totm nov 2023 SpaceX Discussion Thread

[tater]

 

 

 

[sevenperforce]

2 hours ago, magnemoe said:

you also has a bit of not fully burned fuel who continue to burn in contact with oxygen.

Not to nitpick but there really is no significant amount of unburned propellant which burns outside the combustion chamber.

[insert_name]

looks like the USSF will be getting some OPIR satellites using the starlink bus

https://spacenews.com/spacex-l3harris-win-space-development-agency-contracts-to-build-missile-warning-satellites/

[Shpaget]

On 10/3/2020 at 4:32 PM, sevenperforce said:

Scott Manley pointed out on Twitter that SpaceX consistently has more problems with new boosters than flight-proven boosters.

Would this imply some quality and manufacturing issues, which they fix after scrub?

20 hours ago, sh1pman said:

Not a competitor, lighter class rocket. 12t to LEO.

If Superheavy/Starship can launch for $2M they are competitors, regardless of smaller mass to orbit capability. A customer will hire the cheapest/safest option, regardless of unused capacity.*

*Well, not exactly competitors, since nobody would use the Russian thing anyway.

17 hours ago, RCgothic said:

So far block 5 is doing ok on the refurbs.

Probably won't see 24h turnaround. Still quite a way to go from 50 days to 7-14 though! Also that chart needs updating.

 

 

Reflight in <1 hour, that's impressive, even in Elonverse. Just refueling that thing is a marvel of engineering.

Edited October 7, 2020 by Shpaget

[sh1pman]

17 minutes ago, Shpaget said:

If Superheavy/Starship can launch for $2M they are competitors, regardless of smaller mass to orbit capability. A customer will hire the cheapest/safest option, regardless of unused capacity.*

What does Starship/Super Heavy have to do with what I said? Maybe read what I was replying to.

[Shpaget]

I did read what you posted.

By the time Russia make this thing work, Starship is likely to be operational. As for F9, it is a stepping stone until Starship/SH is ready. Once that is done and flying (and assuming they can hit the cost goal) F9 is going to get retired because there will be no sense in using it any more. As remarkable and industry leading as F9 is, it is going to become obsolete the moment SH becomes operational.

[RealKerbal3x]

SN8's looking frosty...

 

[RCgothic]

Appears that SN8 passed its cryo proof test. Both tanks completely frosted and detanked. Waiting for confirmation.

Edited October 7, 2020 by RCgothic

[RealKerbal3x]

3 minutes ago, RCgothic said:

Appears that SN8 passed its cryo proof test. Both tanks completely frosted and detanked. Waiting for confirmation.

We'll see. If the thrust sim gets disassembled and removed in the morning, we'll know it was successful.

[KSK]

19 minutes ago, RCgothic said:

Appears that SN8 passed its cryo proof test. Both tanks completely frosted and detanked. Waiting for confirmation.

Cool. Really cool.

[zolotiyeruki]

On 10/3/2020 at 9:32 AM, sevenperforce said:

Scott Manley pointed out on Twitter that SpaceX consistently has more problems with new boosters than flight-proven boosters.

Sounds like the Waddington effect to me.

The guy's story is pretty interesting--he and his team looked at how the British were waging war, and pointed out seemingly simple (and sometimes counterintuitive) things that made a big difference.  One of their findings was that bombers had the greatest amount of unplanned maintenance (i.e. things broke) right after their 50-hour overhaul, and had fewer and fewer problems the longer they went from the 50-hour maintenance.  And they told the RAF that the 50-hour maintenance period was too short and caused more problems than it solved.

In essence, what they told the RAF was "if it ain't broke, don't fix it."

[Ultimate Steve]

 

 

[sevenperforce]

Another absolutely gorgeous render from Neopork:

 

7 hours ago, Shpaget said:

As remarkable and industry leading as F9 is, it is going to become obsolete the moment SH becomes operational.

The one area where this remains tricky is human spaceflight. People won't just randomly begin flying without an launch abort system, no matter how reliable Starship seems to be.

4 hours ago, RCgothic said:

Appears that SN8 passed its cryo proof test. Both tanks completely frosted and detanked. Waiting for confirmation.

Beautiful.

[Spaceception]

I wonder if they'll build a new crew variant with no usable payload capacity (beyond personal stuff), but the ability to send up lots of people. This version will have launch abort, and can send people around the world, or to LEO, where they can transfer crew to multiple ships once the regular Starship's have been refueled. It can use the same bottom half Starship config, but the payload will be traded in for a detachable upper section (using the methalox thrusters they have for Lunaship?)

I think the biggest questions for this would be, what will the heatshield be like? And how will it affect landing (would it still be able to use the header tank? I imagine so, but I'm not sure)?

[sevenperforce]

4 minutes ago, Spaceception said:

I wonder if they'll build a new crew variant with no usable payload capacity (beyond personal stuff), but the ability to send up lots of people. This version will have launch abort, and can send people around the world, or to LEO, where they can transfer crew to multiple ships once the regular Starship's have been refueled. It can use the same bottom half Starship config, but the payload will be traded in for a detachable upper section (using the methalox thrusters they have for Lunaship?)

I think the biggest questions for this would be, what will the heatshield be like? And how will it affect landing (would it still be able to use the header tank? I imagine so, but I'm not sure)?

