Interstellar spaceships and probes

Launched Spacecrafts and Spacecrafts under Construction

NASA Pioneer 10 and 11 An artist's drawing of the Pioneer 10 spacecraft near Jupiter. Pioneer 10 Distance from the Sun: > 85 AU Speed relative the Sun: 12.1 km/sec (2.6 AU/year, relative the Sun)) Propulsion system: Chemical and gravity assist Power source: Radioisotope Thermoelectric Generators (RTG's), Plutonium 238, 40 W at launch. Last Comunication time: 23 January 2003 Launch vehicle: Atlas(LOX and RP1)/Centaur(LOX and LH)/TE364-4(solid-fueled) Transmitting rate (bit/sec): Thrusters: Six Hydrazine thrusters Launched: 2 March 1972 Scientific Instruments: Helium Vector Magnetometer (Failed), Plasma Analyzer, Charged Particle Instrument, Cosmic Ray Telescope, Geiger Tube Telescope, Trapped Radiation Detector, Meteoroid Detector (ENC)(Failed), Asteroid-Meteoroid Experiment (ENC)(Failed), Ultraviolet Photometer, Imaging Photopolarimeter (ENC), Infrared Radiometer (Failed). Weight: 270 kg Size: 2.9 x 2.7 m Mission status: The power source on Pioneer 10 finally degraded to the point where the signal to Earth dropped below the threshold for detection in its latest contact attempt on 7 February 2003. No more attempts at contact are planned at this time. Pioneer 10 will continue into interstellar space, heading generally for the red star Aldebaran, which forms the eye of Taurus. Aldebaran is about 68 light years away and it will take Pioneer over 2 million years to reach it. Remarks: Spin-stabilized, spinning at approximately 4.28 rpm. Pioneer 10 & 11 carry a graphic message in the form of a 6- by 9-inch gold anodized plaque bolted to the spacecraft's main frame. Pioneer 10 is heading in the opposite direction to the Sun's motion through the Galaxy. An artist's drawing of one of the twin Pioneer spacecraft An artist's drawing of the Pioneer 11 spacecraft near Saturn. Pioneer 11 Distance from the Sun: > 50 AU (2003) Speed: 11.5 km/s (relative the Sun) Propulsion system: Chemical and gravity assist Power source: Radioisotope Thermoelectric Generators (RTG's), Plutonium 238, 40 W at launch. Launch vehicle: Atlas(LOX and RP1)/Centaur(LOX and LH)/TE364-4(solid-fueled) Last Comunication time: November 1995 Transmitting rate (bit/sec): Thrusters: Six Hydrazine thrusters Launched: 5 April 1973 Weight: 270 kg Size: 2.9 x 2.7 m Mission status: The Pioneer 11 Mission ended on 30 September 1995. The spacecraft is headed toward the constellation of Aquila. Pioneer 11 will pass near one of the stars in the constellation in about 4 million years. Scientific Instruments: Helium Vector Magnetometer, Plasma Analyzer, Charged Particle Instrument, Cosmic Ray Telescope, Geiger Tube Telescope, Trapped Radiation Detector, Meteoroid Detector (ENC), Asteroid-Meteoroid Experiment (ENC), Ultraviolet Photometer, Imaging Photopolarimeter (ENC), Infrared Radiometer, Flux-Gate Magnetometer. Remarks: Spin-stabilized, spinning at approximately 4.28 rpm. Pioneer 10 & 11 carry a graphic message in the form of a 6- by 9-inch gold anodized plaque bolted to the spacecraft's main frame. Launch of Pioneer 10 on the Atlas/Centaur/TE364-4 launch vehicle Relative positions of the bow shock, Pioneer 10, Pioneer 11, Voyageer 1 and Voyageer 2. Pioneer 10 and 11 home page

