Galactic Library - User contributions [en]

Photon Rocket

2026-05-23T05:43:34Z

Highscore:

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This is it - the be-all and end-all of reaction drives. No other drive competes with a photon rocket's metrics of output, efficiency, and complexity. Effectively a flashlight of sufficient power to generate practical thrust, the photon rocket is of the same species as chemical and nuclear rockets, but evolved beyond either. Instead of chemical bonds or nuclear fusion and fission, a photon rocket uses one-to-one antimatter-matter annihilation to convert the fuel's mass into radiation. Directed in a single direction, this light is sufficient to create thrust.

The rule for any torch drive is - "Don't point this at planets and other friendly objects." For photon rockets, the rule the same, but in all capitals.

==Introduction==

Reaction drives are all about energy and efficiency. The more energy you can extract and apply to a reaction mass, the greater your efficiency, the mightier your rocket. A chemical rocket might combine two compounds, burning them, and using the released energy to eject the fuel's mass as fast as possible. A nuclear rocket extracts that same energy from nuclear fusion or fission, and due to the nature of nuclear reactions, manages a much greater energy density potential. For example, in the case of hydrogen-hydrogen fusion, 0.645% of the reaction's mass is carried away in the form of radiation<ref> https://books.google.com/books?id=Mg4AAAAAMBAJ&pg=PA99 Bulletin of the Atomic Scientists. </ref> - less than a percent of the mass in play becomes light.

A photon rocket converts 100% of its fuel into energy. Reacting 0.5 grams of antimatter with 0.5 grams of matter results in 0 grams of either, and ~9×10^13 Joules (21.5 kilotons-equivalent) of energy. <ref> http://www.projectrho.com/public_html/rocket/antimatterfuel.php Atomic Rockets. </ref> A nuclear bomb's worth of energy is generated with the mass as an average pen cap. Where batteries, chemical fuels and nuclear bombs all store energy in their mass, antimatter is the ultimate battery, because the entirety of its mass is the energy potential in play.

Some designs choose to apply that energy to accelerating matter, ejecting it to create thrust. Instead, a photon rocket uses the generated radiation directly, reflecting it off the rocket's drive and casting into one direction, thrusting the craft the other way. No mass is ejected, just a cone of radiation. It's an elegant, efficient, and incredibly complicated method - after all, we need to reflect that radiation without absorbing almost any of it, lest we become hot, expanding plasma. The radiation in play is of a vast variety, up to and including gamma and neutron radiation that penetrates meters of lead and water, although workable designs strive to generate as little of those as possible. We also need to store antimatter without allowing it to touch matter, for many months or years, in a acceleration-resistant and secure way that doesn't have the crew constantly fearing an instant and unexpected death.

===Theoretical Performance===

The exact mathematics of a photon drive depend on its design. <ref> https://vixra.org/pdf/1201.0026v1.pdf "Matter-Antimatter GeV Gamma Ray Laser Rocket Propulsion" by F. Winterberg </ref> <ref> https://nets2021.ornl.gov/wp-content/uploads/gravity_forms/12-b63a96649a525ab5aa39d607840d9d9f/2021/04/jackson_exoplanet_202104261.pdf "Antimatter-Based Propulsion for Exoplanet Exploration" by Dr. Gerald P. Jackson </ref>

==Design and Function==

===Reflection and Direction===

===Storage===

By its nature, antimatter containment is unlike any other form of storage imaginable. The fuel tank itself cannot be allowed to touch the fuel it stores. Air, loose particles, evaporation and unfortunate dust coming into contact with the fuel would cause the same reaction as is meant to be within the engine's focus - annihilation. If your vessel is meant to have significant acceleration or withstand sizable impacts, your antimatter containment needs to reflect that with a huge margin of error.

Perfect vacuum, near-zero-kelvin temperature and acceleration resistance are a must.

The primary theorized means of antimatter storage is based around electromagnetic levitation. For this, the antimatter in question has to be both paramagnetic, and cold enough not to evaporate too much.

That's where hydrogen ice comes in. Hydrogen has a melting point of 14.01 Kelvin. You've probably met more people named Kelvin than the degrees required to keep hydrogen solid. However the act of electromagnetic levitation injects energies into the frozen anti-hydrogen, while the only way of cooling it remains black-body radiation. Levitating your anti-hydrogen will cause it to heat up and melt or evaporate, becoming non-paramagnetic and escaping containment.

A possible solution is keeping pellets of anti-hydrogen ice wrapped in a thin later of anti-lithium, preventing evaporation and sublimation.<ref> https://nets2021.ornl.gov/wp-content/uploads/gravity_forms/12-b63a96649a525ab5aa39d607840d9d9f/2021/04/jackson_exoplanet_202104261.pdf "Antimatter-Based Propulsion for Exoplanet Exploration" by Dr. Gerald P. Jackson </ref>

===Performance / Capabilities / Applications===

An antimatter rocket as we know it would never be used in an atmosphere. Not because of our unwillingness to irradiate continents, but because excess of gasses in such an environment would tend to flood reaction chambers and risk annihilation with the antimatter at inopportune times.

==In Fiction==

===The Land of Crimson Clouds===

'The Land of Crimson Clouds' by Boris and Arkady Strugatsky<ref> https://ru.wikipedia.org/wiki/%D0%A1%D1%82%D1%80%D0%B0%D0%BD%D0%B0_%D0%B1%D0%B0%D0%B3%D1%80%D0%BE%D0%B2%D1%8B%D1%85_%D1%82%D1%83%D1%87 "Страна багровых туч" </ref> is set around a prototype photon rocket's mission to Venus. Where nuclear rockets have failed to consistently survive the Venusian environment, due largely to their limited delta-v and acceleration, the spacecraft Khius is meant to overpower the planet with a hyper-efficient and hyper-powerful photon torch.

Khius uses an 'absolute mirror' of mesa-matter to reflect all forms of emitted radiation away from the craft. Khius possesses five fusion rockets around the primary antimatter photon drive, primarily designed for earth-side landings that don't allow for the photon drive's collateral. During the cross-system flight from Earth to Venus, the craft abuses its excessive freedom of motion to set a speed record, at which point the crew experience anomalous behavior in their equipment, attributed to relativistic distortion.

Previous prototypes had a history of failing mirrors and instant vaporization. Later stories - "Way to Amalthea" and "Probationers" - note the insanity of the prototype's single-layer mirror, which, upon failing at even a single crack or fault, would have vaporized the entire craft. In "Way to Amalthea", a photon rocket freighter falls into Jupiter. After re-calibration of a partially broken mirror and drive, the captain risks igniting a chain fusion reaction, with a possibility of turning Jupiter into star, in order to escape.

