4 ms·
And, I presume, much much more efficient
by SubiculumCode 8y ago
And, I presume, much much more efficient
- umeshunni 8y agoWhy is it much more efficient? Doesn't it still have to carry the same mass up to the same altitude and velocity?
- newnewpdro 8y agoIf you accelerate your car 0-60MPH in 3 seconds vs. 30 seconds, which uses less energy?
- sfifs 8y agoShould the energy change be roughly the same = 0.5mv^2 The power would be different (energy is used up much faster in the 3 second case)
- bacon_waffle 8y agoAssuming you're talking about energy transferred through the drive wheels, I'd think the 3 second case would use less energy since less goes in to moving air.
- zik 8y agoNo, because most of a rocket's propellant mass is the oxidiser. With a jet first stage you get the oxygen from the air up to the point where you run out of air.
- jcims 8y agoYes but turbofan engines have a much higher thermal efficiency than rocket engines. Specific impulse is one metric used to describe efficiency, it's units are seconds and the value basically translates to how long a motor could maintain one pound of thrust with one pound of fuel. (Alternatively, how many pounds of thrust could the engine generate if it burns one pound of fuel in one second) The specific impulse of a Merlin engine is on the order of 280s at sea level. The specific impulse of the PW4000's in Stratolaunch is closer to 10,000s. Now the Stratolaunch 'cheats' a little by not carrying onboard oxidizer, but that's almost three orders of magnitude more efficient. Put another way, the Falcon 9 and Boeing 747 carry about the same amount of fuel onboard. However, that same fuel can push a Boeing 747 for 16+ hours while the Falcon 9 burns it in ~2.5 minutes.