totm nov 2023 SpaceX Discussion Thread

[sevenperforce]

15 hours ago, PakledHostage said:

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.

Glad you caught this on your own; I would have felt bad pointing it out.

Moon missions can be done in one of three ways: lunar orbit rendezvous (Saturn V/Apollo), Earth-lunar orbit rendezvous (Constellation), or joint lunar orbit rendezvous. ELOR assembles an Apollo-style stack in LEO, while JLOR sends crew and lander to the moon in separate TLIs.

If we baseline the mass of the command module and lunar module at the ones used in Apollo (28.8 tonnes for the CSM, 16.4 tonnes for the LM), then the cheapest way to do ELOR is to send both of them up together on a 2-core-recovery FH, send crew up on an RTLS F9+Dragon, and then send up another 2-core-recovery FH for the TLI stage. If you do JLOR, then the LM needs to brake itself into low lunar orbit, meaning we shift about six tonnes of propellant off the CSM and onto the LM descent stage, bringing the CSM down to 22.8 tonnes and the LM up to 22.4 tonnes. This brings both vehicles within the direct TLI capability of 2-core-recovery FH, meaning you would still need two of those but no additional booster for TLI. Of course, you still need to either man-rate Falcon Heavy or do an Earth rendezvous with a separately-launched Dragon 2 before the TLI burn.

To do it more cheaply, you'd need to drive down the mass of the modules or somehow incorporate Dragon 2.

8 hours 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.

The Saturn V cost $566 million per launch in inflation-adjusted dollars, so reducing launch vehicle costs by half is not a bad start. Obviously development costs for the spacecraft are an issue; I was just looking at launch vehicle capabilities.

[tater]

10 minutes ago, Terwin said:

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...

What is making them smaller is the problem? You could make it larger, and cheaper, for example.

6 minutes ago, sevenperforce said:

The Saturn V cost $566 million per launch in inflation-adjusted dollars, so reducing launch vehicle costs by half is not a bad start. Obviously development costs for the spacecraft are an issue; I was just looking at launch vehicle capabilities.

Then there are program costs. The supposed marginal launch cost of Shuttle was in that range, too, and they use a 500 M$ figure for the launch cost of SLS. we all know that those figures are nonsense, however. With a commercial provider, the dev costs only matter to the extent the customer pays them. In the case of NASA, they will have paid a couple billion for Dragon 2, plus 100 M (whatever) a flight. I think they are contracted for 4 flights (6 counting the first 2 tests). That leaves them pretty close to 500 M$ per D2 flight in total cost. Any crew missions going forward would drop that cost. CST-100 more like twice that price.

 

[sevenperforce]

7 minutes ago, tater said:

19 minutes ago, sevenperforce said:

The Saturn V cost $566 million per launch in inflation-adjusted dollars, so reducing launch vehicle costs by half is not a bad start. Obviously development costs for the spacecraft are an issue; I was just looking at launch vehicle capabilities.

Then there are program costs. The supposed marginal launch cost of Shuttle was in that range, too, and they use a 500 M$ figure for the launch cost of SLS. we all know that those figures are nonsense, however. With a commercial provider, the dev costs only matter to the extent the customer pays them. In the case of NASA, they will have paid a couple billion for Dragon 2, plus 100 M (whatever) a flight. I think they are contracted for 4 flights (6 counting the first 2 tests). That leaves them pretty close to 500 M$ per D2 flight in total cost. Any crew missions going forward would drop that cost. CST-100 more like twice that price.

Not sure what you're arguing. $566 million per launch was the Saturn V launch vehicle price per mission. Program costs were $2.5 billion per launch ($33 billion, 13 launches).

And Falcon Heavy was not developed with outside funding.

[tater]

Yeah, FH is a different issue. I just figured out the crew dragon stuff on a lark... which looks pretty meh on cost, unless NASA comes up with something else for it to do (they they just pay per launch).

[sevenperforce]

6 minutes ago, tater said:

Yeah, FH is a different issue. I just figured out the crew dragon stuff on a lark... which looks pretty meh on cost, unless NASA comes up with something else for it to do (they they just pay per launch).

Was this treating NASA-sponsored dev for Dragon 1 separately?

SpaceX has incurred dev costs for Dragon 1, dev costs for Dragon 2, dev costs for Falcon 9, and dev costs for Falcon 9 Block 5. How much of these dev costs were passed on to NASA?

Also, as I understand it, NASA flights cost more than commercial F9 flights because NASA is paying SpaceX for an ISS delivery service, which includes the spacecraft, unlike commercial F9 flights where you are paying only for the cost of the launch vehicle and you supply your own spacecraft.

