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Size: 2693
Comment:
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Size: 2703
Comment:
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| Deletions are marked like this. | Additions are marked like this. |
| Line 22: | Line 22: |
| note: Nanotube properties are controversial. The CTE simulation [[ etd.lib.fsu.edu/theses/available/etd-08262005-003434/.../Thesis.pdf | Prakash ]] is used here, but other simulations differ wildly. | note: Nanotube properties are controversial. The CTE simulation by [[ htp://etd.lib.fsu.edu/theses/available/etd-08262005-003434/.../Thesis.pdf | Prakash ]] is used here, but other simulations differ wildly. |
Linear Cables
Stabilization and elevator cables on the launch loop are very long, and propagation delay is a big issue. In most systems people are familiar with, cables are short enough and forces change slowly enough that propagation delay is not a major issue. With a launch loop, forces can change rapidly (milliseconds) while the propagation delays are 10s of seconds.
For example, when an instantaneous force change is applied to one end of a very long cable, the end does not stretch a little, it moves, and keeps moving until the force has had time to propagate to a stationary attachment and back. For a 100km Kevlar 49 stabilization cable, that can be 22 seconds, in which time many meters of cable moves.
Material |
density |
elastic |
strength |
CTE |
Vsound |
Support |
100km |
Therm exp |
notes |
|
|
modulus |
|
|
|
Length |
Round Trip |
100Km*100K |
|
|
gm/cm3 |
GPa |
GPa |
um/m-K |
km/s |
km |
seconds |
m |
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|
|
Steel SAE980x |
7.9 |
200 |
0.65 |
12 |
5.0 |
8.4 |
40 |
120 |
|
Pure Kevlar |
1.44 |
124 |
3.62 |
-2.7 |
9.3 |
250 |
22 |
-27 |
|
Pure Spectra |
0.97 |
168 |
2.58 |
-12 |
13.2 |
270 |
15 |
-120 |
continuous creep |
Pure Diamond |
3.52 |
1140 |
>60 |
1.2 |
18.0 |
1700 |
11 |
12 |
|
Pure nanotube |
~1.4 |
~1000 |
~60 |
-9? |
26.0 |
4400 |
8 |
-90 |
|
composites: |
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80% Kevlar |
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80% Spectra |
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80% nanotube |
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note: Nanotube properties are controversial. The CTE simulation by Prakash is used here, but other simulations differ wildly.