em launch or we’re out! what now? t. vuletić, institute of physics, zagreb višnjan s3++ 2011
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EM launchOr
We’re out! What now?
T. Vuletić, Institute of physics, ZagrebVišnjan S3++ 2011
T. Vuletić, Institute of physics, ZagrebOpen day 2010
Space elevatorOr
How do we get out?
C,D:1st cosmic velocityV1
2/R=g V1=7.9 km/s
E:2nd cosmic velocityV2
2/2R=g V2=11.2 km/s
Earth’s gravity well
Chemical launch: Newton , Jules Verne et al.
Gas expansion V=1-4 km/s : insufficient!
there’s also the atmospheric drag...
Moon:1st cosmic velocityV1
2/(R/2)=g/6 V1=2.2 km/s
2nd cosmic velocityV2
2/R=g/6 V2=3.1 km/s
Moon’s gravity well
EM launch: Moon
shallow well + there’s no air-drag
read... R.A. Heinlein: The Moon is a Harsh Mistress
EM launch: Moon
watch... “Moon” by Duncan Jones
read... R.A. Heinlein: The Moon is a Harsh Mistress
Logistics orbit: Lagrange points
Idea: G.K. O’Neill and his S.S.I. “father” of the particle accelerator
EM gunwhile
we’re still here
Eraser, 1996.
force
fieldforce
How does it work?
Mass Driver:
Electromagnets repel or attract and cary the projectile
Coilgun:
Electromagnet attracts the feromagnetic projectile!
Railgun:
Rails are shorted by the projectile – current in this circuit forces the project out
EM gun
Coil, 30 turns, 4 layers, 1 mm wire
Capacitors, 450V, 8.8mF
coilgun
capacitors railgu
n
solid-state relay
RLC circuit
Solving for the Current:
damping resonant frequency
Damped harmonic oscillator
underdamped
overdamped
critically damped
Capacitance C=8.8 mF
Resistance R=0.3
Inductance L=?
Damped harmonic oscillatorRLC circuit
position (mm)
-10 0 10 20 30
L ( H
)
-200
-150
-100
-50
0
50
100
150
200
250
L' (
H/m
)
-0.01
0.00
0.01
0.02
0.03
0.04
0.05
position (mm)
0 10 20 30 40
Inductance
Inductance L:
Depends on the position of the projectile
Force:
Force maximum occurs where the inductance variation has a maximum
Position:
Projectile tip
- 5 mm inside coil
F= L’·I2
Force, mass...
F=ma~I2
v=at
s= t2a 2
0
500
1000
1500
Coil center
0
5
10
15
0
10
20
30
time (s)
100 101 102 103 104 105 10610-1
100
101
102
103
104
Coil mouth
Coil current
Projectile acceleration
Projectile velocity
Distance covered by the projectile
s (
mm
)v
(m
/s)
a (x
1000
m/s
2 )I
(k
A)
Current, charge
Capacitance C=8.8 mF
Resistance R=0.3
Inductance L=150 H
~4 Coulombs discharge through the coil
~ kiloAmps in milliseconds!
Voltage U=450 V
Charge Q=C·U=4 C
Energy
E=½C·U2=900 J
0.5 m
2.5 m
V=25m/s V=90km/h
0 msec
20 msec
100 msec
0.0 m
Velocity
Energy
E= U2
C 2
E= v2m 2
Electric
~ 900 J
Kinetic
~ 12 J
Diminutive efficiency, kein Schwarzenegger...
25 g
EM gun
Machine & electronics shop Institute of physics:I. Čičko, B. Kiš, A. Vojnović
Thanks:R. Beuc, Đ. Drobac, B.Erjavec, M. Prester, K. Salamon
Take a look:www.youtube.com/user/fizika123coilgun.infowww.powerlabs.orgaudacity.sourceforge.net
Keywords:coilgun, railgun, mass driver, EM launch
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