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Pictorial and Video Description of DigitalSpace's Mission Concept Design
(Click on the images below to view and save larger images for publication or other uses)
II. Still Images and Textual Description of Mission
Launch of mission elements, rendezvous and docking, Trans-NEO-Injection, cruise and arrival at NEO (not true to scale)
Launch and Docking of Mission Elements
Our first two steps on this journey start when the Orion (Crew Exploration Vehicle - CEV) is launched by an Ares I rocket while the Earth Departure Stage (EDS) is launched by the Ares V heavy lift vehicle. The EDS has the NEO Surface Access Module (NSAM) carried on the top under the payload shroud. Rendezvous and docking of the Orion and EDS segments occurs in Low Earth Orbit (LEO).
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Ares I launch of Orion CEV
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Ares V launch of Earth Departure Stage
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Rendezvous and docking of Orion and EDS
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Trans-NEO Burn
The completed "stack" then orbits the Earth until a Trans-NEO-Burn (TNI) occur, placing the vehicle on course to intersect the NEO. The EDS would be jettisoned during the cruise phase, leaving the Orion CEV and NSAM to continue on. The NSAM would serve as extended crew quarters.
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Completed stack orbits the Earth
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Stack effects TNI (Trans NEO Injection) burn |
Vehicle departing the Earth
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Arrival at NEO and Station Keeping
Next, the vehicle would enter a station keeping position, sense and determine likely target landing areas, match the rotation of the NEO and effect one or more close approaches. Please note that this or other NEO targets may have been visited by prior robotic precursor missions and its surface properties may have been characterized, thus lowering the risk to the crewed mission. The Surveyor precursor missions were used in a similar way for the Apollo program in the 1960's.
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Arrival of vehicle at NEO, EDS separation
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Vehicle station-keeping, match NEO rotation
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Descent attitude, testing
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NEOs have very low gravity so a key challenge will be to connect with and stay stably held down on the surface. The Airbag + sensor + harpoon anchor tether proposed by DigitalSpace would be used by the vehicle to effect a safe docking and holdfast. This mimics the system used by insects to secure themselves to surfaces in the presence of air movement. Using the airbags, the vehicle would be able to make a soft surface impact distributed around a ring of bags. Surface “NEOtechnical properties”, including load bearing strength and surface density, could be measured in real-time by probe sensors mounted on the airbag ring. Thus, the quality of a likely “seal” could be determined rapidly and at several locations on subsequent hops. When an optimal seal (stable, penetrable surface) is sensed, the harpoon tether system would then be activated to attempt to create a fast hold.
Design Disclaimer
Please note the following design disclaimer. It is most likely that robotic precursors would determine a NEO's surface properties before the human mission arrives. It is not a given that the configuration of the Orion CEV with NSAM could make an effective "touch down" or that tethers would even work for specific situations and compositions. Thrusters used on a docking exercise would wreak havoc with sample collection given that thrusters contaminate any potential samples. In other words, this is a complete guess as to whether the spacecraft would make contact with the surface or would simply hover.
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Hopping from place to place, searching for optimal docking/securing location, communication via comsat
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Reaction Control System firing on approaches
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Successful docking with NEO surface
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III. Successful Docking and Securing to NEO Surface
In the case of a secure anchor by a suitable proportion of the four or more tethers, the crew would then teleoperate the tether winches to test the anchor strength, much the way a ship secures its anchor in the ocean bottom. A secure holdfast would enable EVA surface operations, as the tethers operate as hand hold aids to astronauts. In the case of an insecure holdfast, tether retrieval by winching or “harpoon drop” could leave the anchor end in the NEO surface and allow the tether to be rewound. Another hop attempt could then be tried. A crew EVA could be engaged to replace a tether harpoon anchor.
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Successful secure docking showing deployment of tethers
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View of EVA under way with astronaut operating sampling robotic arm
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EVA and Science Activities
EVA would occur through an airlock on one end of the NSAM. This airlock would help crew isolate the dust and NEO surface matter from entering the living quarters and Orion. After exiting the airlock, the microgravity environment of a NEO would require crew ("neonauts"?) to move by pulling themselves along, drawing their lower extremities behind them, much as movement occurs on board a space station. Thus, handrails on the vehicle and the deployed tethers will be essential for crew to make their way around the vehicle and to the surface. The use of teleoperated robotic arms attached to the stable vehicle platform for sampling will assist crew in drilling or digging operations. If EVA is not possible, the crew could still use these teleoperated arms to gather samples while inside the NSAM. Samples would be collected later for transport in the Orion CEV.
