Human powered rockets
A human-powered rocket would use steam as a propellant instead of rocket fuel. A group of approximately 100 astronauts would get inside the rocket,and they would pedal to provide power for the rocket. Each seat inside the rocket would have a set of pedals installed on the floor in front of it. When the astronaut pedals,the energy of his leg muscles is converted into electricity. The electricity produced by all the astronauts when they pedal is sent into the water tank,in the rocket. The electricity causes the water to boil. Since the rocket's water tank is large,(it contains thousands of gallons of water)the astronauts must pedal for approximately three days before they build up enough steam pressure to launch the rocket.
To so this.they are split into two groups. Group one pedals for 12 hours while group two sleeps for 12 hours,then they change places,group one sleeps for 12 hours while group two pedals for12 hours. After three days of pedaling,the steam pressure in the boiler is sufficient for launch. At that point,the pilot pushes the launch button,which causes the steam exhaust valve on the bottom of the rocket to open. When the valve opens,the steam escapes from the exhaust nozzle,and the steam provides thrust. The thrust of the steam causes the rocket to rise into the sky.
The astronauts are required to continue pedaling during the ascent phase of the flight. The first and second stage steam boilers are jettisoned,when they run out of water. Finally the third stage carries them into orbit,and the third stage is jettisoned. At this point,the astronauts will experience weightlessness. They can stop pedaling,and get out of their seats,and float freely around the inside of the re-entry module. After orbiting the Earth a few times,the re-entry module re-enters the Earth's atmosphere. The bottom of the re-entry module is covered with heat-resistant ceramic tiles,to protect the vehicle from re-entry heat. When the re-entry module flies near an airport,the landing gear is extended,and it can land on an airport runway,like an airplane.
This system of rocket flight does not require fuel,it does not pollute the Earth's atmosphere,and it does not contribute to global warming.