===Project Hail Mary===

'Project Hail Mary' by Andy Weir <ref> https://en.wikipedia.org/wiki/Project_Hail_Mary "Project Hail Mary" </ref> sprinkles in a healthy dose of handwavium to allow for a photon drive that doesn't rely on antimatter - healthy, because the setting relies on this one consistent piece of handwavium, and follows its rules with admirable strictness. The handwavium/photon torch in question is a species of bacteria - 'Astrophage' - that is capable of converting sunlight into neutrinos, and then back into light. That last part is critical - Astrophage converts its onboard neutrino supply into light, to act as a one-bacteria photon rocket in service of its planet-star life cycle. The technological application of this is simple - grow a bunch of Astrophage, stuff it into fuel tanks, and then selectively trigger their migratory instinct in an 'engine' to generate controlled thrust.

If antimatter storage is plausible, then Astrophage as described is fantasy - a method for photon-neutrino-photon conversion, no less as a bio-chemical mechanism, is unknown.

==References==

[[Category:Transportation & Infrastructure‏‎]][[Category:Transportation]][[Category:Propulsion]]

Photon Rocket

2021-10-16T20:06:29Z

Highscore:

This is it - the be-all and end-all of reaction drives. No other drive competes with a photon rocket's metrics of output, efficiency, and complexity. Effectively a flashlight of sufficient power to generate practical thrust, the photon rocket is of the same species as chemical and nuclear rockets, but evolved beyond either. Instead of chemical bonds or nuclear fusion and fission, a photon rocket uses one-to-one antimatter-matter annihilation to convert the fuel's mass into radiation. Directed in a single direction, this light is sufficient to create thrust.

The rule for any torch drive is - "Don't point this at planets and other friendly objects." For photon rockets, the rule the same, but in all capitals.

==Introduction==

Reaction drives are all about energy and efficiency. The more energy you can extract and apply to a reaction mass, the greater your efficiency, the mightier your rocket. A chemical rocket might combine two compounds, burning them, and using the released energy to eject the fuel's mass as fast as possible. A nuclear rocket extracts that same energy from nuclear fusion or fission, and due to the nature of nuclear reactions, manages a much greater energy density potential. For example, in the case of hydrogen-hydrogen fusion, 0.645% of the reaction's mass is carried away in the form of radiation<ref> https://books.google.com/books?id=Mg4AAAAAMBAJ&pg=PA99 Bulletin of the Atomic Scientists. </ref> - less than a percent of the mass in play becomes light.

A photon rocket converts 100% of its fuel into energy. Reacting 0.5 grams of antimatter with 0.5 grams of matter results in 0 grams of either, and ~9×10^13 Joules (21.5 kilotons-equivalent) of energy. <ref> http://www.projectrho.com/public_html/rocket/antimatterfuel.php Atomic Rockets. </ref> A nuclear bomb's worth of energy is generated with the mass as an average pen cap. Where batteries, chemical fuels and nuclear bombs all store energy in their mass, antimatter is the ultimate battery, because the entirety of its mass is the energy potential in play.

Some designs choose to apply that energy to accelerating matter, ejecting it to create thrust. Instead, a photon rocket uses the generated radiation directly, reflecting it off the rocket's drive and casting into one direction, thrusting the craft the other way. No mass is ejected, just a cone of radiation. It's an elegant, efficient, and incredibly complicated method - after all, we need to reflect that radiation without absorbing almost any of it, lest we become hot, expanding plasma. The radiation in play is of a vast variety, up to and including gamma and neutron radiation that penetrates meters of lead and water, although workable designs strive to generate as little of those as possible. We also need to store antimatter without allowing it to touch matter, for many months or years, in a acceleration-resistant and secure way that doesn't have the crew constantly fearing an instant and unexpected death.

===Theoretical Performance===

The exact mathematics of a photon drive depend on its design. <ref> https://vixra.org/pdf/1201.0026v1.pdf "Matter-Antimatter GeV Gamma Ray Laser Rocket Propulsion" by F. Winterberg </ref> <ref> https://nets2021.ornl.gov/wp-content/uploads/gravity_forms/12-b63a96649a525ab5aa39d607840d9d9f/2021/04/jackson_exoplanet_202104261.pdf "Antimatter-Based Propulsion for Exoplanet Exploration" by Dr. Gerald P. Jackson </ref>

==Design and Function==

===Reflection and Direction===

===Storage===

By its nature, antimatter containment is unlike any other form of storage imaginable. The fuel tank itself cannot be allowed to touch the fuel it stores. Air, loose particles, evaporation and unfortunate dust coming into contact with the fuel would cause the same reaction as is meant to be within the engine's focus - annihilation. If your vessel is meant to have significant acceleration or withstand sizable impacts, your antimatter containment needs to reflect that with a huge margin of error.

Perfect vacuum, near-zero-kelvin temperature and acceleration resistance are a must.

The primary theorized means of antimatter storage is based around electromagnetic levitation. For this, the antimatter in question has to be both paramagnetic, and cold enough not to evaporate too much.

That's where hydrogen ice comes in. Hydrogen has a melting point of 14.01 Kelvin. You've probably met more people named Kelvin than the degrees required to keep hydrogen solid. However the act of electromagnetic levitation injects energies into the frozen anti-hydrogen, while the only way of cooling it remains black-body radiation. Levitating your anti-hydrogen will cause it to heat up and melt or evaporate, becoming non-paramagnetic and escaping containment.

A possible solution is keeping pellets of anti-hydrogen ice wrapped in a thin later of anti-lithium, preventing evaporation and sublimation.<ref> https://nets2021.ornl.gov/wp-content/uploads/gravity_forms/12-b63a96649a525ab5aa39d607840d9d9f/2021/04/jackson_exoplanet_202104261.pdf "Antimatter-Based Propulsion for Exoplanet Exploration" by Dr. Gerald P. Jackson </ref>

===Performance / Capabilities / Applications===

An antimatter rocket as we know it would never be used in an atmosphere. Not because of our unwillingness to irradiate continents, but because excess of gasses in such an environment would tend to flood reaction chambers and risk annihilation with the antimatter at inopportune times.

==In Fiction==

'The Land of Crimson Clouds' by Boris and Arkady Strugatsky<ref> https://ru.wikipedia.org/wiki/%D0%A1%D1%82%D1%80%D0%B0%D0%BD%D0%B0_%D0%B1%D0%B0%D0%B3%D1%80%D0%BE%D0%B2%D1%8B%D1%85_%D1%82%D1%83%D1%87 "Страна багровых туч" </ref> is set around a prototype photon rocket's mission to Venus. Where nuclear rockets have failed to consistently survive the Venusian environment, due largely to their limited freedom of spare acceleration, the spacecraft Khius is meant to overpower the planet with a hyper-efficient and powerful photon torch.

Khius uses an 'absolute mirror' of mesa-matter to reflect all forms of emitted radiation away from the craft. Khius possesses five fusion rockets around the primary antimatter photon drive, primarily designed for earth-side landings that don't allow for the photon drive's collateral. During the cross-system flight from Earth to Venus, the craft abuses its excessive freedom of motion to set a speed record, at which point the crew experience anomalous behavior in their equipment, attributed to relativistic distortion.