NASA Voyager 1 and 2 Voyager 1 Distance from the Sun: > 110 AU (2009) Speed relative the Sun: 17.1 km/s (3.6 AU/year) Propulsion system: Chemical and gravity assist Power source: Radioisotope Thermoelectric Generators (RTG's), 470 W of 30 volt DC at launch. Last Comunication time: - Launch vehicle: Titan/Centaur(LOX and LH) Launched: September 1977 (Voyager 2 was launched before Voyager 1) Scientific Instruments: Television cameras, infrared and ultraviolet sensors, magnetometers, plasma detectors, and cosmic-ray and charged-particle sensors. Mission status: On February 17, 1998, Voyager 1 passed Pioneer 10 to become the most distant human-made object in space. On the 15th of August 2006 Voyager 1 passed 100 AU. There are currently five science investigation teams participating in the Voyager Interstellar Mission. They are: * Magnetic field investigation * Low energy charged particle investigation * Ultraviolet Spectrometer Investigation * Cosmic ray investigation * Plasma wave investigation In December 2004, Voyager 1 crossed the Termination Shock. The two Voyager spacecraft continue to operate, with some loss in subsystem redundancy, but still capable of returning science data from a full complement of VIM science instruments. Both spacecraft also have adequate electrical power and attitude control propellant to continue operating until around 2020 when the available electrical power will no longer support science instrument operation. At this time science data return and spacecraft operations will end. In about 40,000 years, Voyager 1 will drift within 1.6 light years of AC+79 3888, a star in the constellation of Camelopardalis. Remarks: Both Voyager spacecrafts carry a greeting to any form of life, should that be encountered. The message is carried by a phonograph record - a 12-inch gold-plated copper disk containing sounds and images selected to portray the diversity of life and culture on Earth. The contents of the record were selected for NASA by a committee chaired by Carl Sagan of Cornell University. Dr. Sagan and his associates assembled 115 images and a variety of natural sounds. To this they added musical selections from different cultures and eras, and spoken greetings from Earth-people in fifty-five languages. Voyager 2 NSSDC ID:1977-076A Distance from the Sun: > 90 AU (2009) Speed relative the Sun: 15.5 km/s (3.3 AU/year) Direction: RA=338 deg, Dec=-62 deg Propulsion system: Chemical and gravity assist Power source: Radioisotope Thermoelectric Generators (RTG's), 470 W of 30 volt DC at launch. (Pu 238 in the form of PuO2) Launch vehicle: Titan/Centaur(LOX and LH) Communication: standard operating rate of 160 bit/s (Communications were provided through the high-gain antenna with a low-gain antenna for backup. The high-gain antenna supported both X-band and S-band downlink telemetry. ) Launched: 1977-08-20 at 14:29:00 UTC Scientific Instruments: Television cameras, infrared and ultraviolet sensors, magnetometers, plasma detectors, and cosmic-ray and charged-particle sensors. On-orbit dry mass: 721.9 kg Layout: Each Voyager consisted of a decahedral bus, 47 cm in height and 1.78 m across from flat to flat. A 3.66 m diameter parabolic high-gain antenna was mounted on top of the bus. The major portion of the science instruments were mounted on a science boom extending out some 2.5 m from the spacecraft. At the end of the science boom was a steerable scan platform on which were mounted the imaging and spectroscopic remote sensing instruments. Also mounted at various distances along the science boom were the plasma and charged particle detectors. The magnetometers were located along a separate boom extending 13 m on the side opposite the science boom. A third boom, extending down and away from the science instruments, held the spacecraft's radioisotope thermoelectric generators (RTGs). Two 10 m whip antennas (used for the plasma wave and planetary radio astronomy investigations) also extended from the spacecraft, each perpendicular to the other. The spacecraft was three-axis spin stabilized to enable long integration times and selective viewing for the instruments mounted on the scan platform. Mission status: In 2008, Voyager 2 crossed the Termination Shock. There are currently five science investigation teams participating in the Interstellar Mission. They are: * Magnetic field investigation * Low energy charged particle investigation * Ultraviolet Spectrometer Investigation * Cosmic ray investigation * Plasma wave investigation In some 296,000 years, Voyager 2 will pass 4.3 light years from Sirius. Remarks: Voyager 1 and 2 home page The launch of Voyager 2 aboard the Titan-Centaur rocket. Relative positions of the heliosphere, Voyageer 1 and Voyageer 2.

