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and return to earth ")

"Assumes air braking within atmospheres.

TABLE 4-5. Relative Payload Mission Comparison Chart for High-Energy Chemical Multistage Rocket Vehicles

Relative Payload"

Earth satellite 100

Earth escape 35-45

Earth 24-hr orbit 10-25

Moon landing (hard) 35-45

Moon landing (soft) 10-20

Moon circumnavigation (single fly-by) 30-42

Moon satellite 20-30

Moon landing and return 1-4

Moon satellte and return 8-15

Mars flyby 20-30

Mars satellite 10-18

Mars landing 0.5-3

"300 nautical miles (555.6 km) earth orbit is 100% reference.

trajectory-time relation, and other factors that are beyond the scope of this short treatment. Further information on space flight can be found in Refs. 4-2 to 4-4 and 4-11 to 4-13.

For example, for a co-planar earth-moon and return journey it is necessary to undertake the following steps in sequence and provide an appropriate velocity increment for each. This is similar in concept to the diagram for interplanetary flight of Fig. 4-10. For the ascent from the earth and the entry into an earth satellite orbit, the vehicle has to be accelerated ideally to approximately 7300 m/sec; to change to the transfer orbit requires roughly another 2900 m/sec; to slow down and put the spacecraft into an approach to the moon (retro-action) and enter into an orbit about the moon is about 1000 m/sec; and to land on the moon is about another 1600 m/sec. The ascent from the moon and the entry into an earth return orbit is about 2400 m/sec. Aerodynamic drag is used to slow down the earth reentry vehicle and this maneuver does not require the expenditure of propellant. Adding these together and allowing 300 m/sec for various orbit adjustments comes to a total of about 14,500 m/sec, which is the approximate cumulative total velocity needed for the mission. Tables 4-3 and 4-4 compare very rough values of mission velocities and pay-loads for several space missions.

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