It makes a LOT of sense to have this kind of crew variant, but there are a lot of challenges. For one thing, they can't use the header tank with the gas-gas thrusters.

I had speculated upthread about whether the meth-gox thrusters would use accumulator tanks which also fed tank pressures. I also suggested that if they did use accumulator tanks, they could easily modify the baseline Starship model -- more accumulator tanks for longer on-orbit persistence as well as for the lunar landing version. Such a design would also permit the development of a dedicated launch abort system: throw extra accumulator tanks in the payload section and hook them up to extra meth-gox thrusters. Additionally, because Starship is designed to fly rapidly and reusably, you don't have to worry about your payload section having independent lifeboat capabilities a la Crew Dragon; if there is a non-catastrophic on-orbit failure it is easier to just send up a replacement Starship.

Some problems, however:

• The forward canard-flaps make the payload section aerodynamically unstable. They'd either need to add pop-out grid fins (like the Soyuz LAS) or figure out a different way to feather the canards.
• The separation system becomes a new failure mode -- you really don't want the separation system to fail, but you also don't want it to trigger or otherwise initiate at the wrong time.
• It's nice to not have to worry about lifeboat capability, but will it be able to survive a failure during entry? What if the aft flaps lock up? What if the forward canards lock up?
• One of the really unpleasant failure modes for Starship is an engine relight failure at the moment of the kick-flip. In that situation, you're dropping toward the ground at 60 m/s and firing your LAS would only propel you sideways, not vertically. How do you deal with that?
• What's the landing mode -- giant chutes? Independent thrusters? A gliding splashdown on a steerable chute like the fairing halves?

[tater]

 

[sevenperforce]

2 minutes ago, tater said:

 

Dammit.

Then again, this is why they test.

[cubinator]

1 hour ago, sevenperforce said:

Dammit.

Then again, this is why they test.

Yep. Fix leaks now, walk on Mars later.

[Spaceception]

5 hours ago, sevenperforce said:

• One of the really unpleasant failure modes for Starship is an engine relight failure at the moment of the kick-flip. In that situation, you're dropping toward the ground at 60 m/s and firing your LAS would only propel you sideways, not vertically. How do you deal with that?
• What's the landing mode -- giant chutes? Independent thrusters? A gliding splashdown on a steerable chute like the fairing halves?

If the thrusters can use asymmetric thrust and/or gimbal, can they be used to propel Starship to an upright position? Since this isn't like a solid LAS? Then use the thrusters to land, with backup parachutes (like they originally intended for Dragon 2) in nominal situations.

[sevenperforce]

11 minutes ago, Spaceception said:

If the thrusters can use asymmetric thrust and/or gimbal, can they be used to propel Starship to an upright position? Since this isn't like a solid LAS? Then use the thrusters to land, with backup parachutes (like they originally intended for Dragon 2) in nominal situations.

Gimbal won't be enough to do the trick under abort circumstances, but differential thrust might. There's a bit of a dV problem. Of course, with a landing failure, you don't need quite as much dV.

Full-envelope abort for Starship would have quite a few different modes:

• Pad Abort. Triggered by S2 failure before launch. Needs high thrust to be clear of the fireball; needs to boost far enough to be clear of pad debris; needs reliable landing mode.
• Max-Q Abort. Triggered by S2 failure at approximately Mach 1. Needs high thrust to be clear of the fireball; needs reliable landing mode.
• Terminal Abort. Triggered by S2 failure outside of atmosphere. Needs passively-stable re-entry capability; reliable landing mode.
• Entry Abort. Triggered by heat shield or aft flap failure during re-entry. Needs high thrust to be clear of debris, passively-stable re-entry capability, reliable landing mode.
• Landing Abort. Triggered by aft flap failure or relight failure. Needs highly controllable thrust to clear debris, reorient, and boost far enough to be clear of impact debris; needs reliable landing mode.

 

Then the landing mode impacts more stuff. If you're going to be using chutes, then you have to make sure your landing abort boosts you high enough to use them properly. If you're going to be using thrusters, that means more dV. 

My guess is that a severed forward payload compartment with the canards folded halfway would be passively stable in the correct orientation for re-entry, but I don't know for sure. You certainly don't want it to lawn dart. 

[RCgothic]

Err, what...

Lighting 28 Raptors with twice the thrust of Saturn V without a flame diverter is an interesting choice...

 

A few weeks for highbay and superheavy stacking.

 

[RealKerbal3x]

SN8 cryo proof #2 complete. I hope the leak they fixed held up.

 

Edited October 8, 2020 by RealKerbal3x
Link didn't embed

[RCgothic]

Apparently successful. But so was last time!

[sevenperforce]

15 hours ago, RCgothic said:

Lighting 28 Raptors with twice the thrust of Saturn V without a flame diverter is an interesting choice...

I mean, I suppose if you have ENOUGH water pouring out at the bottom then you should be okay. The Saturn 1B was high enough on the milkstool that its interaction with the flame diverter was minimal.

Spoiler

Obviously the flame diverter was still there and so we see the plume coming out, but by that time the rocket is already well off the pad.

 

 

4 hours ago, RCgothic said:

Apparently successful. But so was last time!

We're waiting on Word of Elon again, I guess.

[RealKerbal3x]