New Horizons New Horizons Speed (max.): 16.8 km/s (relative the Sun.) Distance from the Sun: > 14 AU (Past Saturn, September 2009) Propulsion system: Chemical (Hydrazine monopropellant with a delta-V capability of 290 m/s) and Jupiter gravity assist in February 2007. Communications: X-band, 2.5-meter high-gain antenna. 768 bps to a 70m DSN antenna (Pluto distance). Power source: RTGs 202 W (in 2015) Spacecraft mass: 465 kilograms (including fuel) Diameter: 2.5 m Scientific instruments: The Long Range Reconnaisance Imager (LORRI) consists of a visible light, high-resolution CCD Imager. The Pluto Exploration Remote Sensing Investigation (PERSI) is composed of three parts, a visible CCD imager (MVIC), a near-infrared imaging spectrometer (LEISA), and an ultraviolet imaging spectrometer (ALICE). The plasma and high energy particle spectrometer suite (PAM) consists of SWAP, a toroidal electrostatic analyzer and retarding potential analyzer, and PEPSSI, a time-of-flight ion and electron sensor. The Radio Science Experiment (REX) will use an ultrastable oscillator to conduct radio science investigations. A student-built dust counter (SDC) will also be onboard to make dust measurements in the outer solar system. Mission Description: New Horizons seeks to learn more about the surfaces, atmospheres, interiors and space environments of Pluto, Charon and KBOs by using imaging, visible and infrared spectral mapping, ultraviolet spectroscopy, radio science, and in situ plasma sensors. New Horizons was launched the 19th of January 2006 from Cape Canaveral. Launch vehicle was a Atlas V 551. (Atlas V 551 first stage; Centaur second stage; STAR 48B solid rocket third stage) New Horizon is scheduled to arrive at Pluto-Charon in July 2015. It will conduct the first spacecraft reconnaissance of these worlds, then continue into the Kuiper Belt for further encounters. New Horizons will reach 100 AU in December 2038. Mission status: New Horizons was launched the 19th of January 2006. Remarks: Planned total mission cost under 550 million dollar. New Horizons home page

Planned Interstellar Spacecrafts and Never Launched Spacecrafts

Project Orion An artist's vision of Orion. A Put-put test vehicle with pusher plate and tower for six charges. Estimated speed (max.): estimated 60-120 km/s, or even as high as 400 km/s. Propulsion system: Nuclear pulse rocket (Nuclear detonation rocket) Isp: 3000-6000 s, i.e. a exhaust velocity of about 30-60 km/s, or even as high as 200 km/s. (Compare with the NERVA engine which had a Isp of about 900 s.) Power source: Nuclear fission reactor Launched: Only scale models launched with conventional bombs. Weight: 1000-2000 ton (Orion Midrange) / 8'000'000 ton (Orion Super) / 40'000'000 ton (Interstellar Orion) Diameter: 40 m (Orion Midrange) / 400 m (Orion Super) Mission Description: One of the missions objective of the Orion project was to visit Saturn and its moons by 1970. The Orion project was aborted in 1965. Project status: The project was initiated in 1957 and was aborted in 1965, two years after that atomic explosions in outer space were outlawed by the Nuclear Test Ban Treaty in 1963. The organisations behind project Orion was General Atomic (a division of the General Dynamics Corporation), ARPA, the US Air Force and for som brief period NASA. Actual tests of scale models (Put-puts) were performed in 1959 with conventional bombs. A 100 m flight in November 1959, propelled by six charges, was successful and demonstrated that pulse flight could be stable. Much of the actual work is still classified, since it dealt with directing the energy of nuclear explosions. A plan proposed by the Orion team and supported by Werner von Braun was to put a very small Orion type ship on top of a Saturn V stage, making the Orion part the second stage in a multi-stage ship. Remarks: Orion was the offspring of an idea first proposed by Los Alamos mathematician Stanislaw Ulam in the 1940s-1950s. The first proposal submitted to ARPA in early 1958, envisioned a 4000-ton vehicle, carrying up to 2600 bombs and capable of orbiting a payload of 1,600 tons. The ship was to be completed around 1963-1964. About $10 million was spent under the whole project life time. Theodore Taylor, Freeman Dyson et al. was enganged in the project. For more information see Freeman Dyson "Death of a Project," Science, 149, 141-44 (1965), Freeman Dyson "Interstellar Transport," Physics Today, 41 (October 1968), and George Dysons book "Project Orion". Preparation of Orion pulse test vehicle. An USAF Orion design. Helix-shaped containers housing hydrogen bombs, to be ejected through a hole in its pusher plate.

