totm nov 2023 SpaceX Discussion Thread

[YNM]

36 minutes ago, Terwin said:

If you can afford to double the weight of your satellite for extra fuel capacity, it seems likely that the satellite could have a lot more lee-way in where it is dropped off and still get to it's preferred orbit.

 

Indeed the costs are astronomical, but not nearly as astronomical as everyone is currently paying to get anything into space.

Alright...

But.

 

There's one more thing : this stuff is basically a space shuttle. The second stage is something that goes into orbit and lands back. Lands back into a soupy atmosphere, not in nothing.

 

Seriously, if the costs estimates are true, the engineer who done it as so deserves a Nobel prize or something.

Edited February 19, 2018 by YNM

[sevenperforce]

14 hours ago, Ultimate Steve said:

From LEO they just de-orbit it and land as shown in the Earth to Earth video (but with de-orbiting). Like the shuttle did, but without wings. From Mars, IIRC, they Sabatier it for a few months until it has fuel again, and apparently it can SSTO back from there, aerobrake and land like a normal F9 S1. Unless I'm seriously wrong about this.

Well, it does have wings. But the key difference is that it doesn't have to glide down deadstick to a landing; instead, it glides down to landing approach, then pitches up, stalls, fires its engines, and lands on its tail.

If it works, it will be AMAZING to see.

The BFS's fueling connections are on either side of the engines, where it connects to the BFR. They'll use the same connections to transfer prop on orbit, and a relatively small rover can drive underneath, raise a fuel connector probe, and "dock in" to fuel it that way on Mars.

Mars SSTO is not too hard, not if you have high-energy propulsion. 

14 hours ago, YNM said:

Assuming no refuels, direct entry and the ability to turn back to Earth, this could mean that a single BFR would be in Earth-SSTO dV capabilities.

A single BFR, or a single BFS? The booster alone would certainly have SSTO capabilities, just like Falcon 9 already does.

Cargo BFS could do a zero-payload SSTO flight with enough reserves for deorbit, but probably not enough reserves for landing. It would have more margins if it had more SL Raptors, since its low loaded TWR would be killer on liftoff.

[YNM]

2 minutes ago, sevenperforce said:

or a single BFS ?

A single BFS.

[tater]

1 hour ago, YNM said:

No refurb ?

How cheap a manufacturing are we talking about ? They're not just scaling a Coke can upwards right ?

F9 block 5 is designed for operational reuse 10 times with no expensive refurb. 24 hour turn around is about money, not time. A work day for X people is the cost of refurb, vs months of workdays for thousands of people to refurb shuttle.

I included operational costs, which is some refurb. A BFR/BFS combo has a several hundred grand worth of propellant in it. The bulk of the cost is the amortized build cost (a few hundred million per vehicle).

 

[sevenperforce]

13 hours ago, Ultimate Steve said:

I remember Elon saying somewhere that the PICA-X will not ablate much for LEO missions or Mars entry, but will ablate some upon returning to Earth from Mars.

IIRC, highest ablation will actually be Mars entry from Earth TMI, because the Martian atmosphere is more tenuous and so peak heating will be way higher.

2 hours ago, Jaff said:

So the bfr with 150t capability will be used to launch a 5t payload?

Well, if you can deliver your 5 tonne payload direct to GEO, then aerobrake to LEO and transfer 40 tonnes of propellant to a tanker, then land, for operating costs of $4-5 million...why wouldn't you?

[tater]

1 hour ago, Jaff said:

So surely a larger payload ~20-30t that’s too heavy for the top bit to ssto and nowhere near the 150t possible is a waste of a bfr launch? 

 

Ie something a Falcon heavy or a mini bfr whatever the next big thing is is preferable (reusable too of course)

If the per flight cost is below the cost to operate an F9 (operational cost of reused booster and fairing, plus expendable stage 2), then it is worth flying a nearly empty BFR. The math is not that complicated. If they can comanifest even a single additional payload, they’re likely in decent shape. If they have something like PAM, such comanifested flights are easy, since the PAM can be decently large. Alternately, with almost no payload, BFS gets to LEO with loads of excess dv. They can change orbit to deploy comanifested sats, and still land, so they have more options in that regard.

