RSHW 6

Question 1

Apollo 15 CSM - Apollo 15 CSM over Lunar Surface

CSM – command and service module

Units

http://www.braeunig.us/space/units.htm

In the SI System, the basic units are the units of length, mass, and time, and are called respectively, the meter (m), the kilogram (kg), and the second (s). The unit of force, called the Newton (N), is a derived unit and is defined as the force that gives an acceleration of 1 m/s² to a mass of 1 kg.

In the U.S. Customary System the base units are the units of length, force, and time, and are called respectively, the foot (ft), the pound (lb), and the second (s). The unit of mass, called the slug, is a derived unit and is defined as the mass that receives an acceleration of 1 ft/s² when a force of 1 lb is applied to it.

1 slugs = 14.5939029 kilograms

1 slug-g ~ 32 pounds

http://www.digitaldutch.com/unitconverter/

Question 1

The CSM is at rest in space a 5 slug astronaut pushes off of the ship and glides away at 20 ft/sec relative to the resting position. If the CSM has a weight of 80,000 lbs what is its velocity?

Hint: conserve momentum

Part 1. Draw a free body diagram

Part 2. Label the diagram

Part 3. Right down the conservation of momentum for both objects

Part 4. Find the velocity of the CSM

Part 5. What is the kinetic energy of the astronaut?

Question 2

The astronaut is now working on a 500 lbs satellite, they are both at rest. The astronaut pushes off the satellite and moves away from the rest position at 20 ft/sec.

Hint: conserve momentum

Part 1. Draw a free body diagram

Part 2. Label the diagram

Part 3. Right down the conservation of momentum for both objects

Part 4. Find the velocity of the satellite

Part 5. What is the kinetic energy of the astronaut?

Part 6. What is the difference between the velocities for the satellite and the CSM from question 1 after the astronaut pushes off.

Question 3

If the CSM is at rest and it fires its main engine with a trust of 2,000 lbs for 10 seconds find the new velocity of the CSM after the burn. Ignore the small loss of fuel mass and assume that the CSM maintains its total weight of 80,000 lbs during the burn. In other words it consumes a negligible amount of fuel compared to its total mass.

What is the momentum of the CSM after the burn?

What is its velocity?

What is the kinetic energy of the CSM after the burn?

Hints:

The impulse for a constant force = Force x time = Ft = DP = the change in momentum

Momentum = P = mv = mass x velocity

Mass = m = W/g = Weight/acceleration of gravity

Kinetic = K = ½ m v²

Part 1. Draw a free body diagram

Part 2. Label the diagram

Part 3. Write down the impulse equation

Part 4. Find the momentum of the CSM after the burn

Part 5. Find the velocity of the CSM after the burn

Part 6. Find the kinetic energy of the CSM after the burn

Question 4

The CSM burns75 lbs of fuel while producing a thrust of 1,500 lbs for 30 seconds

What is the specific impulse of the fuel?

Hints:

The specific impulse = impulse/weight

or

The specific impulse = thrust/mdot g

mdot = mass/time

Part 1. Draw a picture

Part 2. Determine I_s

Part 3. Based on this above calculation for I_s what type of propellant was used? Use the following website to determine the possible propellants.

http://www.hq.nasa.gov/office/pao/History/conghand/propelnt.htm

http://grin.hq.nasa.gov/ABSTRACTS/GPN-2000-000543.html