Re:NASA, DARPA Will Test Nuclear Engine for Future Mars Miss...
by credit_guy on Wednesday January 25, 2023 @12:51PM
(#34521619)
No, actually it does not depend.
The rocket equation says that the fuel mass of a rocketship is higher than the cargo mass by exp(delta_v/v_exhaust).
When the final velocity is relativistic, delta_v should be replaced with delta_rapidity. In our case this would introduce a factor of 2.65, but the results are so ridiculous that we can ignore that.
So, let's simply say that delta_v is the speed of light, or 300000 km/s.
The exhaust velocity for a nuclear thermal rocket is about 9 km/s.
The ratio between delta_v and the exhaust velocity is about 33000. The exponential of that is roughly speaking 1 followed by 15000 zeros.
There are less than 10^100 atoms in the known universe.
So, even if you want to accelerate just one single atom to 99% of the speed of light, you would need more fuel than the entire universe. Many, many, many times more.
The rocket equation says that the fuel mass of a rocketship is higher than the cargo mass by exp(delta_v/v_exhaust).
When the final velocity is relativistic, delta_v should be replaced with delta_rapidity. In our case this would introduce a factor of 2.65, but the results are so ridiculous that we can ignore that.
So, let's simply say that delta_v is the speed of light, or 300000 km/s.
The exhaust velocity for a nuclear thermal rocket is about 9 km/s.
The ratio between delta_v and the exhaust velocity is about 33000. The exponential of that is roughly speaking 1 followed by 15000 zeros.
There are less than 10^100 atoms in the known universe.
So, even if you want to accelerate just one single atom to 99% of the speed of light, you would need more fuel than the entire universe. Many, many, many times more.