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PropulsionWhy ion propulsion? |
No, NASA could not use ion propulsion for getting spacecraft into space. Ion propulsion is a great technology to move ships once they are in space, and it is especially good for very long journeys. But it can't get a ship into space.
The reason for this is that while the specific impulse for ion propulsion is high, it gives is low amounts of thrust. A high specific impulse means that the gases shooting out of the back of the rocket are moving at a very high speed but the low thrust means that there is not a lot of gas moving at any one time. The DS1 ion propulsion engine only produces 92 mN (milli Newtons) of thrust which is roughly equivalent to the weight of a couple drops of water. This means that the ion propulsion thruster is pushing the spacecraft forward with about as much force as gravity is pushing a couple drops of water down on your hand.
We use ion propulsion in space because it does not take a lot of fuel. On a long trip this is good, because the more fuel a space ship needs, the heavier the ship will be and the harder and more expensive it will be to put the ship into space. However, in order to get a space ship into space, the ship must overcome the Earth's gravity and the resistance of the atmosphere. At the Earth's surface the force of gravity on DS1 is about 3660 Newtons (373 kg x 9.81 m/s^2). So its 0.092 Newton ion engine doesn't come close to being strong enough to lift itself off the surface. Conventional propulsion systems, such as liquid and solid fuel boosters, are used to put a ship into space.
Could ion propulsion move something on Earth?
What is escape velocity?
How do we put a spacecraft into orbit?