Previous prototypes had a history of failing mirrors and instant vaporization. Later stories - "Way to Amalthea" and "Probationers" - note the insanity of the prototype's single-layer mirror, which, upon failing at even a single crack or fault, would have vaporized the entire craft. In "Way to Amalthea", a photon rocket freighter falls into Jupiter. After re-calibration of a partially broken mirror and drive, the captain risks igniting a chain fusion reaction, with a possibility of turning Jupiter into star, in order to escape.

==References==

Photon Rocket

2021-10-16T20:00:00Z

Highscore:

This is it - the be-all and end-all of reaction drives. No other drive competes with a photon rocket's metrics of output, efficiency, and complexity. Effectively a flashlight of sufficient power to generate practical thrust, the photon rocket is of the same species as chemical and nuclear rockets, but evolved beyond either. Instead of chemical bonds or nuclear fusion and fission, a photon rocket uses one-to-one antimatter-matter annihilation to convert the fuel's mass into radiation. Directed in a single direction, this light is sufficient to create thrust.

The rule for any torch drive is - "Don't point this at planets and other friendly objects." For photon rockets, the rule is - "DO NOT UNDER ANY CIRCUMSTANCES POINT THIS AT ANYTHING THAT SHOULD NOT BE PLASMA!"

==Introduction==

Reaction drives are all about energy and efficiency. The more energy you can extract and apply to a reaction mass, the greater your efficiency, the mightier your rocket. A chemical rocket might combine two compounds, burning them, and using the released energy to eject the fuel's mass as fast as possible. A nuclear rocket extracts that same energy from nuclear fusion or fission, and due to the nature of nuclear reactions, manages a much greater energy density potential. For example, in the case of hydrogen-hydrogen fusion, 0.645% of the reaction's mass is carried away in the form of radiation<ref> https://books.google.com/books?id=Mg4AAAAAMBAJ&pg=PA99 Bulletin of the Atomic Scientists. </ref> - less than a percent of the mass in play becomes light.

A photon rocket converts 100% of its fuel into energy. Reacting 0.5 grams of antimatter with 0.5 grams of matter results in 0 grams of either, and ~9×10^13 Joules (21.5 kilotons-equivalent) of energy. <ref> http://www.projectrho.com/public_html/rocket/antimatterfuel.php Atomic Rockets. </ref> A nuclear bomb's worth of energy is generated with the mass as an average pen cap. Where batteries, chemical fuels and nuclear bombs all store energy in their mass, antimatter is the ultimate battery, because the entirety of its mass is the energy potential in play.

Some designs choose to apply that energy to accelerating matter, ejecting it to create thrust. Instead, a photon rocket uses the generated radiation directly, reflecting it off the rocket's drive and casting into one direction, thrusting the craft the other way. No mass is ejected, just a cone of radiation. It's an elegant, efficient, and incredibly complicated method - after all, we need to reflect that radiation without absorbing almost any of it, lest we become hot, expanding plasma. The radiation in play is of a vast variety, up to and including gamma and neutron radiation that penetrates meters of lead and water, although workable designs strive to generate as little of those as possible. We also need to store antimatter without allowing it to touch matter, for many months or years, in a acceleration-resistant and secure way that doesn't have the crew constantly fearing an instant and unexpected death.

===Theoretical Performance===

The exact mathematics of a photon drive depend on its design. <ref> https://vixra.org/pdf/1201.0026v1.pdf "Matter-Antimatter GeV Gamma Ray Laser Rocket Propulsion" by F. Winterberg </ref> <ref> https://nets2021.ornl.gov/wp-content/uploads/gravity_forms/12-b63a96649a525ab5aa39d607840d9d9f/2021/04/jackson_exoplanet_202104261.pdf "Antimatter-Based Propulsion for Exoplanet Exploration" by Dr. Gerald P. Jackson </ref>

==Design and Function==

===Reflection and Direction===

===Storage===

By its nature, antimatter containment is unlike any other form of storage imaginable. The fuel tank itself cannot be allowed to touch the fuel it stores. Air, loose particles, evaporation and unfortunate dust coming into contact with the fuel would cause the same reaction as is meant to be within the engine's focus - annihilation. If your vessel is meant to have significant acceleration or withstand sizable impacts, your antimatter containment needs to reflect that with a huge margin of error.

Perfect vacuum, near-zero-kelvin temperature and acceleration resistance are a must.

The primary theorized means of antimatter storage is based around electromagnetic levitation. For this, the antimatter in question has to be both paramagnetic, and cold enough not to evaporate too much.

That's where hydrogen ice comes in. Hydrogen has a melting point of 14.01 Kelvin. You've probably met more people named Kelvin than the degrees required to keep hydrogen solid. However the act of electromagnetic levitation injects energies into the frozen anti-hydrogen, while the only way of cooling it remains black-body radiation. Levitating your anti-hydrogen will cause it to heat up and melt or evaporate, becoming non-paramagnetic and escaping containment.

A possible solution is keeping pellets of anti-hydrogen ice wrapped in a thin later of anti-lithium, preventing evaporation and sublimation.<ref> https://nets2021.ornl.gov/wp-content/uploads/gravity_forms/12-b63a96649a525ab5aa39d607840d9d9f/2021/04/jackson_exoplanet_202104261.pdf "Antimatter-Based Propulsion for Exoplanet Exploration" by Dr. Gerald P. Jackson </ref>

===Performance / Capabilities / Applications===

An antimatter rocket as we know it would never be used in an atmosphere. Not because of our unwillingness to irradiate continents, but because excess of gasses in such an environment would tend to flood reaction chambers and risk annihilation with the antimatter at inopportune times.

==In Fiction==

'The Land of Crimson Clouds' by Boris and Arkady Strugatsky<ref> https://ru.wikipedia.org/wiki/%D0%A1%D1%82%D1%80%D0%B0%D0%BD%D0%B0_%D0%B1%D0%B0%D0%B3%D1%80%D0%BE%D0%B2%D1%8B%D1%85_%D1%82%D1%83%D1%87 "Страна багровых туч" </ref> is set around a prototype photon rocket's mission to Venus. Where nuclear rockets have failed to consistently survive the Venusian environment, due largely to their limited freedom of spare acceleration, the spacecraft Khius is meant to overpower the planet with a hyper-efficient and powerful photon torch.

Khius uses an 'absolute mirror' of mesa-matter to reflect all forms of emitted radiation away from the craft. Khius possesses five fusion rockets around the primary antimatter photon drive, primarily designed for earth-side landings that don't allow for the photon drive's collateral. During the cross-system flight from Earth to Venus, the craft abuses its excessive freedom of motion to set a speed record, at which point the crew experience anomalous behavior in their equipment, attributed to relativistic distortion.

