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Their one-way delta-v budgets from LEO range upwards from 3.8 km/s (12,000 ft/s), which is less than 2/3 of the delta-v needed to reach the Moon's surface. [10] But NEOs with low delta-v budgets have long synodic periods, and the intervals between times of closest approach to the Earth (and thus most efficient missions) can be decades long. [11 ...
Delta-v (also known as "change in velocity"), symbolized as and pronounced /dɛltə viː/, as used in spacecraft flight dynamics, is a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver such as launching from or landing on a planet or moon, or an in-space orbital maneuver.
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In some cases, it can require less total delta-v to raise the satellite into a higher orbit, change the orbit plane at the higher apogee, and then lower the satellite to its original altitude. [ 1 ] For the most efficient example mentioned above, targeting an inclination at apoapsis also changes the argument of periapsis .
The actual acceleration of the craft is a-g and it is using delta-v at a rate of a per unit time. Over a time t the change in speed of the spacecraft is (a-g)t, whereas the delta-v expended is at. The gravity loss is the difference between these figures, which is gt. As a proportion of delta-v, the gravity loss is g/a.
It takes 250 days (0.68 years) in the transit to Mars, and in the case of a free-return style abort without the use of propulsion at Mars, 1.5 years to get back to Earth, at a total delta-v requirement of 3.34 km/s. Zubrin advocates a slightly faster transfer, that takes only 180 days to Mars, but 2 years back to Earth in case of an abort.
Belbruno's routes from low Earth orbit require a 3.1 km/s burn for trans lunar injection, a delta-v saving of not more than 0.4 km/s. However, the latter require no large delta- v change after leaving low Earth orbit, which may have operational benefits if using an upper stage with limited restart or in-orbit endurance capability, which would ...