Once fusion technology becomes an affordable reality, building a torchship around that technology should be pretty straightforward. This will probably occur about 100 years after being fully operational, or 10 years after the introduction of fusion technology.
The torchship will produce a minimum of one terawatt of power.
For a Helium–3 + Deuterium (3He + 2H) fusion rocket, the amount of X–rays will need to be minimized, so the reactor will have to run at 1.16x109 K, which yields the following parameters:
- 100 keV per particle
- Exhaust Velocity (VEXH) = 7,600 kps
- Thrust = 263,000 N
- Propellant Mass Flow = 0.0346 kg/s.
The spacecraft may have to refill the 3He tanks on the Moon and the 2H tanks on Earth.
For a spacecraft with a mass of 26,300 kg, a constant one–gee acceleration can be maintained.
If the spacecraft has a structural mass of 7,580 kg and a payload mass of 10,000 kg, it will have a propellant mass of 8,720 kg:
Dry Mass = Spacecraft Infrastructure + Payload
Dry Mass = 7580 + 10000
Dry Mass = 17,580 kg
Propellant Mass = Spacecraft Mass – Dry Mass
Propellant Mass = 26300 – 17580
Propellant Mass = 8,720 kg
The engine can therefore run for around 70 hours nonstop:
Engine Run Time = Propellant / Propellant Mass Flow
Engine Run Time = 8720 / 0.0346
Engine Run Time = 252,023 s
Engine Run Time = 70.0 hrs
A torchship can provide constant acceleration by never turning off the engine. This will provide for an Earth–like gravity environment which can be maintained for days on a spaceship headed out into the void.
Just like on the TV series "The Expanse," they will shut the rocket engine down halfway to the destination. The ship will then perform a "flip and burn," where the ship rotates 180 degrees and fires its engines to slow down, again maintaining a one–gee environment.
For a trip to the Moon, this particular torchship that is running a one–gee acceleration will take around 1.74 hours to reach the halfway point. The total one–way time for the trip to the Moon would be around 3.5 hours, with another. 3.5 hours for the trip back to Earth. Total roundtrip time: around 7 hours.
Therefore, this particular spacecraft could do ten roundtrips to the Moon, under a constant one–gee acceleration, on one tank of gas.
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