEO, but not from 100km straight up.

I'd be willing to bet SN8 could come in faster and hotter than an F9 first stage.

Edited October 12, 2020 by RCgothic

[CatastrophicFailure]

Front-end flippy-flap stubs spotted in the wild:

 

1 hour ago, RCgothic said:

I think so. Once you've got engine relight and the landing manoeuvre sorted the limiting factor becomes thermal protection.

You'd need a heat shield for a return from LEO, but not from 100km straight up.

I'd be willing to bet SN8 could come in faster and hotter than an F9 first stage.

Assuming it survives that long (my money’s against it), with three Raptors how much fuel could SN8 realistically carry? Enough for 100km? How bout a downrange-then-boostback like said first stage?

[tater]

Terminal velocity for a sideways SS is what it is. When it gets into thick air I think it's closer to 70 m/s (~250 kph, or 0.2Mach).

[RCgothic]

Assuming a TWR of 1.2 with 0 payload, 120t dry mass, 210t thrust per Raptor and an average ISP of 340:

SN8 would have 395t of propellant and 4.9km/s of DV.

F9 first stage with 15.8t payload and 116t second stage on top has about 3km/s DV.

 

But I don't really think this is a test they'll actually perform!

Edited October 13, 2020 by RCgothic

[Flying dutchman]

54 minutes ago, RCgothic said:

Assuming a TWR of 1.2 with 0 payload, 120t dry mass, 210t thrust per Raptor and an average ISP of 340:

SN8 would have 395t of propellant and 4.9km/s of DV.

F9 first stage with 15.8t payload and 116t second stage on top has about 3km/s DV.

 

But I don't really think this is a test they'll actually perform!

Only 4.9 km/s of dv? I really don't see Them doing point tot point with those nummers, or even getting tot Orbit with no payload when on top of super heavy.

 

Edit: the prop load is twr limited in this case...

Edited October 13, 2020 by Flying dutchman

[RCgothic]

1 hour ago, Flying dutchman said:

Only 4.9 km/s of dv? I really don't see Them doing point tot point with those nummers, or even getting tot Orbit with no payload when on top of super heavy.

 

Edit: the prop load is twr limited in this case...

Yes, SN8's propellant is limited by only having 3 engines and the requirement to get off the pad. Add 3 fixed thrust-optimised raptors instead of vacuum raptors blanks and that's another 750t of propellant (1150 total) it can carry.

~8km/s DV with 0 payload and 120t dry mass.

 

That's ballpark P2P2Anywhere, but I'd expect any suborbital version to either *not* have range to anywhere on the planet, or to have more than six engines. Starship can comfortably fit nine sea level raptors.

Edited October 13, 2020 by RCgothic

[sevenperforce]

20 hours ago, RCgothic said:

 

How exactly did the shuttle solve this problem? The rudder was completely in the leeward side of the vehicle during re-entry but the aft control surface seams experienced some of the highest heat fluxes anywhere on the vehicle.

17 hours ago, CatastrophicFailure said:

Front-end flippy-flap stubs spotted in the wild:

 

Squid fins!!

[tater]

TPS is a long pole issue. Will be interesting to watch iterative testing on orbital EDL.

[sevenperforce]

32 minutes ago, tater said:

TPS is a long pole issue. Will be interesting to watch iterative testing on orbital EDL.

My best guess is that we see an overlap joint where the TPS on the fixed skin/chine extends out a few feet to cover the seam, leaving a gap.

It's going to be difficult for them to get Starship anywhere close to orbital speeds without achieving full orbit, too, because they need to get back to Boca Chica. They can't do a half-speed EDL because that would put the Starship landing zone off the coast of Africa. And I doubt Starship would have enough dV for a sufficiently high-energy boostback.

[magnemoe]

2 hours ago, sevenperforce said:

My best guess is that we see an overlap joint where the TPS on the fixed skin/chine extends out a few feet to cover the seam, leaving a gap.

It's going to be difficult for them to get Starship anywhere close to orbital speeds without achieving full orbit, too, because they need to get back to Boca Chica. They can't do a half-speed EDL because that would put the Starship landing zone off the coast of Africa. And I doubt Starship would have enough dV for a sufficiently high-energy boostback.

Thought the same the fixed part overlap the flap on the hot side, unlike the shuttle you are not trying to make an lifting surface. 
Coming strait down might be an better stress test than jumping the Atlantic. 
 

[tater]

 

[mikegarrison]

3 hours ago, sevenperforce said:

My best guess is that we see an overlap joint where the TPS on the fixed skin/chine extends out a few feet to cover the seam, leaving a gap.

It's going to be difficult for them to get Starship anywhere close to orbital speeds without achieving full orbit, too, because they need to get back to Boca Chica. They can't do a half-speed EDL because that would put the Starship landing zone off the coast of Africa. And I doubt Starship would have enough dV for a sufficiently high-energy boostback.

This raises yet another interesting issue regarding abort modes.

[sevenperforce]

1 hour ago, magnemoe said:

Thought the same the fixed part overlap the flap on the hot side, unlike the shuttle you are not trying to make an lifting surface. 

But you have really bad heat flux on the fixed overlapping zone.

1 hour ago, magnemoe said:

Coming strait down might be an better stress test than jumping the Atlantic. 

Stress test, yes. But it's not a good heat shield test. You need horizontal velocity for that.

42 minutes ago, mikegarrison said:

This raises yet another interesting issue regarding abort modes.

