Speaker
Description
Our idea addresses the two biggest problems of space activities: their extreme costs as well as space debris reduction. Beside comments and feedback from the audience, we were looking for research & industry partners who would be interested in working with us on this concept.
The challenge
Space debris is a serious issue. Although only few humans reached out into space, humanity polluted the orbit already with thousands of tons of waste. The current approach of voluntarily deorbiting space debris within 25 years or by moving it to graveyard orbits seems to be not adequate anymore in the era of satellite mega constellations. One day in the future, even graveyard orbits will be filled up like waste dumps today. And beside negative ecological aspects, the exponential waste growth put any future space mission at risks of unplannable collisions.
The opportunity
Like waste on Earth, space debris should not be considered only as a burden but as an opportunity, too. The recycling industry in Europe has become a multi-billion Euro industry in the past few decades. The concept could be applied to space, too. It’s only important to understand, what the value of space debris would be and what commercial use case lies beneath it: From our perspective, the core value of space debris lies in its location in space as it doesn’t require to be launched into the orbit again. A simplified calculation clarifies this advantage: A single Ariane 5 launch transports around 10 tons of material into orbit. With 8,000 tons of space debris, more than 800 Ariane launches would be needed. With estimated costs of 100 Million Euro each, this would result into 80 billion Euro launch costs alone to take an equivalent weight into space (ignoring the additional costs for this material).
The solution
Unfortunately, not all space debris material could be reused / recycled with affordable efforts: either the pieces are far too small to be collected, or the material cannot be reused (like fuel droplets), or the objects consist of complex material mixtures or individual shapes and forms like many scientific satellites which makes automated recycling processes a nightmare.
Luckily, there are “perfect” objects which seems to be ideal for recycling: rocket upper stages. Rocket upper stages have simple, geometric shapes (without large solar panels or antennas), have dedicated, well described connectors (where the payload was attached) and consists mainly of fuel tanks. Especially the European ESC-A upper stage from the Ariane launcher consists of 4 tons of aluminum for its two LH2 and LOx tanks. More than 60 of them are circulating in our orbits for the next decades or even centuries. Simplified, their shape is a geometric cylinder with a connector for the lower payload adapter and / or the Sylda on the top. By using currently developed technology described below, upper stages could be caught in space (e.g. with a net) and transported to the Moon (with a “space tug”). On the Moon, either the aluminum could be recycled and used as new construction material for the planned Moon station or the upper stages could be reused for the same purpose they had been designed for initially: as fuel tanks. Ice (water) on the Moon could be split into hydrogen and oxygen and used in fuel-cells to power the Moon station. To store the hydrogen and oxygen, the tanks of the ESC-A upper stages are ideally suited. Each ESC-A stage could store 14 tons of liquid hydrogen and oxygen in the right ratio. With the identified 60+ upper stages, the whole storage capacity would be 850 tons resulting in approx. 5500 MWh energy supply, enough for the largest Moon station.
Our concept could be applied to upper stages from different types and sizes to accommodate the needs in different scenarios like larger tanks for space / planetary stations or smaller ones for asteroid mining facilities in the future. Our proposal helps to reduce construction costs wherever water (ice) will be processed in space.
The technology
Our concept is based on special space tugs: space ships capable of catching an upper stage e.g. with a net and moving it afterwards to the Moon. The space tug concept would be based on the following ESA projects:
- ESA has identified active removal technologies as a strategic goal. Active Debris Removal (ADR) is necessary to stabilize the growth of space debris. This includes technology currently developed in different research projects under the e.Deorbit umbrella like a net to catch objects in space or efficient propulsion technologies to move objects from GTO to the Moon. In 2018, a pilot project was sent to the ISS (RemoveDEBRIS) to test the necessary technology and to prepare the larger e.Deorbit mission in upcoming years. Especially the net-technology is well understood and the geometry of upper stages without solar panels or large antennas is ideally suited for this process.
- Space Servicing Vehicle from Europe`s space industry. This proposal offers new use cases for these SSVs. A partnership with such an industry solution is aspired with lots of development synergies.
- Electric Propulsion Innovation & Competitiveness (EPIC) research cluster. Shared research and development of efficient propulsion technologies for the Moon transfer will offer new use cases and synergies including overall cost savings.
- ESA’s Moon projects from Orion via PROSPECT to current RFIs. This proposal nicely complements ESA’s Moon (village) activities but also depends on the commitment from ESA to consider recycled material.
Our proposed concept is an additional use case for all of these projects and complements the activities. Over time, technology will improve and affordable metal recycling might become feasible in space, too. This would allow to recycle the 4 tons of aluminum of the ESC-A upper stage to construct new aluminum elements. Aluminum could be reused as foils, foam, structures or powder for 3D printing for all kind of construction purposes. By using material from space instead of from the Earth’s surface, similar launch cost savings like in the tank scenario above would be possible. With 250 tons of aluminum already in orbit today, commercial recycling would be feasible if the commitment of space agencies to use recycled material in their space construction would be made. This would allow the space industry to purchase the recycled material and reuse it in space at lower costs than comparable Earth material.
Legal Aspects
While the removal targets should be selected from a global perspective, legal constraints dealing with the ownership of space debris objects, and the validation thereof, cannot be neglected. In the case of Ariane ESC-A upper stages, the ownership is clear (Ariane Group with France as the corresponding country). With strong relationships, especially in the development of the Ariane launchers, combined ADR activities between ESA, France and the Ariane Group should be more than realistic, including all legal aspects.
