I Doubt It: $500K Visits To Mars (Roundtrip?) By 2040

March 22, 2012


According to space transport company SpaceX founder Elon Musk, humans will be traveling to Mars in the next 10 years (15 at most), and by 2040 we'll be sending people there on roundtrip vacations for $500,000. Yeaaaaaaah, how bout we start with the moon?

The secret to cheap space travel, Musk says, is modeling spacecraft after airplanes.

Musk's long term plan is to take this philosophy of reusability and ride it all the way to Mars. To do this, he'll have to get the lifetime cost of the rocket down to the point where fuel is the primary expense, implying a per pound cost to orbit of just $10 or $20.

If SpaceX can get a reusable deep-space system in place, that could potentially remove a large part of the infrastructure cost from an Earth-Mars passenger service, and all people would have to be able to afford would be the fuel. And at that point, SpaceX will be able to "offer a round trip to Mars that the average person could afford -- let's say the average person after they've made some savings."

First of all, with the value of money over time, $500,000 will barely be enough to buy a large popcorn at the hologram movies in 2040. Secondly, A ROUND-TRIP TO MARS IS 520 DAYS. Imagine riding on an airplane with a bunch of people you hate for that long. I'd go f***ing crazy by the second day and the pilot would have to turn around.

$500,000 round trip to Mars by 2040? SpaceX says yes [dvice]

Thanks to Logan, who has every intention of upgrading to first class to avoid having a kid sitting behind him who perpetually kicks his seat.

  • Im only going if the Total Recall "Three-Boob Chick" and Midget Prostitute can be had as a three-some. "You make a brother wish he had three hands!"

  • Well, lets see. I'm not even going to include landing on Mars. Just round trip to Mars' orbit.

    The ship will have to first leave Earth and establish LEO. LEO is 7.8km/s, but due to gravity and drag, the actual burn is equivalent to 9.4km/s.

    From LEO, the ship needs to escape Earth's gravity. Escape velocity is 11.2 km/s, so the ship needs to accelerate by another 3.4km/s.

    Now the ship is in orbit around the Sun, going 29.8km/s relative to the later. The optimal trajectory to reach mars is an elliptic orbit intercepting both planets' orbits. Establishing that orbit, the ship needs to go to 32.7 km/s. That's 2.9km/s faster than it's already going.

    Eight and a half months later, the ship will reach Mars' orbit, now traveling at 21.5 km/s. Mars itself is traveling at 24km/s, and you have to match that before trying to establish orbit. So you need to burn for another 2.5km/s.

    Now you are plunging onto Mars. The escape velocity is 5km/s. You'll need to break to 3.6km/s to establish orbit. That's a 1.4km/s burn.

    So the total from LEO to Mars' orbit is 10.2km/s. Return trip is exactly the same in reverse order. That's another 10.2km/s. And there were 9.4km/s to establish LEO in the first place. Re-entry would require some fuel, but to be honest, I have no idea how much, so lets just discard it. I'm pretty sure it's negligible compared to the rest of it.

    So what you need is equivalent of sufficient fuel to reach velocity of 29.8km/s. What fuel would be used? Well, cryogenic LH2, almost certainly, with LO2 oxidizer. That fuel has specific impulse of 4.4km/s. So the amount of fuel needed per 1kg of mass is e^(29.8/4.4)-1 = 872.7kg.  Only about 10%-20% of the ship's mass is going to be useful cargo. Lets say 20%.

    For each person, you need a year and a half worth of supplies. So we are looking at the bare minimum a ton of cargo per passenger. That's at least 5 tons of ship's mass, and that's 4360 tons of fuel per passenger.

    Note that this is an unreasonable quantity of fuel for one ship, so refueling will be required, but with a good scheme of getting the fuel to orbit, the total amount of fuel needed will not be significantly increased.

    Right now, LH2 is about $5 per kg. It won't get cheaper. Liquid oxygen is almost free in comparison, since it's produced by extraction from atmosphere. And you need 2kg of LH2 per 16kg of LO2. So that comes out to $2.5M in LH2 costs per passenger.

    And this is absolutely the best case scenario for a flight in a tiny cramped cabin with recycled water and air and dry rations for food for a year and a half.

    tl;dr, the $500k price tag is unreasonably optimistic. Best you can hope for is a few million. More realistically, the price tag will be 10-20 times higher, in $5-$10M range. Which is still unbelievably good, considering that right now you wouldn't be able to fly to LEO for that much money.

  • Your comment was very well thought out. However I think there's a possibility that the 29.8 km/s velocity's worth of fuel you said would be required for the mission could be reduced to (29.8-10.2 = 19.6) km/s worth of fuel, which is e^(19.6/4.4) = 86.1 Kg of fuel/kg of payload.
    The 10.2 km/s can be decreased if you make you of "Mars Direct's" proposal to produce methane propellant from mar's atmosphere, using equipment permanently placed in Mars. Which would mean the fuel required for the 10.2 km/s on the return trip can be produced directly on Mars instead of carrying it from Earth.
    The reduction in fuel requirement from 872.2 kg to 86.1 kg/1 kg of payload will drop the fuel costs to 1/10th of what you had originally proposed.
    Also, I believe, advances in renewable sources of energy (especially solar energy) can bring down the cost of producing LH2 as well, over the period of the next 28 years.

  • Andyman7714

    And when you come back you will be blind and unable to walk in Earth's gravity.

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