Friday, December 03, 2010
In 1927 Charles Lindbergh flew non-stop from Long Island to Paris. He was catapulted to instant fame by doing so and won the Orteig Prize. He didn't have a co-pilot. He didn't have an army of engineers monitoring his plane or a flight surgeon monitoring his heart rate, it was just him and his trusty single-engine monoplane, the Spirit of St. Louis. His achievement is heralded today as kick-starting the commercial aviation industry and opening up the skies to the everyman.
But what of space? Could a modern Lindbergh fly an impossible journey and change the way we look at spaceflight forever? I think it can be done, and for cheaper than you might imagine.
In 1968 the first humans left the vicinity of Earth, flew 6 days and nearly a million miles to the Moon and back. Their mission not only was the first, it also proved the feasibility of the missions to follow. Apollo 8 would have been much easier to achieve had they only wanted to swing-by the Moon, and still a significant achievement. Instead, they entered lunar orbit, circling it 10 times before returning home.
If the flight is to be attempted today, the cheapest available launcher is the Falcon 9 from SpaceX. It can put 10,450kg into LEO. The Dragon capsule is also available - they say the crew configuration is not much different from the cargo configuration - and after removing the 310kg Common Berthing Mechanism, and another 60kg of miscellaneous mass savings, a dry mass of 1926kg is achievable.
For a single crew member, assumed to be less than 90kg, the consumables requirements for one week are: 11.839kg cabin air and pressurization, 25.83kg oxygen candles, 52.71kg LiHo CO2 scrubbers, 45kg food and water. Adding this to the dry mass gives a final mass to run the rocket equation on: 2152kg.
The delta-v required to leave Earth orbit and head towards the Moon is a whopping 3107m/s. Entering low Lunar orbit requires another 837m/s, and returning home requires another 837m/s. So we need a grand total of 4781m/s.
All the propulsive maneuvers are achieved using the Draco thrusters on the Dragon capsule, which I estimate to have a specific impulse of 309 seconds. dv = 9.8 * 309 * ln(10450 / 2152) gives us an uncomfortable 4m/s of margin. :) [edit: it occurs to me that the Dragon dry mass already includes a life support system, and a 78.54kg reduction in mass has a massive effect on delta-v. So this is more like 115m/s of margin, which should make anyone happy.]
In order to win the Orteig, Lindbergh had the Spirit built custom for his needs. Benjamin Mahoney is said to have built it for cost. Perhaps Elon Musk could be similarly persuaded, but at current prices it'll cost around $130M.