Previous prototypes had a history of failing mirrors and instant vaporization. Later stories - "Way to Amalthea" and "Probationers" - note the insanity of the prototype's single-layer mirror, which, upon failing at even a single crack or fault, would have vaporized the entire craft. In "Way to Amalthea", a photon rocket freighter falls into Jupiter. After re-calibration of a partially broken mirror and drive, the captain risks igniting a chain fusion reaction, with a possibility of turning Jupiter into star, in order to escape.

==References==

Photon Rocket

2021-10-16T19:26:29Z

Highscore: Added "In Ficiton" section.

This is it - the be-all and end-all of reaction drives. No other drive competes with a photon rocket's metrics of output, efficiency, and complexity. Effectively a flashlight of sufficient power to generate practical thrust, the photon rocket is of the same species as chemical and nuclear rockets, but evolved beyond either. Instead of chemical bonds or nuclear fusion and fission, a photon rocket uses one-to-one antimatter-matter annihilation to convert the fuel's mass into radiation. Directed in a single direction, this light is sufficient to create thrust.

==Introduction==

Reaction drives are all about energy and efficiency. The more energy you can extract and apply to a reaction mass, the greater your efficiency, the mightier your rocket. A chemical rocket might combine two compounds, burning them, and using the released energy to eject the fuel's mass as fast as possible. A nuclear rocket extracts that same energy from nuclear fusion or fission, and due to the nature of nuclear reactions, manages a much greater energy density potential. For example, in the case of hydrogen-hydrogen fusion, 0.645% of the reaction's mass is carried away in the form of radiation<ref> https://books.google.com/books?id=Mg4AAAAAMBAJ&pg=PA99 Bulletin of the Atomic Scientists. </ref> - less than a percent of the mass in play becomes light.

A photon rocket converts 100% of its fuel into energy. Reacting 0.5 grams of antimatter with 0.5 grams of matter results in 0 grams of either, and ~9×10^13 Joules (21.5 kilotons-equivalent) of energy. <ref> http://www.projectrho.com/public_html/rocket/antimatterfuel.php Atomic Rockets. </ref> A nuclear bomb's worth of energy is generated with the mass as an average pen cap. Where batteries, chemical fuels and nuclear bombs all store energy in their mass, antimatter is the ultimate battery, because the entirety of its mass is the energy potential in play.

Some designs choose to apply that energy to accelerating matter, ejecting it to create thrust. Instead, a photon rocket uses the generated radiation directly, reflecting it off the rocket's drive and casting into one direction, thrusting the craft the other way. No mass is ejected, just a cone of radiation. It's an elegant, efficient, and incredibly complicated method - after all, we need to reflect that radiation without absorbing almost any of it, lest we become hot, expanding plasma. The radiation in play is of a vast variety, up to and including gamma and neutron radiation that penetrates meters of lead and water, although workable designs strive to generate as little of those as possible. We also need to store antimatter without allowing it to touch matter, for many months or years, in a acceleration-resistant and secure way that doesn't have the crew constantly fearing an instant and unexpected death.

===Theoretical Performance===

The exact mathematics of a photon drive depend on its design. <ref> https://vixra.org/pdf/1201.0026v1.pdf "Matter-Antimatter GeV Gamma Ray Laser Rocket Propulsion" by F. Winterberg </ref> <ref> https://nets2021.ornl.gov/wp-content/uploads/gravity_forms/12-b63a96649a525ab5aa39d607840d9d9f/2021/04/jackson_exoplanet_202104261.pdf "Antimatter-Based Propulsion for Exoplanet Exploration" by Dr. Gerald P. Jackson </ref>

==Design and Function==

===Reflection and Direction===

===Storage===

By its nature, antimatter containment is unlike any other form of storage imaginable. The fuel tank itself cannot be allowed to touch the fuel it stores. Air, loose particles, evaporation and unfortunate dust coming into contact with the fuel would cause the same reaction as is meant to be within the engine's focus - annihilation. If your vessel is meant to have significant acceleration or withstand sizable impacts, your antimatter containment needs to reflect that with a huge margin of error.

Perfect vacuum, near-zero-kelvin temperature and acceleration resistance are a must.

The primary theorized means of antimatter storage is based around electromagnetic levitation. For this, the antimatter in question has to be both paramagnetic, and cold enough not to evaporate too much.

That's where hydrogen ice comes in. Hydrogen has a melting point of 14.01 Kelvin. You've probably met more people named Kelvin than the degrees required to keep hydrogen solid. However the act of electromagnetic levitation injects energies into the frozen anti-hydrogen, while the only way of cooling it remains black-body radiation. Levitating your anti-hydrogen will cause it to heat up and melt or evaporate, becoming non-paramagnetic and escaping containment.

A possible solution is keeping pellets of anti-hydrogen ice wrapped in a thin later of anti-lithium, preventing evaporation and sublimation.<ref> https://nets2021.ornl.gov/wp-content/uploads/gravity_forms/12-b63a96649a525ab5aa39d607840d9d9f/2021/04/jackson_exoplanet_202104261.pdf "Antimatter-Based Propulsion for Exoplanet Exploration" by Dr. Gerald P. Jackson </ref>

===Performance / Capabilities / Applications===

An antimatter rocket as we know it would never be used in an atmosphere. Not because of our unwillingness to irradiate continents, but because excess of gasses in such an environment would tend to flood reaction chambers and risk annihilation with the antimatter at inopportune times.

==In Fiction==

'The Land of Crimson Clouds' by Boris and Arkady Strugatsky<ref> https://ru.wikipedia.org/wiki/%D0%A1%D1%82%D1%80%D0%B0%D0%BD%D0%B0_%D0%B1%D0%B0%D0%B3%D1%80%D0%BE%D0%B2%D1%8B%D1%85_%D1%82%D1%83%D1%87 "Страна багровых туч" </ref> is set around a prototype photon rocket's mission to Venus. Where nuclear rockets have failed to consistently survive the Venusian environment, due largely to their limited freedom of spare acceleration, the spacecraft Khius is meant to overpower the planet with a hyper-efficient and powerful photon torch.

Khius uses an 'absolute mirror' of mesa-matter to reflect all forms of emitted radiation away from the craft. Khius possesses five fusion rockets around the primary antimatter photon drive, primarily designed for earth-side landings that don't allow for the photon drive's collateral. During the cross-system flight from Earth to Venus, the craft abuses its excessive freedom of motion to set a speed record, at which point the crew experience anomalous behavior in their equipment, attributed to relativistic distortion.

Previous prototypes had a history of failing mirrors and instant vaporization. Later stories - "Way to Amalthea" and "Probationers" - note the insanity of the prototype's single-layer mirror, which, upon failing at even a single crack or fault, would have vaporized the entire craft. In "Way to Amalthea", a photon rocket freighter falls into Jupiter. After re-calibration of a partially broken mirror and drive, the captain risks igniting a chain fusion reaction, with a possibility of turning Jupiter into star, in order to escape.