[sevenperforce]

1 hour ago, YNM said:

Here is the real key to answer whether BFR is really far cheaper than F9 or Saturn V.

BFR is larger than Saturn V and F9.

> It's more expensive to build.

> It's more expensive to run (mind the emphasis - running costs != sunken costs).

> It can carry more stuff.

>> Extra difference is that it can be reused.

Saturn V was 10 meters; BFR is 9. BFR will be substantially cheaper to build, in inflation-adjusted dollars, than the Saturn V. Remember that even if SpaceX flew the Falcon family fully-expendable, they'd still undercut their competition at every level. They build sturdy rockets cheaply.

1 hour ago, magnemoe said:

An smaller launcher would be more economical but this rocket don't exist.
Closest we get would be new Glen with an reusable upper stage who should work if the 40 ton capacity is with reuse of first stage who makes sense. If that is true 

Main question is if BFR is robust enough for rapid and long term reuse. The good side is that they have lots of margins if weight goes up
 

NG has a reusable upper stage?

 

13 minutes ago, tater said:

If the per flight cost is below the cost to operate an F9 (operational cost of reused booster and fairing, plus expendable stage 2), then it is worth flying a nearly empty BFR. The math is not that complicated. If they can comanifest even a single additional payload, they’re likely in decent shape. If they have something like PAM, such comanifested flights are easy, since the PAM can be decently large. Alternately, with almost no payload, BFS gets to LEO with loads of excess dv. They can change orbit to deploy comanifested sats, and still land, so they have more options in that regard.

And once you have a launcher with a 150-tonne payload, you can start talking about a third-party payload delivery service that would buy the BFR launch slot for ~$10M, pack on a dozen tonnes of hypergolics, and sell fifty smallsat slots at $500k each, with promised delivery to whatever orbit you desire.

[YNM]

14 minutes ago, sevenperforce said:

Saturn V was 10 meters; BFR is 9. BFR will be substantially cheaper to build, in inflation-adjusted dollars, than the Saturn V. Remember that even if SpaceX flew the Falcon family fully-expendable, they'd still undercut their competition at every level. They build sturdy rockets cheaply.

Alright for BFR core or F9 and such (though I really wonder what "magic" is in it); but BFS ? That's no cigar...

But seriously. Is SpaceX secretly obtaining some very clever materials or something ? Is it the carbon fibre+aluminum ?

Edited February 19, 2018 by YNM

[tater]

All of it will be composite, that’s the plan, anyway.

BFS is largely cylindrical, actually.

[magnemoe]

12 minutes ago, sevenperforce said:

NG has a reusable upper stage?

Not in current version however if it can take 40 ton to leo with reusable first stage they have margins for it for smaller payloads. No other candidates. 
 

[YNM]

2 minutes ago, tater said:

All of it will be composite, that’s the plan, anyway.

BFS is largely cylindrical, actually.

Ah. Space architecture...

 

But this is seriously the single biggest thing it could change. Materials. If it figures a material sweet spot between strong and cheap they're really off.

 

The next question is dynamics then... then man.

[sevenperforce]

And now, on a completely non-BFR-related topic....

Ever since Falcon Heavy's test launch, I've been working on building a table of Falcon family payload performance. I've come up with a pretty robust and (I think) accurate model, and so I've got payload and performance for a wide range of destinations. I haven't seen anything this complete or this useful anywhere online.

