A Fuelless Future

1
A Fuel-less Future

• Presented by
• Laila Al-Marashi, Deva Chan, Josh Kellogg, John
  Kuo Lin, Gary Chung, Ashley Bacon, Matthew Fong

2
The Present

• Chemical rockets are the current method of
  propelling objects across our solar system and
  beyond.
• Rockets are inefficient and have a large fuel to
  payload ratio for both weight and volume.
• They are expensive to get into space, costing
  millions for each rocket that reaches orbit.
• Rockets cannot be recycled and after their fuel
  runs out, they become space junk.

3
Our Solution

• Tethers
• Electrodynamic
• Momentum
• Solar Sails
• Square
• Disk
• Heliogyro

4
Tethers

• What is a tether?
• A tether is a long cable that can be used for
  many purposes, but it is generally used to
  connect two objects.
• Tethers can also be used to connect spacecraft,
  space stations, satellites, and any other space
  objects that have a considerable mass.
• There are two different types
• Electrodynamic the tether takes advantage of
  the Earths magnetic field.
• Momentum the tether connects two objects and
  they trade momentum.

5
Electrodynamic Tethers

• Electrodynamic tethers, or conducting tethers as
  theyre otherwise known, use the laws of
  electromagnetism to move objects in space.
• The Earths magnetic field causes a current to
  run through the tether and exerts a force on the
  wire. The direction of the force depends on the
  direction of the current.
• By sending a current through the tether, a
  magnetic field can be formed around the tether
  and by changing the direction of the current, the
  tether can be forced up or down in relation to
  the Earths magnetic field. This can be used to
  raise or lower an objects orbit or even propel
  it into space.

6
Electrodynamic Tethers
The Principles of the Electrodynamic Tether
7
Momentum Tethers

• The momentum-exchange tether works under the same
  principle as the bolo, a weapon of the aboriginal
  Australians.
• Kinetic energy from the object on one end of a
  tether is transferred to the object at the other
  end as they rotate around each other.

8
Momentum Tethers

• This concept can be used in two ways
• In order to maintain a stable orbit, two objects
  can be tethered together and the object in
  far-earth orbit can maintain the orbit of the
  near-earth object at the expense of its own
  altitude.
• If there is a high-mass counterweight in
  near-Earth orbit, a tether can be attached
  between it and an object in the atmosphere and
  the object would be spun into orbit with minimal
  loss of energy.

9
Momentum Tethers
10
Tethers

• Tethers are the first example of a propulsion
  system that does not use a propellant, thus
  making them very cost-effective. The production
  and launching of tethers is estimated to cost
  about 120 million dollars.
• Tethers are not fail-safe. They are susceptible
  to tearing due to the tremendous forces exerted
  on them. In addition, the magnetic fields of the
  Earth have burnt electromagnetic tethers. More
  work will have to be done to solve these problems
  before tethers are viable space technologies.

11
Solar Sails

• Imagine sitting on a boat and holding a large
  mirror up to catch solar rays to propel you into
  the unknown of the deep blue sea. It wont work
  as well on a conventional canvas-sailed boat on
  Earth, but if the sea were actually
  interplanetary space and your ship were a
  spacecraft, youd be in luck.

12
Solar Sails

• There are three main designs

• Square sail - requires booms to support the sail
  material

• Disc sail - circular sail that must be
  controlled by moving the center of mass relative
  to the center of pressure

Heliogyro sail - bladed like a helicopter, the
sail must be rotated for stability
13
Solar Sails

• Solar sails are like large mirrors that use the
  photons that hit its surface to impart momentum
  to the entire spacecraft.
• A perfectly reflecting surface translates into
  photons hitting and leaving it at the same
  momentum. This impact imparts a force that is
  determined by surface area and the pressure, P.

• W is the intensity of the Suns light in power
  per area, a is the angle between the Sun and a
  line perpendicular to the surface, and R is
  defined as the solar distance in AU.

14
Solar Sails

• At 1 AU, the distance from the Sun to the Earth,
  a perfect solar sail that is directly facing the
  Sun will experience a force of about 7.8 N.
• If the mass of the spacecraft is 800 kg, this
  translates into about 1 mm/s2, which produces a
  velocity of only about 3.5 m/s after an hour of
  acceleration.
• While this may not seem like a lot, the
  acceleration is constant and velocity increases
  continually, resulting in a speed of over 800 m/s
  and a distance traveled of over 360 million
  meters in just 10 days.

15
Solar Sails
16
Conclusion

• In conclusion, both space tethers and solar sails
  have the ability to propel objects in space with
  better efficiency than rockets used today.  They
  are more energy efficient and provide propulsion
  for longer periods of time than the conventional
  rocket. 
• These two technologies are still in the
  experimental phase, but when they mature, they
  will revolutionize the space industry.