This document discusses various concepts and technologies related to interstellar travel, including: 1) Current rocket technologies are insufficient to reach other stars due to limitations of chemical fuels; multistage rockets and new fuels like nuclear or antimatter could help. 2) The nearest star is over 4 light years away, so travel at current speeds would take tens of thousands of years; new propulsion methods like ion drives, solar sails, and ramjets could enable much faster travel. 3) However, special relativity shows that nothing can travel faster than light speed, posing a fundamental limit to interstellar travel; speculative ideas like wormholes or generation ships may be needed to overcome this.

1. INTERSTELLAR TRAVELINTERSTELLAR TRAVEL
 Name:Amit samrat mauryaName:Amit samrat maurya
 Branch: ECE 3Branch: ECE 3rdrd
yearyear

2. Motivation: Fermi’s ParadoxMotivation: Fermi’s Paradox
 If the chances of developing aIf the chances of developing a
technological civilization are 1 in atechnological civilization are 1 in a
million:million:
 100,000100,000 civilizationscivilizations in the galaxyin the galaxy
 This is an application of theThis is an application of the DrakeDrake
EquationEquation, but, but ignoringignoring thethe LifetimeLifetime
of civilizationsof civilizations
If these are spread over the lifetime of theIf these are spread over the lifetime of the
Galaxy, the time between civilizations is aboutGalaxy, the time between civilizations is about
50,000 years50,000 years

3. Fermi’s ParadoxFermi’s Paradox
 With such a long time, a civilization mightWith such a long time, a civilization might
be able to colonize the Galaxy or at leastbe able to colonize the Galaxy or at least
make its presence knownmake its presence known
 They could at least send self-replicatingThey could at least send self-replicating
machinesmachines

4. Solutions to Fermi’s ParadoxSolutions to Fermi’s Paradox
 There are three solutions to Fermi’sThere are three solutions to Fermi’s
Paradox:Paradox:
1.1. We are aloneWe are alone
2.2. A galactic civilization exists, but it remainsA galactic civilization exists, but it remains
hidden from ushidden from us
3.3. Other civilizations exist, but none haveOther civilizations exist, but none have
colonized the galaxy. Why?colonized the galaxy. Why?
1.1. No interest in doing soNo interest in doing so
2.2. Self-annihilationSelf-annihilation
3.3. Technological difficultiesTechnological difficulties

5. IntroductionIntroduction
 In order to travel toIn order to travel to
the stars, colonizethe stars, colonize
other worlds, andother worlds, and
establish anestablish an
Everlasting GalacticEverlasting Galactic
Empire, we will needEmpire, we will need
interstellar travelinterstellar travel

6. Rocket ScienceRocket Science
 Current rockets useCurrent rockets use
chemicalchemical fuelsfuels
 These can be solids,These can be solids,
liquids, or gasesliquids, or gases
 Efficiency of a rocketEfficiency of a rocket
measured with themeasured with the
mass ratiomass ratio ==
 Mass with fuel / MassMass with fuel / Mass
without fuelwithout fuel

7. Rocket ScienceRocket Science
 To escape the gravityTo escape the gravity
of the Earth need aof the Earth need a
mass ratio of ~39mass ratio of ~39
 Single stage rocketsSingle stage rockets
have mass ratios ofhave mass ratios of
~15 or less~15 or less
 This is not enough, soThis is not enough, so
we can’t leave thewe can’t leave the
EarthEarth
 Or can we?Or can we?

8. Multistage RocketsMultistage Rockets

9. Distances to StarsDistances to Stars
 The nearest star system (Alpha Centauri)The nearest star system (Alpha Centauri)
is 4 light-years away (40 trillion km)is 4 light-years away (40 trillion km)
 At 60mph, this would take… 44 millionAt 60mph, this would take… 44 million
yearsyears
 At 17,000mph, this would take just 160,000At 17,000mph, this would take just 160,000
yearsyears
At this speed, it would take aAt this speed, it would take a
billion years to reach the centerbillion years to reach the center
of our Galaxyof our Galaxy

10. What can we do?What can we do?
 We need to go faster!We need to go faster!
 It’s all a mater of getting higher efficiencyIt’s all a mater of getting higher efficiency
from our fuelfrom our fuel
I can make 0.5
past light speed!