[tater]

6 minutes ago, sevenperforce said:

Was this treating NASA-sponsored dev for Dragon 1 separately?

SpaceX has incurred dev costs for Dragon 1, dev costs for Dragon 2, dev costs for Falcon 9, and dev costs for Falcon 9 Block 5. How much of these dev costs were passed on to NASA?

Also, as I understand it, NASA flights cost more than commercial F9 flights because NASA is paying SpaceX for an ISS delivery service, which includes the spacecraft, unlike commercial F9 flights where you are paying only for the cost of the launch vehicle and you supply your own spacecraft.

Yeah, I think I looked into this before, and the Dragon cargo flights  (COTS) have been a great deal, including F9 dev costs. But the cadence is so much better (CRS-14 and counting). The trouble with crew is that they are only contracted for 1 flight a year for each provider (4 SpaceX, 4 Boeing). If they don't use more, then the cost is high by SpaceX standards at 500 M$/flight---but that is including dev costs, so that maps to the 1.5 B$ cost of Shuttle, so it's still a deal for NASA in that respect.

[magnemoe]

20 hours ago, SaturnianBlue said:

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.

This is an interesting point, main cost is the electronic. you could use more redundancy up to bolting multiple complete system on the buss. 
Shielding with water or lead is also an option if you can take some extra tons regarding station keeping. 
You can also scale up the system making it more capable. 

[sevenperforce]

If you allow one expendable Falcon 9 flight for Dragon 2, you'd have more than enough margin to add a propulsion pallet to get out of lunar orbit and back to Earth, and to do so without man-rating FH. F9 with Dragon 2 then takes the role of Ares 1 with Orion in the Constellation mission profile, and you merely need to develop a lander with enough propellant in its descent stage to do the lunar insertion burn and drop it on a Falcon Heavy with two-core recovery; launch vehicle costs are then just $187 million.

Unfortunately, with the 311-second isp on Apollo-class hypergolic engines, you'd only be able to allow a lander assembly massing 5.31 tonnes post-LOI, which wouldn't work. If you used something like Blue Origin's Blue Moon vehicle, which is presumably built around a vacuum-optimized BE-3 engine, then you could manage an 11.1-tonne lander assuming isp in the range of 425 seconds.

EDIT: Of course, with an isp of 425 on your lander, you could afford to simply make the Dragon 2 stock, and use the lander's ascent engine for the lunar exit burn, which saves you $30M in launch vehicle costs and drives your allowable LM mass up to 14.8 tonnes. Should be plenty; even if it was single-stage, it would still be able to manage a dry mass of 4.36 tonnes. That's if you want to trust the crew's lives to a hydrolox engine.

Edited February 20, 2018 by sevenperforce

[tater]

 

[CatastrophicFailure]

@tater I’ll see your booster and raise you one more rising. 

 

[tater]

 

Fairing 2.0.

[sevenperforce]

5 minutes ago, tater said:

 

Fairing 2.0.

That DEFINITELY looks bigger.

[tater]

I can't tell any difference, honestly, I just pulled up an old image to compare.

[sevenperforce]

 

9 minutes ago, tater said:

I can't tell any difference, honestly, I just pulled up an old image to compare.

I pulled up the source image and measured the pixels. Unless my pixel-spotting is WAY off, that's a 5.28-meter fairing.

Edited February 20, 2018 by sevenperforce

[tater]

28 minutes ago, sevenperforce said:

 

I pulled up the source image and measured the pixels. Unless my pixel-spotting is WAY off, that's a 5.28-meter fairing.

Hardly obvious from a glance, however. That's a 1.5% difference in diameter.

A small change, but I would assume the goal is fitting the recovery stuff while keeping the interior specs identical (due to sat manufacturers having used that interior dimension in their planning).

[sevenperforce]

6 minutes ago, tater said:

Hardly obvious from a glance, however. That's a 1.5% difference in diameter.

A small change, but I would assume the goal is fitting the recovery stuff while keeping the interior specs identical (due to sat manufacturers having used that interior dimension in their planning).

I'd wager the available interior space has increased slightly.

My "at-a-glance" assessment was like-as-not colored by the fact that I can only see the top half of the rocket, which probably messed with perception.