Comprehensive Derived Falcon Family Payload Table (metric tonnes)

Vehicle	LEO (tanker only)	LEO (payload)	GTO (2.27km/s)	TLI (2.73km/s)	LLO (4.04km/s)	GEO (4.33km/s)	TMI (4.30km/s)	price (USD)
Falcon Heavy (expendable)	96.91	63.80	26.70	25.17	16.68	15.22	16.80	$150M
Falcon Heavy (booster recovery x2)	87.22	57.42	24.03	22.65	15.01	13.70	15.12	$95M
Falcon Heavy (booster recovery x3)	23.53	18.11	8.00	6.66	3.65	3.12	3.17	$90M
Falcon 9 (expendable)	24.99	22.80	8.30	7.74	4.25	3.65	4.02	$92M
Falcon 9 (ASDS recovery)	17.04	13.30	5.50	4.50	2.14	1.71	1.75	$62M
Falcon 9 (RTLS recovery)	11.74	9.41	3.51	2.70	0.85	0.52	0.56	<$62M

 

Underlined values are values actually provided on by official SpaceX sources; italicized values came from statements made publicly by Elon. All other values are produced by the model. RTLS performance values were estimated by carefully comparing staging velocities for RTLS missions to staging velocities for ASDS missions; this is likely an underestimate of RTLS capabilities because SpaceX has probably not pushed RTLS to its limits in missions to date.

Falcon Heavy with three-core recovery may also be underestimated for LEO performance, since Falcon Heavy's TWR is so much higher than Falcon 9's, but it should be accurate for BLEO destinations.

LLO and GEO delivery assume extended restart capability for the MVac and do not account for propellant boil-off; this must be factored in.

LEO tanker performance assumes that the payload is nothing but an International Docking Adapter (mass: 526 kg), so that it could be docked to a vehicle waiting in LEO for an ejection burn.

For ASDS payloads below the maximum payload, SpaceX sends the ASDS only part of the way out and uses the extra margin for a boostback burn to save money and time. ASDS performance above assumes no boostback burn and maximum downrange ASDS position.

[tater]

Seems like once the new asds is available, another option is an expended core, and 2 asds side booster landings maximally downrange.

Add another asds, and you could have all 3 recovered down range.

[sh1pman]

@sevenperforceThe difference between 2x and 3x booster recovery is huge. You sure it's accurate?

Edited February 19, 2018 by sh1pman

[Ultimate Steve]

19 minutes ago, sh1pman said:

@sevenperforceThe difference between 2x and 3x booster recovery is huge. You sure it's accurate?

If you ASDS the two side cores the fuel loss isn't much for them (less than half of RTLS), and the center core is free to expend all of its delta-V, eliminating the entry burn (more than usual due to velocity) and the landing burn. It might be off by a little bit, but the gains definitely are bigger than you would expect.

[sevenperforce]

11 minutes ago, tater said:

Seems like once the new asds is available, another option is an expended core, and 2 asds side booster landings maximally downrange.

Add another asds, and you could have all 3 recovered down range.

"Falcon Heavy (booster recovery x2)" is the Falcon Heavy core expended with two side boosters landing maximally downrange on OCISLY and ASOG.

Adding a third ASDS would not help; if the two side boosters are landing maximally downrange, the core is going to be going far too fast for recovery. Any added margins would need to be reserved for a longer boostback burn.

9 minutes ago, sh1pman said:

@sevenperforceThe difference between 2x and 3x booster recovery is huge. You sure it's accurate?

The recovery x2 values (expending the core and landing the two side boosters on droneships) are taken from Elon's statement on Twitter that this approach is only a 10% performance penalty in comparison to expending all three. I wasn't really able to tackle the accuracy of that quote, but it is not beyond reason; the amount of propellant that the side boosters will need to reserve for ASDS landing is really quite low in comparison to what it does to lifting the whole core and upper stage stack.

A 10% payload penalty means that staging occurs around 230 m/s slower. 230 m/s for the whole stack equates to many times more for a nearly-empty booster...back of the envelope would say 800-1000 m/s per booster, which is plenty for entry and landing burns.