==References==

Photon Rocket

2021-10-09T21:13:06Z

Highscore:

This is it - the be-all and end-all of reaction drives. No other drive competes with a photon rocket's metrics of output, efficiency, and complexity. Effectively a flashlight of sufficient power to generate practical thrust, the photon rocket is of the same species as chemical and nuclear rockets, but evolved beyond either. Instead of chemical bonds or nuclear fusion and fission, a photon rocket uses one-to-one antimatter-matter annihilation to convert the fuel's mass into radiation. Directed in a single direction, this light is sufficient to create thrust.

==Introduction==

Reaction drives are all about energy and efficiency. The more energy you can extract and apply to a reaction mass, the greater your efficiency, the mightier your rocket. A chemical rocket might combine two compounds, burning them, and using the released energy to eject the fuel's mass as fast as possible. A nuclear rocket extracts that same energy from nuclear fusion or fission, and due to the nature of nuclear reactions, manages a much greater energy density potential. For example, in the case of hydrogen-hydrogen fusion, 0.645% of the reaction's mass is carried away in the form of radiation<ref> https://books.google.com/books?id=Mg4AAAAAMBAJ&pg=PA99 Bulletin of the Atomic Scientists. </ref> - less than a percent of the mass in play becomes light.

A photon rocket converts 100% of its fuel into energy. Reacting 0.5 grams of antimatter with 0.5 grams of matter results in 0 grams of either, and ~9×10^13 Joules (21.5 kilotons-equivalent) of energy. <ref> http://www.projectrho.com/public_html/rocket/antimatterfuel.php Atomic Rockets. </ref> A nuclear bomb's worth of energy is generated with the mass as an average pen cap. Where batteries, chemical fuels and nuclear bombs all store energy in their mass, antimatter is the ultimate battery, because the entirety of its mass is the energy potential in play.

Some designs choose to apply that energy to accelerating matter, ejecting it to create thrust. Instead, a photon rocket uses the generated radiation directly, reflecting it off the rocket's drive and casting into one direction, thrusting the craft the other way. No mass is ejected, just a cone of radiation. It's an elegant, efficient, and incredibly complicated method - after all, we need to reflect that radiation without absorbing almost any of it, lest we become hot, expanding plasma. The radiation in play is of a vast variety, up to and including gamma and neutron radiation that penetrates meters of lead and water, although workable designs strive to generate as little of those as possible. We also need to store antimatter without allowing it to touch matter, for many months or years, in a acceleration-resistant and secure way that doesn't have the crew constantly fearing an instant and unexpected death.

===Theoretical Performance===

The exact mathematics of a photon drive depend on its design. <ref> https://vixra.org/pdf/1201.0026v1.pdf "Matter-Antimatter GeV Gamma Ray Laser Rocket Propulsion" by F. Winterberg </ref> <ref> https://nets2021.ornl.gov/wp-content/uploads/gravity_forms/12-b63a96649a525ab5aa39d607840d9d9f/2021/04/jackson_exoplanet_202104261.pdf "Antimatter-Based Propulsion for Exoplanet Exploration" by Dr. Gerald P. Jackson </ref>

==Design and Function==

===Reflection and Direction===

===Storage===

By its nature, antimatter containment is unlike any other form of storage imaginable. The fuel tank itself cannot be allowed to touch the fuel it stores. Air, loose particles, evaporation and unfortunate dust coming into contact with the fuel would cause the same reaction as is meant to be within the engine's focus - annihilation. If your vessel is meant to have significant acceleration or withstand sizable impacts, your antimatter containment needs to reflect that with a huge margin of error.

Perfect vacuum, near-zero-kelvin temperature and acceleration resistance are a must.

The primary theorized means of antimatter storage is based around electromagnetic levitation. For this, the antimatter in question has to be both paramagnetic, and cold enough not to evaporate too much.

That's where hydrogen ice comes in. Hydrogen has a melting point of 14.01 Kelvin. You've probably met more people named Kelvin than the degrees required to keep hydrogen solid. However the act of electromagnetic levitation injects energies into the frozen anti-hydrogen, while the only way of cooling it remains black-body radiation. Levitating your anti-hydrogen will cause it to heat up and melt or evaporate, becoming non-paramagnetic and escaping containment.

A possible solution is keeping pellets of anti-hydrogen ice wrapped in a thin later of anti-lithium, preventing evaporation and sublimation.<ref> https://nets2021.ornl.gov/wp-content/uploads/gravity_forms/12-b63a96649a525ab5aa39d607840d9d9f/2021/04/jackson_exoplanet_202104261.pdf "Antimatter-Based Propulsion for Exoplanet Exploration" by Dr. Gerald P. Jackson </ref>

===Performance / Capabilities / Applications===

An antimatter rocket as we know it would never be used in an atmosphere. Not because of our unwillingness to irradiate continents, but because excess of gasses in such an environment would tend to flood reaction chambers and risk annihilation with the antimatter at inopportune times.

==References==

Photon Rocket

2021-10-06T05:53:33Z

Highscore:

This is it - the be-all and end-all of reaction drives. No other drive competes with a photon rocket's metrics of output, efficiency, and complexity. Effectively a flashlight of sufficient power to generate practical thrust, the photon rocket is of the same species as chemical and nuclear rockets, but evolved beyond either. Instead of chemical bonds or nuclear fusion and fission, a photon rocket uses one-to-one antimatter-matter annihilation to convert the fuel's mass into radiation. Directed in a single direction, this light is sufficient to create thrust.

==Introduction==

Reaction drives are all about energy and efficiency. The more energy you can extract and apply to a reaction mass, the greater your efficiency, the mightier your rocket. A chemical rocket might combine two compounds, burning them, and using the released energy to eject the fuel's mass as fast as possible. A nuclear rocket extracts that same energy from nuclear fusion or fission, and due to the nature of nuclear reactions, manages a much greater energy density potential. For example, in the case of hydrogen-hydrogen fusion, 0.645% of the reaction's mass is carried away in the form of radiation<ref> https://books.google.com/books?id=Mg4AAAAAMBAJ&pg=PA99 Bulletin of the Atomic Scientists. </ref> - less than a percent of the mass in play becomes light.

A photon rocket converts 100% of its fuel into energy. Reacting 0.5 grams of antimatter with 0.5 grams of matter results in 0 grams of either, and ~9×10^13 Joules (21.5 kilotons-equivalent) of energy. <ref> http://www.projectrho.com/public_html/rocket/antimatterfuel.php Atomic Rockets. </ref> A nuclear bomb's worth of energy is generated with the mass as an average pen cap. Where batteries, chemical fuels and nuclear bombs all store energy in their mass, antimatter is the ultimate battery, because the entirety of its mass is the energy potential in play.

