totm nov 2023 SpaceX Discussion Thread

[tseitsei89]

They might eventually be able to do single engine landings and do the flip manouver without the help of raptors (with aerodynamic surfaces + gas thrusters). Then 1 or even 2 engine failures wouldn't necessarily mean certain death if they can just use the remaining working engine to land.

[YNM]

4 minutes ago, tseitsei89 said:

They might eventually be able to do single engine landings and do the flip manouver without the help of raptors (with aerodynamic surfaces + gas thrusters). Then 1 or even 2 engine failures wouldn't necessarily mean certain death if they can just use the remaining working engine to land.

Man-rating is one where even a 99% success record can look bad enough. They'll still have to prove themselves for years (I'd wager a whole decade) once the whole stack works unmanned-ly.

[RealKerbal3x]

1 minute ago, tseitsei89 said:

They might eventually be able to do single engine landings and do the flip manouver without the help of raptors (with aerodynamic surfaces + gas thrusters). Then 1 or even 2 engine failures wouldn't necessarily mean certain death if they can just use the remaining working engine to land.

Thing is, if you're using only one engine the flip has to occur at a higher altitude, which means the flight computer would have to detect engine failures before they happen and adjust its landing accordingly. 

[tseitsei89]

4 minutes ago, YNM said:

Man-rating is one where even a 99% success record can look bad enough. They'll still have to prove themselves for years (I'd wager a whole decade) once the whole stack works unmanned-ly.

Yes of course Raptors still need to be made extremely reliable and it will be a slow process. But if you look at Merlin in its current state, it really is super reliable nowadays.

3 minutes ago, RealKerbal3x said:

Thing is, if you're using only one engine the flip has to occur at a higher altitude, which means the flight computer would have to detect engine failures before they happen and adjust its landing accordingly. 

They can just flip higher up for manned flights anyway, engine failure or not. Yes it will need more propellant to slow down in the end but it will be safer. I mean they could plan the landing for 1 engine to begin with. Then if the planned engine doesn't ignite, just immediately try to ignite another one.

Edited January 18, 2021 by tseitsei89

[YNM]

5 minutes ago, tseitsei89 said:

Yes of course Raptors still need to be made extremely reliable and it will be a slow process. But if you look at Merlin in its current state, it really is super reliable nowadays.

They can just flip higher up for manned flights anyway, engine failure or not. Yes it will need more propellant to slow down in the end but it will be safer.

Merlin has flown for 12 years (Falcon 1 also used them), and the design had started since at least 2002.

And the problem so far hasn't been with the engine itself, but the fuel management (fuel plumbing is extremely hard). Or at least we haven't tested the engine in-flight enough times until there is an issue that arose solely on the engine itself.

Like I said, it'll take them a whole decade since the first full-profile unmanned mission happened.

Edited January 18, 2021 by YNM

[tseitsei89]

Just now, YNM said:

Merlin has flown for 12 years (Falcon 1 also used them), and the design had started since at least 2002.

And the problem so far hasn't been with the engine itself, but the fuel management (fuel plumbing is extremely hard). Or at least we haven't tested the engine in-flight enough times until there is an issue that arose solely on the engine itself.

Yes that is exactly why I said it will be a slow process but not impossible. Falcon 9 is already quite reliable today.

[YNM]

1 minute ago, tseitsei89 said:

Yes that is exactly why I said it will be a slow process but not impossible. Falcon 9 is already quite reliable today.

I'm not sure what the Promised Elon Time is rn but I'd wager we'll see them mid-2030s starting to launch customers from Earth and back.

[tseitsei89]

Just now, YNM said:

I'm not sure what the Promised Elon Time is rn but I'd wager we'll see them mid-2030s starting to launch customers from Earth and back.

Yeah obviously Elon-time is vastly different from reality.

[RealKerbal3x]

4 minutes ago, YNM said:

Merlin has flown for 12 years (Falcon 1 also used them), and the design had started since at least 2002.

And the problem so far hasn't been with the engine itself, but the fuel management (fuel plumbing is extremely hard). Or at least we haven't tested the engine in-flight enough times until there is an issue that arose solely on the engine itself.

The first mention of Raptor was in 2009. Back then it was a hydrolox upper-stage engine, and it only became a methalox engine around 2014. Since flight testing on Starhopper began in 2019, by 2030 that'll have been 11 years of flights. So if we're going off the Falcon 9 analogy, then 2030 seems reasonable for the first crewed launch.

Or maybe they'll have refined their development by then and we'll see Starship crew launches sooner. Who knows.

[Clamp-o-Tron]

12 minutes ago, tseitsei89 said:

Yes of course Raptors still need to be made extremely reliable and it will be a slow process. But if you look at Merlin in its current state, it really is super reliable nowadays.

The question is: would you put a crew in a F9 first stage? If not (which you shouldn’t), then the Starship crew-rating will take a lot more than Raptor certification.

[YNM]

1 minute ago, RealKerbal3x said:

The first mention of Raptor was in 2009. Back then it was a hydrolox upper-stage engine, and it only became a methalox engine around 2014. Since flight testing on Starhopper began in 2019, by 2030 that'll have been 11 years of flights. So if we're going off the Falcon 9 analogy, then 2030 seems reasonable for the first crewed launch.

