totm nov 2023 SpaceX Discussion Thread

[KSK]

1 hour ago, kerbiloid said:

So, at the moment they hadn't started R&Ding the key component which may or may not make sense of the whole delivery system?

No - they've started researching a component that's critical for their Mars aspirations but no more than a nice-to-have for their satellite launching business or even lunar business, should any lunar business actually materialise. Unless their Sabatier reactors will let them manufacture methane more cheaply than they can buy it (which seems unlikely in the short to medium term), then they don't need them to get BFR flying to LEO, GEO or cis-lunar (not cis-munar - darn my muscle memory  ) space.

In other words, their ISRU research is (for the moment) utterly superfluous to their business model. The only reason they're doing it is because it's an honest-to-goodness space exploration technology which they might need at some point in the future if a whole other bunch of things come together. And the fact that they're investing in that sort of stuff makes me very excited.

 

Edited June 15, 2018 by KSK

[hms_warrior]

aditionaly: the whole ISRU stuff is not new. It is done here on earth every day. It is not a question about if it will work, but "How to make it light/compact enough and as reliable as possibe".

But there is no question that it will work.

[magnemoe]

2 hours ago, hms_warrior said:

aditionaly: the whole ISRU stuff is not new. It is done here on earth every day. It is not a question about if it will work, but "How to make it light/compact enough and as reliable as possibe".

But there is no question that it will work.

However not much use for the Sabatier process on earth. Yes it makes sense that them make some test beds to get an rugged and lightweight version. 
And no it make no economical sense to use it on earth other than testing and have something running for years is an god measure of reliability. 
No its not environmental friendly even if solar powered because its inefficient, had been better to sell the power and buy the methane but then they can not test their isru. 
 

[Wjolcz]

It would be pretty cool if they could produce their own fuel on Earth. But since the BFR/BFS will be fully reusable even if they buy fuel and ship it they would probably charge less than for a F9 launch.

BTW, does anyone know how much money will they be charging per launch? The fuel can't cost more than a brand new F9, right?

[Nefrums]

11 minutes ago, Wjolcz said:

It would be pretty cool if they could produce their own fuel on Earth. But since the BFR/BFS will be fully reusable even if they buy fuel and ship it they would probably charge less than for a F9 launch.

BTW, does anyone know how much money will they be charging per launch? The fuel can't cost more than a brand new F9, right?

Fuel cost is not significant. It is less than 1% of launch cost

[magnemoe]

20 minutes ago, Nefrums said:

Fuel cost is not significant. It is less than 1% of launch cost

it will be an larger part of an fully reusable launcher with fast turnaround. 
Methane on the other hand is cheap, far cheaper than RP1, lots is used in power plants to produce electricity and replaced lots of coal because of lower cost. 

[tater]

 

[NSEP]

3 hours ago, Nefrums said:

Fuel cost is not significant. It is less than 1% of launch cost

The fuel itself doesn't cost much, but then again, the fuel determines the cost of the rocket.

An orbital rocket that uses Alcohol instead if Kerosene, might have a lower fuel cost, but because Alcohol is very inefficient, the Alcohol rocket would need to be bigger and have more stages, wich also means more engines, a bigger launchpad, et cetera, et cetera, thus, making it more expensive than the Kerosene rocket.

Not related to the discussion, im just throwing it in here .

[tater]

2 hours ago, magnemoe said:

it will be an larger part of an fully reusable launcher with fast turnaround. 
Methane on the other hand is cheap, far cheaper than RP1, lots is used in power plants to produce electricity and replaced lots of coal because of lower cost. 

True, but that's at a point when fuel starts to dominate launch costs (meaning launch costs are incredibly cheap), which is a long way away.

[Mad Rocket Scientist]

16 hours ago, Wjolcz said:

It would be pretty cool if they could produce their own fuel on Earth. But since the BFR/BFS will be fully reusable even if they buy fuel and ship it they would probably charge less than for a F9 launch.

BTW, does anyone know how much money will they be charging per launch? The fuel can't cost more than a brand new F9, right?

 

16 hours ago, Nefrums said:

Fuel cost is not significant. It is less than 1% of launch cost

SpaceX has stated that they want to make their operation carbon-neutral someday, which would mean producing methane from CO2 in the atmosphere. In fact, they could even become carbon negative, which, although it wouldn't really make much of a dent in atmospheric CO2, would be a great precedent.

[sevenperforce]

10 hours ago, Mad Rocket Scientist said:

SpaceX has stated that they want to make their operation carbon-neutral someday, which would mean producing methane from CO2 in the atmosphere. In fact, they could even become carbon negative, which, although it wouldn't really make much of a dent in atmospheric CO2, would be a great precedent.

Yeah, any methane they produce on-world and cart off-world is a net decrease.

[CatastrophicFailure]

Apparently this exists: 

And apparently model rockets now have gimballing engines and active guidance. 

I had no idea...

[sh1pman]

14 minutes ago, CatastrophicFailure said:

model rockets now have gimballing engines and active guidance. 

I had no idea...

Apparently, reusable boosters as well.

Edited June 17, 2018 by sh1pman

[StrandedonEarth]

13 minutes ago, sh1pman said:

Apparently, reusable boosters as well.