11. Nuclear RocketsNuclear Rockets
 Use fission to heatUse fission to heat
hydrogen gas, whichhydrogen gas, which
provides the thrustprovides the thrust
 Fuse small pellets ofFuse small pellets of
hydrogen, the energyhydrogen, the energy
released moves itreleased moves it
forwardforward
 Set off a nuclearSet off a nuclear
bomb behind youbomb behind you

12. Ion DrivesIon Drives
 Shoot out ions from light-weight gasesShoot out ions from light-weight gases
 Little thrust, but can work for longer times andLittle thrust, but can work for longer times and
therefore get large velocitiestherefore get large velocities

13. Solar SailsSolar Sails
 Use the pressureUse the pressure
from photons of lightfrom photons of light
to push the craftto push the craft
forward- like wind onforward- like wind on
a sail.a sail.
 Can also use lasersCan also use lasers

14.  Antimatter is like regular matter but withAntimatter is like regular matter but with
opposite chargeopposite charge
 When antimatter and matter meet, theyWhen antimatter and matter meet, they
completely annihilate each other producingcompletely annihilate each other producing
energyenergy
Antimatter EnginesAntimatter Engines

15.  Like the solar sail, anLike the solar sail, an
interstellar ramjetinterstellar ramjet
carries no fuelcarries no fuel
 Take hydrogen fromTake hydrogen from
space and fuse itspace and fuse it
RamjetsRamjets

16. To Infinity, and Beyond!To Infinity, and Beyond!
 These newThese new
technologies allowtechnologies allow
light-weight spacelight-weight space
craft to reach verycraft to reach very
high speeds with veryhigh speeds with very
little fuel.little fuel.
 In order to go fasterIn order to go faster
we just need to runwe just need to run
the engine for athe engine for a
longer timelonger time

17. But then this guy came along…But then this guy came along…
Image credit: Kevin Hainline

18. A Maximum SpeedA Maximum Speed
 The speed of light in aThe speed of light in a
vacuum is always avacuum is always a
constantconstant with respect towith respect to
anyany observer.observer.
 This speed, c, isThis speed, c, is
 300,000 km/s300,000 km/s
 186,000 miles/s186,000 miles/s
 1.8 terra furlongs/fortnight1.8 terra furlongs/fortnight
 Nothing can travel fasterNothing can travel faster
than lightthan light

19. Special RelativitySpecial Relativity
 All motion is relativeAll motion is relative
 Many weird effects will happen whenMany weird effects will happen when
special relativity is applied, but I’ll onlyspecial relativity is applied, but I’ll only
mention a few:mention a few:
Moving clocks run slower as seen by aMoving clocks run slower as seen by a
stationary observerstationary observer  time dilationtime dilation
Distances are contracted along the directionDistances are contracted along the direction
of motion of a moving objectof motion of a moving object  lengthlength
contractioncontraction

20. Special RelativitySpecial Relativity
 At 99.99% of c, to go to Vega (25At 99.99% of c, to go to Vega (25
light-years away) and back:light-years away) and back:
 Space ship frame: 8 monthsSpace ship frame: 8 months
 Earth (stationary) frame: 50 yearsEarth (stationary) frame: 50 years
 But light takes 50 years to travelBut light takes 50 years to travel
50 light-years, yet you do this in 850 light-years, yet you do this in 8
months:months:
 Length contraction: you travel 0.4Length contraction: you travel 0.4
light-year rather than 25 light-yearlight-year rather than 25 light-year

21. General Relativity to the Rescue?General Relativity to the Rescue?

22. WormholesWormholes
 A highly curvedA highly curved
region of space couldregion of space could
intersect anotherintersect another
region of space andregion of space and
form a hole betweenform a hole between
themthem
 These wormholes areThese wormholes are
unstable and collapseunstable and collapse
if anything goesif anything goes
through themthrough them

23. The Alternative: Interstellar ArksThe Alternative: Interstellar Arks
 Use conventional technology, but be preparedUse conventional technology, but be prepared
to wait a very long timeto wait a very long time
 The original travelers will die and new ones willThe original travelers will die and new ones will
be born before reaching the destinationbe born before reaching the destination
Or you could placeOr you could place
everyone in suspendedeveryone in suspended
animation for thousandsanimation for thousands
of yearsof years

24. QuestionsQuestions
?