totm nov 2023 SpaceX Discussion Thread

[sevenperforce]

1 hour ago, wumpus said:

The landing sequence (with crew) looks far, far worse.  I suspect they will be returning in dragons at least until 2030 (possibly modified for landing on land).

Yeah, if the skydive-kick-flip-burn maneuver was backup (for low-altitude aborts or something), that would be one thing. Making it the baseline landing mode just seems scary.

[sh1pman]

11 minutes ago, sevenperforce said:

Yeah, if the skydive-kick-flip-burn maneuver was backup (for low-altitude aborts or something), that would be one thing. Making it the baseline landing mode just seems scary.

Seems scary for us. Who knows, after 100th landing it may become normal and mundane. Like Falcon 9 landings.

[mikegarrison]

52 minutes ago, sh1pman said:

Seems scary for us. Who knows, after 100th landing it may become normal and mundane. Like Falcon 9 landings.

Do Falcon 9 landings seem mundane to you?

(Also, I have to admit that no matter how many times I have flown, when an airplane that I'm in lands, it never quite feels "mundane".)

Edited June 8, 2020 by mikegarrison

[RealKerbal3x]

59 minutes ago, sevenperforce said:

Yeah, if the skydive-kick-flip-burn maneuver was backup (for low-altitude aborts or something), that would be one thing. Making it the baseline landing mode just seems scary.

 

45 minutes ago, sh1pman said:

Seems scary for us. Who knows, after 100th landing it may become normal and mundane. Like Falcon 9 landings.

 

2 minutes ago, mikegarrison said:

Do Falcon 9 landings seem mundane to you?

(Also, I have to admit that no matter how many times I have flown, when an airplane that I'm in lands, it never quite feels "mundane".)

On some YouTube video I saw about Starship, someone in the comments mentioned how scary its landing maneuver looks, and someone else responded with an interesting analogy - if you showed someone from the early 20th century a video of a 747 landing, they would probably think it looked terrifying. But nowadays, an aircraft like that landing is regarded as completely normal and safe. It'll be the same for Starship - we find its landing scary, but a Martian colonist in 2040 will consider it trivial.

Besides, unlike an aircraft, SpaceX can fly Starships completely uncrewed until they get the landing down - I reckon crew won't fly on them until the late 2020s. Once it's landed successfully hundreds of times, it'll become routine. And unlike Falcon 9, which doesn't have crew onboard (at least not during the first stage landing) Starship will need to be super safe, so it'll have a lot of redundancies and backups built in.

[wumpus]

1 hour ago, sh1pman said:

Seems scary for us. Who knows, after 100th landing it may become normal and mundane. Like Falcon 9 landings.

Falcon-9 flights 86 and 89 failed to return their boosters, along with all but one Falcon-Heavy centers.  And I'm not even sure these make it to space, much less orbital velocity (the FH centers probably make it to space).  So it will likely take far more than 100 landings, maybe more than 100 landings in a row...

I'm all in favor of Starship, but that doesn't mean I'd like to be on that return path anytime soon.  Space is hard.  Returning from orbit might be the hardest part.

[sevenperforce]

11 minutes ago, wumpus said:

Falcon-9 flights 86 and 89 failed to return their boosters, along with all but one Falcon-Heavy centers.  And I'm not even sure these make it to space, much less orbital velocity (the FH centers probably make it to space).  So it will likely take far more than 100 landings, maybe more than 100 landings in a row...

All make it into space but the FH center cores are still closer to a 747's speed than they are to orbital speed.

11 minutes ago, wumpus said:

I'm all in favor of Starship, but that doesn't mean I'd like to be on that return path anytime soon.  Space is hard.  Returning from orbit might be the hardest part.

Agreed.

1 hour ago, sh1pman said:

Seems scary for us. Who knows, after 100th landing it may become normal and mundane. Like Falcon 9 landings.

The final powered touchdown of the Falcon 9 boosters has never been the problem, not since they got it working. It's the other stuff that keeps tripping them up. A jammed grid fin. An engine that doesn't restart when it's supposed to. A GPS signal with the wrong path length. A landing leg that doesn't deploy all the way.

SpaceX has got the hoverslam landing maneuver solved. No question about it. It's all the other stuff that scares me.

[Barzon]

28 minutes ago, RealKerbal3x said:

a Martian colonist in 2040

[tater]

2 minutes ago, Barzon said:

Spoiler

The Reeds, from the Donner-Reed party.

 

[RealKerbal3x]

24 minutes ago, sevenperforce said:

The final powered touchdown of the Falcon 9 boosters has never been the problem, not since they got it working. It's the other stuff that keeps tripping them up. A jammed grid fin. An engine that doesn't restart when it's supposed to. A GPS signal with the wrong path length. A landing leg that doesn't deploy all the way.

