8,100 tons of space debris has accumulated in low Earth orbit consisting of spent rocket bodies, mission-related debris, and collision fragments. The vast majority of these objects are too small to detect with radar systems, but there are over 29,000 known objects larger than 10 cm. Impacts between these objects and operating missions have damaged costly equipment, required expensive collision avoidance maneuvers, and endangered the lives of astronauts on the international space station. In 1979 the NASA Orbital Debris Program Office, in conjunction with Donald J. Kessler, released research on the “Kessler Syndrome” which predicted that collisions would continue to increase. This would lead to an exponential growth in debris that would render access to space impossible within several generations. A partial solution to stabilizing the debris population was also proposed which required new missions to incorporate post mission disposal measures, as well as missions dedicated to Active Debris Removal (ADR) by placing the largest objects into decaying orbits of less than 25 years. This proposal addresses how one might succeed in achieving this latter objective.
Successful realization of the CHARON concept would have a major impact on several NASA mission objectives. An orbital vehicle that could utilize in-situ upper atmospheric resources would enable a host of missions, and in particular ADR, that require extremely high delta-V in a fast, responsive, and repeatable manner. The concept proposed here, the Crosscutting, High Apogee, Refueling Orbital Navigator (CHARON) will provide such capability. CHARON accomplishes this in the following manner: first it obtains fuel by scooping up and storing the low density N2 and O encountered during the low altitude perigee periods of the highly elliptical orbits. Incorporation of the ultra-lightweight, high thrust-to-power Electrodeless Lorentz Force thruster developed at MSNW enables CHARON to operate efficiently on stored gas in a variety of configurations depending upon mission requirements. As CHARON can thrust at apogee, it can achieve the extensive orbit lowering needed for ADR. Additionally, CHARON can thrust at perigee to provide drag compensation for very low perigee refueling, stable non-Keplerian orbits, or rapid phase changes. CHARON requires only 5 kW of on-board solar power as energy collected during the higher altitude portions of its elliptical orbit can be stored for higher power operation later. Functioning in this manner CHARON can generate 1.2 N of thrust at 2500 sec of Isp for ADR. During a 10-year mission life, CHARON will process 5500 kg of propellant to ferry 80 spacecraft, perform 850 degrees of plane change, with over 100km/s of delta-V, all with a single spacecraft launch, and requiring no additional onboard propellant.
As the largest concentrations of high mass debris are in the inclination band of 81 to 83 degrees and in the altitude range of 800 to 1300 km, it is removal of debris from these regions of space that will first be analyzed. Therefore, the phase I effort proposed here will focus on the mission analysis and orbit calculations for the retrieval of the more massive objects at a range of altitudes centered about 950km and 82 degrees inclination. In addition, plans to experimentally determine the properties and behavior of various scoop designs for CHARON will be made. The more promising designs from the analysis will be fabricated and characterized in phase II. This is made quite doable by utilizing the large vacuum chamber and thrust stand at MSNW along with the newly constructed large aperture, LEO neutral flow generator. Both drag coefficients as well as neutral compression ratios can be accurately determined in subscale testing which will allow for the design of the prototype CHARON that would be deployed for further space-based operation and development.
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
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Beware orbital carrots. Got it.
So if our scoop ship does have a big whipple shield that it uses to destroy the small debris, that sort of IS a robot arm with a catchers mitt, right?
That’s a great way to produce more debris. No matter what the material, collisions at orbital velocity have enough energy to vaporize it. Bigger objects will keep going until they encounter enough mass per unit area to get vaporized, or they punch through what they hit. In the latter case, you have a spray of smaller bits flying out the back. Watch this video to get a better understanding:
https://www.youtube.com/watch?v=kStpU1bU-oc
Salvage laws apply to defunct space hardware. If they want to claim ownership, you can bill them for cleaning up their mess. If they declare it abandoned, or it de-facto is, like an empty stage whose batteries are run down, then you can do what you want with it.
Since everything launched to orbit is made of aerospace-grade parts and materials, they may have future salvage value. Some “dead” satellites are perfectly fine except for one critical part that broke, or they ran out of propellant. The rest could be used for something. We just haven’t had a feasible way to do salvage and recycling yet.