Some designs choose to apply that energy to accelerating matter, ejecting it to create thrust. Instead, a photon rocket uses the generated radiation directly, reflecting it off the rocket's drive and casting into one direction, thrusting the craft the other way. No mass is ejected, just a cone of radiation. It's an elegant, efficient, and incredibly complicated method - after all, we need to reflect that radiation without absorbing almost any of it, lest we become hot, expanding plasma. The radiation in play is of a vast variety, up to and including gamma and neutron radiation that penetrates meters of lead and water, although workable designs strive to generate as little of those as possible. We also need to store antimatter without allowing it to touch matter, for many months or years, in a acceleration-resistant and secure way that doesn't have the crew constantly fearing an instant and unexpected death.

===Theoretical Performance===

The exact mathematics of a photon drive depend on its design. <ref> https://vixra.org/pdf/1201.0026v1.pdf "Matter-Antimatter GeV Gamma Ray Laser Rocket Propulsion" by F. Winterberg </ref> <ref> https://nets2021.ornl.gov/wp-content/uploads/gravity_forms/12-b63a96649a525ab5aa39d607840d9d9f/2021/04/jackson_exoplanet_202104261.pdf "Antimatter-Based Propulsion for Exoplanet Exploration" by Dr. Gerald P. Jackson </ref>

==Design and Function==

===Reflection and Direction===

===Storage===

By its nature, antimatter containment is unlike any other form of storage imaginable. The fuel tank itself cannot be allowed to touch the fuel it stores. Air, loose particles, evaporation and unfortunate dust coming into contact with the fuel would cause the same reaction as is meant to be within the engine's focus - annihilation. If your vessel is meant to have significant acceleration or withstand sizable impacts, your antimatter containment needs to reflect that with a huge margin of error.

Perfect vacuum, near-zero-kelvin temperature and acceleration resistance are a must.

The primary theorized means of antimatter storage is based around electromagnetic levitation. For this, the antimatter in question has to be both paramagnetic, and cold enough not to evaporate too much.

That's where hydrogen ice comes in. Hydrogen has a melting point of 14.01 Kelvin. You've probably met more people named Kelvin than the degrees required to keep hydrogen solid. However the act of electromagnetic levitation injects energies into the frozen anti-hydrogen, while the only way of cooling it remains black-body radiation. Levitating your anti-hydrogen will cause it to heat up and melt or evaporate, becoming non-paramagnetic and escaping containment.

A possible solution is keeping pellets of anti-hydrogen ice wrapped in a thin later of anti-lithium, preventing evaporation and sublimation.<ref> https://nets2021.ornl.gov/wp-content/uploads/gravity_forms/12-b63a96649a525ab5aa39d607840d9d9f/2021/04/jackson_exoplanet_202104261.pdf "Antimatter-Based Propulsion for Exoplanet Exploration" by Dr. Gerald P. Jackson </ref>

===Performance / Capabilities / Applications===

==References==

Photon Rocket

2021-10-03T20:41:20Z

Highscore: Spelling

Photon Rocket

2021-10-03T20:39:38Z

Highscore: Init Push

Hydrolox Engine

2021-09-17T22:34:21Z

Highscore: Image work.

[[Image:Common Extensible Cryogenic Engine.jpg|thumb|RL10]]

When you need to get off of a habitable planet and want to be welcome to return, you need a high thrust rocket that doesn’t destroy real estate values. A hydrolox engine is one of the better choices for this.

A hydrolox engine is a chemical fueled rocket that uses cryogenic hydrogen and oxygen to produce thrust. It is one of the most efficient chemical rocket engines available.

{| class="wikitable floatright"
|+Engine Performance
|-
|Name
|Hydrogen-Oxygen Chemical Rocket
|-
|ISP or Exhaust Velocity
|459s <-> 4500 m/s (vacuum)
|-
|Thrust
|1,000,000 N
|-
|Efficiency
|98%
|-
|Drive Power
|2205 MW
|-
|T/W
|102
|-
|Energy Source (Fuel)
|Hydrogen + Oxygen at 6:1 ratio
|-
|Propellant
|Water exhaust
|-
|Reactor
|Combustion chamber
|-
|Power Density
|2205 kW/kg
|}

==Introduction==
Since the early 1960s, hydrogen/oxygen rockets have been the practical pinnacle of high performance for space-borne maneuvers where you can afford its tradeoffs. Other higher performance engines, from nuclear thermal to the Fluorine or tripropellant mixtures get measured against Hydrolox. Lower performing combinations like methane or kerosene/oxygen had to justify lower performance for orbital applications by making up for some of hydrogen’s drawbacks.

The drawbacks for that performance are serious though: liquid hydrogen is one of the hardest of common cryogens, requiring extensive cooling and thermal management, and its low density makes for heavier tanks. Even so, some of the best-performing stages for interplanetary launches have been Hydrolox, among them the Centaur and the Saturn V’s S-IVB.

Hydrolox is well suited for near-future rockets that can’t or won’t use nuclear thermal, or for cislunar maneuvering vehicles where Hydrolox has a dry mass advantage over heavier nuclear options. It is poorly suited to long-duration spacecraft that need performance above 500 seconds and mission durations measured in years.

==Design and Function==
Hydrogen-oxygen engines are, like most chemical engines, fairly simple. You get some hydrogen, you get some oxygen, you pump them into a chamber, you introduce a spark or other ignition source, and steam comes out the back glowing with a very pretty clear flame, sometimes with varying minor coloration. They are essentially universally fuel-rich (since you want more hydrogen in the exhaust anyway) and hydrogen’s such a great coolant that there’s minimal temptation to use oxygen for regenerative cooling. Ablative or radiatively cooled nozzles exist, but regenerative cooling is pretty standard. The big decision is powering your pumps. The J-2 used a gas generator, having a secondary burner to power the turbopumps. The J-2S cut that, by tapping off a portion of the main chamber gas flow, and avoiding a separate combustion chamber. You can get more complex, like the multi-stage booster pumps the SSME used to get to nearly 3,000 psi (more than 200 atmospheres!). Alternately, you can go dead simple--the expander cycle cleverly manages to harvest all the pumping energy it needs for low-pressure vacuum engine operation from the hydrogen used to cool the chamber and nozzle bell, meaning the turbine inlet gas is in the realm of kitchen appliance, not even a car turbopump, and the rotor can be made of aluminum! Literally very cool.

