Transcript Interstellar Travel

Interstellar Travel Now
February 18, 2006
HYPERION
ERAU
1
Agenda
• RFP
• Proposal
• Sub-topics
February 18, 2006
HYPERION
ERAU
2
Request for Proposal
• Under current or near term technology what
can be done to send a robotic probe to a
nearby star?
• Define reasonable cost and flight time
• What is the minimum probe and engine
mass?
• How long from launch until stellar arrival?
• How much will it cost?
• Why is this preferred to telescopes?
February 18, 2006
HYPERION
ERAU
3
Issues
If this is done via
propulsive methods
the following are
issues
-Fuel Energy Density
-Specific Impulse
-Thrust/Acceleration
February 18, 2006
HYPERION
ERAU
4
Assumptions
• Consider a probe launched from a C3=0
orbit on a fly-by mission of α-Centari
• Consider vehicle mass fractions of
20000, 2000, and 200
• All probes with ΔV’s of less than 0.05c
require 6 months of acceleration
• All probes with a ΔV of more than 0.05c
require 18 months of acceleration
• Trip time is a function of Isp
February 18, 2006
HYPERION
ERAU
5
Flight Time (years) vs. Isp
Specific Impulse vs. Time of Flight to Alpha Centari
500
450
-Rapid interstellar flight requires millions of seconds of Isp
Time of Flight relative to Earth (years)
400
-This can only be accomplished via antimatter propulsion,
laser accelerated proton propulsion or solar sails
350
300
MR 20000
-All of the above systems are out of current technical grasp
250
MR 2000
MR 200
200
150
100
50
0
0
1
2
3
4
5
6
7
Specific Impulse (million seconds)
February 18, 2006
HYPERION
ERAU
6
Flight Time (years) vs. Isp
February 18, 2006
HYPERION
ERAU
7
Flight Time (years) vs. Isp
February 18, 2006
HYPERION
ERAU
8
Case Studies
ΔV (%c)
Time of Flight (years)
MR 20000 Isp (ks)
MR 2000 Isp (ks)
MR 200 Isp (ks)
500
0.91
28.189
36.729
52.692
200
2.28
70.581
91.962
131.927
100
4.58
141.516
184.386
264.518
75
6.16
190.281
247.924
355.671
50
9.3
287.364
374.417
537.134
25
19
586.702
764.435
1096.649
10
50.6
1564.539
2038.493
2924.398
6
91.2
2816.171
3669.28
5263.918
NEP
Fusion
Antimatter
February 18, 2006
HYPERION
ERAU
9
Investigated Propulsion Systems
• Plasma Core Nuclear Thermal Rocket (NTR)
• Nuclear Electric Propulsion
- 10 MWe core or larger
- Consider Ion, Hall Effect, MPD thrusters
• Nuclear Fusion
- Different fuel cycles (D-T, D-D, D-He3+, pB, spin polarized fuels)
- Magnetic Confinement Fusion (MCF)
- Inertial Confinement Fusion (ICF)
- Magnetically Insulated ICF (MICF)
- Antiproton Initiated Fusion (AIF)
• Antimatter Propulsion (beamed core)
- proton-antiproton
- electron-positron
- hydrogen-antihydrogen
February 18, 2006
HYPERION
ERAU
10
Plasma Core NTR
- Requires 106 K for 20,000 s + Isp
- Contamination a problem
- Plasma containment a
problem
-Probably not feasible
February 18, 2006
HYPERION
ERAU
11
NEP
-Fission Reactor produces
electrical power
-Electrical power runs
electrostatic or electromagnetic
thruster
-Can run Ion, MPD, Arc Jets,
and Hall Effect thrusters
-Very realistic
Problems include power processing, grid erosion, high temperature
Materials, but it is feasible to build engines at 30,000-100,000 second
Isp’s
February 18, 2006
HYPERION
ERAU
12
NEP Thrusters
MPD
Ion
~ 3000 – 100,000 s of Isp
Isp can depend on propellant
Isp can depend on efficiency
Isp depends largely on input power
February 18, 2006
HYPERION
ERAU
13
30 ks NEP
• What input power is required to
obtain 30 ks of specific impulse?
• How much waste heat does this
produce?
• How do we dissipate the waste heat?
February 18, 2006
HYPERION
ERAU
14
100 ks NEP
• What input power is required to
obtain 100 ks of specific impulse?
• How much waste heat does this
produce?
• How do we dissipate the waste heat?
February 18, 2006
HYPERION
ERAU
15
Fusion
• Fusion of light elements provides
propulsive source of energy
• Releases ~ 1014 J/kg
February 18, 2006
HYPERION
ERAU
16
Fusion Fuel Cycles
D-T: Low ignition temp.
