Jeffery L. Hall

Cost-benefit analysis of the aerocapture mission set

Calculations have been performed to quantify the cost and delivered mass advantages of aerocapture at all destinations in the Solar System with significant atmospheres. A total of eleven representative missions were defined for the eight possible destinations and complete launch-to-orbit insertion architectures constructed. Direct comparisons were made between aerocapture and competing orbit insertion techniques based on state-of-the-art and advanced chemical propulsion, solar electric propulsion, and aerobraking. The results show that three of the missions cannot be done without aerocapture: delivery of spacecraft into Neptune elliptical orbits, Saturn circular orbits, and Jupiter circular orbits. Aerocapture was found to substantially reduce the cost per unit mass delivered into orbit for five other missions based on a heavy launch vehicle: Venus circular orbits (55% reduction in

Venus Aerobot Multisonde Mission

/kg costs), Venus elliptical orbits (43% reduction); Mars circular orbits (12% reduction), Titan circular orbits (75% reduction), and Uranus circular orbits (69% reduction). These results were found to be relatively insensitive to 30% increases in both the estimated aerocapture system mass and system cost, suggesting that even modestly performing aerocapture systems will yield substantial mission benefits. Two other missions consisting of spacecraft inserted into high eccentricity elliptical orbits at Mars and Jupiter were shown to be not improved by aerocapture. The last mission in the set consisting of an aeroassisted orbit transfer at Earth showed that aerocapture offered a 32%

GONDOLA DESIGN FOR VENUS DEEP-ATMOSPHERE AEROBOT OPERATIONS

/kg reduction compared to chemical propulsion, but that aerobraking offered even better performance. Nevertheless, the

Mars Balloon Flight Test Results

Robotic exploration of Venus presents many challenges because of the thick atmosphere and the high surface temperatures. The Venus Aerobot Multisonde mission concept addresses these challenges by using a robotic balloon or aerobot to deploy a number of short lifetime probes or sondes to acquire images of the surface. A Venus aerobot is not only a good platform for precision deployment of sondes but is very effective at recovering high rate data. This paper describes the Venus Aerobot Multisonde concept and discusses a proposal to NASAs Discovery program using the concept for a Venus Exploration of Volcanoes and Atmosphere (VEVA). The status of the balloon deployment and inflation, balloon envelope, communications, thermal control and sonde deployment technologies are also reviewed.

Major Progress in Planetary Aerobot Technologies

Aerobots are balloon-based AEROnautical RoBOTS with autonomous navigation capabilities. An aerobot mission has been proposed for exploration of the upper atmosphere through near-surface regions of Venus. The wide range of atmospheric conditions from the relatively benign upper atmosphere to the hot, high-pressure surface require thermal protection of the scientific instruments, and the mass constraints of a balloon system require that the thermal protection system be lightweight. To meet the thermal control challenges, we propose use of lightweight vacuum dewar technology combined with a phase-change material (PCM) thermal damper. For the proposed aerobot mission, the total thermal control mass is estimated to be 7.1 kg out of a total gondola mass of 25 kg. The design allows 7.3 kg for science instruments and communication hardware. Four kilograms of PCM are required to provide a repeatable 15-hour mission sequence that includes a 3.5-hour descent to the surface, 1 hour of surface operations, a 2.5-hour ascent to the cooler upper atmosphere, and 8 hours to refreeze the PCM. Lastly, aerobot system design tradeoffs are discussed, and the extension of vacuum dewar/PCM technology to outer planet probes is briefly explored.

