Sunday, July 11, 2010

Flight To An Asteroid With SpaceX Hardware

John Hare has an article about commercial beyond Earth orbit exploration in a world where cheap access to space has lowered the cost of a kg to LEO to $1000 or less. But I think it begs the question, how much does it cost now?

Warning: contains Machiavellian humor.

The biggest problem with commercial human beyond LEO flight right now is the lack of an affordable LH2 upper stage. In SpaceX terms: they don't have Raptor yet. But hey, no-one ever said you have to use LH2/LOX stages to go beyond LEO.

If you're aiming at an asteroid at an optimal time, there's at least one target you can hit with only 2.8km/s of delta-v from LEO, and 1km/s of delta-v to rendezvous with the asteroid, 2006 RH120. (Note that you can divide this up any way that makes sense to you, but more than 1km/s of delta-v at rendezvous is probably undesirable. For a flyby of 2006 RH120 you need 3.733km/s). See this list. Personally, I'd rather aim at 2009 BD as it is almost always "close" to the Earth.

Now the vehicle. Let's say a Dragon with a full service module, crew of 2 or 3 and some supplies: that's 10t. Even in the ISS servicing configuration it has sufficient delta-v to do the 1km/s delta-v rendezvous, and do the 1km/s delta-v needed to get back. Slowing down when you get to Earth orbit will be a dicey situation, but if you can burn off some delta-v with a lunar flyby then the PICA heatshield on the Dragon should be sufficient to get us safely back on the ground. But hey, who said anything about coming back anyway.

Using Kirk Sorensen's great formulas, the initial mass in LEO will be less than 27t (for anyone who cares, I'm using lambda=0.0133707, phi=0.0216, ISP=342s). This means you need about 17t of fuel, minus tankage, and that's not so bad. First flight will be the Falcon 9 to deliver 10t of LOX in an insulated tank payload. Depending on how much boil-off there is before the next flight, and taking into account the mixture ratio, the next flight will carry 5200kg of RP-1 and 4800kg of LOX in payload. Both the upper stages will remain SpaceX's, so they can reuse it or whatever they think they can do with it.

Finally the manned Dragon is launched to join up with the propellant tanks. Unlike the other two flights, ownership of the upper stage is transferred from SpaceX to us, as is the Dragon, but I hear they're prettimuch assuming that model for GTO flights, so it shouldn't be a problem. And they can have the Dragon back if they really want our smoking corpses, uhh, I mean, ya know.

The entire stack heads off to the asteroid. Note that it's the upper stage of the manned Dragon flight that is acting as the trans-asteroid-injection stage. Depending on how close the target is, it's a few month voyage. If you want to get fancy you can take along a really long tether and swing up the vehicle to get artificial gravity.. but remember that it'll eat into the Dragon's propellant mass, reducing contingency on rendezvous.

It's quite an adventure, so what's the price tag? The two tanking flights are just stock Falcon 9 flights at $56M each. The manned flight is probably going to be something like $150M. The tank hardware with its insulation and such is in the noise. All up, $265M.

That's a lot of money to go asking a venture capitalist for. You're going to need a pretty fancy view graph presentation to convince them that you can pull it off without dying horribly, do it better than a 1t robotic probe that could be sent direct on a single Falcon 9 flight, and bring back something worth at least 10 times as much as it cost to execute [the crew, no really, just kidding].


  1. john hare12:59 AM

    $265M for a manned asteroid mission should be a slam dunk compared to anything currently on the books.

  2. Anonymous1:16 AM

    How are you breaking down the manned flight? Are you including any notion of leasing the Dragon?

  3. Anonymous1:48 AM

    Look feasible, dragon + SM would be the return vehicle, hypogolics should work for that. The other launch would be a mission module ie extra power, storage, sleeping, airlock etc and a EDS, The EDS could be a expanded upper stage with enough fuel to do both jobs. Having a falcon heavy for the second launch would make things easier margin wise.

  4. Yeah, the Falcon Heavy could loft it all at once. Also, this is a heckuva lot cheaper than what a similar Constellation endeavor would cost. It's a great idea. Speaks to the idea of a privately-financed asteroid mission. Though, really, to really make anything out of any asteroid, you're going to want to send a ton of probes and ISRU drones before you send any people. Sure, flags and footprints, but speaking from a practical perspective.

  5. Great reply, now let's add John Hare's point about CATS kicking in hard at 1K $ per kilo and you can very roughly divide your price by 20.

    $13.25M all up then.

    You'd only need 2 or 3 rich "nuts" then or about 30 comfortably wealthy "nuts" ^_^ (neither includes me I should add and not because of the "nut" part).

    John Hare is obviously right about great elasticity at such a price as far as I am concerned (if the prices start dropping significantly I think we'll see a whole lot of activity far earlier than at a 1K $ per kilo price ^_^).

    -- Habitat Hermit / Gla'funk (I'm signed in at the moment that's all)

  6. I'm informed that the delta-v of the Dragon is more like 500m/s not 2000m/s.. so our brave adventurers are going to have to trade half the supplies for storable propellant.

  7. > I'm informed that the delta-v of the Dragon is more like 500m/s not 2000m/s..

    I wonder what the delta-v of the push-based escape system will be...

  8. Shanuson7:28 PM

    not much more since it should use the same propellant as far as i understand. so not more propellant mass

  9. Anonymous1:37 AM

    Why not bolt on an Ad Astra Vasimir engine to the upper stage to reduce the trip time and mass to orbit?

  10. Dennis7:55 PM

    Is Dragon equiped to handle deep space radiation problems, like Orion?

  11. Dragon is a transfer vehicle. It's enough to get people to and from orbit. For a one time cost a reusable fuel and go spaceship could be put in orbit to go anywhere, but built specifically for the environment it will travel in... high radiation, never below orbit.

  12. Radiation protection? It's only a 15 day one-way trip to the asteroid I identified. In any case, you've got much bigger problems than radiation. Radiation is a *known*. Rendezvous with a asteroid, doing something useful when you get there, that's either a massive study or some seat-of-the-pants thinking.

  13. It's great, fantastic really, to show the naysayers that $235m will do the job with existing hardware. You do a great job Trent.

    But a one time cost of $2b or so could put a ship made for the journey in orbit. A ship that can be used over and over to amortize it's cost to that of resupply. $2b is a big nut to crack, but afterward the reward is tremendous.

  14. ken, that would indeed be awesome, and it's not so much that it couldn't be done commercially, but I think that right now it really is a too big nut to crack. What would completely change the giggle factor is an asteroid mining demonstration that actually turned a profit.. it'd be a gold rush.

  15. One of the comments made when I read up on the DC-X is they made a mistake by not going to a full scale vehicle from the start.

    Naysayers can always say there nay if you don't go all the way. A good demonstration is just never good enough for them.

    Even though I think suborbital is worth the effort only an orbital effort gets my attention.

    We don't have to have a $2b ship as our first one. A BA330 and F9 upper stage would make a perfectly good starter ship for about $250m to orbit. Once both Bigelow and SpaceX are putting their respective pieces in LEO I'm thinking the bulb might just light up?