For later excursions away from the docking site, neonauts would use a kind of jet-pack such as the "Manned Maneuvering Unit (MMU)" once used in the Shuttle program. They would essentially become free flying spacecraft, free to explore and sample the NEO to quite a distance. This would be the NEO equivalent of the Apollo "Moon buggy". Scientists would also perform internal structure measurements of the NEO which are key for understanding the impact history and hazard mitigation strategies. Knowledge of the internal makeup of NEOs is critical to working out what to do if a NEO were on a collision course with Earth. These measurements could be performed from a close distance or through a deployed science package similar to the LSEP, used for longer term studies of the Moon during Apollo.
IV. Return Mission
Trans-Earth Injection, dropping of mission segments and reentry (not true to scale)
On departure from the surface of the NEO, the decking section below the NSAM, with its airbags and tethers, along with fuel or solar collectors for continued operations, and a deployed communications antenna, would be detached and left on the surface as a long term science station. Prior to separation, crew would pack sample cannisters and rock boxes on board the Orion CEV. On the return flight, the NSAM would again serve as extended crew quarters.
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Departure from NEO leaving stay-behind science station
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Burn of main Orion engine for Earth return
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Dropping of service module for Orion reentry
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The vehicle would then effect a trans-Earth injection (TEI) burn and return to Earth, jettison the NSAM and service module and reenter, landing with parachutes on land using another series of air bags.
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| Reentry of Orion crew module |
Descent and landing of Orion crew module (on airbags) |
V. NSAM - Detailed Views
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| View of NEO Surface Access Module (NSAM) |
NSAM showing airbag and penetrometer sensor rings |
These views show the NSAM with its separable instrument deck, ring of airbags and penetrometer sensors and tanks of consumables.
VII. Concluding Thoughts: Function and Benefits of the NSAM Docking Design
1. Multiple mission profiles and safe fallback positions with increasing level of engagement:
- engage NEO target at a station-keeping distance;
- make one or more close approaches for remote sensing;
- attempt one or more “touch, sample and go” surface contacts;
- create a temporary (possibly unstable) holdfast on the surface with more extensive sampling (non EVA);
- secure long term holdfast on surface (with EVAs);
- secure multiple long term holdfasts on surface (with EVAs).
2. A flexible NEO berthing technique using multiple modalities and levels of safe fallback is another benefit of the design. The Airbag + sensor + harpoon anchor tether approach mimics the system used by insects to secure themselves to surfaces in the presence of air movement, analogous to a heavy object trying to grapple a possibly unstable surface in low gravity. Using the airbags, the vehicle would be able to make a soft surface impact distributed around a ring of bags. Surface “neotechnical properties”, including load bearing strength and surface density, could be made instantly by probe sensors mounted on the airbag ring. Thus, the quality of a likely “seal” could be determined rapidly and at several locations on subsequent hops. When an optimal seal (stable, penetrable surface) is sensed, the harpoon tether system could be activated to attempt to create a fast hold.
In the case of a secure hold, on a suitable proportion of the four or more tethers, teleoperating of the tether winches could be engaged to tighten or loosen the tethers. Safe berthing could enable EVA and manual adjustment of the tether or the harpoon end. In the case of an insecure hold tether retraction could be attempted. Teleoperated retraction, EVA assisted retraction or “harpoon drop” could leave the anchor end in the NEO surface and allow the tether to be rewound. Another hop attempt could be tried. EVA could be engaged to replace a tether harpoon.
In the case of a highly risky tether (falling stack) an emergency abort could be effected by dropping the entire stay-behind base and departing the NEO surface.
3. A substantial stay-behind science station is another benefit of this design. The NSAM base, including decking, RCS station keeping fuel tanks, airbag, sensor and instrument ring, would be decoupled from the Orion/NSAM habitat module at departure and remain behind, secured to the NEO surface. A communications and solar power package (or fuel cell with source) could permit longer-term science and communications with earth with enough power to position the dish and track Earth if the NEO is a presumed slow rotator. Any externally deployed science package could be power/data cabled to the station. This station is effectively a NEO version of the Apollo LSEP (an NSEP). Lastly, the mass left behind on the NEO will lower fuel costs for the Trans Earth Injection (TEI).
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