Nuclear pulse propulsion

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Project Orion[edit]

A nuclear pulse propulsion unit. The explosive charge ablatively vaporizes the propellant, propelling it away from the charge, and simultaneously creating a plasma out of the propellant. The propellant then goes on to impact the pusher plate at the bottom of the Orion spacecraft, imparting a pulse of 'pushing' energy.






Project Daedalus[edit]

Main article: Project Daedalus





Conceptual diagram of a Medusa propulsion spacecraft, showing: (A) the payload capsule, (B) the winch mechanism, (C) the optional main tether cable, (D) riser tethers, and (E) the parachute mechanism.
Operating sequence of the Medusa propulsion system. This diagram shows the operating sequence of a Medusa propulsion spacecraft (1) Starting at moment of explosive-pulse unit firing, (2) As the explosive pulse reaches the parachute canopy, (3) Pushes the canopy, accelerating it away from the explosion as the spacecraft plays out the main tether with the winch, generating electricity as it extends, and accelerating the spacecraft, (4) And finally winches the spacecraft forward to the canopy and uses excess electricity for other purposes.

The Medusa design is a type of nuclear pulse propulsion which has more in common with solar sails than with conventional rockets. It was created by Johndale Solem[8] in the 1990s and published in the Journal of the British Interplanetary Society (JBIS).[9]

A Medusa spacecraft would deploy a large “spinnaker” sail ahead of it, attached by separate independent cables, and then launch nuclear explosives forward to detonate between itself and its sail. The sail would be accelerated by the plasma and photonic impulse, running out the tethers as when a fish flees the fisherman, and generating electricity at the “reel”. The spacecraft would then use some of the generated electricity to reel itself up towards the sail, constantly smoothly accelerating as it goes.[10]

In the original design, multiple tethers connected to multiple motor generators. The advantage over the single tether is to increase the distance between the explosion and the tethers, thus reducing damage to the tethers.

For heavy payloads, performance could be improved by taking advantage of lunar materials, for example, wrapping the explosive with lunar rock or water, likely stored previously at a stable Earth-Moon Lagrange point to be subsequently acquired by the Medusa spacecraft.[11]

Medusa performs better than the classical Orion design because its sail intercepts more of the explosive impulse, its shock-absorber stroke is much longer, and all its major structures are in tension and hence can be quite lightweight. Medusa-type ships would be capable of a specific impulse between 50,000 and 100,000 seconds (500 to 1000 kN·s/kg).

Medusa is widely known to the public in the BBC documentary film To Mars By A-Bomb: The Secret History of Project Orion.[12] A short film shows an artist’s conception of how the Medusa spacecraft works “by throwing bombs into a sail that's ahead of it!”[13]

Project Longshot[edit]

Main article: Project Longshot


Antimatter-catalyzed nuclear pulse propulsion[edit]

In the mid-1990s research at the Pennsylvania State University led to the concept of using antimatter to catalyze nuclear reactions. In short, antiprotons would react inside the nucleus of uranium, causing a release of energy that breaks the nucleus apart as in conventional nuclear reactions. Even a small number of such reactions can start the chain reaction that would otherwise require a much larger volume of fuel to sustain. Whereas the "normal" critical mass for plutonium is about 11.8 kilograms (for a sphere at standard density), with antimatter catalyzed reactions this could be well under one gram.


MSNW magneto-inertial fusion driven rocket[edit]

MSNW Magneto-Inertial Fusion Driven Rocket
The Fusion Driven Rocket powered spacecraft.jpg
Concept graphic of a Fusion Driven Rocket powered Spacecraft arriving at Mars
Designer MSNW LLC
Application Interplanetary
Status Theoretical
Specific impulse 1,606 s to 5,722 s (depending on fusion gain)
Burn time 1 day to 90 days (10 days optimal with Gain of 40)
References [15]

Fuel: Deuterium-Tritium Cryogenic Pellet

Propellent: Lithium or Aluminum

Power Requirements: 100 kW to 1,000 kW

NASA funded MSNW LLC and the University of Washington in 2011 to study and develop a fusion rocket through the NASA Innovative Advanced Concepts NIAC Program.[16]

The rocket uses a form of magneto-inertial fusion to produce a direct thrust fusion rocket. Powerful magnetic fields cause large metal rings (likely made of lithium, where a set for one pulse has a total mass of 365 gram) to collapse around the deuterium-tritium plasma, compressing it to a fusion state. Energy from these fusion reactions heat up and ionize the shell of metal formed by the crushed rings. The hot, ionized metal is shot out of a magnetic rocket nozzle at a high speed (up to 30 km/s). Repeating this process roughly every minute would propel the spacecraft.[17] The fusion reaction is not self-sustaining and requires electrical energy to induce fusion. With electrical requirements estimated to be between 100 kW to 1,000 kW (300 kW average), spacecraft designs incorporate solar panels to produce the electrical energy needed for the fusion engine.[15]


The performance characteristics of the engine are highly dependent on the Fusion energy gain factor achieved by the reactor. Gains are expected to be between a factor of 20 and 200, with an estimated average of 40. With higher fusions gains comes higher exhaust velocity, higher specific impulse and lower electrical power requirements. The table below summarizes difference performance characteristics for a theoretical 90 day Mars transfer at gains of 20, 40 and 200.

FDR parameters for 90 Mars transfer burn[15]
Total Gain Gain of 20 Gain of 40 Gain of 200
Liner Mass (kg) 0.365 0.365 0.365
Specific Impulse (s) 1,606 2,435 5,722
Mass Fraction 0.33 0.47 0.68
Specific Mass (kg/kW) 0.8 0.53 0.23
Mass Propellant (kg) 110,000 59,000 20,000
Mass Initial (kg) 184,000 130,000 90,000
Electrical Power Required (kW) 1,019 546 188



See also[edit]


  7. ^ Solem, J. C. (1994). "Nuclear explosive propelled interceptor for deflecting objects on collision course with Earth". Journal of Spacecraft and Rockets 31 (4): 707–709. 
  8. ^ Gilster, Paul (2004). Centauri Dreams: Imagining and Planning Interstellar Exploration. Copernicus Books, Atlanta Book Company. p. 86. ISBN 038700436X. Retrieved 2015-10-26. 
  10. ^ Solem, J. C. (June 1994). "Nuclear explosive propulsion for interplanetary travel: Extension of the Medusa concept for higher specific impulse". Journal of the British Interplanetary Society 47 (6): 229–238. Bibcode:1994JBIS...47..229S. ISSN 0007-084X. 
  11. ^ Solem, J. C. (2000). "The Moon and the Medusa - Use of Lunar Assets in Nuclear-Pulse-Propelled Space Travel". Journal of the British Interplanetary Society 53 (1): 362–370. 
  12. ^ British Broadcasting Corp. (BBC). (2003). “To Mars By A-Bomb: The Secret History of Project Orion”, a documentary film.
  13. ^ Stevens, Nick. (2014). “The Medusa - An advanced nuclear pulse spacecraft”, a film.
  14. ^ Beals, Keith A.; et al. "Project Longshot An Unmanned Probe To Alpha Centauri" (PDF). NASA. Retrieved March 14, 2011. 
  15. ^ a b c d Slough et al. "Nuclear Propulsion through Direct Conversion of Fusion Energy:The Fusion Driven Rocket", NASA
  16. ^ 2011 NIAC Phase I Selections
  19. ^

External references[edit]