The Kuiper Belt is a distant region of the outer Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU69, a cold classical Kuiper Belt object approximately 30 kilometers in diameter. Such objects have never been substantially heated by the Sun and are therefore well preserved since their formation. We describe initial results from these encounter observations. MU69 is a bilobed contact binary with a flattened shape, discrete geological units, and noticeable albedo heterogeneity. However, there is little surface color or compositional heterogeneity. No evidence for satellites, rings or other dust structures, a gas coma, or solar wind interactions was detected. MU69’s origin appears consistent with pebble cloud collapse followed by a low-velocity merger of its two lobes.

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A conceptual design was performed for a 6-U cubesat for a technology demonstration to be launched on the NASA Space Launch System (SLS) test launch EM-1, to be launched into a free-return translunar trajectory. The mission purpose was to demonstrate use of electric propulsion systems on a small satellite platform. The candidate objective chosen was a mission to visit a Near-Earth asteroid. Both asteroid fly-by and asteroid rendezvous missions were analyzed. Propulsion systems analyzed included cold-gas thruster systems, Hall and ion thrusters, incorporating either Xenon or Iodine propellant, and an electrospray thruster. The mission takes advantage of the ability of the SLS launch to place it into an initial trajectory of C3=0. Nomenclature C3= Hyperbolic excess, km 2 /s 2 EM-1 = Initial Exploration Mission, the first launch of the SLS vehicle g = Earth's gravitational constant, 9.82 m/s 2 Isp = Specific impulse, seconds SLS = The Space Launch System launch vehicle T b = Duration of thrust (burn time), seconds U = Cubesat unit. One unit is 10 cm by 10 cm by 10 cm V e = Exhaust velocity, m/s α = Specific power of the electric power system, watts of exhaust energy per unit mass, W/kg ∆V = Velocity change, km/s η t = Energy efficiency of the thruster system, equal to kinetic energy of exhaust divided by energy input to the thruster

The nuclear thermal rocket (NTR) has frequently been discussed as a key space asset that can bridge the gap between a sustained human presence on the Moon and the eventual human exploration of Mars. Recently, a human mission to a near Earth asteroid (NEA) has also been included as a "deep space precursor" to an orbital mission of Mars before a landing is attempted. In his "post-Apollo" Integrated Space Program Plan (1970 -1990), Wernher von Braun, proposed a reusable NTPS to deliver cargo and crew to the Moon to establish a lunar base initially before sending human missions to Mars. The NTR was selected because it was a proven technology capable of generating both high thrust and high specific impulse (I sp ~900 s) -twice that of today's best chemical rockets. During the Rover and NERVA programs, twenty rocket reactors were designed, built and successfully ground tested. These tests demonstrated the (1) thrust levels; (2) high fuel temperatures; (3) sustained operation; (4) accumulated lifetime; and (5) restart capability needed for an affordable in-space transportation system. In NASA's Mars Design Reference Architecture (DRA) 5.0 study, the "Copernicus" crewed NTR Mars transfer vehicle used three 25 klb f "Pewee" engines -the smallest and highest performing engine tested in the Rover program. Smaller lunar transfer vehicles -consisting of a NTPS with three ~16.7 klb f "SNRE-class" engines, an in-line propellant tank, plus the payload -can be delivered to LEO using a 70 t to LEO upgraded SLS, and can support reusable cargo delivery and crewed lunar landing missions. The NTPS can play an important role in returning humans to the Moon to stay by providing an affordable in-space transportation system that can allow initial lunar outposts to evolve into settlements capable of supporting commercial activities. Over the next decade collaborative efforts between NASA and private industry could open up new exploration and commercial opportunities for both organizations. With efficient NTP, commercial habitation and crew delivery systems, a "mobile cislunar research station" can transport crews to small NEAs delivered to the E-ML2 point. Also possible are week-long "lunar tourism" missions that can carry passengers into lunar orbit for sightseeing (and plenty of picture taking), then return them to Earth orbit where they would re-enter and land using a small reusable lifting body based on NASA's HL-20 design. Mission descriptions, key vehicle features and operational characteristics are described and presented. NomenclatureE-ML2 = Earth-Moon L2 Lagrange point K = temperature (degrees Kelvin) klb f = thrust (1000's of pounds force) LEO = Low Earth Orbit (= 407 km circular) LOX / LH 2 = Liquid Oxygen / Liquid Hydrogen propellant NERVA = Nuclear Engine for Rocket Vehicle Applications SLS / HLV = Space Launch System / Heavy Lift Vehicle SNRE = Small Nuclear Rocket Engine t = metric ton (1 t = 1000 kg) ΔV = velocity change increment (km/s) ---

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