Space Tug, The Stairway to Heaven

Mar 5, 2020
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This design is meant to use passage through the thin upper atmosphere as a means of increasing the velocity of a spacecraft that is already in low Earth orbit.

This would be a highly elliptical orbit that intersects Earth’s atmosphere where it is thin and ionized. I call it a space tug since the weight and configuration of this design is pretty dedicated and specialized. This Tug will take space craft or probes from low Earth orbit (LEO) to nearly escape velocity. The tug would release the space craft and a small engine firing will allow it to achieve full escape velocity. Then the Tug would return to low Earth orbit and begin the process all over again.

This concept is meant to conserve fuel between LEO and escape velocity. It doesn’t look good for manned missions but it might work well for something that isn’t time dependent (or vaporize in screaming agony).

Normally an orbit that intersects with the upper atmosphere is the last thing that you want to do. If the ionization levels of the atmosphere are high enough (or can be increased) the Tug can use MHD on those ions to increase its velocity (in spite of the increased drag). Each passage through the upper atmosphere could increase both its velocity and its altitude at apogee. (There might be an orbital mechanics problem with this scenario because of where thrust is applied during the orbit.)

Thrust has to be greater than drag during these atmospheric passages. The second problem is not being torn to shreds by impacting the atmosphere at orbital velocity. The mass loss from ablation might be considered a cost of doing business. The Tug might need considerable maintenance on its ablative surfaces even when the atmosphere would qualify as a vacuum.

You could also use some sort of magnetohydrodynamics MHD ram scoop design to compress and ionize the atmosphere rather like a plasma version of a jet engine compressor. At these intake velocities you are better off using fields rather than surfaces to initiate and produce propulsion. A design might be found that produces, concentrates and manipulates ions produced from the atmosphere as a means of propulsion based on MHD.

You might release metals like caesium or potassium to increase the ionization of the atmosphere to usable levels. Ionization could also use radiation or X-ray emitters whose output would probably need to be ridiculously high.

Yes, those are giant radioactive spines sticking out on the front of my spaceship, (which would look cool).

Other (very energetic) satellites might use ultraviolet lasers to increase the ionization along the tugs path through the atmosphere. These lasers will be blocked by the atmosphere so they will have no effect on observers on the ground. To other satellites these lasers might act like “bug zappers”. It might be appropriate to issue a warning to other satellite operators before powering the system.

Rather than trying to create fluctuating magnetic fields directly with wire and current you might use microwaves with a light metallic lattice to interact with the atmospheric plasma. You need to affect the largest volume of ionized space with the least amount of surface drag.

A fundamental problem with this entire concept is that you might start with levels of atmospheric ionization of only 1 part in a 100,000 (temperature and Solar UV dependent). The non-ionized particles would represent particles which are unaffected by MHD and would probably represent drag. This low level of ionization is why the preliminary numbers for any atmospheric ion propulsion simulation will look really bad.

This would be good project for a bunch of expendable doctoral candidates. First, they can try to find a design that has good simulation numbers. Second, they can design and build an engine that will have lightning crawling all over it while it is in operation.

For some reason insurance companies blacklist inventors. That isn’t a smoking crater it’s a… volcano.

Big Words: Magnetohydrodynamics (MHD) Some ion thrusters use MHD. Some magnetically contained fusion reactors also use MHD.
 

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