Returning from Geo-stationery Orbit

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SUMMARY

The discussion centers on the complexities of returning from geostationary orbit, specifically the challenges faced when dropping capsules directly from the Clarke zone. Participants highlight that capsules retain tangential velocity, resulting in elliptical orbits unless proper de-orbiting techniques are employed. The conversation also touches on the potential for control systems to maintain proximity during reentry and compares the process to WWII paratrooper actions. Key insights include the necessity of managing velocity and trajectory for successful reentry, with estimates of required Δv ranging from 750 m/s to 1500 m/s depending on the launch point.

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  • Understanding of orbital mechanics, particularly geostationary and elliptical orbits.
  • Familiarity with reentry physics and heat shielding technologies.
  • Knowledge of Δv calculations and their implications for space travel.
  • Awareness of control systems for maintaining proximity during descent.
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  • Research the physics of geostationary orbit and its implications for spacecraft design.
  • Explore advanced heat shielding materials and techniques for reentry vehicles.
  • Study Δv calculations for various orbital maneuvers and reentry trajectories.
  • Investigate control systems used in modern spacecraft for precision landing and proximity maintenance.
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Aerospace engineers, space mission planners, and enthusiasts interested in the mechanics of orbital reentry and capsule deployment strategies.

Chatterton
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I know when a Soyuz capsule returns from the ISS it has to orbit Earth a few times before re-entry due to all the momentum it borrowed from ISS.

What would happen if your ship was in the Clarke zone? Assuming we have the radiation shielding covered already. Would it be conceivable that a ship parked like that could just drop capsules in a fairly straight down manner? Assuming we have all the heat-shielding worked out.
 
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Chatterton said:
I know when a Soyuz capsule returns from the ISS it has to orbit Earth a few times before re-entry due to all the momentum it borrowed from ISS.

It's more because they don't want to carry the fuel required to de-orbit in less than a single orbit. Instead, they can break a little bit, fall towards Earth, and then use the air friction to slow them down further and further over successive orbits until the density of the air is high enough that they finally fall back to Earth instead of making another orbit.

Chatterton said:
What would happen if your ship was in the Clarke zone? Assuming we have the radiation shielding covered already. Would it be conceivable that a ship parked like that could just drop capsules in a fairly straight down manner? Assuming we have all the heat-shielding worked out.

No, because the ships would still be moving tangentially "around" the Earth. Firing a capsule straight towards the Earth would just result in an elliptical orbit since the capsule would retain all of the tangential velocity and gain an additional radial component.
 
So, to do it right, my team of commandos will have to de-orbit the old fashioned way, spinning around the globe a few times before hopefully landing in relatively the same area, which would make even clumsier and more random than WWII paratrooper action and oh my God I think that cold be wicked cool. And it would take a while too, right? I think I remember something from Chris Hadfield's book about sleeping on the way down.
 
Chatterton said:
So, to do it right, my team of commandos will have to de-orbit the old fashioned way, spinning around the globe a few times before hopefully landing in relatively the same area, which would make even clumsier and more random than WWII paratrooper action

Not necessarily. They could have control systems designed to keep them in close proximity prior to and during reentry.
Chatterton said:
And it would take a while too, right?

I'm not sure how long it would take. Geostationary orbit is about 22,000 miles above sea level, so I assume it would take a while, with the exact time depending on the velocity the capsules were launched at, the exact orbit, and a few other details.
 
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Chatterton said:
So, to do it right, my team of commandos will have to de-orbit the old fashioned way, spinning around the globe a few times before hopefully landing in relatively the same area, which would make even clumsier and more random than WWII paratrooper action and oh my God I think that cold be wicked cool. And it would take a while too, right? I think I remember something from Chris Hadfield's book about sleeping on the way down.

Consider a reverse escape from lunar gravity. Then your paratroopers can hang out in a bunker complex in lava tubes. You can also magnetic launch artillery. No need for explosives in the shells. Just crack the heat shield at the altitude you want. Between 2500 and 2600 m/s for Δv. If you give them 3,000 m/s they can launch at multiple angles and all arrive at once.

Dropping from Earth-Moon Lagrange point 1 is easier than dropping to Earth from geosynchronous. That can be done with 750 m/s. Geo requires around 1500 m/s before you can aerobrake. Launchers and fuel tanks sitting in geo are huge targets.
 
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