Recovery x3 is based on the quoted performance of Falcon Heavy; it is advertised at $90M for up to 8 tonnes to GTO, which is lower than the maximum GTO performance of an expendable Falcon 9. So yeah, there's a huge jump. It makes sense, though, because the core is going so blindingly fast at staging that it needs to reserve a lot of propellant, either for a boostback or for a longer entry burn.

They will never do a 3x RTLS flight, because it would drop performance down into the Falcon 9 ASDS range.

[SaturnianBlue]

I assume that the cost of spacecraft is significantly increased by the use of expensive materials to lighten spacecraft while making them more capable. With the BFR's much bigger payload capacity, could spacecraft be built to use less expensive materials, which would increase the mass of the spacecraft, yet still decrease the overall cost of the spacecraft?

The big problem I suppose with this is that such a type of spacecraft is reliant on the BFS to launch itself into orbit.

Edited February 19, 2018 by SaturnianBlue

[sevenperforce]

Spoiler

3 hours ago, sevenperforce said:

And now, on a completely non-BFR-related topic....

Ever since Falcon Heavy's test launch, I've been working on building a table of Falcon family payload performance. I've come up with a pretty robust and (I think) accurate model, and so I've got payload and performance for a wide range of destinations. I haven't seen anything this complete or this useful anywhere online.

Comprehensive Derived Falcon Family Payload Table (metric tonnes)

Vehicle	LEO (tanker only)	LEO (payload)	GTO (2.27km/s)	TLI (2.73km/s)	LLO (4.04km/s)	GEO (4.33km/s)	TMI (4.30km/s)	price (USD)
Falcon Heavy (expendable)	96.91	63.80	26.70	25.17	16.68	15.22	16.80	$150M
Falcon Heavy (booster recovery x2)	87.22	57.42	24.03	22.65	15.01	13.70	15.12	$95M
Falcon Heavy (booster recovery x3)	23.53	18.11	8.00	6.66	3.65	3.12	3.17	$90M
Falcon 9 (expendable)	24.99	22.80	8.30	7.74	4.25	3.65	4.02	$92M
Falcon 9 (ASDS recovery)	17.04	13.30	5.50	4.50	2.14	1.71	1.75	$62M
Falcon 9 (RTLS recovery)	11.74	9.41	3.51	2.70	0.85	0.52	0.56	<$62M

 

Underlined values are values actually provided on by official SpaceX sources; italicized values came from statements made publicly by Elon. All other values are produced by the model. RTLS performance values were estimated by carefully comparing staging velocities for RTLS missions to staging velocities for ASDS missions; this is likely an underestimate of RTLS capabilities because SpaceX has probably not pushed RTLS to its limits in missions to date.

Falcon Heavy with three-core recovery may also be underestimated for LEO performance, since Falcon Heavy's TWR is so much higher than Falcon 9's, but it should be accurate for BLEO destinations.

LLO and GEO delivery assume extended restart capability for the MVac and do not account for propellant boil-off; this must be factored in.

LEO tanker performance assumes that the payload is nothing but an International Docking Adapter (mass: 526 kg), so that it could be docked to a vehicle waiting in LEO for an ejection burn.

For ASDS payloads below the maximum payload, SpaceX sends the ASDS only part of the way out and uses the extra margin for a boostback burn to save money and time. ASDS performance above assumes no boostback burn and maximum downrange ASDS position.

 

A cursory look will show that a single Falcon Heavy with the core expended can deliver a payload 4X the launch mass of MSL direct to TMI. Red Dragon would have posed no problem for side booster recovery. 

The Apollo lunar stack was 45.9 tonnes. This could be lifted in a single launch by FH with the core expended, or two launches with three-core recovery. Expending the core is cheaper. Of course, you'd need another F9 RTLS launch to get the astronauts up to the stack if FH wasn't man-rated. Then a single core-expenditure tanker launch docks to the nose for TLI. Apollo for $252M.

