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| The low cost of launch into high apogee orbits enables the assembly of large spacecraft from 5 tonne components. If the apogee is very high, then a small Δv at apogee can raise the perigee of the orbit well above relatively crowded LEO orbits. For this discussion, assume 2000 km altitude is adequate, and a 5 stellar day delivery cycle, hence a [[ http://launchloop.com/StellarDayOrbits || 244597 ]] apogee. At the first apogee, the initial perigee radius of 6378+80 = 6458 km is raised to 8378 km | |
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| ||<-8> Mission summary, 5 stellar day (s.d.) construction orbit . . . . [[ attachment:construction5.ods | spreadsheet ]] || || Mission Segment || duration || perigee || apogee || v,,p,, || v,,a,, || South perigee || entry Δv || || || s.d. or sec ||<)> km ||<)> km ||<)> m/s ||<)> m/s || inclination ||<)> m/s || || [[ #11 | Loop launch, 80 km, 30 m/s² ]] ||<)> x ||<)> 6428 ||<)> 6458 ||<)> 0.471 ||<)> x ||<)> 8° ||<)> x || || [[ #21 | Climb to 238200 km ]] ||<)> x ||<)> 6458 ||<)> 238200 ||<)> x ||<)> x ||<)> 8° ||<)> 0 || || [[ #31 | Construction orbit (months) ]] ||<)> 5*n s.d. ||<)> 8378 ||<)> 238200 ||<)> x ||<)> x ||<)> 8° ||<)> x || || [[ #41 | Transfer orbit ]] ||<)> x ||<)> 8378 ||<)> 212200 ||<)> x ||<)> x ||<)> 8° ||<)> x || || [[ #51 | circular GEO ]] ||<)> permanent ||<)> 42164 ||<)> 42164 ||<)> x ||<)> x ||<)> 0° ||<)> x || |
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| The launch loop will be located south of the equator for gentle and steady weather. 8 degrees south latitude, east of French Polynesia and the west coast of South America may be the best region for launch loop deployments. | The low cost of launch into high apogee orbits enables the assembly of large spacecraft from 5 tonne components. If the apogee is very high, then a small Δv at apogee can raise the perigee of the orbit well above relatively crowded LEO orbits. For this discussion, assume 2000 km altitude is adequate, and a 5 stellar day delivery cycle, hence a [[ http://launchloop.com/StellarDayOrbits | 246578 km ]] -(6378+2000 km) = 238200 km apogee. |
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| The earth rotates once per stellar day (relative to the fixed stars) every 86174.0989 seconds. The launch loop rotates under the perigee of an orbit at exactly this rate. In order to add another component to an orbiting assembly, it should be launched as the assembly is near perigee, overhead, timed within milliseconds. This can only happen if perigee is synchronized with the Earth's stellar day rotation, with corrections for tidal effects and the equatorial bulge. | ---- |
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| The first component of the assembly will be a thrust platform, with enough precision ΔV capability to line up exactly with subsequent components. | <<Anchor(11)>> === Launch from the Loop === The launch loop will be located south of the equator for gentle and steady weather. 8 degrees south latitude, east of French Polynesia and the west coast of South America may be the best region for launch loop deployments. The earth rotates once per stellar day (relative to the fixed stars) every [[ https://en.wikipedia.org/wiki/Earth%27s_rotation#Stellar_and_sidereal_day | 86164.0989 seconds ]]. The launch loop rotates under the perigee of an orbit at exactly this rate. In order to add another component to an orbiting assembly, it should be launched as the assembly is near perigee, overhead, timed within milliseconds. This can only happen if perigee is synchronized with the Earth's stellar day rotation, with corrections for tidal effects and the equatorial bulge.' The minimum launch loop is designed for 5 tonne vehicles at a 45 second cadence. We will presume one vehicle per 5 stellar day cycle. All components will need some initial thrust to raise perigee above LEO. At the first apogee, the initial perigee radius of 6378+80 = 6458 km is raised to 8378 km with a relatively small and inexpensive thrust package. The first component of the assembly will be a thrust platform, with enough precision ΔV capability to rendezvous with subsequent components. |