SpaceX has got the hoverslam landing maneuver solved. No question about it. It's all the other stuff that scares me.

Falcon 9 has no backups or redundancies for its landing legs, grid fins or other systems because the first stage landing isn't mission-critical. With Starship, landing the ship is necessary for a successful mission (and perhaps human lives) so they'll have backups upon backups to avoid a failure at all costs.

When SpaceX first rolled out a rocket with landing legs, people said landing a rocket was impossible.  Now they do it with increasing regularity. I have no doubt that they can do the same with Starship, given time.

[mikegarrison]

33 minutes ago, RealKerbal3x said:

Falcon 9 has no backups or redundancies for its landing legs, grid fins or other systems because the first stage landing isn't mission-critical. With Starship, landing the ship is necessary for a successful mission (and perhaps human lives) so they'll have backups upon backups to avoid a failure at all costs.

When SpaceX first rolled out a rocket with landing legs, people said landing a rocket was impossible.  Now they do it with increasing regularity. I have no doubt that they can do the same with Starship, given time.

You think? It's hard for me to figure out what backups and redundancies might be possible. I'm sure they are working on the issue, but it seems like a crewed Starship is going to have even fewer escape/abort/redundant modes than the Space Shuttle, and I've heard for years in this forum about how concerned people here were with the Space Shuttle in that respect. (It did end up killing two crews, so I'm not denying there were reasons for the concerns.)

Edited June 8, 2020 by mikegarrison

[sevenperforce]

43 minutes ago, mikegarrison said:

You think? It's hard for me to figure out what backups and redundancies might be possible. I'm sure they are working on the issue, but it seems like a crewed Starship is going to have even fewer escape/abort/redundant modes than the Space Shuttle, and I've heard for years in this forum about how concerned people here were with the Space Shuttle in that respect. (It did end up killing two crews, so I'm not denying there were reasons for the concerns.)

Right. There are part redundancies and there are modal redundancies. Airliners are safe because they have modal redundancies...they can land in water if they lose an engine, they can belly-slide if need be, they can use differential engine thrust to compensate for a stuck rudder. Even the Shuttle, for all its ills, had redundant landing modes for contingencies (although they all required successful booster separation, which was a problem).

Starship has only one landing mode and it has to work exactly the same way every time. You can try to make all the parts redundant so that it works every time, but there are still no contingencies.

[tater]

1 hour ago, mikegarrison said:

You think? It's hard for me to figure out what backups and redundancies might be possible. I'm sure they are working on the issue, but it seems like a crewed Starship is going to have even fewer escape/abort/redundant modes than the Space Shuttle, and I've heard for years in this forum about how concerned people here were with the Space Shuttle in that respect. (It did end up killing two crews, so I'm not denying there were reasons for the concerns.)

Yeah, the idea of SS as a crew vehicle, or a higher bar, P2P travel seems... unlikely to me (particularly the latter, which I would put well past "unlikely.").

I could imagine a LES crew cabin at the top for space missions as they will never require huge numbers of crew, it's not like mass is a problem, the bulk of the crew compartment is empty space.

[RCgothic]

Space colonisation is risky. If SpaceX straight up said "this will kill one in every hundred crews" there would still be volunteers.

That's not too minimise the risk. But perfect safety isn't a thing.

I absolutely believe Starship can be made with a safer record than shuttle, even without abort modes. It has more margin in hand.

Edited June 8, 2020 by RCgothic

[mikegarrison]

18 minutes ago, RCgothic said:

I absolutely believe Starship can be made with a safer record than shuttle, even without abort modes. It has more margin in hand.

What is the basis for your belief?

20 minutes ago, tater said:

I could imagine a LES crew cabin at the top

Hmm. Perhaps an F-111-style escape pod system?

[CatastrophicFailure]

2 hours ago, mikegarrison said:

Starship is going to have even fewer escape/abort/redundant modes than the Space Shuttle, and I've heard for years in this forum about how concerned people here were with the Space Shuttle in that respect.

Trouble with the Shuttle was, it was supposed to be so reliable it didn’t need all those abort modes, yet it only flew 135 times and was never really “operational,” as opposed to experimental. 

SS/SH could conceivably fly that much in a year, or even a month. That’s a large part of its MO. With that kind of flight rate, finding all the possible bugs in its systems and actually making it “reliable enough” at least becomes plausible. 

[tater]

31 minutes ago, mikegarrison said:

Hmm. Perhaps an F-111-style escape pod system?

An old Phil Bono design from the 60s had that:

Shot out sideways from his SSTO (with drop tanks) VTVL rocket.

 

I was thinking the entire nose down to some point.

Some subset of the bit above the tanks, anyway.

