TECH UPDATE - NEO Mission Design for a Human Mission to a Near Earth Object

A privately held company based in Santa Cruz, California, today released their design simulation of a notional crewed mission to an as-yet unidentified asteroid (also refered to as a Near Earth Object, or NEO) which might pass near the Earth sometime in the future. This visualization is DigitalSpace's design concept for the mission, produced by DigitalSpace as an independent effort for the benefit of an internal NASA feasibility study completed in 2007. The NASA study was performed to show that such a mission is possible with NASA's new Constellation architecture which was designed to return humans to the moon. DigitalSpace received input from numerous experts inside and outside of NASA to produce the following

It is important to note that this is not a NASA concept; it is a conceptual design created by the DigitalSpace team to stimulate discussion in the space community. The challenge of traveling beyond the Earth and Moon to NEOs inspires some of the first new human spacecraft and mission design since the days of the Apollo project and DigitalSpace hopes this will excite both the extended space community and the general public.

DigitalSpace has been engaged with NASA since 1999 delivering interactive real-time visualizations for a variety of NASA projects. These visualizations feature Digital Spaces, a unique open source platform created by DigitalSpace for rapid mission prototyping. The platform harnesses the power of 3D graphics found in game hardware coupled with leading-edge physics engines. Recently, DigitalSpace completed a series of real-time visualizations in the Digital Spaces platform which support NASA's "Vision for Space Exploration" simulating robotic and human missions to the Moon and Mars.

DigitalSpace founder and CEO Bruce Damer has long had a passionate interest in the "lesser known" objects in our solar system including asteroids and icy bodies such as comets. In a recent Q&A with technology journalist Allan Lundell, Bruce explains:

How did you come to work with NASA on producing these compelling designs and visualizations?

In the Summer of 2006 DigitalSpace was approached by NASA requesting help in visualizing a human mission to a NEO. When NASA's internal feasibility study got underway a few months later, DigitalSpace met with members of the feasibility study group and from my own earlier ideas I sketched out the design you see pictured below: the Orion spacecraft with attached "NSAM" (NEO Surface Access Module) component which has underneath it a ring of airbags and sensors to enable a "soft contact touch-and-tether " with the NEO surface. This will allow the crew to rapidly determine the surface firmness (asteroids could have crumbly surfaces) and then permit them to deploy tethers to create a secure holdfast or else rebound off the surface to try another target area. Those same tethers would support astronauts as handholds on an EVA to the surface.

DigitalSpace was happy to provide this independent effort to our colleagues at NASA involved in the study. It is important to make clear that this is not a NASA concept, nor has NASA given it any kind of technical blessing; it is a conceptual design created by myself and the DigitalSpace team to stimulate discussion in the space community.

Why are NEOs (Near Earth Objects) of interest to you and DigitalSpace?

In a real sense, these objects, more than the moon or the planets, represent our long term future in space. Asteroids and icy objects such as comets contain critical elements including water, organic materials and minerals that could provide the stepping stones for human exploration and settlement of the solar system. For example, a small object brought into Earth orbit could provide thousands of tons of easily accessible consumables for rocket fuel and crew life support which could lower the cost of exploration dramatically. Similar refuelling stations could be set up on objects further out, enabling humans to reach destinations including Mars and the outer planets.

It is important to stress that this idea of NEO capture is one of my pet concepts (and was explored years ago by people such as Gerard O'Neill) but does not represent anything being considered by NASA.

Why not focus only on reaching the Moon as a stepping stone and then go directly on to Mars?

We know from prior experience that the return to the moon is an attainable, appropriate and exciting goal. Mars, on the other hand, is so distant that it is hard to imagine current technology being able to keep a crew safe and deal with all the unknowns for one or more years when we need constant resupply of supplies and parts to simply keep a space station functioning just two hundred miles above our heads. So perhaps the optimal way to learn how to do deep space flight is to visit a NEO that is just a few weeks' flight out and back from the Earth/Moon system. And if you think of this as a prospector trip, we may find a whole lot out there we can really use.

Perhaps the biggest payback from a mission like this is sample collection which would truly generate a huge science return. Scientists would also perform internal structure measurements of the NEO which are key for understanding the impact history and hazard mitigation strategies. You have to know about the internal makeup of NEOs to work out what to do if a NEO were on a collision course with Earth.

Of course any crewed mission to a NEO carries its own significant risks including solar radiation events after the craft leaves the Earth's protective magnetosphere as well as hazards encountered while safely docking with and operating on a NEO's surface.

How is a mission to a NEO relevant to early 21st Century concerns about protecting the Earth and as a possible goal for the US when new space policy is discussed during the current election season?

By crafting this visualization of the human exploration of an asteroid, DigitalSpace aimed to create a vision that might be exciting to the public and at the same time support the NASA feasibility study, which sought to show that NASA's Constellation hardware (which is designed for returning humans to the moon) can also enable a NEO mission. In addition, asteroids represent a true "green destination" as they are the most likely source of future resources for sustainable spaceflight. Last but perhaps most important, by going to a NEO we will not only do great science, learning more about the origin of life and the early Solar System, but we will also be better prepared to protect the Earth should a threatening object come our way in the future. With recent successes such as Deep Impact and upcoming missions such as Dawn and New Horizons, the next decade may be one in which we really learn about asteroids and comets. In my view, a human trip might be an excellent follow-on to that investment.

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. Completed stack orbits the Earth Stack effects TNI (Trans NEO Injection) burn Vehicle departing the Earth 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. Arrival of vehicle at NEO, EDS separation Vehicle station-keeping, match NEO rotation Descent attitude, testing 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. Hopping from place to place, searching for optimal docking/securing location, communication via comsat Reaction Control System firing on approaches Successful docking with NEO surface 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. Successful secure docking showing deployment of tethers View of EVA under way with astronaut operating sampling robotic arm 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. Departure from NEO leaving stay-behind science station Burn of main Orion engine for Earth return Dropping of service module for Orion reentry 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. Reentry of Orion crew module Descent and landing of Orion crew module (on airbags) V. NSAM - Detailed Views 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).

Other Quesions and Answers on the DigitalSpace Design for a Human NEO Mission and Resources from Other Groups and Individuals Focused on the NEO Issue

What NEO would we go to and how would we get there? There are several potential NEO targets that could be visited as early as 2017, and many in the 2020's. In addition, we will discover more viable NEO targets in the coming years. NEOs we would choose to visit would be crossing our orbit close to the Earth/Moon system and within the plane of our orbit. We would travel out and rendezvous with the NEO on its approach in the general direction of Earth and then depart the NEO at a convenient trajectory to return to Earth. When will NASA make the Human NEO mission feasibility study public (and who at NASA or outside NASA can one contact about the study)?