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| ''' Note:''' While it may be possible to group the vehicles more closely than 45 seconds, each payload adds tension and deflection to the track, which is maximum at low speed near west station. Tight grouping will increase stress over the entire track, and reduce total throughput. In 45 seconds, the earth turns 0.19 degrees, and apogee "turns" 780 kilometers. Since higher orbits are slower orbits, it may be possible to send a string of vehicles to a series of cascaded higher orbits that intersect the construction orbit at somewhat higher velocities, and maneuver them towards rendezvous a few orbits later, permitting higher total througput during a multimonth construction program. I'll leave such complexities to future misssion designers. | |
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| <<Anchor(21)>> === Ballistic Orbit to 238200 km === |
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| <<Anchor(31)>> | === Construction orbit === |
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<<Anchor(41)>> === Transfer orbit === MoreLater <<Anchor(51)>> === Circular GEO === MoreLater |
High Apogee Construction Orbit
Mission summary, 5 stellar day (s.d.) construction orbit . . . . spreadsheet |
|||||||
Mission Segment |
duration |
perigee |
apogee |
vp |
va |
South perigee |
entry Δv |
|
s.d. or sec |
km |
km |
m/s |
m/s |
inclination |
m/s |
x |
6428 |
6458 |
0.471 |
x |
8° |
x |
|
x |
6458 |
238200 |
x |
x |
8° |
0 |
|
5*n s.d. |
8378 |
238200 |
x |
x |
8° |
x |
|
x |
8378 |
212200 |
x |
x |
8° |
x |
|
permanent |
42164 |
42164 |
x |
x |
0° |
x |
|
The low cost of launch into high apogee orbits enables the assembly of large spacecraft from 5 tonne components. If the apogee is very high, then a small Δv at apogee can raise the perigee of the orbit well above relatively crowded LEO orbits. For this discussion, assume 2000 km altitude is adequate, and a 5 stellar day delivery cycle, hence a 246578 km -(6378+2000 km) = 238200 km apogee.
Launch from the Loop
The launch loop will be located south of the equator for gentle and steady weather. 8 degrees south latitude, east of French Polynesia and the west coast of South America may be the best region for launch loop deployments.
The earth rotates once per stellar day (relative to the fixed stars) every 86164.0989 seconds. The launch loop rotates under the perigee of an orbit at exactly this rate. In order to add another component to an orbiting assembly, it should be launched as the assembly is near perigee, overhead, timed within milliseconds. This can only happen if perigee is synchronized with the Earth's stellar day rotation, with corrections for tidal effects and the equatorial bulge.'
The minimum launch loop is designed for 5 tonne vehicles at a 45 second cadence. We will presume one vehicle per 5 stellar day cycle. All components will need some initial thrust to raise perigee above LEO. At the first apogee, the initial perigee radius of 6378+80 = 6458 km is raised to 8378 km with a relatively small and inexpensive thrust package.
The first component of the assembly will be a thrust platform, with enough precision ΔV capability to rendezvous with subsequent components.
Note: While it may be possible to group the vehicles more closely than 45 seconds, each payload adds tension and deflection to the track, which is maximum at low speed near west station. Tight grouping will increase stress over the entire track, and reduce total throughput. In 45 seconds, the earth turns 0.19 degrees, and apogee "turns" 780 kilometers. Since higher orbits are slower orbits, it may be possible to send a string of vehicles to a series of cascaded higher orbits that intersect the construction orbit at somewhat higher velocities, and maneuver them towards rendezvous a few orbits later, permitting higher total througput during a multimonth construction program. I'll leave such complexities to future misssion designers.
Ballistic Orbit to 238200 km
|
Construction orbit
Transfer orbit