[PakledHostage]

1 hour ago, sevenperforce said:

  Reveal hidden contents

 

The Apollo lunar stack was 45.9 tonnes. This could be lifted in a single launch by FH with the core expended, or two launches with three-core recovery. Expending the core is cheaper. Of course, you'd need another F9 RTLS launch to get the astronauts up to the stack if FH wasn't man-rated. Then a single core-expenditure tanker launch docks to the nose for TLI. Apollo for $252M.

You're forgetting that the Apollo lunar stack was delivered onto a lunar intercept trajectory by the Saturn's S-IVB stage via a 6 minute long burn of that Saturn stage. The Apollo lunar stack did not perform the TLI burn on its own.

Falcon heavy may well be able to deliver a 45.9 tonne payload into LEO, but your 45.9 tonne payload would need another booster to get beyond LEO.

 

Edit: Never mind. I read too fast and missed your last sentence.

Edited February 19, 2018 by PakledHostage

[Bill Phil]

7 hours ago, sevenperforce said:

  Hide contents

 

A cursory look will show that a single Falcon Heavy with the core expended can deliver a payload 4X the launch mass of MSL direct to TMI. Red Dragon would have posed no problem for side booster recovery. 

The Apollo lunar stack was 45.9 tonnes. This could be lifted in a single launch by FH with the core expended, or two launches with three-core recovery. Expending the core is cheaper. Of course, you'd need another F9 RTLS launch to get the astronauts up to the stack if FH wasn't man-rated. Then a single core-expenditure tanker launch docks to the nose for TLI. Apollo for $252M.

And how much would it cost to develop the related spacecraft? You're looking at billions.

Even now launch costs are not as significant as the cost of the payload. This is why ULA has a good chance of sticking around. For launch, cost is generally not as important as reliability.

[tater]

4 minutes ago, Bill Phil said:

And how much would it cost to develop the related spacecraft? You're looking at billions.

Even now launch costs are not as significant as the cost of the payload. This is why ULA has a good chance of sticking around. For launch, cost is generally not as important as reliability.

This is true, but it's at least partially circular, IMO. Payloads are expensive because launches have been relatively expensive, so the payloads are designed for long life, etc. If launch cost substantially less, then it's worth risking less robust spacecraft.

[Bill Phil]

Just now, tater said:

This is true, but it's at least partially circular, IMO. Payloads are expensive because launches have been relatively expensive, so the payloads are designed for long life, etc. If launch cost substantially less, then it's worth risking less robust spacecraft.

True. But for things like scientific probes? I think they'll be expensive for a good while. GEO sats? I could see those becoming cheaper with less expensive launches.

[tater]

55 minutes ago, Bill Phil said:

True. But for things like scientific probes? I think they'll be expensive for a good while. GEO sats? I could see those becoming cheaper with less expensive launches.

No doubt. Even at a "cheap" 150 M$, an expendable FH to a distant planet would mean that you'd want the probe to be pretty bulletproof, in terms of reliability.

If that ride to Pluto was only 5 million? Then maybe we see them making a few, cheaper probes.

[Val]

If your post concerns itself with colonization, ISRU, survival on extra-terrestrial planets, satellite internet, or flamethrowers, then it doesn't belong in this thread and will be moved.

Consider posting it in one of these threads, instead.

If you have questions or comments regarding this, please do NOT post here. Either report this post with your question or concern or PM me or another moderator.

Edited February 23, 2018 by Val
you're -> your :-p

[Terwin]

7 hours ago, tater said:

No doubt. Even at a "cheap" 150 M$, an expendable FH to a distant planet would mean that you'd want the probe to be pretty bulletproof, in terms of reliability.

If that ride to Pluto was only 5 million? Then maybe we see them making a few, cheaper probes.

I believe most of the costs for a majority of satellites and probes are related to designing the satellite/probe.  If it is cheaper to improve reliability by making 3 of the same satellite/probe, there is no reason not to pursue that path.  It is just less likely for that to be the case if you are mass constrained and the cost per launch is high.

As an added benefit, if your redundant probes/satellites are spread across multiple launches, you also reduce the per launch risk to your project...