[Scotius]

2 hours ago, sevenperforce said:

If you allow one expendable Falcon 9 flight for Dragon 2, you'd have more than enough margin to add a propulsion pallet to get out of lunar orbit and back to Earth, and to do so without man-rating FH. F9 with Dragon 2 then takes the role of Ares 1 with Orion in the Constellation mission profile, and you merely need to develop a lander with enough propellant in its descent stage to do the lunar insertion burn and drop it on a Falcon Heavy with two-core recovery; launch vehicle costs are then just $187 million.

Unfortunately, with the 311-second isp on Apollo-class hypergolic engines, you'd only be able to allow a lander assembly massing 5.31 tonnes post-LOI, which wouldn't work. If you used something like Blue Origin's Blue Moon vehicle, which is presumably built around a vacuum-optimized BE-3 engine, then you could manage an 11.1-tonne lander assuming isp in the range of 425 seconds.

EDIT: Of course, with an isp of 425 on your lander, you could afford to simply make the Dragon 2 stock, and use the lander's ascent engine for the lunar exit burn, which saves you $30M in launch vehicle costs and drives your allowable LM mass up to 14.8 tonnes. Should be plenty; even if it was single-stage, it would still be able to manage a dry mass of 4.36 tonnes. That's if you want to trust the crew's lives to a hydrolox engine.

Or, one could send a BFR to the Moon, deliver the cargo\crew\whatever, launch and met with a tanker in Moon orbit. Then return to LEO for another refuelling and another payload. Or land for refurbishment. If BFR can do SSTO launch from Mars and return to Earth, dV for Moon trip should not be a problem.

[sevenperforce]

54 minutes ago, Scotius said:

Or, one could send a BFR to the Moon, deliver the cargo\crew\whatever, launch and met with a tanker in Moon orbit. Then return to LEO for another refuelling and another payload. Or land for refurbishment. If BFR can do SSTO launch from Mars and return to Earth, dV for Moon trip should not be a problem.

Oh, indeed.

Musk stated the planned lunar mission profile was to place a tanker in elliptical Earth orbit, launch the crew BFR to rendezvous with it, refuel, and then go on to the Moon, land, and come back without refueling. Of course, it would take multiple flights to get the tanker up to full capacity.

Edited February 20, 2018 by sevenperforce

[tater]

 

[DAL59]

2 hours ago, sevenperforce said:

Of course, it would take multiple flights to get the tanker up to full capacity.

Are you sure?  When did he say that?  

[tater]

1 minute ago, DAL59 said:

Are you sure?  When did he say that?  

It would take multiple flights of the tanker to get the cargo/crew vehicles to the lunar surface and back. It's basically a full tank, no different than going to Mars. TLI, LOI, landing, liftoff, LOI, TEI, landing. Needs a full tank (comes back mostly empty, too).

[sevenperforce]

21 minutes ago, tater said:

It would take multiple flights of the tanker to get the cargo/crew vehicles to the lunar surface and back. It's basically a full tank, no different than going to Mars. TLI, LOI, landing, liftoff, LOI, TEI, landing. Needs a full tank (comes back mostly empty, too).

Realistically, you'd probably want to put the tanker up in elliptic orbit first, fill it by successive fuel runs, and then send up the crew vehicle, rather than sending multiple tanker flights to a loitering crew vehicle.

Also, I think I may have spoken too soon. The OML of the Falcon 9 fairing 1.0 is already 5.2 meters, not 5 meters as I misremembered, so this may not be Fairing 2.0 after all.

[tater]

I assumed that the new one might only be marginally bigger. At minimum it oly need to be big enough that it can hold the recovery gear without interfering with payloads, right?

 

The next NSF article is about this, and apparently it is indeed slightly bigger, very slightly, your estimate might well be correct.

11 minutes ago, sevenperforce said:

Also, I think I may have spoken too soon. The OML of the Falcon 9 fairing 1.0 is already 5.2 meters, not 5 meters as I misremembered, so this may not be Fairing 2.0 after all.

It's fairing 2.0 says Chris B.

[tater]

 

[magnemoe]

1 hour ago, sevenperforce said:

Realistically, you'd probably want to put the tanker up in elliptic orbit first, fill it by successive fuel runs, and then send up the crew vehicle, rather than sending multiple tanker flights to a loitering crew vehicle.

Also, I think I may have spoken too soon. The OML of the Falcon 9 fairing 1.0 is already 5.2 meters, not 5 meters as I misremembered, so this may not be Fairing 2.0 after all.

Depending on fuel need you might just top tanker up in leo and put it in an elliptic orbit, perhaps some more topping up missions then have the crewed version meet with tanker. 
You don't need an 150 ton mission to moon unless you want to set up an base.