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Back of the envelope calculation for the price of an Earth-to-Earth ticket: Musk's stated goal is $500k/ticket to Mars. It's a shorter trip, so perhaps ~5x as
by tbabb 9y ago
Back of the envelope calculation for the price of an Earth-to-Earth ticket:
Musk's stated goal is $500k/ticket to Mars.
It's a shorter trip, so perhaps ~5x as many passengers in the same volume (i.e. 500 total; cf. a380 which seats 850).
It takes five (?) orbital refuel trips for the martian journey, but we'd need none of those. Depending on how much less than a full tank the passenger vehicle needs (payload could be smaller; the ship would also not reach fully orbital velocity), the fuel cost would be between 1/5 and 1/10 the Mars fuel cost.
So that would bring the cost down to between $10 and $20k/ticket, within reach of business travelers.
If maximum the number of flight cycles per vehicle is greater for Earth-to-Earth trips than for Mars, then that could further reduce the ticket cost. It's unclear to me which direction that number would go-- Earth's atmosphere is much thicker on re-entry, though the velocities will be much lower than an interplanetary re-entry. Since aerodynamic drag goes as the cube of velocity but only linearly with density, I'm guessing the speed would matter far more. That would imply much better lifetime on Earth.
So if the E2E fuselage gets (conservatively) only 2x as many flight cycles as a Mars trip, that could bring down the per-seat cost to $5k-- now getting close to the cost of an ordinary international ticket. Of course this is all assuming that Musk's baseline of $500k to Mars is reasonable.
Would be curious to hear from some rocket engineers about these guesses at the numbers/efficiency.
Not accounted for is amortized development cost for E2E-only vehicles, as well as all the infrastructure and ground support at the destinations.
Edit: If you wanted to be less conservative, you could pack in 1000 people instead of 500 (0.5x ticket price multiplier), or use a different source for the Mars ticket price (0.4x), which would bring it to $1k.
- neuronexmachina 9y agoIn general, I think the only part which is supposed to need regular replacing is the ablative heatshield. Regarding Earth vs Mars reentry, he said the following during the talk (my quick transcription follows): "You're going in, you're going very quickly, 7.5 km/s. For Mars, there will be some ablation of the heat shield. So, it's just like a brake pad wearing away. It is a multi-use heatshield, but unlike for Earth operations it's coming in hot enough that you will see some wear of the heatshield."
- cryptoz 9y agoElon's stated goal for ticket price to Mars is $200k, not $500k.
- Osmium 9y agoIronically, I think SpaceX will have a lot more trouble with any E2E ambitions than they would with missions to Mars. So much red tape, no one's going to want a space-port in their backyard, different/difficult economics, safety concerns, terrorism concerns, etc. etc.
- extrapickles 9y agoThats why they show the spaceport out at sea, as it kills the standard NIMBY objections. Also the cities they want to fly out of don’t have enough room to easily build a spaceport.
- Osmium 9y agoIf you think putting it a little out to sea would kill NIMBY objections .... still, we can but dream. I'm not entirely sure how serious SpaceX are about their E2E idea anyway, I took it as more of a "hey, isn't this neat? totally physically possible and practical too." I imagine it would take a long time to scale up to that point though, probably decades(?) after the Moon/Mars.
- trevyn 9y agoObjections, sure, but any enforcement ability? That’s international waters.
- mastazi 9y agoInternational waters start more than 20km out from the coastline (12 nm)[1], that would be a very long ferry just to reach the spaceport, not just a short hop like shown in the video... [1] https://www.un.org/Depts/los/convention_agreements/texts/unclos/part2.htm https://www.un.org/Depts/los/convention_agreements/texts/unc...
- jerven 9y agoThat's about half an hour at a not that fast 25 knots. 30 minutes from a city center. For any coastal city, that is likely to be no worse as the time to get to an intercontinental airport. Still means about 2h00 from NYC to Shangai, door to door. Quite an improvement over the 17hours today. Non coastal cities have a problem... In any case it takes care of most nimby as it's to far away for the neighbors to care. So reasonable, in that aspect. Of course ITAR, fear of nuclear strikes etc... general FAA/EASA regulations remain issues for this business plan. Weather will also be an issue. Flights rarely get canceled for weather issues. But transferring from a ferry onto a barge at high sea in bad wind seems like an non fun experience in a three piece suit.
- modeless 9y agoElon says on Instagram: "Cost per seat should be about the same as full fare economy in an aircraft. Forgot to mention that."
- jlebrech 9y agoI hope he creates methane collection facilities on earth, it would reduce co2 as well.
- TeMPOraL 9y agoThere's nothing stopping anyone from building them except the one thing that's always stopping people from doing things that need to be done - economics. It's cheaper to get methane from the ground than to make it from air and water.
- DiThi 9y agoI think the mars ticket includes many other things, like food and everything required to live for 2 years.
- DrBazza 9y agoOne problem with Earth-to-Earth is noise. A quick google tells me Saturn 5 was 220 decibels. So it has to be sea launches or desert launches. Also, Concorde couldn't go supersonic until it was significantly out to sea.