The plan

Musk envisions up to 100 Mars-bound colonists boarding an oblong spacecraft perched atop a massive rocket at Kennedy Space Center's launch pad 39A. The rocket's width would be 12 meters; the entire stack would top 122 meters. By comparison, the Saturn V was 111 meters tall and 10 meters wide at the bottom; NASA's Space Launch System will debut at 98 meters tall and 8.4 meters wide.

The rocket would be powered by a staggering 42 engines, generating 28.7 million pounds of thrust at liftoff. That's almost exactly four times more powerful than the Saturn V, which had just five engines. The only other vehicle to attempt an engine configuration on this scale was the Soviet N-1 moon rocket, which had 30 engines and was destroyed four times in four launch attempts.

The booster rocket blasts the Mars colonists into a parking orbit before returning directly to its launch pad for an upright landing. Next, a pad crane lifts a nearby propellant tanker—shaped similarly to the colonists' spaceship—onto the reused booster. The rocket launches again, sending the tanker into orbit to rendezvous with the passenger ship. After a fuel transfer, it's on to Mars for the colonists, while the booster and tanker return to Florida to repeat the process.

Musk's diagrams showed an intention to reuse the booster 1,000 times and the fuel tanker 100 times. That sort of reusability is utterly without precedent; the most re-flown spacecraft of all time is space shuttle Discovery, which completed 39 missions in 27 years. Discovery and its sibling shuttles could carry a crew of seven into low-Earth orbit for a couple weeks; the Mars colonial spaceship would spend between 90 and 150 days en route to Mars.

The cost

Musk estimated it would take $10 billion to develop his transport system. That's optimistic, but in the realm of possibilities. In 1972, NASA estimated space shuttle development would cost $5.15 billion—roughly $30 billion in today's dollars (not counting cost overruns).

SpaceX's estimated cost to build a single booster, tanker and transport ship is $560 million dollars. After the Challenger disaster, NASA paid $1.7 billion for space shuttle Endeavour. By the time the shuttles retired in 2011, it was estimated the program had cost of $209 billion.

Whatever the price tag, it remains to be seen exactly how SpaceX would pay for all this. During the presentation, Musk jokingly used a South Park reference (underpants gnomes) before saying the company would continue focusing on its core business of launching satellites and sending NASA crew and cargo missions to the International Space Station.

At the moment, it can do neither. Earlier this month, a Falcon 9 rocket exploded during a routine propellant filling operation, marking the company's second payload loss in 15 months. SpaceX has yet to find the cause of the accident, though they recently said the problem appeared to have originated in the rocket's upper stage helium pressurization system (notably, Musk said the company's new rocket booster would be autogeneously pressurized and not require such a design).