==Performance / Capabilities / Applications==
The main benefit of Hydrolox is its performance: even a moderate pressure engine with a vacuum nozzle can break 440 seconds of specific impulse. No other engine type in present-day service can reach those levels of performance. At the same time, hydrogen is a ''fantastic'' coolant, more than an order of magnitude better than any other fuel, meaning it’s possible to build some incredibly clever engine cycles without problems like turbine temperature or propellant “coking” of hydrocarbons. As an example of the cleverness this allows, the turbine inlet temperature on the expander cycle RL-10 is below the boiling point of water, more like a ''kitchen appliance'' than the complex high-temperature turbomachinery needed in other fuels. Similar endurance and robustness was seen with the J-2 engines for Saturn. The ''Space Shuttle Decision'' by T A Heppenheirner quotes Rocketdyne's Paul Castenholz, one of the engineers managing J-2 development. "We never wore out an engine of the J-2 type. We could run it repeatedly; there was no erosion of the chamber, no damage to the turbine blades. If you looked at a J-2 after a hot firing, you would not see any difference from before that firing. The injectors always looked new; there was no erosion or corrosion on the injectors.” As Heppenheimer reports, this was inspired by examples like a single test engine which ran for 103 starts and 6.5 hours without overhaul. Higher performance Hydrolox engines like the Space Shuttle Main Engine (SSME) have a more complex reputation, though more recent tests of the AR-22 variant demonstrated 10 firings in 10 days with no major overhaul. With good performance from even relatively simple engines, it’s no wonder that rocket pioneers like Werner Von Braun were swayed to the Cult of Hydrolox from initial skepticism. For more than half a century, it’s been the propellant of choice for upper and sustainer stages for most American launch vehicles from Atlas to Delta to the Space Shuttle. For that reason, if you want performance with near-term engines, hydrolox has a lot to recommend it.

The downside of Hydrolox is the blasted hydrogen. Its performance comes from hydrogen’s low molecular mass--about the smallest anything can get and be legitimately called a molecule--but that also means it has to be incredibly cold to be liquid, at about 20 C colder than liquid oxygen. That’s troublesome for long duration storage, making “boiloff” the word of the day. Heat will get to your hydrogen any way it can, and before long, you won’t have any left. Even once kept liquid, the density is incredibly poor. That means heavier and physically larger tanks for the same performance. Even with hydrogen’s improved specific impulse, the Hydrolox Delta IV lower stage had to be five meters in diameter to lift the same payloads as the 3.8m Atlas V, since Hydrolox has about a third the mixed density of Kerolox.

==Worked Example(s)==
Planned to go here:

*RL-10 expander
*J-2S gas-gen
*SSME
*Maybe M-1 massive gas gen?

==Additional References==
GRAB SHUTTLE DECISION LINKS

Hydrolox Engine

2021-09-17T22:24:28Z

Highscore: Image framing.

{| style="float: right; border: 1px solid #BBB; margin: .46em 0 0 .2em;"
|- style="font-size: 86%;"
| style="vertical-align: top;" |[[File:Common Extensible Cryogenic Engine.jpg|right|300px]]
|}

When you need to get off of a habitable planet and want to be welcome to return, you need a high thrust rocket that doesn’t destroy real estate values. A hydrolox engine is one of the better choices for this.

A hydrolox engine is a chemical fueled rocket that uses cryogenic hydrogen and oxygen to produce thrust. It is one of the most efficient chemical rocket engines available.

{| class="wikitable floatright"
|+Engine Performance
|-
|Name
|Hydrogen-Oxygen Chemical Rocket
|-
|ISP or Exhaust Velocity
|459s <-> 4500 m/s (vacuum)
|-
|Thrust
|1,000,000 N
|-
|Efficiency
|98%
|-
|Drive Power
|2205 MW
|-
|T/W
|102
|-
|Energy Source (Fuel)
|Hydrogen + Oxygen at 6:1 ratio
|-
|Propellant
|Water exhaust
|-
|Reactor
|Combustion chamber
|-
|Power Density
|2205 kW/kg
|}

==Introduction==
Since the early 1960s, hydrogen/oxygen rockets have been the practical pinnacle of high performance for space-borne maneuvers where you can afford its tradeoffs. Other higher performance engines, from nuclear thermal to the Fluorine or tripropellant mixtures get measured against Hydrolox. Lower performing combinations like methane or kerosene/oxygen had to justify lower performance for orbital applications by making up for some of hydrogen’s drawbacks.

The drawbacks for that performance are serious though: liquid hydrogen is one of the hardest of common cryogens, requiring extensive cooling and thermal management, and its low density makes for heavier tanks. Even so, some of the best-performing stages for interplanetary launches have been Hydrolox, among them the Centaur and the Saturn V’s S-IVB.

Hydrolox is well suited for near-future rockets that can’t or won’t use nuclear thermal, or for cislunar maneuvering vehicles where Hydrolox has a dry mass advantage over heavier nuclear options. It is poorly suited to long-duration spacecraft that need performance above 500 seconds and mission durations measured in years.

==Design and Function==
Hydrogen-oxygen engines are, like most chemical engines, fairly simple. You get some hydrogen, you get some oxygen, you pump them into a chamber, you introduce a spark or other ignition source, and steam comes out the back glowing with a very pretty clear flame, sometimes with varying minor coloration. They are essentially universally fuel-rich (since you want more hydrogen in the exhaust anyway) and hydrogen’s such a great coolant that there’s minimal temptation to use oxygen for regenerative cooling. Ablative or radiatively cooled nozzles exist, but regenerative cooling is pretty standard. The big decision is powering your pumps. The J-2 used a gas generator, having a secondary burner to power the turbopumps. The J-2S cut that, by tapping off a portion of the main chamber gas flow, and avoiding a separate combustion chamber. You can get more complex, like the multi-stage booster pumps the SSME used to get to nearly 3,000 psi (more than 200 atmospheres!). Alternately, you can go dead simple--the expander cycle cleverly manages to harvest all the pumping energy it needs for low-pressure vacuum engine operation from the hydrogen used to cool the chamber and nozzle bell, meaning the turbine inlet gas is in the realm of kitchen appliance, not even a car turbopump, and the rotor can be made of aluminum! Literally very cool.

==Performance / Capabilities / Applications==
The main benefit of Hydrolox is its performance: even a moderate pressure engine with a vacuum nozzle can break 440 seconds of specific impulse. No other engine type in present-day service can reach those levels of performance. At the same time, hydrogen is a ''fantastic'' coolant, more than an order of magnitude better than any other fuel, meaning it’s possible to build some incredibly clever engine cycles without problems like turbine temperature or propellant “coking” of hydrocarbons. As an example of the cleverness this allows, the turbine inlet temperature on the expander cycle RL-10 is below the boiling point of water, more like a ''kitchen appliance'' than the complex high-temperature turbomachinery needed in other fuels. Similar endurance and robustness was seen with the J-2 engines for Saturn. The ''Space Shuttle Decision'' by T A Heppenheirner quotes Rocketdyne's Paul Castenholz, one of the engineers managing J-2 development. "We never wore out an engine of the J-2 type. We could run it repeatedly; there was no erosion of the chamber, no damage to the turbine blades. If you looked at a J-2 after a hot firing, you would not see any difference from before that firing. The injectors always looked new; there was no erosion or corrosion on the injectors.” As Heppenheimer reports, this was inspired by examples like a single test engine which ran for 103 starts and 6.5 hours without overhaul. Higher performance Hydrolox engines like the Space Shuttle Main Engine (SSME) have a more complex reputation, though more recent tests of the AR-22 variant demonstrated 10 firings in 10 days with no major overhaul. With good performance from even relatively simple engines, it’s no wonder that rocket pioneers like Werner Von Braun were swayed to the Cult of Hydrolox from initial skepticism. For more than half a century, it’s been the propellant of choice for upper and sustainer stages for most American launch vehicles from Atlas to Delta to the Space Shuttle. For that reason, if you want performance with near-term engines, hydrolox has a lot to recommend it.

