totm nov 2023 SpaceX Discussion Thread

[tater]

 

6 minutes ago, mikegarrison said:

Depends on the 777. You can get them used for around $10M, if you are looking for an early 777-200. Brand new is more like 20x that.

 Don't get into the weeds.

OK, you buy one for 10M, and I buy one for 10M. We both charter them totally full. I continue to use mine for many more charters over time, and you burn yours after landing. Which flight has a higher marginal cost, including amortized cost of the plane?

[CatastrophicFailure]

1 minute ago, mikegarrison said:

There is nothing on an empty Mars that Earth needs. But once there are people there, people generate value. The economic value in Mars is that, eventually, it  can be self-sustaining for people to live there. It won't be Mars that provides the value, it will be the people living on Mars who do.

Maybe they'll export autonomous electric cars or something. 

[mikegarrison]

1 minute ago, tater said:

 

 Don't get into the weeds.

OK, you buy one for 10M, and I buy one for 10M. We both charter them totally full. I continue to use mine for many more charters over time, and you burn yours after landing. Which flight has a higher marginal cost, including amortized cost of the plane?

Profit margins are always found in the weeds. Details matter.

[tater]

1 minute ago, mikegarrison said:

There is nothing on an empty Mars that Earth needs. But once there are people there, people generate value. The economic value in Mars is that, eventually, it  can be self-sustaining for people to live there. It won't be Mars that provides the value, it will be the people living on Mars who do.

In other words some people will do some intellectual work that will have value on Earth. They will send it digitally to Earth, and make money. OK, that'll be what they do---until their intellectual work is replaced by AGI, lol.

They need not go to Mars to do that work, however, where they live is incidental, and if they don't stumble upon the next big intellectual work, then what, they starve?

Just now, mikegarrison said:

Profit margins are always found in the weeds. Details matter.

Doesn't matter, both start with identical cost aircraft, one uses it 1000s of times, the other has to buy a new one every flight.

[sevenperforce]

11 minutes ago, mikegarrison said:

Actually, it's probably not. You can buy a Cessna for what, $100K? Less?

The whole point of his example was that you can't buy used rockets.

A new 172 will run you $250-300K, but if you actually want to be able to have meaningful range, you'd probably want to pick up a Citation or a Citation II. A new Citation will run you around $35M. For that price, you can charter any airliner for a round-trip between any two airports in the world. Much better than buying a new Cessna Citation and crashing it into the tarmac at the end of the trip.

[mikegarrison]

2 minutes ago, sevenperforce said:

The whole point of his example was that you can't buy used rockets.

A new 172 will run you $250-300K, but if you actually want to be able to have meaningful range, you'd probably want to pick up a Citation or a Citation II. A new Citation will run you around $35M. For that price, you can charter any airliner for a round-trip between any two airports in the world. Much better than buying a new Cessna Citation and crashing it into the tarmac at the end of the trip.

I understood his point. But like I just said above, details matter.

That's exactly why his claim that he can do suborbital flights for the same price per ticket as a coach seat in an airplane is screwy. Details matter, and he's glossing over a heck of a lot of them.

[mikegarrison]

Let me give just one example of his P2P suborbital flights are a pipe dream.

Currently, aviation regulations require that the entire airplane must be able to be evacuated on the ground within 90 seconds -- with half the doors blocked. How is his emergency escape system going to work? Ziplines? Giant slides? Teleportation? Personal jetpacks?

[sevenperforce]

20 minutes ago, tater said:

I'm not sanguine about point to point rocket travel, but the BFS (whatever they call it) doesn't need all that tankage for P2P. It could hold 800 people in orbital fit out, minus most of the tankage (it needs very little, the booster does the work), it could likely hold many more. If the marginal cost is (total vehicle cost/total flights)+fuel cost, then it might well only cost a couple million (or less) to fly a trip. That's well into long-haul ticker prices/seat.

I'm still not sold that the booster is required. You only need about 4000-5000 m/s for most suborbital spaceflight hops. Surely the upper stage alone can manage that if you swap out the vacuum raptors for SL ones.

Potential trouble is that the optimal trajectory has an apogee of around 500 km...

[sevenperforce]

2 minutes ago, sh1pman said:

If it did,  the Apollo program would never happen. Or Sputnik. Or any space exploration at all. 

The economics of the Apollo program and Sputnik (and current space exploration) worked because the idea was worth something to the people who paid for it. 

[Nibb31]

2 minutes ago, sh1pman said:

If it did,  the Apollo program would never happen. Or Sputnik. Or any space exploration at all. 