Ram Jet Estimated speed (max.): 0.1 (Bussard) - 0.2c (Ramjet Runway) Propulsion system: Fusion with interstellar hydrogen as fuel Power source: Nuclear fusion reactor Weight: Size: A scoop radius of 1000-2000 km Mission Description: First proposed in 1960 by R. W. Bussard. The RAIR concept: Efficiency can be improved by using Ram-Augmented Interstellar Rocket (RAIR) with one internal (exhaust from the fusion drive) and one external flow (the mass scooped and exhausted from the interstellar medium). The RAIR concept was first designed by Alan Bond in 1974. The laser ramjet concept: In 1977 Whitmire and Jackson proposed that laser could be used to transmit power to a ramjet. The power is then used to accelerate ions from the instellar medium in a linear ion accelerator. The ramjet runway: Micropellets would be deposited by a series of slow tanker crafts launched years before the ram jet. The ram jet would then scoop up the micropellets and produce power and thrust in a fusion process. Proposed by Whitmire and Jackson in 1977. Remarks: Ramjets require a secondary propulsion system to get them to a few percent of lightspeed for light-up. References: Bond A., "The Potential Performance of the Ram-Augmented Interstellar Rocket", Journal of the British Interplanetary Society 27, pp 674-685 (1974) Whitmire and Jackson, "Laser Powered Interstelllar Ramjet", Journal of the British Interplanetary Society 30, pp 223-226 (1977) An artist's view of the Bussard Ram Jet. Bussard Ram Jet schematics by Rick Sternbach.

