April 19, 2012

Details around Asteroid Retrieval plans and what is in the Near Earth Asteroids

Wired - In 2011, there was a four-day workshop dedicated to investigating the feasibility and requirements of capturing a near-Earth asteroid, bringing it closer to our planet and using it as a base for future manned spaceflight missions.

Asteroid retrieval mission study workshop website

An Asteroid Retrieval Mission Study is being conducted to investigate the feasibility of finding, characterizing, robotically capturing, and returning an entire Near Earth Asteroid (NEA) to the vicinity of the Earth for scientific investigation, evaluation of its resource potential, determination of its internal structure and other aspects important for planetary defense activities, and to serve as a possible testbed for human operations at an asteroid. The study team will evaluate different mission concepts and destinations for the Near Earth Asteroid (NEA) including the Lagrange points (Earth-Moon L1/L2/L4/L5 or Sun-Earth L2) as well as other Earth orbits. The asteroid will be 2-5 meter in diameter.

Moving an asteroid is a huge idea – never has a celestial object been moved by humans. It is a huge idea, but not an impossible one. A recent study at JPL has already shown possible feasibility to move a small asteroid, with a mass of ~10,000 kg, deep into the Earth's gravity well – even to the orbit of the International Space Station.

Asteroid Return Feasibility Study (2010, 29 page presentation)

Self Imposed Rules
1. Launch by the end of this decade
2. Require only a single Evolved Expendable Launch Vehicle (EELV)
3. Total round-­‐trip flight time of ~5 years
4. Select an asteroid that has an unrestricted Earth return Planetary Protection categorization
5. Return asteroid to the ISS

Use 40 kilowatt Solar Electric Propulsion system (launch mass of 13.7 tons)
Return a 10 ton asteroid to low earth orbit
But if return to high earth orbit can return 50 times more. 508 tons.


Professor John Lewis discusses the resource potential of near earth asteroids. (28 pages)

• About 1000 one-kilometer-sized NEAs
• About 400,000 100-meter sized NEAs
• Periods generally 0.9 to 7 years
• Orbital inclinations generally 10-20o
• Eccentricities 0 to 0.9; mostly near 0.5
• About 30% will eventually hit Earth
• About 20% are easier to land on than the Moon





Easy Access from low earth orbit

• Perihelion (or aphelion) close to 1 AU
• Small eccentricity
• Low inclination

These factors combined allow low outbound ΔVs (from LEO to soft landing)

Easy Return to low earth orbit

• Perihelion (aphelion) close to 1 AU
• Small cross-range distance between orbits
• Favorable orbital phasing (different every time)
• Use of aerocapture at Earth

These factors allow low inbound ΔVs (from asteroid surface to LEO).

Many NEAs have ΔVin < 500 m s-1 (some as low as 60 m s-1, compared to 3000 m s-1 for Moon) Abundance of Useful Materials

What are the most useful materials?
– Water (ice, -OH silicates, hydrated salts) for
• Propellants
• Life support
– Native ferrous metals (Fe, Ni) for structures
– Bulk regolith for radiation shielding
– Platinum-group metals (PGMs) for Earth
– Semiconductor nonmetals (Si, Ga, Ge, As,…) for Earth or Solar Power Satellites

Comparative abundances
– Water
• C, D, P chondrites have 1 to >20% H2O; extinct NEO comet cores may be 60% water ice
• Mature regolith SW hydrogen reaches maximum of about 100 ppm in ilmenite-rich mare basins (water equivalent 0.1% assuming perfect recovery)
– Metals
• To 99% in M asteroids; 5-30% in chondrites
• Lunar regolith contains 0.1 to 0.5 % asteroidal metals

Simple Processing Schemes
“Simple and Efficient” means:
– Low energy consumption per kg of product
– Processes require little or no consumables
– Few mechanical parts
– Modular design for ease of repair
– Highly autonomous operation
– On-board AI/expert systems for process control
– Self-diagnosis and self-repair capabilities
– Maximal use of low-grade (solar thermal) energy
– Regenerative heat capture wherever possible

Examples of Processing Schemes

• Ice extraction by melting and sublimation of native ice using solar or nuclear power
• Water extraction from –OH silicates or hydrated salts by solar or nuclear heating
• Electrolysis of water and liquefaction of H/O
• Ferrous metal volatilization, separation, purification, and deposition by the gaseous Mond process
– Feo(s) +5CO < -- > Fe(CO)5(g)
– Nio(s) + 4CO < -- > Ni(CO)4(g)

Magnitude of what is in Near Earth Asteroids

• Total NEA mass about 4x10^18 g
• About 1x1018 g ferrous metals
• About 1x1018 g water
• Earth-surface market value of NEA metals
– Fe iron $300/Mg x 10^12 Mg = $300 T
– Ni $28000/Mg x 7x10^10 Mg = $2000 T
– Co $33000/Mg x 1.5x10^10 Mg = $500 T
– PGMs $40/g x 5 x 10^7 Mg = $2000 T


Highly useful material for use in Space

• Structural metals for SPS, bases, etc.
– High-purity iron from Mond process
• 99.9999% Fe: strength and corrosion resistance of stainless steel
– High-precision chemical vapor deposition (CVD) of Ni in molds
• Custom CVD of Fe/Ni alloys
• Bulk radiation shielding
– Regolith, metals, water (best)

• LEO
– Propellants for GTO/GEO/HEEO/Moon/Mars
– Radiation shielding

• GEO
– Structural metals for Solar Power Satellites
– Station-keeping propellants
– Photovoltaics for SPS

• Direct use of water as propellant
– Solar Thermal Propulsion-- STP (“Steam rocket”)
– Nuclear Thermal Propulsion– NTP
• Electrolysis of water to H/O
– H2 STP
– H2 NTP
– H2/O2 chemical propulsion

One Asteroid Amun has over 30 times all the metal mined in human history

• 3554 Amun: smallest known M-type NEA
• Amun is 2000 meter in diameter
• Contains about 30x the total amount of metals mined over human history
• Contains 3x10^16 g of iron
• Contains over 10^12 g of PGMs with Earth surface market value of about $70 Trillion

Near Earth Asteroids as traveling hotels

• Typical NEAs have perihelia near Earth and aphelia in the heart of the asteroid belt
• NEA regolith provides radiation shielding
• Asteroid materials provide propellants
• Earth-Mars transfer orbits possible
• Traveling hotels/gas stations/factories… colonies?

• Typical NEAs have perihelia near Earth
and aphelia in the heart of the asteroid belt
• NEA regolith provides radiation shielding
• Asteroid materials provide propellants
• Earth-Mars transfer orbits possible
• Traveling hotels/gas stations/factories…
colonies?

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