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1 ABSTRACT Aside from the Exploration of Mars, the Objects That IAC-07-B3.5.06 INTO THE BEYOND: A CREWED MISSION TO A NEAR-EARTH OBJECT David J. Korsmeyer, NASA Ames Research Center, Intelligent Systems Division, Moffett Field, CA, USA, [email protected] Rob R. Landis, NASA Johnson Space Center, Mission Operations Directorate, Houston, TX, USA [email protected] Paul A. Abell, NASA Johnson Space Center, Astromaterials Research & Exploration Science, Houston, TX, USA [email protected] ABSTRACT utility and opportunities for the developing Aside from the exploration of Mars, the Constellation infrastructure, particularly, the objects that most capture our interest for a Ares Launch vehicles and the Orion crewed new human visit are the Near-Earth Objects spacecraft, to be used for missions that were (NEOs). These objects are ideal candidates not directly in the design specifications (aka for deep space operations and explorations as non-lunar missions). The Ares and Orion we extend the human presence out into the systems are designed to launch 4-6 crew to solar system. The notion of a crewed mission the International Space Station (ISS), and to to a NEO was first discussed in the Apollo eventually take 4 crew back to lunar orbit era. The most recent assessment has been where a lunar lander would take the crew to undertaken by the Advanced Projects Office the surface. within NASA’s Constellation Program. This particular study examined the feasibility of The NASA Constellation Program wanted to sending NASA’s new Orion spacecraft (also understand what are some other feasible, referred to as the Crew Exploration Vehicle, high-value uses of the Orion spacecraft and or CEV) to a NEO. Depending on the Ares launch system other than a lunar return. specifications of spacecraft and integrated One of the key feasible uses was the notion of components, a mission profile would include the Orion spacecraft taking astronauts to visit two or three astronauts on a 90- to 180-day a Near Earth Object, most likely an asteroid. spaceflight; including a 7- to 14-day stay at The results of this study1 and its potential the NEO itself. These missions to NEOs place in the manned exploration on the inner provide Exploration with an excellent suite of solar system are discussed in this paper. benefits: operational experience beyond cislunar space; risk reduction for space WHAT ARE NEAR-EARTH OBJECTS? hardware; confidence building for future Near-Earth objects (NEOs) include asteroids mission scenarios; in situ resource utilization and comets whose orbits approach or evaluation; as well as a rich scientific return. intersect the Earth’s orbit about the Sun (and This incremental step along the way towards are, therefore, distinguished from main belt Mars would mark humanity’s first foray asteroids which orbit the Sun between Mars beyond the Earth-Moon system. and Jupiter). NEOs range in size from a few meters across to as large as ~30 kilometers INTRODUCTION (km) across, with smaller objects greatly In August of 2006, the Advanced Programs outnumbering larger objects. Because of the Office within NASA’s Constellation Program volatiles they contain, near-Earth comets, decided to fund an initial set of concept while in Earth’s vicinity to the Sun, would feasibility studies. These were to assess the not make an attractive target for a crewed mission, so the study will focus on what we 1 know to be near-Earth asteroids. However, relative positions of the NEO and the Earth the term ‘NEO’ will be used to refer to all requires a good characterization of the NEO near-Earth objects throughout this paper. trajectory prior to the NEO’s close approach From ground-based observations and the to Earth. study of meteorites that have fallen to Earth, we know that the general makeup and NEOs are often found when their orbits cause structure of NEOs is wide-ranging – from them to approach Earth and thus become a those comprised of loose conglomerations of brighter magnitude object in the sky. The rock and stone to those consisting of mostly older surveying telescopes do not have the iron. Due to their small size and relative sensitivity to detect NEOs below 1km in size similarity of their orbits to Earth, many NEOs without the NEOs coming very close to the require significantly less Δv to access than is Earth. The current NASA NEO program required to get to the Moon. The Moon is assesses a new NEO to determine whether it more frequently accessible due to its captive is a Potential Hazardous Object (PHO) or not. orbit around the Earth. Due to the