Or maybe they'll have refined their development by then and we'll see Starship crew launches sooner. Who knows.

Merlin was first tested in space from 2010. Merlin has only been propulsively landed back on Earth since 2015, and that's not the ones that goes to space. NASA hasn't accepted to use re-used boosters yet, although they're open to the idea. We'll see when a reused booster will be manifested for a crew launch on F9.

Plus, Starship hasn't even had the thermal protection system tested at all. 2030 is the fastest time IMO, but mid-2030s is much more likely.

[RealKerbal3x]

2 minutes ago, YNM said:

Merlin was first tested in space from 2010. Merlin has only been propulsively landed back on Earth since 2015, and that's not the ones that goes to space. NASA hasn't accepted to use re-used boosters yet, although they're open to the idea. We'll see when a reused booster will be manifested for a crew launch on F9.

Actually, they have. Crew-2 will reuse the first stage from Crew-1 and the Dragon spacecraft from Demo-2. NASA seems to now be fully leaning into utilising SpaceX's reusability.

[YNM]

32 minutes ago, RealKerbal3x said:

Actually, they have. Crew-2 will reuse the first stage from Crew-1 and the Dragon spacecraft from Demo-2. NASA seems to now be fully leaning into utilising SpaceX's reusability.

Sadly not actually in the quoted article, the article just says that NASA "will allow reuse of Capsule and Booster starting with Crew-2" but there's nothing that says it's what is in the manifest of Crew-2.

Don't get me wrong, I myself hope that the propulsive landings of Dragon V2 will be used by NASA as well. It'd provide the precedent for Starship.

Edited January 18, 2021 by YNM

[mikegarrison]

3 hours ago, YNM said:

Man-rating is one where even a 99% success record can look bad enough. They'll still have to prove themselves for years (I'd wager a whole decade) once the whole stack works unmanned-ly.

If there were only a 99% chance of avoiding injury in a car trip, there would be 11,000,000 injury accidents in the US every day. 99% is completely unacceptable.

Edited January 18, 2021 by mikegarrison

[linuxgurugamer]

1 hour ago, mikegarrison said:

If there were only a 99% chance of avoiding injury in a car trip, there would be 11,000,000 injury accidents in the US every day. 99% is completely unacceptable.

Your idea is correct, but somehow I don't think that there are 1.1 billion car trips per day.  
regardless of the actual nulber, it sucks to be in the 1%

[mikegarrison]

9 minutes ago, linuxgurugamer said:

Your idea is correct, but somehow I don't think that there are 1.1 billion car trips per day. 

According to Google, there are (or rather were in 2017) 1.1 billion car trips per day in the US.

I believe that this includes, for example, driving to Starbucks, then to the office, working there, then to a pizza place, and then home as four trips, even though conceptually it could be argued they are two trips or even one round trip.

(It's more usual to compare accident rates per passenger-mile or passenger-km rather than trips.)

Edited January 18, 2021 by mikegarrison

[tater]

49 minutes ago, mikegarrison said:

(It's more usual to compare accident rates per passenger-mile or passenger-km rather than trips.)

Trips makes more sense for this comparison, doesn't matter how far you hop, every other engine start needs to happen or BOOM.

The short answer is that SS as a crew vehicle is a long way off, IMO, or at the very least many flights in a row with no failures (hundreds for commercial crew level safety, dunno, millions for airline level?)

[YNM]

58 minutes ago, mikegarrison said:

(It's more usual to compare accident rates per passenger-mile or passenger-km rather than trips.)

I suppose it's not really useful for space travel though, unless we're talking stuff like the pressurized compartment or the electrical system etc.

For the engines and the manoeuvres it's more useful to count it against the number of occurrences it happens.

8 minutes ago, tater said:

The short answer is that SS as a crew vehicle is a long way off, IMO, or at the very least many flights in a row with no failures (hundreds for commercial crew level safety, dunno, millions for airline level?)

Airplane-level seems to need like another decade or more...

[tater]

27 minutes ago, YNM said:

Airplane-level seems to need like another decade or more...

At least, lol.

Airline travel is about the safest thing people can do right now. Not only are crashes rare, they are almost always pilot error when they do happen.

Commercial crew has a LOC event requirement of 1:270.

Presumably SpaceX could fly their way to that sort of rating with a combination of engine start data, and actual flights/landings at some value below 270 flights. It seems.... sketchy, regardless of the math, however. Spaceship 2 might be every bit as safe as New Shepard's capsule based on the calcs, but I'd get on New Shepard if given a free ride, but I'm not sure I'd ever trust Spaceship 2. I'd think in any sort of shot to medium term use as a crew vehicle I'd want a robust LES for Starship. There's not a reason to put huge numbers of crew on any spacecraft yet. Even 10-20 people would be a really large crew for any plausible use case for current space programs with a good lunar base established. Seems like they could "waste" cargo capacity on a crew vehicle and have the top separate taking all 10-20 crew.

Actually, a crew vehicle is a different thing than cargo/tanker. Cargo is empty coming back, hence the LOX tank in the nose.

