Interstellar travel is difficult because (i) Distance (ii) Energy (iii) Technology
-Very large distances
-Most distant planetary probes (PIONEER 10 & 11 (has plaques for ET) -- VOYAGER
(1and 2) (has complicated messages such as pictures and messages) have travelled 8-120
- Alpha Centuri (The nearest star to sun) is about 2,700 AU; 4.4 light years away.
-Speed/Cosmic Speed Limit (c=300,000km/s) according to Einstein’s theory of relativity.
-dependant on object’s (mass and speed ) 2
-Star-ship with few thousand people would have mass of 100 million kg; and if moved
10% at speed of light would take 40 years to reach nearest star.
-Energy would be 100X the world’s current annual energy use.
-Would take about 2.5 Quintillion dollars (about 400,000 times the world’s current GDP)
-As the ship speed increases, mass increases, and requires greater Energy for
-Newton’s 3 Law of Motion (Conservation of Momentum) “For Every Action there is
an opposite and equal reaction”.
-A rocket vaporizes on-board fuel at the back which moves the rocket forward
-Can work in a vacuum of space (unlike jet or aircraft)
-Concept of Rockets [ Tsiolkovsky (Russia) , Herman Oberth(Germany) ,Goddard
M=mass after velocity Mo= Launch Mass V=Velocity attained Ve=Exhaust Velocity of
-multistage rockets are used.
-WWII German Rocket (V2) ; Soviet/Russian (Proton) ; America(Saturn V); used to
carry Apollo Astronauts to the Moon, the most powerful rocket yet built.
Chemical Rocket: uses the energy binding electrons to the nucleus Nuclear-Power Rocket:
Nuclear energy of 1kg of matter= Chemical energy from 8 billion liters of gasoline
Nuclear Fission: involves splitting of the large nuclei into parts (uranium and plutonium) Nuclear Fusion:
0.07%of mass is lost to energy; results in unprotect waste, needs a special fuel source 0.7% of mass is lost to energy; not dangerous waste; uses -PROJECT ROVER (1955): Project on using nuclear energy to power spacecraft.
-NASA cancelled the mission to send manned mission to Mars in 1973.
-PROJECT ORION (1960s): was the first real starship and was propelled by mini-nuclear
bombs detonated just behind the rocket.
-PROJECT DAEDALUS (1970s): used the nuclear fusion for propulsion . (Could reach 10%
speed of light)
ION ENGINE: could be used instead of chemical or solid fuel. It emits charged particles as
exhaust and has very high exhaust velocity. It has continuous acceleration. (Could reach 1% of
the speed of light)
SOLAR SAIL: very thin sail, that could accelerate a craft through radiation pressure from a star.
-inexpensive (could reach a few percentage the speed of light and then coast to target)
Limitations: solar intensity decreases with the distance.
INTERSTELLAR ARKS: conventional technology to reach to nearest stars.
Limitations: Would require large crew. Humans cannot hibernate, great leaps in medicine and
INTERSTELLAR RAMJETS: Interstellar space contains some hydrogen. This ship can scoop
this hydrogen as a fuel and can expel to high velocity.
Limitations: (i) The scoop would have to be hundreds of km across to collect sufficient fuel
(ii) The impact of any debris at near light speed could destroy the ship.
Time Dilation: As speed increases; Time slows down (relative to Earth)
v=speed at which the rocket is moving
c=speed of light
-While time slows down it causes the length and distances to contract called “Length Contractions”.
There are two twin brothers. On their thirtieth birthday, one of the brothers goes on a space journey in a
superfast rocket that travels at 99% of the speed of light and comes back after a year for his 31 birthday,
the other brother will be 37 years olTime is stretched by factor 7. People on Earth would have
Time elapsed for people travelling near th