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Propulsion

Following are select methods, currently in use and proposed, for propelling spacecraft that are already in space.

Present Day Space Propulsion
MethodEnergy SourceUse CaseExample ProjectExhaust Velocity (if applicable)RationaleChallenges
Chemical RocketChemical ReactionLaunch, upper stagesWidely usedUp to 4.5 km/sEstablished technology
HydrazineChemical ReactionSatellite ManeuveringWidely used2.3 km/sEasily used as a monopropellantHighly toxic
Gravity AssistGravitational Potential EnergyInterplanetary TravelVoyager, many other interplanetary missionsDepends on circumstances. Galileo gained 18.3 km/s from a Venus-Earth-Earth assist.Save propellantMay require slow, indirect routes
Pulsed Plasma ThrusterElectricity (solar, radioisotope)Small Satellite ManeuveringEarth Observing 1 satellite5-60 km/sSimple designLess efficient than other electric options
Ion DriveElectricitySatellites, low-mass robotic probesDawn20-50 km/sHigh impulseLow thrust. Thrust may increase with next generation Hall thruster.

Space Propulsions in Development
MethodEnergy SourceUse CaseExample ProjectExhaust Velocity (if applicable)RationaleChallenges
Nuclear Thermal RocketNuclear FissionCrewed Mission to MarsNERVA8.3 km/sMost promising near-term option for large, high-impulse craftSafety may preclude use as a booster stage
Magnetoplasmadynamic ThrusterElectricity, most likely from fissionLarge interplanetary spacecraftSpace Flyer Unit15-60 km/sHigh impulse and thrustHigh power needed, likely necessitating a new reactor design, degradation of cathodes limits lifespan.
Variable Specific Impulse Magnetoplasma RocketFissionCrewed interplanetary missionsAd Astra Rocket Company50 km/sBalance between low thrust, high impulse and high thrust, low impulse designsRequired power system might not be feasible.
Solar SailSolar PowerInterplanetary transport of goods, deorbiting satellitesIKAROSc (propellantless)Low cost, propellantless craft, faster travel to outer Solar SystemCannot operate in Earth orbit below 800 km.
Direct Fusion DriveNuclear FusionInterplanetary travelPrinceton Satellite Systems100 km/sHigh thrust and exhaust velocityMuch R&D required on the fusion generator

Speculative Space Propulsion
MethodEnergy SourceUse CaseExample ProjectExhaust Velocity (if applicable)RationaleChallenges
Beamed PropulsionLaserInterstellar ProbeBreakthrough Starshotc (Propellantless)Nearest term possibility for interstellar missionKeeping laser focused on the craft is extremely challenging.
Magnetic SailStellar WindLow cost interplanetary travel, interstellar travel------Reduce need for propellant, onboard energy---
Nuclear Pulse PropulsionNuclear explosions or inertial confinement fusionInterplanetary, Interstellar TravelProject Orion, Project Daedalus10,000 km/sVery high exhaust velocity and thrustSafety, craft is necessarily very large

Theoretical Space Propulsion
MethodEnergy SourceUse CaseExample ProjectExhaust Velocity (if applicable)RationaleChallenges
Antimatter-catalyzed nuclear pulse propulsionPrimarily fusionInterplanetary, interstellar travel---8,000 km/sMore compact than nuclear pulse rocketDifficulty in producing and storing antimatter
AntimatterMatter-Antimatter ReactionInterstellar TravelProject Valkyrie100,000 km/sExhaust velocity and thrust near theoretical maximumDifficulty in producing and storing antimatter
Black HoleHawking RadiationInterstellar Travel---cPure mass to energy conversionPhysics are highly uncertain.
Wormhole, Warp Field, Reactionless Drive, etc.??????EmDrive??????Not permitted under established physics.

Data sources are as follows: chemical rockets (see above), hydrazine 1, 2, gravity assist 3, pulsed plasma thruster 4, ion drives 56, nuclear thermal rockets 7, magnetoplasmadynamic thruster 5, 8, VASIMR 9, 10, solar sail 11, Direct Fusion Drive 12, beamed propulsion 13, magnetic sails 14, nuclear pulse propulsion 15, ACNP 16, antimatter rocket 17, and black hole drive 18, 19.

The best propulsion options depend on the application. For more efficient satellite maneuvering and for uncrewed interplanetary probes, further improvement to ion drives may be the most promising option. For crewed interplanetary missions, nuclear thermal rockets may hold the most potential. There is little prospect for interstellar probes, let alone crewed interstellar flight, on the horizon.

References

  1. European Space Agency. "Considering hydrazine-free satellite propulsion". November 2013. ↩

  2. Michele, R. "Monopropellant Engines". Aerospace Engineering. November 2013. ↩

  3. D'Amario, L., Bright, L., Wolf, A. "Galileo trajectory design". Space Science Reviews 60(1-4), pp. 23-78. May 1992. ↩

  4. Ling, W., Zhang, Z., Tang, H. "Progress in Fundamental Pulsed Plasma Thruster Research". Presented at the 35th International Electric Propulsion Conference Georgia Institute of Technology - Atlanta, Georgia - USA. October 2017. ↩

  5. Choueiri, E. "New Dawn for Electric Rockets". Scientific American. 2009. ↩ ↩2

  6. National Aeronautics and Space Administration. "Overview | Dawn". Accessed November 10, 2019. ↩

  7. Dujarric, C., Santovincenzo, A., Summerer, L. "The NTER: A Proposed Innovative Propulsion Concept for Manned Interplanetary Mission". 4th European Conference for Aerospace Sciences. 2011. ↩

  8. Jahn, R., Choueiri, E. "Electric Propulsion". Encyclopedia of Physical Science and Technology, Third Edition, Volume 5. 2002. ↩

  9. Ad Astra Rocket Company. "Facts About the VASIMR® Engine and its Development". 2011. ↩

  10. Longmier et al. "VASIMR® VX-200 Performance Measurements and Helicon Throttle Tables Using Argon and Krypton". Presented at the 32nd International Electric Propulsion Conference, Wiesbaden, Germany. September 2011. ↩

  11. Wright, J. Solar Sailing. ISBN-13: 978-2881248429, Routledge. January 1992. ↩

  12. Thomas, S., Paluszek, M., Cohen, S. "Fusion-Enabled Pluto Orbiter and Lander". Phase 1 Final Report, NASA Innovative Advanced Concepts grant. April 2017. ↩

  13. Parkin, K. "The Breakthrough Starshot system model". Acta Astronautica 152, pp. 370-384. November 2018. ↩

  14. Andrews, D., Zubrin, R. "Magnetic Sails and Interstellar Travel". 39th Congress of the International Astronautical Federation, IAF-88-553. Published in the Journal of the British Interplanetary Society, 1990. 1988. ↩

  15. The British Interplanetary Society. "Project Daedalus - Interstellar Mission". Accessed November 11, 2019. ↩

  16. Perkins, J., Orth, C., Tabak, M. "On the Utility of Antiprotons as Drivers for Inertial Confinement Fusion". Lawrence Livermore National Laboratory. June 2003. ↩

  17. Frisbee, R. "How to Build an Antimatter Rocket for Interstellar Missions - Systems Level Considerations in Designing Advanced Propulsion Technology Vehicles". 39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, Huntsville Alabama. July 2003. ↩

  18. Crane, L., Westmoreland, S. "Are Black Hole Starships Possible". August 2009. ↩

  19. Lee, J. "Acceleration of a Schwarzschild Kugelblitz Starship". Journal of the British Interplanetary Society, pp. 105-116. 2015. ↩