The fraction of the total initial mass \(m\) that is propellant is \[\frac{\text { propellant mass }}{\text { total initial mass }}=\frac{m-m_{e}}{m}=1-\frac{m_{e}}{m} \text {. }\] Eq. \(\PageIndex{2}...The fraction of the total initial mass \(m\) that is propellant is \[\frac{\text { propellant mass }}{\text { total initial mass }}=\frac{m-m_{e}}{m}=1-\frac{m_{e}}{m} \text {. }\] Eq. \(\PageIndex{2}\) tells what fraction of the rocket's total mass must be fuel in order to achieve a desired change in rocket velocity \(\Delta v\). In this case, the rocket's velocity will need to change by an amount \(\Delta v=17,000 \mathrm{mph}\), or about \(7600 \mathrm{~m} / \mathrm{s}\).
A rocket is a vehicle that propels itself through space by ejecting a propellant gas at high speed in a direction opposite the desired direction of motion. The largest and most powerful rocket ever bu...A rocket is a vehicle that propels itself through space by ejecting a propellant gas at high speed in a direction opposite the desired direction of motion. The largest and most powerful rocket ever built is the United States Saturn V Moon rocket, which took the Apollo astronauts to the Moon in the 1960s and 1970s. As we'll see here, such arguments are silly—one needs only to make use of the conservation of momentum to show that rockets can work in space.