Navigation and Perception for an Autonomous Titan Aerobot

This paper describes a set of four Earth atmosphere flight test experiments on prototype helium superpressure balloons designed for Mars. Three of the experiments explored the problem of aerial deployment and inflation, using the cold, low density environment of the Earth’s stratosphere at an altitude of 30 -32 km as a proxy for the Martian atmosphere. Auxiliary carrier ba lloons were used in three of these test flights to lift the Mars balloon prototype and its supporting system from the ground to the stratosphere where the experiment was conducted. In each case, deployment and helium inflation was initiated after starting a parachute descent of the payload at 5 Pa dynamic pressure, thereby mimicking the conditions expected at Mars after atmospheric entry and high speed parachute deceleration. Upward and downward looking video cameras provided real time images from the fligh ts, with a dditional data provided by onboard temperature, pressure and GPS sensors. One test of a 660 m 3 pumpkin balloon was highly successful, achieving deployment, inflation and separation of the balloon from the flight train at the end of inflation; how ever, some damage was incurred on the balloon during this process. Two flight tests of 12 m diameter spherical Mylar balloons were not successful, although some lessons were learned based on the failure analyses. The final flight experiment consisted of a ground -launched 12 m diameter spherical Mylar balloon that ascended to the designed 30.3 km altitude and successfully floated for 9.5 hours through full noontime daylight and into darkness, after which the telemetry system ran out of electrical power and t racking was lost. The altitude excursions for this last flight were ±75 m peak to peak, indicating that the balloon was essentially leak free and functioning correctly. This provides substantial confidence that this balloon design will fly for days or week s at Mars if it can be deployed and inflated without damage.

Balloon precursor mission for Venus Surface Sample Return

Aerobots (robotic balloons) may significantly change the future of in situ planetary exploration. On Venus, aerobots may serve as the scientific platforms for the in situ measurement of atmospheric gases and for the study of atmospheric circulation. They can be used to drop imaging and deep sounding probes at sites of interest and to acquire and relay high-rate imaging data. Balloon technology is enabling for any Venus surface sample return mission because of the need to lift the sample above most of the atmosphere for rocket return to Earth or Venus orbit. On Mars, aerobots can fill the gap in imaging resolution/coverage between the orbiters and rovers, and perform investigation involving atmospheric sampling, atmospheric circulation, magnetic field mapping and subsurface radar sounding. Solar-heated balloons could be used as low atmospheric decelerators for low-speed landing. On Titan, powered aerobots or even passive balloons can perform long duration low-altitude flight for surface mapping, in situ atmospheric measurements, periodic in situ surface sampling and deployment of surface packages.

Venus Surface Sample Return: Role of Balloon Technology

[Abstract] The Huygens probe arrived at Saturn’s moon Titan on January 14, 2005, unveiling a world that is radically different from any other in the Solar system. The data obtained, complemented by continuing observations from the Cassini probe, show methane lakes, river channels and drainage basins, sand dunes, cryovolcanos and sierras. This has lead to an enormous scientific interest in a follow-up mission to Titan, using a robotic lighter-than-air vehicle (or aerobot). Aerobots have modest power requirements, can fly missions with extended durations, and have very long distance traverse capabilities. They can execute regional surveys, transport and deploy scientific instruments and in-situ laboratory facilities over vast distances, and also provide surface sampling at strategic science sites. This paper describes our progress in the development of the autonomy technologies that will be required for exploration of Titan. We provide an overview of the autonomy architecture and some of its key components. We also show results obtained from autonomous flight tests conducted in the Mojave desert.

Pinhole Effects on Venus Superpressure Balloon Lifetime

This paper proposes a precursor mission to the Venus Surface Sample return Mission (VSSR). The present scenario of the VSSR includes delivery by a balloon of the Venus Ascent Vehicle (VAV) from the surface to an altitude of approximately 60 km, where it can be launched without huge penalty for atmospheric losses. The mission includes a number of critical technologies that can be validated in this proposed precursor mission. The other objective of the proposed mission is to collect more accurate data on the Venus atmosphere that is essential for the VSSR mission design. The paper discusses the basic mission and system elements for the proposed precursor mission.

