NEP for a Kuiper Belt Object rendezvous mission

Abstract

3Los Alamos National Luborato~, i% Alamos, NM 87545, poston@lanl.gov AbstracL Kuiper Belt Objects (KBOS) are a recently-discovered set of solar system bodies which lie at about the orbit of Pluto (40 AU) out to about 100 astronomical units (AU). There are estimated to be about 100,000 KBOS with a diameter greater than 100 km. KBOS are postulated to be composed of the pristine material which formed our solar system and may even have organic materials in them. A detailed study of KBO size, orbit distribution, structure, and surface composition could shed light on the origins of the solar system and perhaps even on the origin of life in our solar system. A rendezvous mission including a lander would be needed to perform chemical analysis of the surface and sub-surface composition of KBOS. These requirements set the size of the science probe at around a ton. Mission analyses show that a fission-powered system with an electric thruster could rendezvous at 40 AU in about 13.0 years with a total AV of 46 krnk. It would deliver a 1000-kg science payload while providing ample onboard power for relaying data back to earth. The launch mass of the entire system (power, thrusters, propellant, navigation, communication, structure, science payload, etc.) would be 7984 kg if it were placed into an earth-escape trajectory (C=O). Alternatively, the system could be placed into a 700-kmearth orbit with morepropellant,yieldinga total mass in LEO of 8618 kg, and then spiral out of earth orbit to arrive at the KBO in 14.3 years. To achieve this performance, a fission power system with 100 kW of electrical power and "atotal mass (reactor, shield, conversion, and radiator) of about 2350 kg. Three possible configurations are proposed: (1) a UZrH-fueled, NaK-cooled reactor with a steam Rankine conversion system, (2) a UN-fueled gas-cooled reactor with a recuperated Brayton conversion system, and (3) a UN-fueled heatpipe-cooled reactor with a recuperated Brayton conversion system. (Boiling and condensation in the Rankine system is a technical risk at present.) All three of these systems have the potential to meet the weight requirement for the trip and to be built in the near term.

Fission-based electric propulsion for interstellar precursor missions

“…A simple orbital mechanics code was developed and used to analyze the requirements for a KBO rendezvous mission, and the results are reported elsewhere in thk symposium (Lipinski, 2000). That analysis showed that a KBO rendezvous could be achieved in 13.0 years with a 1000 kg science payload if the dry mass of the rest of the spacecraft (power, thrusters, navigation, communication, tankage, etc.)…”

“…All three systems use the same assumed low-mass deployable thermal radiator to maximize the conversion efficiency. Subsequent sections describe the options in more detail, and examples for the KBO mission are given in a companion paper in this conference (Lipinski, 2000). There has not been sufficient detailing of the designs to perform an accurate weight estimate for each system, but rough estimates indicate that all of these systems have the potential to have specific masses less than 35 kg/kWe.…”