High neutron yield
1st generation fuel
D-D: Large energy yield
Thermal radiation
D-He3+: Large energy yield
Thermal radiation
Spin Polarized Fuels
February 18, 2006
HYPERION
ERAU
17
Magnetic Confinement Fusion
Tokomak
-Torodial fields
-Polodial field
Spheromak
-Similar to Tokomak
-Slightly higher Q
-Slightly higher α
- Plasma is ejected as rocket exhaust
-Under Lawson’s criteria all MCF techniques require low ion densities
and long burn times
-All MCF techniques are very heavy and have no applications as an
electrical power producing device
February 18, 2006
HYPERION
ERAU
18
Magnetic Confinement Fusion
Gas Dynamic Mirror
-Similar to a z-pinch
-Ions with precise θ escape
-Escaping ions produce thrust
-Potentially 50-100,00 s of Isp
-Very heavy
-Potentially near term if it burns D-T mixture
February 18, 2006
HYPERION
ERAU
19
Inertial Confinement Fusion
-Particle beams or lasers
compress fusile targets
-Magnets must contain plasma
for short time frames
-Drivers are very heavy
must be ~1.6 MJ
-Higher Q’s than MCF
-Higher α than MCF
-High ion densities (neutron star), short confinement time
- If weight can be negated this has serious potential in propulsion!!
February 18, 2006
HYPERION
ERAU
20
Magnetically Insulated ICF
-Tungsten or gold surrounds
target pellet
-Low thermal impulse
on tungsten shield
-Produces transient magnetic
field
-Reduces need for magnets
-Ablated Tungsten reduces
Isp
-Drastically reduces mass of drivers
and electromagnets!!
February 18, 2006
HYPERION
ERAU
21
Antiproton Initiated ICF
Muon Catalyzed Fusion
-Antiproton annihilation creates
μ-mesons (muons)
-muons displace electrons around
nucleus
-must occur at low energies
(1200 – 1600 K)
-no or little need for drivers
-combined with MICF makes
a lightweight engine
Requires nano-grams of antiprotons
February 18, 2006
HYPERION
ERAU
22
Antiproton Initiated ICF
Antimatter Initiated Micro-Fusion/Fission
-Antiprotons induce U238 fission
-Released neutrons help compress fusion fuel
-Larger α than muon catalyzed fusion
-Isp ~ 50,000 s – 1,000,000 s
February 18, 2006
HYPERION
ERAU
23
Antimatter Propulsion
-Highest performance under the laws of impulse and momentum
-Requires kilograms of antimatter which is not yet available
-Offers Isp near the theoretical limit (30.6 x 106 seconds
-The only hope for rapid robotic or manned
interstellar propulsion
February 18, 2006
HYPERION
ERAU
24
Antiproton
-~35% of annihilation energy
is lost to massive particles
-Requires 2 km long nozzle
-Large radiation levels due
to pions and muons
February 18, 2006
HYPERION
ERAU
25
Positron
-Uses momentum from 0.511 MeV
photons
-Requires reflection of high energy
photons
-Positrons easier to produce than
antiprotons
- Very high burnout velocities
February 18, 2006
HYPERION
ERAU
26
Investigation Questions
• Does the technology exist now?
• If not can it be developed in 15 years
assuming unlimited funds?
• Or can the system not be developed
with current physical understanding?
February 18, 2006
HYPERION
ERAU
27
Investigated Parameters
•
•
•
•
What is the system mass?
What is the system thrust?
What is the system Isp?
What is the fastest the system can reach αcentari?
• What is the systems TRL now?
• What is the cost of developing this system?
• What is the cost of launching this system?
February 18, 2006
HYPERION
ERAU
28
Investigated Parameters
• What is the cost of transferring the
craft from LEO to C3=0? (assume the
use on an NTR)
• What the minimum engine mass?
February 18, 2006
HYPERION
ERAU
29
Probe Design
• What are the data transfer signal
requirements for transmitting over 4.56 ly?
- beam vs. isotropic signal
- S/N ratio
- Transmission Power
- Pointing accuracy
• What are the thermal control, attitude control,
and navigation requirements
- The stars will not be in the same place to use star trackers
• What are the total power requirements for the
probe?
- Do we need an onboard fission reactor or can we shut down
the craft during flight and use solar arrays when it arrives near
its target, or even use batteries that only last 15 minutes?
February 18, 2006
HYPERION
ERAU
30
Probe Question
• How does the info. from the previous
slide drive the probe mass?
• What is the craft dry mass when the
probe mass is combined with the engine
mass?
• At MR’s of 20,000, 2000, and 200 what is
the total craft mass for each case, when
propellant is added to the dry mass?
February 18, 2006
HYPERION
ERAU
31
Questions
• ???
February 18, 2006
HYPERION
ERAU
32