Apollo was economically feasible because it was actually done.

[sh1pman]

1 minute ago, Canopus said:

What event would make Earth less habitable than Mars though?

Alien invasion!

But seriously, there are plenty of those. Consider the Florence asteroid for example.

4 minutes ago, sevenperforce said:

The economics of the Apollo program and Sputnik (and current space exploration) worked because the idea was worth something to the people who paid for it. 

Both programs were government-funded. Just like the idea of being an interplanetary species can be worth something to some government somewhere.

5 minutes ago, Nibb31 said:

Apollo was economically feasible because it was actually done.

Might've used the wrong word there. "Profitable" is what I meant to say.

[Rune]

38 minutes ago, sevenperforce said:

I'm still not sold that the booster is required. You only need about 4000-5000 m/s for most suborbital spaceflight hops. Surely the upper stage alone can manage that if you swap out the vacuum raptors for SL ones.

Potential trouble is that the optimal trajectory has an apogee of around 500 km...

Fire up KSP, install RSS, try it out. Or, you know, have a little faith in the guy that did and commented a couple pages back (not me!), and quotes 9,1km/s as a likelier figure.

 

Rune. It also works if you consider the fraction of kerbin's orbital velocity and kerbin's P2P requirements. Basically >90% of orbital speed.

Edited September 29, 2017 by Rune

[sh1pman]

1 minute ago, Canopus said:

Sorry but even after an Asteroid impact you could still walk around the Earth without a spacesuit. There is nothing short of the complete resurfacing of the Earth that would make life on Mars favourable.

Well, the dinosaurs were probably wiped out by an enormous asteroid strike. Too bad they didn't reach Mars in time!

[Rune]

5 hours ago, sh1pman said:

@Rune what if they only refuel the BFR ship just enough to land on the Moon, and ISRU (if it's possible) the fuel required to get back to Earth? Will it decrease the number of launches significantly?

LEO-Moon is less than 6km/s, so the BFR would have no trouble getting there, and it would in fact be easier than reaching Mars (<8 tanker flights). BUT. ISRU on the Moon is a very different beast than in Mars. You don't have an ubiquituous CO2 atmosphere, and you have much less water ice, and the ice is locked in hard-to-reach, permanently shadowed craters.

 

Rune. So probably more difficult.

Edited September 29, 2017 by Rune

[RedKraken]

Just watched Scott Manly's reaction to iac 2017 : https://www.youtube.com/watch?v=wEokBZkZWxo

He makes a good point with the engines for a moon landing.

170t thrust engines are way too big (for an 85t+cargo craft on the moon) and can't throttle deep enough.

They will be moon landing on something 10 times smaller.... maybe a pair of 17t thrusters?

 

[sh1pman]

1 minute ago, Rune said:

LEO-Moon is less tha 6km/s, so the BFR would have no trouble getting there, and it would in fact be easier then reaching Mars (<8 tanker flights). BUT. ISRU om the Moon is a very different beast than in Mars. You don't have an ubiquituous CO2 atmosphere, and you have much less water ice, and the ice is locked in hard-to-reach, permanently shadowed craters.

Understandably. But I was considering an already existing Moon base and ice mining operation underway. Best case scenario, like what is theoretically possible and what isn't.

[RedKraken]

In the nasa forums,  I saw a reference to CO2 and CO locked in the lunar ice.....

This could be very interesting for lunar methane ISRU if correct.

Edited September 29, 2017 by RedKraken

[Rune]

5 hours ago, magnemoe said:

However taking 150 ton to the moon surface only make sense if you set up an permanent base. 
An science mission even one far larger in scope than Apollo would not need 150 ton cargo or an giant lander. 
Now an tourist mission would want an huge lander but would not need so much cargo,

Yeah, but maximum payload would be the more favorable case in terms of mass efficiency, and therefore if you are building a base, the best bang for your buck. If you take a partially empty vehicle there, that means a smaller one could do the job just as well, and/or you will pay more per kg on the long run.

 

Rune. Besides, the square/cube law kinda guarantees better results the bigger you go.

5 minutes ago, sh1pman said:

Understandably. But I was considering an already existing Moon base and ice mining operation underway. Best case scenario, like what is theoretically possible and what isn't.

Well yeah, if that's the case, maybe. But, again, how did you build that base in the first place? BFR is the thing that build the thing, because it needs no prior infrastucture, or can deploy it in more or less a single flight.

 

Rune. Giving that out would be giving out its reason for existing in the first place.

