How Much Energy Is Required to Launch a Satellite into Orbit?

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Homework Help Overview

The discussion revolves around calculating the energy required to launch a satellite into orbit, specifically focusing on a satellite with a mass of 200 kg intended to reach an altitude of 205 km above Earth's surface. Participants are exploring concepts related to gravitational potential energy and kinetic energy in the context of orbital mechanics.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants are attempting to calculate both kinetic and potential energy for the satellite in orbit and at the Earth's surface. Questions are raised regarding the appropriate radius to use for calculating initial potential energy, with some suggesting the Earth's radius is relevant since the satellite starts from the surface.

Discussion Status

The discussion is active, with participants sharing calculations for kinetic and potential energy. There is an ongoing exploration of the assumptions regarding the radius to be used in energy calculations, indicating a productive examination of the problem without reaching a consensus.

Contextual Notes

Participants are working under the assumption of no air friction and are considering the implications of Earth's rotational effects on initial kinetic energy calculations. The problem context includes specific values for mass, altitude, and orbital parameters, which are central to the discussion.

crr2010
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1. Homework Statement

A satellite of mass 200 kg is launched from a site on Earth's equator into an orbit at 205 km above the surface of Earth. What is the minimum energy necessary to place the satellite in orbit, assuming no air friction? I also figured the orbital period to be 5300 s and the orbital velocity to be 7788 m/s

2. Homework Equations
P = -GMm/r
K = .5*m*v^2

3. The Attempt at a Solution
I plugged the numbers into the kinetic energy equation
.5*200 kg*(7788 m/s)^2
and got 6.07 E 9
 
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What's the potential energy of the satellite in orbit?
What's the total energy of the satellite in orbit?
What's the kinetic and potential energy of the satellite sitting at the equator?
 
final kinetic = 6.065 E 9 J
final potential = 1.211 E 10 J
final total energy = -6.049 E9 J

initial kinetic = 2.153 E 7 J (using Earth's rotational period of 463.9 s to find Earth's v)
now here's where I am not sure
for initial potential energy do you use the total radius or just the radius of the earth?
 
crr2010 said:
final kinetic = 6.065 E 9 J
final potential = 1.211 E 10 J
final total energy = -6.049 E9 J

initial kinetic = 2.153 E 7 J (using Earth's rotational period of 463.9 s to find Earth's v)
now here's where I am not sure
for initial potential energy do you use the total radius or just the radius of the earth?

Since it is sitting on the surface of the Earth, doesn't it make sense to use the Earth's radius?
 

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