An aerobot for global in situ exploration of Titan

The rocks and soils on the surface of Venus record the secrets of why this planet evolved so differently from its sister planet Earth: Both NASA and the European Space Agency are now studying missions for bringing samples from the surface of Venus back to Earth where they can be analyzed with state-of-the-art techniques. Balloon technology will play a key role in such a mission. It will be used for raising samples from the Venus surface when the temperature is 460C and the pressure is 90 bars to the upper atmosphere from where the samples can be launched into orbit around Venus. Three approaches to the implementation of a solidrocket based Venus Ascent Vehicle (VAV) have been considered in the NASA study carried out at JPL. In the first approach, similar to the ESA concept, the solid rocket is an integral part of the surface sampling system, is carried to the surface of Venus and lifted back to the upper atmosphere on the same balloon. In the second approach, the VAV is deployed in the upper atmosphere and suspended there on a blimp which performs a rendezvous with the balloon carrying the surface sample and effects a sample transfer. In the third approach, the VAV is deployed into the atmosphere on a winged vehicle that performs a rendezvous with the balloon carrying the surface sample and also performs sample transfer. The paper compares the three approaches. It also includes the developments in balloon technology and in materials and devices for use in severe environments. INTRODUCTION Thirty years ago, human and robotic missions to the moon, performed the first sample return of extraterrestrial materials. The Apollo astronauts Affiliations: (1) Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California (2) Winzen Engineering, San Antonio, Texas brought back lunar rock, soil and drill core samples in six successful manned missions between 1969 and 1972. The Soviet Union carried out two successful robotic lunar sample return missions in the same period: Luna 16 and Luna 20 that returned drill core samples. A second wave of sample return missions is now under way. On February 7, 1999, NASA launched the STARDUST mission that will fly through the tail of a comet at more than 6km/sec, capture intact particles of comet dust in a low density aerogel collector and bring the samples back to Earth five years later. In January 2001, NASA will launch the GENESIS spacecraft to collect samples of the solar wind in an ultrapure silicon wafer. Then in 2003, NASA in collaboration with CNES (the French Space Agency), will launch the first phase of the Mars Surface Sample Return (MSSR) mission that will collect surface soil, rock core and atmospheric samples from Mars. The samples will be returned to Earth in 2008. With the launch of the first element of the Mars Surface Sample Return mission only four years away, both NASA and the European Space Agency (ESA) are now turning their attention to sample return from other solar system bodies. Earth’s sister planet Venus has high priority for a sample return mission. However, the problems of acquiring and returning samples from Venus are formidable. Venus is comparable in size to Earth and almost 10 times the mass of Mars, but it possesses an inhospitable surface environment with temperatures near 460C, surface pressures of 90 bars and sulfuric acid particles in the upper atmosphere. As discussed in companion papers in this issue, advanced balloon technology can play a key role in carrying out the in situ exploration of Venus including close up observations of the surface. Balloon technology also will play a critical role in returning samples of soils and rocks from the surface of Venus. 1 American Institute of Aeronautics and Astronautics ARCHITECTURE OF MARS SURFACE SAMPLE RETURN MISSION The philosophy underlying the NASA approach to Venus Surface Sample Return (VSSR) is to build on the mission architecture used for the Mars Surface Sample Return (MSSR) mission. In this section, we first give a simplified description of the architecture of the MSSR mission and then describe how a VSSR mission can incorporate key subsystem elements. In the MSSR, a vehicle is delivered to the Mars surface consisting of sample collection equipment and a three-stage solid-rocket Mars Ascent Vehicle (MAV). Once samples have been placed in a canister in the MAV, the canister is propelled into a low but stable near-circular orbit around Mars. A second spacecraft performs an autonomous rendezvous with the sample canister, solid rockets and minimal overhead in guidance and control systems such that it can lift a sample from the surface and delivering it to a stable although not precisely defined orbit. VENUS SURFACE SAMPLE RETURN The philosophy of the recent JPL study of VSSR was to apply as much as possible of the architecture, technology and, where possible, specific hardware of the MSSR to sample return from Venus. However, there are significant differences in the operating enviornment (Table 1) that require significant modification to the MSSR architecture.