BIS Project Daedalus Daedalus arrives at Barnards' Star. Estimated speed (max.): 0.12c-0.15c Propulsion system: Pulsed fusion (Internal Confinement Fusion) Isp: about 1'000'000 s Power source: Transmitting rate: Scientific Instruments: Weight: 54 000 ton (incl. 50 000 ton of He3/H2 and 450 ton for the probe). Size: Mission Description: Designed by technical group of the British Interplanetary Society between 1973-77 led by Alan Bond. The target chosen for the Daedalus study was Barnards Star, 5.91 light years distant. Daedalus was an unmanned probe with a high degree of autonomy intended for a one-way trip to Barnard's Star. The vehicle would not be decelerated at the target system, and would continue flying through, making the encounter last for about 70 hours. The trip to Barnard's star would take about 50 years. The spacecraft itself would consist of two stages, so that one could be jettisoned to reduce mass and speed up the flight. The First Stage would be fired for two years and the second for for 1.8 years before being shut down to begin the 47-year cruise. Hugh tanks would hold the fuel, while the 40m-diameter engine of the Second Stage would double as a communications dish. On top of the Second Stage would be a payload bay containing 18 probes of 10 ton each to investigate the star and its planets, two 5m telescopes, and two 20m radio telescopes. There would also be "robot wardens" able to make in-flight repairs. A 50 Ton disc of beryllium would protect the payload bay from collisions with dust and meteoroids on the flight. Project status: The project was active 1973-1978. Remarks: Daedalus uses a fuel consisting of pellets of solid deuterium and helium-3. H2 can be extracted from seawater, but He3 is a rare isotope on Earth. These fuel pellets are sent to a chamber where they are struck by a high-energy electron beam or lasers, beginning the fusion process. A super-hot plasma is created, and directed for thrust using magnetic fields generated by superconducting coils. The explosion repetition rate is estimated to about 250 per second. The main problem with the use of Internal Confinement Fusion as starship propulsion would be obtaining the fuel. In the study, the team suggested mining the atmosphere of Jupiter for the He3. Since the 1970s, though, studies of the moon have revealed that the surface is covered in He3 deposited by the solar wind. Japan has already suggested mining this in order to construct fusion reactors on Earth, so it could also be a solution to fuelling spacecraft. See Bond, A., Martin, A. R., Buckland, R. A., Grant, T. J., Lawton, A. T., et al. "Project Daedalus." Journal of the British Interplanetary Society, 31 (Supplement, 1978). The second and first stage separate. Daedalus first stage under operation. A warden outside the Daedalus. Daedalus schematics by Rick Sternbach.

Interstellar Precursor Mission Mission Description: Investigation of Pluto/Charon, Kupier belt objects et.c. Project status: The project was active 1977-1979. Remarks: Never implemented. References: Jaffe, L. D., et al., “An Interstellar Precursor Mission”, JPL Publication 77-70, 1977 Jaffe, L. D., and Ivie, C. D., “Science Aspects of a Mission Beyond the Planets”, Icarus, 39, 486, 1979.

Helios Propulsion system: Pulsed fusion microexplosion engine Isp: about 800 - 1000 s Mission Description: Project status: Never implemented. Remarks: Several laser beams strike a small pellet of fusionable material compressing it to high density and temperature, causing a fusion reaction. The fusion occurs in a chamber filled with hydrogen, which superheats the gas, before it is cooled and expanded out the nozzle. Studies by Lawrence Livermore Laboratory in the 1950s and Convair in 1960. References:

Blascon and Sirius Propulsion system: Pulsed fusion microexplosion engine Mission Description: Project status: Never implemented. Remarks: Several laser beams strike a small pellet of fusionable material compressing it to high density and temperature, causing a fusion reaction. The fusion occurs behind the spaceship and the plasma strikes a pusher plate to send the ship forward. References:

Project Longshot Estimated speed (max.): about 2500-3000 AU/s Propulsion system: Pulsed fusion microexplosion engine Isp: 1'000'000 s (10'000'000 m/s exhaust velocity, i.e. about 0.03c) Power source: Long-life fission reactor providing 300 kW Transmitting rate: 250 kilowatt communications laser at 1 kbit/s at maximum range. Weight: About 6.4 ton Size: Mission Description: Project Longshot was developed by the U.S. Navy and NASA in 1988 as a design for an unmanned probe to Alpha Centauri (4.3 light years, 273'000 AU) with a flight time over 100 years. The primary missions of Longshot were investigation of the interstellar medium, investigation of the Alpha Centauri system, and Earth-Centauri astrometry. Project status: Project ended 1988. Remarks: A fuel pellet is fired upon by high power laser beams, causing a fusion reaction. The fusion reaction products are directed, using magnetic fields, in a specific direction (i.e. the rear of the vehicle), causing thrust. Superconducting coils surround the exit port. As the fusion products pulse past these coils, they induce a current which is used to power the ship. Compare with the Daedalus project. References: Beals, K. A., M. Beaulieu, F. J. Dembia, J. Kerstiens, D. L. Kramer, J. R. West and J. A. Zito. Project Longshot: An Unmanned Probe To Alpha Centauri. U. S. Naval Academy. NASA-CR-184718. 1988.