The crew version will have a lot of heavy stuff that stays in the nose all the time, and won't need the header tank there. It will have all the life support hardware, plus consumables. With a payload of 100-150t to LEO, and a crew compartment that is mostly empty space, they will actually need to ballast the crew area if anything to get close to 100t in the nose. Adding a capsule with solid motors to pull it off would make a lot of sense early on.

[tseitsei89]

4 hours ago, mikegarrison said:

If there were only a 99% chance of avoiding injury in a car trip, there would be 11,000,000 injury accidents in the US every day. 99% is completely unacceptable.

Well, spaceflight is not driving a car and will obviously never (or at least for a VERY long time) be as safe as driving a car. 99% might be unacceptable for manned flights but comparing it to car trips is pretty dumb.

Exploration has always been quite dangerous and required big risks to be taken.

Edited January 18, 2021 by tseitsei89

[tater]

21 minutes ago, tseitsei89 said:

Well, spaceflight is not driving a car and will obviously never (or at least for a VERY long time) be as safe as driving a car. 99% might be unacceptable for manned flights but comparing it to car trips is pretty dumb.

Exploration has always been quite dangerous and required big risks to be taken.

There are 2-3 different use cases being discussed here for Starship. Comparing it to car trips is not dumb at all, it depends on the use.

1. Crew flights per NASA guidelines. Assuming they have to meet Commercial Crew standards at the very least, that's a standard of one Loss of Crew incident every 270 flights. That's 99.6%.

2. Crew flights to Mars. This is goofy for the time being, but it's SpaceX's internal goal. The risk to life and limb might be greater than commercial crew (<cough> Donner Party <cough>) even without spacecraft failures, dunno for that.

3. Point to point transport on Earth. SpaceX has discussed this, and this needs to be airline safe to be a thing, which is 1 fatal crash every 3,700,000 flights (99.99997% safe).

Apparently 99.885% safe is really terrifying to people.

Edited January 18, 2021 by tater

[tater]

SN9 static fire moved to tomorrow because of wind it looks like.

[tseitsei89]

1 hour ago, tater said:

1. Crew flights per NASA guidelines. Assuming they have to meet Commercial Crew standards at the very least, that's a standard of one Loss of Crew incident every 270 flights. That's 99.6%.

Yeah well, obviously 99.6% would be completely unacceptable for a car trip safety as well. But as I said: spaceflight is not and will not be like driving a car.

 

1 hour ago, tater said:

2. Crew flights to Mars. This is goofy for the time being, but it's SpaceX's internal goal. The risk to life and limb might be greater than commercial crew (<cough> Donner Party <cough>) even without spacecraft failures, dunno for that.

0.5% or even 1% chance of death during landing seems quite irrelevant in the grand scheme of things here to me. You are probably much more likely to die of some other cause when trying to live on Mars than that 1%.

 

1 hour ago, tater said:

3. Point to point transport on Earth. SpaceX has discussed this, and this needs to be airline safe to be a thing, which is 1 fatal crash every 3,700,000 flights (99.99997% safe).

 

Possible point to point transportation of starship is still FAR FAR away in the future (even compared to starships possible crewed spaceflights and going to mars) and I doubt it will never even happen. It would need amazing safety margins and it would still probably be really expensive compared to airplanes. Fast of course but you can already fly across atlantic in less than a day.

[kerbiloid]

While I still keep treating the SpaceX interplanetary plans as nonsense, first of all because they look suicidally,
it's a time to bring again the statistics of the mor.... mortuary of the heroes climbing the highest mountains

https://www.bbc.com/news/world-47418215#:~:text=Everest deaths,has fallen to below 1%.

Spoiler

 

So, LES  is optional.

1. They don't prohibit the suicidal climbing on mountains.

2. A mountain is a "high ground".

3. Mars and Moon are a "high ground", too. Very high, up to 2.5 AU high for Mars.

4. They are outstandingly high ground. But still a ground. Say, Jupiter isn't.

5. They will register their Martian trip in the alpinist association as (idk how it's called), not in FAA, NASA, or else.
as
"To climb on an outstandingly high ground, using an atmospheric taxi at the very foot, and as a camp tent during the rest part of the trip."
(That's a truth, they will switch off the engines right near the Earth, far from top,, then just be floating).

6. After getting to the Mars, they plant a flag somewhere, and nobody can't say that they are not alpinists.

So, the SpaceX should start registering the Mars as a part of the Earth, separated by air mass.
(Say, as a remote part of Antarctica, just to avoid undesired arguing).

Upd.

A. SpaceX says the Starship is an intercontinental atmospheric  taxi. Coincidence? I don't think so.

B. Mars and Moons can be declared Antarctic mountains. No definition of "mountain" makes it to be non-spherical. So, two spherical mountains in Antarctica.

Edited January 18, 2021 by kerbiloid

[mikegarrison]

Mountain climbing and space travel actually have very few similarities, as far as I can tell. (I have climbed mountains. I have not travelled in space.)

One thing that is perhaps relevant here is that climbers are generally very much in control of their risk. This is unlike being a passenger in a plane, and more like being the pilot of the plane.