[RedKraken]

The guys over at reddit are arguing about dv costs for point to point.: https://www.reddit.com/r/spacex/comments/736po1/some_quick_calculations_about_point_to_point/

Some people are using wikipedia's 6100 m/s calculated for icbms : https://en.wikipedia.org/wiki/Sub-orbital_spaceflight#Speed.2C_range_and_altitude

Some guys (nzvpn and sudohack) have pointed out 27000 kph needs > 8000 m/s.

Nothing on deltaV cost from the nasa forums yet : http://forum.nasaspaceflight.com/index.php?topic=43849.0

It will be interesting to see where this goes.

Checking my deltav with a modified BFR. 12 sealevel engines. 

KSC to London is about 7100km. 

Single stage is looking closer to 8700m/s than 9100.....apologies for my previous post....

but add 300-400m/s landing fuel... and you are back to 9100m/s

Aggressive turn plus high twr plus atmospheric braking overshoot.

Most of the distance is gained in the last few hundred m/s of the apogee burn.

Two stage approach for point to point will have the booster providing 4000m/s+ to the solution.

Edited October 2, 2017 by RedKraken
add landing fuel

[sh1pman]

8 minutes ago, Rune said:

Well yeah, if that's the case, maybe. But, again, how did you build that base in the first place?

With BFRs of course! The first ones will have to be refueled with 20 or so launches each, true. But when the hotel base is all done, next ships can benefit from it, needing fewer refuels. Just thinking about how cheap a tour can get.

[Ultimate Steve]

I understand that BFR is all the rage right now, and it's sort of a bad time, but I found this cool graph:

Now, we just need one of those lines to intersect...

[tater]

1 hour ago, mikegarrison said:

No it's not. You think it costs a couple million to fly a single A380 trip?

You just gave a best-case scenario assuming all kinds of advantages for the rocket, and you still came up with a number that is not competitive with an airplane. The market for this would be like the Concorde. It would be limited to people who were willing to pay a hefty premium either for the speed or just for the experience.

I said do the math. Fuel cost plus amortized vehicle cost/flight is the marginal cost, right? If you can put 1500 people on it (most tanks gone), or 800 and no booster, then you're in the ballpark of long haul tickets (at cost). Charge 1st class prices for the window seats (literally 10X coach), and you're likely OK. They could charge more, as well, since a 40 minute flight time is still worth something. It's worth a lot. If you only can take a week off, and your international vacation has a couple days each way wrecked with air travel, the opportunity cost of the lost days is huge. Most high-price travel is business, as well, and you're not jet lagged, etc, worth extra.

1 hour ago, mikegarrison said:

Let me give just one example of his P2P suborbital flights are a pipe dream.

Currently, aviation regulations require that the entire airplane must be able to be evacuated on the ground within 90 seconds -- with half the doors blocked. How is his emergency escape system going to work? Ziplines? Giant slides? Teleportation? Personal jetpacks?

This is actually a primary reason (along with overflights of huge rockets) why I think it's a nonsense idea for at least a long time. The ground evac is just to get out of the aircraft, even just at that level, with many hundreds of people, they'd need multiple doors to the gantry, and they'd likely want that blast-proofed or something. The FAA requirements would be impossibly hard as "air travel," though perhaps they get around it by calling it space tourism, and having special rules for such "adventure" travel.

The overflight issue is also non-trivial. I think if it were ever allowed at all, it would be routes like LA<-->Sydney, or other over-water flights (launch and landing corridors over water). Maybe after they fly many thousands with no problems they could argue to fly over inhabited areas... maybe. Seems unlikely.

[Spaceception]

Cool video!

https://youtu.be/i_3GPliquidV8

[YNM]

Regarding BFR Earth-to-Earth concept...

 

So, how do we differ a BFR from an ICBM, again ?

[magnemoe]

1 hour ago, sh1pman said:

With BFRs of course! The first ones will have to be refueled with 20 or so launches each, true. But when the hotel base is all done, next ships can benefit from it, needing fewer refuels. Just thinking about how cheap a tour can get.

Thinking of it, BFR capacity is so idiotic high you could probably have cargo capacity on tanker 10 ton would not reduce fuel load much. Granted this would fix the orbit. 
However you might even have an reusable tug taking satellite to GTO, return to LEO and dock with the next tanker for return. 
 

11 minutes ago, YNM said:

Regarding BFR Earth-to-Earth concept...

So, how do we differ a BFR from an ICBM, again ?

ICBM is smaller than an falcon 9
If this is an issue you would also raise warnings with all sort of rockets even tactical ones 
You can also predict the trajectory of an ballistic missile after 5 minutes of flight.