Re-exploring an orbiting momentum transfer system concept

It can be fun to explore a potential new technology and what could be achieved with it.

On a yahoo group focused on the future and particularly the part of it in space, I recently mentioned that back in the early 1980's I had a brief idea about something that seemed able to make routine space travel far more energy efficient; but I did not explore the idea much in detail, and eventually in 1982 I read about Keith Lofstrom's "Launch Loop" concept describing a whirling belt of trapezoidal shape with four pulleys at its corners, that would lift rockets to the fringes of the atmosphere for their efficient launch up there, and that seemed a better idea, and my own idea went back in the mental storage bins.

Anyway, a month or so ago, I remembered my idea of the early 1980's, an only partially fleshed out concept, and casually mentioned it on the email chat forum. It mostly got catcalls and raspberries, but one person who was skilled at math and delta-vee analysis, took on the task of shooting me and my idea down once and for all.

So I discovered that my qualitative analysis of a casual concept's mentioning, which I naively thought useful for some fun exploration by the group, was suddenly enmeshed in quantitative analysis debate, not my favorite thing, but I can deal with it.

My concept as I had envisioned, circa 1980, was of a satellite in low Earth orbit, a satellite that was in the form of a long platform. The idea was that an incoming spacecraft would graze the platform while electrodynamically dragging against it, which would thus transfer some of the spacecraft's momentum to the orbiting platform, and greatly reducing the kinetic energy that the spacecraft would need to dissipate on re-entry of the Earth's atmosphere. That energy would have increased the velocity of the platform, raising it to a somewhat higher orbit.

And subsequently a newly launched spacecraft from the ground would be timed so it grazed the orbiting platform, slowing the platform back down to its earlier velocity, and giving the spacecraft a velocity boost as it headed toward higher orbit, saving it energy that otherwise would need to be provided by lifting heavy fuel from the ground, as is done nowadays conventionally.

In other words, an orbiting momentum transfer system, effectively coupling the momentum of falling spacecraft over to rising spacecraft.

The timing involved was something I did not want to think much about, but timing is everything in space launches routinely anyway, and thus probably solvable.

This concept was hardly a favorite one of mine. It clearly was not developed more than the basics. And largely forgotten for the past thirty years.

But the idea came to mind in the present-day context of space access, that it might be able to be used to be combined with the White-Knight Spaceship Two level of technology, to be used to give a spacecraft that merely peaked out at the altitude of the orbiting platform and thus be able to access full earth orbit; and later give the momentum back to the platform, enabling it to lose much of its velocity so as to enable a very easy return to the atmospheric environment for a flyback return to the ground.

It was a casual thought, but perhaps worth exploring.

And it resulted in the above-mentioned flack and challenge, instead of an OK lets see what can be done with it. Not an enjoyable situation for me. But I was stuck in it.

The challenger wanted numbers. I hazarded a mass for the orbiting platform to be about ten times that of the spacecraft it services, so that its orbital altitude would not change much. He put numbers to it and concluded it would have to be too long to keep the g-load on the spacecraft from being too high, and that length would be hard to make stiff enough with that little mass for the platform.

I thus found myself in an uncomfortable position; debate has never been a skill I had. But I was stuck in the situation, and the flack from the side was joining in the effort to ridicule me.

So I suddenly had the idea of making the orbiting platform in the form of a spring, a mechanical thing, a compression spring. The orbiting spring's orbit would be intersected by the peak of the rising spacecraft's trajectory, and the spacecraft would be punted by the orbiting spring giving it a horizontal component to its velocity.

My challenger then accurately pointed out that if the orbiting spring were ten times the mass of the spacecraft, that in bouncing off the spring, the spacecraft would have taken on the velocity of the orbiting spring but also the push of the spring decompressing, giving a velocity to the spacecraft of nearly twice the spring's orbital velocity; applying the numbers showed that it was far higher than escape velocity and the spacecraft would be punted totally out of the earth's gravitational field. Not something casual passengers on an excursion cruise would want; not to mention the extremely high accelerations involved would turn them into jelly.

But it might well work for routine transfer of mass between, say, Mars orbit and the earth surface, transferring much of the incoming spacecraft's high velocity over to then later boost a spacecraft headed back to Mars, very efficiently.

But the original thought was to make access to say the ISS orbit or GEO orbit, including by human passengers.

So I made a qualitative guess and hazarded making the mass of the orbiting platform spring to be somewhere less than twice the mass of the spacecraft involved, see what could be made of that. There could be calculated a curve of transfer velocities, and orbital changes in the orbiting spring platform.

At that point, the challenger of my concept suddenly vanished. No one mentioned my concept again; acted as if the discussion never happened. And that is still the situation; the space activist group suddenly got totally engrossed in power struggles amongst themselves, doing meetings and such kind of things, lots of distracting uproar of whose-boss-here kind of people stuff. Not my kind of thing.

But the idea still sounds a little interesting to me. What would be the variations and capabilities that might be found by exploring it further, I wonder. Clearly the space activist group would not like that, which seems very odd to me. But, as I have pointed out in other posts, I am still learning, from my Asperger's viewpoint, of what people actually do do.

And thus the idea was at least worth the effort of making the blog post here about it. Who knows, fortunes might be made with it someday. If so, past experience shows they will never mention me or my effort, however. But, such ideas are fun to explore for their own sake, anyway.