While the colonization of the Solar system is underway, a new sport emerges: Spatial Rowing.
The rules are the following:
Each spacecraft has one driver (the contestant)
The loaded mass of each spacecraft (defined as rest mass including the driver, its spacesuit, and the propellant) may not exceed two metric tons.
The linear size of the spacecraft may not exceed 4 meters in any direction.
Any form of stored energy is forbidden on the spacecraft, except energy stored inside the driver (in its muscles, fat...) Of course, this is impossible to literally comply, so the following subrules exist:
No antimatter, fission and fusion fuel.
No gas under pressure exceeding 1000 Pa (at launch), except the breathing mix of the driver.
The breathing mix cannot be used as cold gas thruster, except if it is directly blown out by the driver.
Temperature difference exceeding 20 K between two parts of the craft (at launch) is forbidden.
No solar panels or beamed power receivers.
At launch on the craft may not have any two chemical substances which produce exothermic chemical reaction with each other with ignition temperatures between 0-600 K, except if both are inside the living, organic tissue of the driver, or one is inside the driver, and the other is oxygen (for life support) or nutrients for the driver.
No temperatures (during the whole race) exceeding 600 K are allowed.
Burning life support oxygen and nutrients externally to the driver is forbidden during the race.
No spinning flywheels and parts under tension or torsion exceeding 10 J are allowed(at launch).
The spacecraft have to have a small accumulator, for providing emergency transmission power and life support power, if something should happen to the driver, but using it means giving up the race.
So in one word, the craft must be entirely man-powered, including life support and propulsion. (Of course, there can be accumulators on board, but charging them is to be done by the driver.)
The objective of the race is to go through a racetrack, situated in the space, which is some kilometers long, and contains obstacles and momentum exchange wheels. A pre-set trajectory should be followed, and the obstacles not touched. A typical racetrack takes about one hour and 50 m/s delta V (minimally)
The aim is to do it with the minimum amount of faults, and in minimal time.
What kind of propulsion system should such a racing craft have?