1. Goal to understand how Ion Propulsion works.
Objectives:
To recap the need for a new propulsion system
To learn about what Ion Propulsion is
To understand how Ion Propulsion allows for higher velocities
To examine the limitations to Ion Propulsion

2. Chemical Propulsion Takes lots of mass
Only good for humans in the region of the Earth
Once we try to get to Mars it gets dangerous and expensive.

3. What is Ion Propulsion
Ion Propulsion is similar to chemical rockets in that it throws something out the end so that it can go forward
However, instead of tossing out gas it tosses out protons and/or electrons (aka charged particles)

4. How it works
If you have a charged particle in an Electro-magnetic field the charge will be accelerated.
The stronger the field the greater the acceleration.
Therefore the particles can be thrown out at much higher velocities (up to 100,000 times higher).
Since the fuel has a higher velocity you need a lot less of it.

5. Current Ion Propulsion
Deep Space 1
encountered Comet Borrelly
$150 million
Used solar panels to power the 2100 Watt Ion Propulsion engines (Xenon)
However, this engine ran for 678 days

6. Result
Due to the 40 km/s fuel the craft accelerated by 4.3 km/s over the 2 years.
If this had been put into Earth orbit initially then set off it would almost be enough to get to Mars.
All for 74 kg of fuel.

7. From NASA.gov
Ion propulsion could be used for a manned mission to Mars. The decision on whether that would be the preferred approach would involve many questions such as which technique might get the crew there the fastest (independent of how fuel efficient the trip might be) in order to reduce the radiation exposure and effects of long periods of near weightlessness.

8. Current limitations Design limits fuel speed to 40 km/s.
This could be vastly improved in the future
Low thrust – have to put it into space.
Takes a long time to speed up.

9. But
If you used a $500 million conventional rocket to put a space shuttle sized ion propulsion craft into Earth orbit you could blast off from orbit for a LOT less cost wise.
Does not require expensive or exotic fuel.

10. What Ion Propulsion holds in the future:
Now lets design a more ideal futuristic Ion Propulsion vehicle:
Two possibilities
1) straight acceleration
2) particle collider like set up

11. Straight. Requires a large electric field for the length of the ship.
Could use Xenon but lighter elements will go faster.
We trade thrust for
fuel efficiency

12. For Hydrogen: Acceleration = Electric field * e / Mp
e = charge of proton and Mp is mass
Velocity = (2 * Acceleration * length)1/2
Examples:
1 km long ship with a 1* 109 V/m electric field
Exhaust velocity = 99.95% the speed of light
100 m long ship with a 10,000 V/m electric field
Exhaust velocity = 140,000 km/s (almost half the speed of light)
10 m long ship with 200 V/m electric field
Exhaust velocity = 60,000 km/s (20% the speed of light)

13. Notes Xenon gets 1/10th the velocity but gives 10 times the thrust
Energy is going to be the key though as to how much Hydrogen you can ionize and eject and how fast.
Also, powering that large of an electric field can use a lot of energy.

14. Ship 2: Magnetic
This would involve a more circular shaped ship which would slowly accelerate up the Hydrogen ions.
As the ions speed up they circle around a central magnetic field.
The faster they go the bigger a circle they make.
R = mv/qB
Where q is the charge and B is the magnetic field

15. Velocity So, the exhaust velocity now becomes: V = qBr / m Examples:
1 km in diameter ship with 15 Tessla magnets
Exhaust velocity = 99.99% speed of light
100 meter in diameter ship with 1 Tessla magnets
Exhaust velocity = 98% the speed of light
10 meter in diameter ship with Tessla magnets (hair dryer)
Exhaust velocity = 2000 km/s (almost 1% the speed of light)

16. So what is the hold up? Energy How do we produce the energy?
Solar power only does so much
Ten times velocity means ten times the energy overall (100 times energy per mass but 10 times less mass).
Nuclear power? Fusion power?

17. Take the example…
Get a 100 metric ton spacecraft to 20 km/s using Hydrogen we speed up to 2000 km/s (need 1% of mass of ship as fuel).
Energy needed:
2 Quintillion Joules (amount of energy USA uses in 12 minutes)
Cost: $56 million dollars
Would require a 63 Megawatt power generator to work non stop for a year

18. 73 Megawatt power plant in Thailand

19. 60 Megawatts

20. Conclusion Ion Propulsion is a CURRENT technology
It is very fuel efficient
It can get is to much greater velocities
However, it cannot currently launch itself
And the ultimate problem is that it takes a lot of energy.