[mikegarrison]

10 minutes ago, CatastrophicFailure said:

SS/SH could conceivably fly that much in a year, or even a month.

Lots of things are conceivable. At this stage of the design process for the shuttle, it was conceivable that the shuttle could have that rate of operations too.

1 minute ago, tater said:

I was thinking the entire nose down to some point.

Some subset of the bit above the tanks, anyway.

What about "header tanks"?

Maybe SpaceX is busy designing solutions to this problem. I hope they are. But if they are, they aren't showing it to us yet.

[RealKerbal3x]

18 minutes ago, CatastrophicFailure said:

Trouble with the Shuttle was, it was supposed to be so reliable it didn’t need all those abort modes, yet it only flew 135 times and was never really “operational,” as opposed to experimental. 

SS/SH could conceivably fly that much in a year, or even a month. That’s a large part of its MO. With that kind of flight rate, finding all the possible bugs in its systems and actually making it “reliable enough” at least becomes plausible. 

Exactly. And unlike the Shuttle, it's not flying from the outset with crew on board. So they can afford to work out the bugs with a few failures without killing crews unnecessarily.

[Raven Industries]

1 hour ago, RCgothic said:

Space colonisation is risky. If SpaceX straight up said "this will kill one in every hundred crews" there would still be volunteers.

I don't know that the Gov would necessarily appreciate a company getting several dozen to a hundred people killed on a semi-regular basis. NASA would definitely protest the optics of it, at the very least. 

[CatastrophicFailure]

26 minutes ago, mikegarrison said:

Lots of things are conceivable. At this stage of the design process for the shuttle, it was conceivable that the shuttle could have that rate of operations too.

Indeed, but in that regard the shuttle was a foray into the great unknown. SpaceX has had these 40-some years of lessons on how not to do rapid reusability and reliability to reflect on in its own plans. Even the Soviet Buran, which flew only a few years after the shuttle, fixed a great many of the flaws in the design, except for the whole “ridiculously expensive and not really needed” part. 
 

 

 

[tater]

32 minutes ago, mikegarrison said:

Maybe SpaceX is busy designing solutions to this problem. I hope they are. But if they are, they aren't showing it to us yet.

They've said that their solution is redundancy/reliability.

I'll need to see a LOT of successful landings with zero failures to consider it safe enough for space travel—something I would put up there with Himalayan mountaineering in terms of danger. For regular people? LOL, they;d need more flights than they could fly, probably. I mean, I get that they could do the math and somehow show failure to be as unlikely as 1940s airline travel or something... but would I take my family on it? LOL. No.

[sevenperforce]

9 minutes ago, tater said:

They've said that their solution is redundancy/reliability.

I'll need to see a LOT of successful landings with zero failures to consider it safe enough for space travel—something I would put up there with Himalayan mountaineering in terms of danger. For regular people? LOL, they;d need more flights than they could fly, probably. I mean, I get that they could do the math and somehow show failure to be as unlikely as 1940s airline travel or something... but would I take my family on it? LOL. No.

I would want to see it recover and land safely after sustaining some sort of damage or other malfunction. Stuck fins, a bad engine, whatever. Show that you can sustain failures and still keep the crew alive, and THEN I'll get on.

47 minutes ago, mikegarrison said:

At this stage of the design process for the shuttle, it was conceivable that the shuttle could have that rate of operations too.

No one ever seriously suggested that the Shuttle would have less than a week of turnaround time. Certainly not multiple flights per day.

47 minutes ago, mikegarrison said:

What about "header tanks"?

Maybe SpaceX is busy designing solutions to this problem. I hope they are. But if they are, they aren't showing it to us yet.

I wonder if they could use a head pressure reservoir (usually tapped for RCS) to run pressure-fed methalox thrusters.

[tater]

5 minutes ago, sevenperforce said:

I would want to see it recover and land safely after sustaining some sort of damage or other malfunction. Stuck fins, a bad engine, whatever. Show that you can sustain failures and still keep the crew alive, and THEN I'll get on.

LOL... dunno, once the kids are out in the world I might go myself on such a trip, but I'd not put my kids on it

 

5 minutes ago, sevenperforce said:

No one ever seriously suggested that the Shuttle would have less than a week of turnaround time. Certainly not multiple flights per day.

Actually, the breakeven was supposed to be flying over 50 times a year, though I don;t know how many vehicles they assumed for that (that was the calc I remember seeing for Shuttle to be cost effective vs Titan for sat launch.

5 minutes ago, sevenperforce said:

I wonder if they could use a head pressure reservoir (usually tapped for RCS) to run pressure-fed methalox thrusters.

Yeah, right now a tank way up in the nose...

[tater]

 

 

 

 

[sh1pman]

High winds on the Moon can be dangerous.