TAU An artist's view of the tau probe after seperation from the enginge module. Estimated speed (max.): 95 km/s (20 AU/year) Propulsion system: Xenon ion engine Exhaust velocity: 70 km/s Power source: Fission reactor 150 kW Transmitting rate: 10 watt laser communications system capable of transmitting 10-20 kbits/s from interstellar space. Launched: Never launched. Scientific goals: Exploring the heliopause, measurements of star parallaxes et.c. Weight: 1200 kg Mission Description: An interstellar percursor mission. The TAU (Thousand Astronomical Units) was designed to travel about 1000 AU out in about 50 years and perform astrophysical science studies (stellar parallax studies). The ion engine was proposed to operate continuously for about 10 years. Mission status: Suggested by NASA JPL. Project abandoned. Remarks: Many alternatives to propulsion by NEP (nuclear electric propulsion) were considered, for example solar and laser sailing, fusion and antimatter. References: Etchegaray, M. I., “Preliminary Scientific Rationale for a Voyage to a Thousand Astronomical Units”, JPL Publication 87-17, 1987. Nock, k. T., “TAU – A Mission to a Thousand Astronomical Units”, 19th AIAA/DGLR/JSASS International Electric Propulsion Conference, Colorado Springs, 1987.

Pluto Express Pluto Express Estimated speed (max.): 18 km/s Propulsion system: Chemical and gravity assist Communication: Communications will be via a fixed, 1.47 m high-gain antenna employing an X-band uplink receiver and downlink transponder. 1+ gigabit of science data over a one year period. Power source: Spare RTGs from the Cassini mission. Weight: 220 kg (spacecraft including 7 kg for science instruments) Diameter: 1.47 m Experiments: Planned experiments for the spacecraft includeded a multi-color visible-light imaging system, an infrared mapping spectrometer, an ultraviolet airglow and solar occultation spectrometer, and a radio occultation experiment utilizing an ultrastable oscillator (USO) and the on-board telecommunications system. Mission Description: Originally designated the Pluto Fast Flyby (PFF), the Pluto Kuiper Express mission was designed to fly by and make studies of the planet Pluto and its satellite Charon. The mission was intended to reach Pluto before the tenuous Plutonian atmosphere could refreeze onto the surface as the planet receded from the Sun. Project status: Work has been stopped on the Pluto Kuiper Express mission for budgetary reasons. It was designed to study Pluto and its moon Charon during a flyby 2012 and to continue on to the Kuiper belt. Launch of the Pluto Kuiper Express was scheduled for December 2004. The Pluto Kuiper Express mission would have returned the first close up images of Pluto, Charon, and any Kuiper belt objects it encountered. This mission has been cancelled for budgetary reasons. A other probe to Pluto and the Kuiper Belt was launched instead, see "New Horizons".

