In section 2.4.3, the nature of near Earth objects (NEOs) was described. In section 2.5.1 some of the technologies for mining these bodies were discussed. This section will now briefly describe a precursor mission that aims at getting water from a NEO to Earth orbit for later use.

Rationale

With today's launch cost of 1,000 to 10,000 US$/ kg to low Earth orbit (LEO) and 25,000 to 50,000 US$/kg to geostationary Earth orbit (GEO), one metric ton of water in LEO represents up to 10-million US$ and up to 50-million US$ in GEO. Once water is brought to these locations, it could be used either directly or be delivered to a special service spacecraft (provider) with an electrolyzer aboard that splits the water into oxygen and hydrogen. With this, several services could be provided:

• Water, oxygen and propellant for the ISS in LEO
   
• Water, oxygen and propellant for human missions to the Moon, Mars, and beyond
   
• Refueling communication satellites in GEO that run out of fuel but are technically still operational
   
• "Road assistance" for satellites. In the past, a number of communication satellites that were launched to orbit were complete losses due to failures of simple components (e.g. stuck solar panel or defective apogee kick stage). The service spacecraft fuelled with propellants from NEOs could provide defective satellites with the necessary "hammer kick". It could also perform the orbit insertion into GEO in the case of a failure of the apogee kick stage.
   
• Refueling service in LEO. Satellites could be launched to LEO empty and then fueled up and brought to their destination orbit. This could also make possible a new generation of jumbo-sized communication satellites. These could be about twice as big as currently available. By being empty at launch, they could still be transported by existing launchers. With cheaper propellants from NEOs the cost per payload (transponder) mass could be reduced.

The idea of bringing water from NEOs to Earth orbit points clearly towards commercialization of space. In order to be profitable though, the mission has to have to have a certain economy of scale. The project described in this section will not necessarily be profitable but it will serve as a feasibility demonstration for later full-scale missions. After one cycle, all the hardware in this mission can be reused. It does not even need to be supplied with propellants - since it brings its own propellant from the target NEO. So after the accomplishment of the first roundtrip it could either go back to the same asteroid or encounter another one to establish a new mine.

In theory, over its projected lifetime the equipment could be capable of bringing water/propellant mass from NEOs to Earth orbit that is several times its own mass.

Part of this precursor mission is to find out whether robotic mining can be carried out for extended periods of time - without the possibility of human intervention in case of malfunctions. It could be that it turns out to be impossible - mining equipment on Earth is known for needing constant repair. In this case, a team of astronauts would follow the equipment that has been sent to the target in advance. During the mining process, the crew's task would consist of the teleoperated repair of hardware glitches.

Using these ideas, the following mission statement for the NEO water extraction precursor was defined:

Mission Statement

Bring 1000 kg of water from a Near Earth Object to Geostationary Transfer Orbit before mid-2005 to provide customers there with either water, oxygen and/or hydrogen and repeat the mission at least one more time.

Mission Architecture

The NEO Tanker Shuttle Mission consists of five main parts:

1. Trans-NEO injection of the mining equipment with a lunar swing-by; rendezvous with the target and deployment of mining equipment on the target
    
2. Acquisition and processing of the water material
    
3. Trans-Earth injection of water with aerocapture and injection into geostationary transfer orbit (GTO)
    
4. Delivery of the water to a propellant manufacturing plant in GTO (the "gas station") and refilling of the trans-NEO injection stage
    
5. Re-injection into trans-NEO Orbit (similar to Step 1)

These five steps are performed by three different mission components:

A. The shuttle, which transports the mining equipment to the target and the water from the target. This will incorporate a heat shield for Earth aerocapture.

B. The miner, which extracts the regolith and processes the water out of it.

C. The provider ("gas station / road assistant"), which delivers water, propellants and oxygen as well as services to customers in Earth orbit.

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