Lol, always did, as long as the parachutes functioned

[Delay]

39 minutes ago, CatastrophicFailure said:

Apparently this exists: 

Why not?

[Ultimate Steve]

1 hour ago, CatastrophicFailure said:

Apparently this exists: 

And apparently model rockets now have gimballing engines and active guidance. 

I had no idea...

This guy is sort of the king of rocketry now, he's pretty much the only one who has tried to do gimballing, active guidance, and propulsive landing... yes, propulsive landing with solid rockets. He never got close, though, unfortunately.

Looking at this I wonder, how much each flight costs. It's probably above $50 due to the sheer number of engines...

[CatastrophicFailure]

Just now, Ultimate Steve said:

This guy is sort of the king of rocketry now, he's pretty much the only one who has tried to do gimballing, active guidance, and propulsive landing... yes, propulsive landing with solid rockets. He never got close, though, unfortunately.

O.o

Why is this dude not working for SpaceX already?

[CatastrophicFailure]

41 minutes ago, Ultimate Steve said:

This guy is sort of the king of rocketry now, he's pretty much the only one who has tried to do gimballing, active guidance, and propulsive landing... yes, propulsive landing with solid rockets. He never got close, though, unfortunately.

Looking at this I wonder, how much each flight costs. It's probably above $50 due to the sheer number of engines...

Just did some quick reminiscing googling. Might want to multiply by at least 3. 

Wow, model rockets sure have a come a long way in the last, oh 25 or so years since I was first dumbstruck by the awesome, mind-boggling power of the first Estes E engine. 

[cubinator]

1 hour ago, Ultimate Steve said:

This guy is sort of the king of rocketry now, he's pretty much the only one who has tried to do gimballing, active guidance, and propulsive landing... yes, propulsive landing with solid rockets. He never got close, though, unfortunately.

Looking at this I wonder, how much each flight costs. It's probably above $50 due to the sheer number of engines...

[Ultimate Steve]

1 hour ago, CatastrophicFailure said:

 

Wow, model rockets sure have a come a long way in the last, oh 25 or so years since I was first dumbstruck by the awesome, mind-boggling power of the first Estes E engine. 

Both times I fired off E engines they have exploded.

[Val]

Moved half a page's worth to the colonization thread.

 

[StarStreak2109]

12 hours ago, CatastrophicFailure said:

Apparently this exists: 

And apparently model rockets now have gimballing engines and active guidance. 

I had no idea...

I saw that in my twitter feed... Quite amazing modelling if you ask me.

[wumpus]

15 hours ago, Ultimate Steve said:

This guy is sort of the king of rocketry now, he's pretty much the only one who has tried to do gimballing, active guidance, and propulsive landing... yes, propulsive landing with solid rockets. He never got close, though, unfortunately.

Looking at this I wonder, how much each flight costs. It's probably above $50 due to the sheer number of engines...

Why would you bother with gimballing if you stay in the atmosphere?  Even Spacex uses active fins (titanium paddles) on the way down.  But looking at the picture that is definitely gimballing.

[sevenperforce]

15 hours ago, Ultimate Steve said:

This guy is sort of the king of rocketry now, he's pretty much the only one who has tried to do gimballing, active guidance, and propulsive landing... yes, propulsive landing with solid rockets. He never got close, though, unfortunately.

The way to do propulsive landings with solid rockets is to use oversized pop-out grid fins as airbrakes, low-drag legs with shock absorbers, and a weak central landing rocket with just enough thrust to lower terminal velocity to something that the legs can handle (TWR < 1).

Calculate terminal velocity with your grid fins out and use that to determine time from apogee to impact. Then you pop your grid fins at apogee and have your legs and your solid motor timed to activate about 10 seconds before would-be impact. The additional drag from the legs, plus the solid motor's thrust, will slow the rocket enough for the legs to absorb the remaining velocity. The landing motor will continue to burn after touchdown but thrust is low enough that it won't take off again.

The only problem is torching whatever you end up landing on.

[ment18]

1 hour ago, sevenperforce said:

The way to do propulsive landings with solid rockets is to use oversized pop-out grid fins as airbrakes, low-drag legs with shock absorbers, and a weak central landing rocket with just enough thrust to lower terminal velocity to something that the legs can handle (TWR < 1).

Calculate terminal velocity with your grid fins out and use that to determine time from apogee to impact. Then you pop your grid fins at apogee and have your legs and your solid motor timed to activate about 10 seconds before would-be impact. The additional drag from the legs, plus the solid motor's thrust, will slow the rocket enough for the legs to absorb the remaining velocity. The landing motor will continue to burn after touchdown but thrust is low enough that it won't take off again.

The only problem is torching whatever you end up landing on.

I actually did a SRB propulsive landing in KSP for the laughs.  I just gave the landing thrusters a certain amount of deltaV that I thought would be enough, and then tweaked that deltaV by removing and adding more thrusters (sepatrons).  I used KOS to trigger the thrusters at a very specific height from the ground, which I tweaked until it worked properly.  I eventually got it to work, though the engine burned a little too long and it jumped after touchdown, non-destructively.  Here is the video.