NASA Interstellar Probe Propulsion system: Solar sail and gravity assist Power source: Three 8.5 kg Advanced Radioisotope Power System (ARPS) units with Alkali Metal Thermal-to-Electric Converters (AMTEC). Each unit initially delivers 106 W. Speed (max): > 70 km/s Transmitting rate: The average science data rate should be 25 bps at 200 AU. (Ka band) A downlink data rate of 350 bps at 200 AU is achieved with a 220 W transmitter. Scientific Instruments: Magnetometer, Plasma and Radio Waves. Solar Wind/Interstellar Plasma/Electrons Suprathermal Ion Charge-States, Pickup and Interstellar Ion Composition Interstellar Neutral Atoms Cosmic Ray H, He, Electrons, Positrons Resource Requirements, Anomalous & Galactic Cosmic Ray Composition Dust Composition, Infrared Instrument, Energetic Neutral Atom (ENA) Imaging, UV Photometer. Total weight: about 250 kg, including sail (100 kg), the spacecraft and antenna (125 kg), instruments (25 kg) Diameter: 400 m (Sail), 2.7 m (Probe) Mission Description: * Send a spacecraft to 200 AU in 15 years with solar sail propulsion * Use sail to decelerate, swing by the Sun at 0.25 AU, and then accelerate the spacecraft towards the nose of the heliosphere * Jettison the sail at ~5 AU and coast to >200 AU, exploring the Kuiper Belt, heliospheric boundaries, and interstellar medium with a goal of reaching ~400 AU. Mission status: Proposed in 2000 by R. A. Wewaldt and P. C. Liewer of Caltech and JPL. Remarks: Density of sail 1-2 g/m2. References: Liewer, P. C., Mewaldt, R. A., Ayon, J. A., Garner, C., Gavit, S., Wallace, R. A., Interstellar Probe Using a Solar Sail: Conceptual Design and Technological Challenges, COSPAR Colloquium, The Outer Heliosphere: the next frontiers, Potsdam, Germany, July 24-28, 2000. Mewaldt, R. A., Liewer, P. C., An Interstellar Probe Mission to the Boundaries of the Heliosphere and Nearby Interstellar Space, Space 2000, Long Beach (CA), Sept. 19-21, 2000. ISP home page The Interstellar Probe would pass through the boundaries of the heliosphere and explore nearby interstellar space.

Nuclear salt water rocket (NSWR) Estimated speed (max.): about 0.02c Propulsion system: Nuclear salt water fission (UBr4/H2O). Exhaust velocity: about 0.01c Power source: Weight: 3000 ton (incl. 2700 ton of salt water fuel consiting of 90% enriched uranium.) Size: Mission Description: First proposed by Zubrin. Project status: Remarks: Alpha Centauri could be reached in about 200 years with this technology. He proposes to use most of the fuel for acceleration and to use a magnetic sail for deceleration by creating drag against the interstellar medium. The fuel tank would be made from long tubes of boron carbonate, a strong structural material that strongly absorbs thermal neutrons, preventing the fission chain reaction that would otherwise occur in the fuel. The liquid fuel is pumped from the storage tank into a absorber-free cylindrical reaction chamber which allows buildup of neutron flux to the critical point where sustained nuclear fission can occur. The fuel has only low-level alpha activity, the fission products from the consumed fuel are vented into space, and the induced activity from the large neutron flux produced by the fission burning can be minimized by constructing the engine from such low activation materials as graphite and silicon carbide. Once the engine is turned off, therefore, there should be no significant radioactive inventory present to endanger the crew of a manned mission.

SunBurn MITEE (MIniature ReacTor EnginE) Estimated speed (max.): 100 km/s with sun burn gravity assist Propulsion system: Hydrogen is heated to over 3000 K by passage through a fission reactor. Isp: 1000 s (about 10000 m/s) Power source: 75 MW Nuclear Fission reactor Weight: 10000-40000 kg (200 kg for the engine including reactor.) Size: Mission Description: The SunBurn missions involve a MITEE engine burn as the spacecraft passes close to the Sun Project status: See Ultra Technologies Inc. Remarks: Burn time capability of hours. The mass of the MITEE reactor is very low, ~100 kg, and the weight of the complete engine only about 200 kg. (To be compared to previous engines like NERVA (-1972) which had a weight of several tons. The spacecraft could reach the Kuiper Belt in 3 years and the gravitational lensing point in 15 years.

Aurora Estimated speed (max.): 52 km/s with sun gravity assist (11 AU/year) Propulsion system: Solar sail. Power source: Solar power? Weight: 150 kg (total, i.e. including sail, payloadand structure) Size: 250 x 250 m (a square thin-film sail) Mission Description: Investigation of the heliopause, use of the sun gravitational lens effect at 550 AU for study of the galatic core, Kupier belt et.c. Project status: Never built. Remarks: A thin-film 250 m square sail supported by booms and struts made of carbon reinforced plastics. References: Genta, G. and Brusa, E. "Project Aurora: Preliminary Structural Definition of the Spacecraft", in Missions to the Outer Solar System an Beyond, 1st IAA Symposium on Realistic Near-Term scientific Space Missions, ed. G. Genta, Levrotta and Bella, Turin (1996), pp 25-36.