Eh, I doubt it. From t₀ to t₁, Starship does a boost-back to a landing zone at Boca Chica. From t₁ to t₂, Starship does either boost-forward or boost-back to a landing zone at the Cape. From t₂ to t₃, Starship does a boost-forward to a landing zone in Africa. After t₃, Starship does an abort-once-around (AOA) to Boca Chica. The t₂..t₃ period may not be necessary; Starship may have enough dV to AOA after crossing t₂.

1 hour ago, tater said:

 

IT'S HAPPENING

Interesting that the squid fins do NOT appear to have a lateral edge parallel to the rest of the vehicle, as in Neopork's fan renders.

 

[tater]

See the tip of the nose? The 2 bands above the band where the fin fairing is? ~4.68m (guestimate) diameter. Those 2 rings easily fit the Apollo CM inside them. The Orion capsule would fit withthe base even with a point just above the flap fairing top.

Starship is insane.

[SOXBLOX]

Look at this site's new article on SpaceX.

I mean, c'mon. USTRANSCOM wants Starship P2P to deliver cargo?!?!? Good grief. 

The author speculates about a ballistic insertion of a cargo capsule, rather than a hot landing. Off-loading vehicles or cargo from SS won't be easy in rugged environments. Capsule would be easier.

My questions:

Can SS off-load at the destination fast enough to offset its advantage over the C-17? If so, how cost effective is it?

What kind of infrastructure is needed at the destination, if SS lands? (Note: if this is a peer-state warzone, it won't be flying again. 'Cause BOOM!) How feasible is a cargo capsule released from orbit? It would have to deorbit itself, right? IDK if SS can deorbit the capsule, and then push its periapsis up again.

If infrastructure is required at the endpoint, then SS becomes considerably less useful. If it requires a spaceport, and those are at select locations, then what good did we do? Now the cargo has to move over conventional transport routes. Easier to hit, and slower than a non-stop C-17.

Besides the RIM-161 SM-3 and GBMD, what systems could intercept SS, especially on a theatre scale?

What kind of self-protection suites and decoys could be put on Starship to make it survivable? Maybe something along the lines of ICBM terminal-phase decoys, coupled with EW suites?

What would need to be transported so rapidly that we have to fly it by Starmail? What kind of payload can this grain silo move without SH? Can't move an Abrams without special mounting options, to stand the Abrams on its rear end so it *maybe* fits in the fairing. That also makes it really tough to drop it in a capsule; not much room left, right?

So, can anyone tell me why this is a good idea?

Edited October 14, 2020 by SOXBLOX

[magnemoe]

10 hours ago, sevenperforce said:

But you have really bad heat flux on the fixed overlapping zone.

Stress test, yes. But it's not a good heat shield test. You need horizontal velocity for that.

Eh, I doubt it. From t₀ to t₁, Starship does a boost-back to a landing zone at Boca Chica. From t₁ to t₂, Starship does either boost-forward or boost-back to a landing zone at the Cape. From t₂ to t₃, Starship does a boost-forward to a landing zone in Africa. After t₃, Starship does an abort-once-around (AOA) to Boca Chica. The t₂..t₃ period may not be necessary; Starship may have enough dV to AOA after crossing t₂.

IT'S HAPPENING

Interesting that the squid fins do NOT appear to have a lateral edge parallel to the rest of the vehicle, as in Neopork's fan renders.

 

An wrapping around the hinge as seen in render might solve it, as you say it will be an heat spot but it will protect the hinge. You can not have this on the other side as it will stop you from folding back the fins nor is it needed on the back.

 

[mikegarrison]

3 hours ago, SOXBLOX said:

So, can anyone tell me why this is a good idea?

I doubt that it is.

Most civilian cargo is carried by ship and train because it's amazingly cheap and cargo often doesn't care when it gets where it is going. Time-sensitive packages are carried by airplane, but there is not much advantage to carrying them any faster because they can already be delivered overnight. The real trick is the "last mile" -- getting them to and from the airport quickly and doing all the sorting and tracking.

Certain high-value, low weight items are worth shipping by plane just because of the inventory cost. This actually includes airplanes themselves -- both Boeing and Airbus ship airplane parts by airplane.

And a lot of cargo flies as belly freight. Passengers are paying for the flight, but there is space in the hold so might as well send some cargo too.

I don't think Starship P2P is a real thing anyway, but there isn't a lot of cargo that would be so time-valuable that it would be better shipped by sub-orbital missile than by airplane. (Except, of course, for nuclear weapons, which are the traditional payload for sub-orbital P2P missiles.)

Transporting some kind of rapid-response military force by rocket sounds like a possibly useful idea (and it was thought up back in the 60s), but it has drawbacks. One of them is that there is no way that's going to be a stealth insertion, and often it wouldn't be worth sending a few hundred soldiers anywhere that fast unless it can be stealthy.

Let's say, however, that you had something like a Dragon that could land safely at an airfield. Your main air defense radar at a large base goes dead and you need a part right now. You put it into this Dragon, launch it, and land the capsule at your forward air base an hour later. Part delivered. The capsule can later be flown back in the hold of an airplane like a C-17 or C-5 or 747. This kind of delivery of very important people or equipment is maybe the only thing I can think of using this for, but what does a Falcon 9 launch cost? $60M? Even if it's only half that, that better be a *really* vital payload.

Edited October 14, 2020 by mikegarrison

[RCgothic]

Gorgeous: