--------- #1270 - The Space Shuttle’s Last Flight
- The Space Shuttle is taking its last flight today, July 8, 2011. Why don’t we take it to the Moon?
- Attachments - Astronauts on the Moon
- The answer: It would not make it there. Not enough fuel at maximum payload. The maximum payload the Shuttle can carry is 55,000 pounds. It would need 65,000 pounds of fuel to make a one way trip to the Moon.
- When the Space Shuttle is in orbit 236 miles up it is traveling 17,180 miles per hour.
- If it moved out to geostationary orbit at 22,236 miles it orbiting speed would only need to be 6,870 miles per hour. You would think that all the Shuttle would have to do would be to put on the brakes, slow down and drift right out there. When you get out to the Moon the orbiting speed is only 2,237 miles per hour. So, the speed change needed to slow down is 15,000 mph change to get from the Shuttle orbit to the Moon’s orbit.
- Unfortunately, your intuition is wrong. Each higher orbit requires more kinetic energy to reach. More burn time for the rockets. More fuel in bigger rockets.
- The Shuttle can accomplish a speed change of 0.6 meters / second / second at full burn. To get the orbit speed change of 15,000 mph how much time do we need of rocket burn? 15,000 mph is 6,680 meters / second. At the Shuttle burn rate it needs 11,000 seconds which is 3 hours of burn.
- The Shuttle consumes 9,700 pounds of fuel to change speeds by 2,337 mph. To change 15,000 mph we need 65,000 pounds of fuel. But, the maximum we can carry is 55,000 pounds. We are 20% short for a one way trip. The Moon is 239,000 miles away and we only made it to 191,000 miles. Maybe the Moon’s gravity will pull us the rest of the way?
- Orbits are the balance between the Kinetic Energy of motion and the Potential Energy of Gravity.
--------------------- Potential Energy of Gravity = G * m * M / r
----------------------- where “M” is the mass of the Earth and “r” is the radius from its center, and “G” is the gravitational constant of proportionality for the units used.
--------------------- Kinetic Energy = ½ m * v^2
--------------------- where “m” is the mass of the Shuttle, and “v” is the velocity of the Shuttle. Mass times velocity is momentum. So, this formula is the Shuttle’s momentum times its velocity.
--------------------- v^2 = 2 * G * M / r
---------------------v^2 = 2 * 6.67*10^-11 m^3/ (kg*sec^2) * 5.97 *10^24 kg /6.76 * 10^6 meters
-------------- v = 17,169 miles per hour ( 7,670 m/sec)
---------------- The total energy is just ½ the potential energy for a circular orbit.
---------------- April 12, 1981 ------------- Columbia space Shuttle launched
---------------- April 4, 1983 -------------- Challenger launched
---------------- August 30, 1984 ---------- Discovery launched
---------------- October 3, 1985 ---------- Atlantis launched
---------------- January 28, 1986 ---------- Challenger explodes
---------------- May 4, 1989---------------- Atlantis launched Venus Spacecraft
---------------- October 18, 1989 -------- Atlantis launched Jupiter Spacecraft
---------------- April 24, 1990 ------------ Discovery launched Hubble Space Telescope
---------------- May 7, 1992 -------------- Endeavour launched
---------------- February 1, 2003 ---------- Columbia explodes
---------------- July 8, 2011 -------------- Atlantis launched for last Shuttle flight.
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