Starwisp Estimated speed (max.): 0.2c Propulsion system: Maser sail. (A stationary maser of 10'000 MW propels the sail probe to a speed of 0.2c in a few days.) Power source: Weight: A 4 gram microrobot and a 16 gram sail made of very thin wires. Diameter: 1 km (sail) Mission Description: It could reach Alpha Centauri in 20 years. Project status: Remarks: Main problems with laser sails are associated with the very large power needed, and with the difficulty of maintaining a well-collimated beam stationary in space.

AIM Star Estimated speed (max.): 0.002-0.003c Propulsion system: A small amount of antimatter and fissionable material react to ignite a fusion reaction. The propulsion system uses H2 and He3 nuclear fuel and requires about 100 microgram of antiprotons. Isp: 61 000 s (600 000 m/s) Mission Description: The spacecraft is intended for long range unmanned missions. For example reaching the Oort cloud at 10'000 AU in 50 years. The AIM Star probe consists of an AIM rocket and a scientific payload. The payload would be undeployed during the first stage of the mission. The AIM drive would fire constantly for 22 years, accelerating the craft to 0.003c. At this point the main drive would disconnect from the payload, and the payload would deploy to allow communication with Earth. The probe would then coast the rest of the way through the Oort cloud. Project status: A preliminary design for a spacecraft that would use the AIM drive concept has been developed by Pennsylvania State University. Remarks: AIM (Antiproton Initiated Microfission/fusion Engine). The first idea of using matter/antimatter annihilation for space propulsion was put forward by Eugene Sängner in the 1950s. References: Gaidos, Lewis, Meyer, Schmidt, Smith "AIMStar: Antimatter Initiated Microfusion for Precursor Interstellar Missions", in Misions to the Outer Solar System and Beyond , 2nd IAA Symposium on Realistic Near-Term Scientific Space Missions , Turin (1998), pp. 111-114 An artist's concept of a robotic antimatter-powered probe. Credit: Laboratory for Energetic Particle Science at Pennsylvania State University.

The Alcubierre Warp Drive Ship Solution showing the curvature of space in the region of the travelling warp. Estimated speed (max.): >c Propulsion system: Positive and negative warping of the space time structure Remarks: Speculative solution to the general relativity equations making it possible to push a ship forward through warping the space time structure. Beyond the technological level of mankind for the foreseeable future, i.e. at least the next hundred years. (Requries that very large energy densities and negative mass-energy can be created and controlled.) References: Miguel Alcubierre, Classical and Quantum Gravity, v. 11, pp. L73-L77, (1994), and The Micro-Warp Drive: C. Van Den Broeck, preprint hep-ph/9805217 , LANL Archive, (April 2, 1999).

Laser Accelerated Plasma Propulion System (LAPPS) Isp: about 3 Msec (0.1 c) Power supply: 1 MW Thrust: about 30 mN Mass: 5000 kg Propulsion system: Nuclear powered Laser Accelerated Plasma Propulion System (LAPPS). Pulsed laser. Remarks: The propulsion system consists of a power supply (nuclear), the laser it drives and target of gold foil to generate plasma. The laser will be used to accelerate a beam of protons to relativistic speeds. These protons emerge in a nearly collimated form along with an equal number of electrons so that the beam is electrically neutral when it leaves the vehicle to provide thrust. Possible mission targets are the objects in the Oort Cloud. Possible mission time could be in the range of 20 (25 N) - 700 (30 mN) years depending on thrust. References: Kammash, T., Nuclear Powered Laser Accelerated Plasma Propulion System, Journal of the British Interplanetary Society, vol 58 (2005), No 11/12, pp 407-411.