nature of most NEO orbits, the phasing of NEOs and the Earth to meet The orbits of many NEOs are quite similar to occurs only every tens of years for most the Earth’s heliocentric orbit, and therefore NEOs. At the time of most NEO discoveries, require a small Δv for rendezvous provided the NEO is likely already not in a position launch occurs near a close approach. In with respect to the Earth where a crewed addition, due to their small size and mission could easily be sent to visit. It is consequent shallow gravity wells, only a very likely that it will be several decades before small Δv (~0.06 km/sec) is required to brake the specific NEO returns close enough to the into the vicinity of, and to depart from, a Earth for a mission to be sent. typical NEO. For comparison, the Δv required to brake into or depart from lunar In 1998, NASA accepted the mandate to detect and catalogue 90% of NEOs larger than 1 km. orbit is on the order of 0.8 km/sec, which As of 9 August 2007, 4754 NEOs have been when combined with the 3.2 km/sec lunar discovered and over 800 were identified as transfer v means that an Apollo 8 type Δ PHOs. A 2005 update to the NASA mission requires a Δv ~4.8 km/sec. For Authorization Act now directs NASA to comparison, the Apollo 17 mission total Δv detect and characterize NEOs down to 140 2 was ~9.1 km/sec . So it can require less meters in size. The number of such smaller energy to get to a NEO than would take to asteroids is vastly greater than the number of land on the Moon. larger asteroids. This means that the discovery rate of NEO will increase greatly Why then, have we not attempted to send over the next ten years, even if only two new crews to NEOs already? This is due in part to search telescopes begin operations. The two two things: the current lack of capable new telescopes are the Pan-STARRS spacecraft and boost stages; and the difficulty (Panoramic Survey Telescope and Rapid in identifying when a NEO of interest will be Response System) and the Large Synoptic passing by close enough to the Earth to Survey Telescope (LSST). The number of enable reasonable travel times for a crewed known NEOs will grow especially if NASA spacecraft. To plan for a NEO mission, we is provided funds to perform the greater than would want to know that a NEO would be 140 meter survey to 90% completeness by coming in close proximity to the Earth 2020. By the middle of the next decade we several years in advance. Knowing the expect that there will be hundreds of possible 2 new candidate NEOs accessible for a CEV a piloted mission to a NEO was first mission. discussed in 1966 as an alternate follow-on utilization of the Apollo spacecraft and Saturn 5 hardware. The mission5 would have Cumulative PHOs and NEOs 1990-2020 been a flyby for the 1975 opposition of 433 #NEO>140m #PHO>140m Yr Eros. During the 1975 opposition, Eros came #NEO>100m #PHO>100m within 0.15 AU of the Earth. The 1966 study 100 20 1990 examined the necessary capabilities to 100 20 upgrade the Apollo/Saturn 5 hardware for a 300 60 500+ day round trip mission. More than 20 1995 300 60 years later, NASA re-examined6 the idea of 800 160 visiting NEOs in greater depth as part of the 2000 800 160 Space Exploration Initiative in 1989. Since 3000 600 2005 then, four other studies have examined the 3000 600 details of sending humans to NEOs7,8,9,10. 6000 1200 2010 10000 2000 The Advanced Projects Office within 30000 6000 2015 NASA’s Constellation Program sponsored 50000 10000 the most recent official NASA study. This 40000 8000 2020 six-month (Sept 2006 – Feb 2007) study was 80000 16000 conducted by a team led from NASA Ames Table 1: Cumulative PHOs and NEOs Research Center. That team included members from NASA Johnson Space Center Past discovery rates of NEOs in Table 1 are (including astronaut Ed Lu), the Jet from the NASA-JPL NEO Program Office Propulsion Laboratory, NASA Headquarters, 3 website . Future discovery rates are estimated and former astronaut Tom Jones, the author from Figure 13 of the NASA 2006 Near-Earth of two previous NEO studies. The study 4 Object Survey and Deflection Study . Note examined the feasibility of sending a CEV to that while the NASA metric for future a NEO11. The ideal mission profile would surveys is defined for PHOs 140m or larger, involve a crew of 2 or 3 astronauts on a 90- to the LSST will discover almost twice this 180-day flight, which would include a 7- to number that are greater that 100m in size The 14-day stay for proximity operations at the estimates in Table 1 for the numbers >100m target NEO.
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