The article above says they will chase down the larger space junk, i.e. the stuff you can find with radar. Smaller pieces can be defended against or intentionally destroyed with “Whipple shields”. At orbital velocity, collisions vaporize the debris, and part of what they hit. So on the Space Station, there are thin metal shields spaced away from the pressure hull. Small debris hits that first, vaporizes, and the vapor can’t penetrate the pressure hull (although it makes a large “bang” sound).
You can purposely destroy small debris by deploying the Whipple shields by themselves. The problem is keeping them in orbit, since they have a lot of drag area. The scoop mining concept above can solve that.
..there you need cooling to not overheat your equipment, and to make it possible to store the gas in a reasonable way. A gas at thousands of degrees isn’t going to store well. I would put radiators near the back end of the funnel, where the shock forms, then more cooling after the compressor.
I’ve studied and written about “scoop mining”. The shape of the scoop shown in the illustration is incorrect. It needs to be something similar to a trombone horn if it were straightened out. The reason is molecules at the scooping height (about 200 km) are hot. They are in a region called the “thermosphere”. This altitude also is in “free molecular flow”, meaning molecules act individually. The mean collision distance between molecules is larger than your typical spacecraft parts. So they bounce off the walls of the funnel individually.
Your ship is moving about 7500 m/s relative to the atmosphere, and the molecules are moving ~1000 m/s on their own. If you want them to continue down the funnel, you need a glancing blow as the fast moving funnel runs into randomly moving molecules. Otherwise you just bounce them out the mouth again. The deeper shape of the funnel is an exponential horn, imparting gentler side blows to the molecules as they progress. Towards the back of the funnel, the molecules are dense enough to start acting like a fluid, rather than free molecules. A shock forms at this point, behind which the pressure is higher. You compressor can now work with this denser gas in stages.
The other thing missing in their diagram is radiators. The gas was already hot before entering the scoop. The shock raises the temperature more, similar to the shock you get during reentry, but not as dense. A compressor would further heat this gas. So somewhere in ..
I think that the simplest solution to get rid of small debris in orbit would be to launch a satellite with a dense metal shield made of steel or maybe tungsten with a spall liner on both sides and send it straight into the path of debris. Anything that impacts will be caught in the liner, and stopped by the metal with the back liner there to prevent the shield from making more debris.
All you’d need to do is figure out an appropriate diameter then launch your cosmic vacuum cleaner.
Solar powered atmospheric scoop is probably tech that will really help space development long term, and this is as good as any a reason to actually develop and make one.
But they have completely left out how said scoop ship actually catches the space junk. We are talking about stuff that is too small to track and travelling faster, much faster, than bullets. How do you catch that? Robot arms with catcher’s mitts?
Hey, my junk is worth a LOT more than $5/kg, it is…. oh… wait….
Wrong sort of website. Sorry.
Carry on.
The main takeaways of this project is really they wanted a platform for electrodeless lorentz force thruster development, but if they get the atmosphere scooping right it’s a win-win. Especially since that means PROFAC (and the more modern PHARO) scoop system designs will finally become reality. Oxygen scooping is kinda hard due to total available amounts, but nitrogen collection is comparatively easy, which has interesting knock-on effects in LEO space economy, as that favors electric thrusters that can use nitrogen gas. With a solar electric scooper than can self reboost with collected propellant, you just leave the thing running and can effectively make propellant at the top of the gravity well effectively forever (tankage/propellant depot availability notwithstanding…)
Some of that debris might belong to someone. There is no cost to you if you abandon your junk in situ, but junk transforms into a revenue generating resource if someone else wants to collect that and reuse it.
My junk is worth $5k/kg in LEO, who pays?
With the amount of future junk we’ll launch in orbit over the next few decades, we’ll need this or something like it urgently.
Self de-orbiting spacecraft in LEO are a very good idea, so Starlink doesn’t worry me that much, but not everyone will show the same good sense and a lot of them will need some help picking up the trash.