The downside of Hydrolox is the blasted hydrogen. Its performance comes from hydrogen’s low molecular mass--about the smallest anything can get and be legitimately called a molecule--but that also means it has to be incredibly cold to be liquid, at about 20 C colder than liquid oxygen. That’s troublesome for long duration storage, making “boiloff” the word of the day. Heat will get to your hydrogen any way it can, and before long, you won’t have any left. Even once kept liquid, the density is incredibly poor. That means heavier and physically larger tanks for the same performance. Even with hydrogen’s improved specific impulse, the Hydrolox Delta IV lower stage had to be five meters in diameter to lift the same payloads as the 3.8m Atlas V, since Hydrolox has about a third the mixed density of Kerolox.

==Worked Example(s)==
Planned to go here:

*RL-10 expander
*J-2S gas-gen
*SSME
*Maybe M-1 massive gas gen?

==Additional References==
GRAB SHUTTLE DECISION LINKS

Hydrolox Engine

2021-09-17T22:07:58Z

Highscore:

[[File:Common Extensible Cryogenic Engine.jpg|right|300px]]

When you need to get off of a habitable planet and want to be welcome to return, you need a high thrust rocket that doesn’t destroy real estate values. A hydrolox engine is one of the better choices for this.

A hydrolox engine is a chemical fueled rocket that uses cryogenic hydrogen and oxygen to produce thrust. It is one of the most efficient chemical rocket engines available.

{| class="wikitable floatright"
|+Engine Performance
|-
|Name
|Hydrogen-Oxygen Chemical Rocket
|-
|ISP or Exhaust Velocity
|459s <-> 4500 m/s (vacuum)
|-
|Thrust
|1,000,000 N
|-
|Efficiency
|98%
|-
|Drive Power
|2205 MW
|-
|T/W
|102
|-
|Energy Source (Fuel)
|Hydrogen + Oxygen at 6:1 ratio
|-
|Propellant
|Water exhaust
|-
|Reactor
|Combustion chamber
|-
|Power Density
|2205 kW/kg
|}

==Introduction==
Since the early 1960s, hydrogen/oxygen rockets have been the practical pinnacle of high performance for space-borne maneuvers where you can afford its tradeoffs. Other higher performance engines, from nuclear thermal to the Fluorine or tripropellant mixtures get measured against Hydrolox. Lower performing combinations like methane or kerosene/oxygen had to justify lower performance for orbital applications by making up for some of hydrogen’s drawbacks.

The drawbacks for that performance are serious though: liquid hydrogen is one of the hardest of common cryogens, requiring extensive cooling and thermal management, and its low density makes for heavier tanks. Even so, some of the best-performing stages for interplanetary launches have been Hydrolox, among them the Centaur and the Saturn V’s S-IVB.

Hydrolox is well suited for near-future rockets that can’t or won’t use nuclear thermal, or for cislunar maneuvering vehicles where Hydrolox has a dry mass advantage over heavier nuclear options. It is poorly suited to long-duration spacecraft that need performance above 500 seconds and mission durations measured in years.

==Design and Function==
Hydrogen-oxygen engines are, like most chemical engines, fairly simple. You get some hydrogen, you get some oxygen, you pump them into a chamber, you introduce a spark or other ignition source, and steam comes out the back glowing with a very pretty clear flame, sometimes with varying minor coloration. They are essentially universally fuel-rich (since you want more hydrogen in the exhaust anyway) and hydrogen’s such a great coolant that there’s minimal temptation to use oxygen for regenerative cooling. Ablative or radiatively cooled nozzles exist, but regenerative cooling is pretty standard. The big decision is powering your pumps. The J-2 used a gas generator, having a secondary burner to power the turbopumps. The J-2S cut that, by tapping off a portion of the main chamber gas flow, and avoiding a separate combustion chamber. You can get more complex, like the multi-stage booster pumps the SSME used to get to nearly 3,000 psi (more than 200 atmospheres!). Alternately, you can go dead simple--the expander cycle cleverly manages to harvest all the pumping energy it needs for low-pressure vacuum engine operation from the hydrogen used to cool the chamber and nozzle bell, meaning the turbine inlet gas is in the realm of kitchen appliance, not even a car turbopump, and the rotor can be made of aluminum! Literally very cool.

==Performance / Capabilities / Applications==
The main benefit of Hydrolox is its performance: even a moderate pressure engine with a vacuum nozzle can break 440 seconds of specific impulse. No other engine type in present-day service can reach those levels of performance. At the same time, hydrogen is a ''fantastic'' coolant, more than an order of magnitude better than any other fuel, meaning it’s possible to build some incredibly clever engine cycles without problems like turbine temperature or propellant “coking” of hydrocarbons. As an example of the cleverness this allows, the turbine inlet temperature on the expander cycle RL-10 is below the boiling point of water, more like a ''kitchen appliance'' than the complex high-temperature turbomachinery needed in other fuels. Similar endurance and robustness was seen with the J-2 engines for Saturn. The ''Space Shuttle Decision'' by T A Heppenheirner quotes Rocketdyne's Paul Castenholz, one of the engineers managing J-2 development. "We never wore out an engine of the J-2 type. We could run it repeatedly; there was no erosion of the chamber, no damage to the turbine blades. If you looked at a J-2 after a hot firing, you would not see any difference from before that firing. The injectors always looked new; there was no erosion or corrosion on the injectors.” As Heppenheimer reports, this was inspired by examples like a single test engine which ran for 103 starts and 6.5 hours without overhaul. Higher performance Hydrolox engines like the Space Shuttle Main Engine (SSME) have a more complex reputation, though more recent tests of the AR-22 variant demonstrated 10 firings in 10 days with no major overhaul. With good performance from even relatively simple engines, it’s no wonder that rocket pioneers like Werner Von Braun were swayed to the Cult of Hydrolox from initial skepticism. For more than half a century, it’s been the propellant of choice for upper and sustainer stages for most American launch vehicles from Atlas to Delta to the Space Shuttle. For that reason, if you want performance with near-term engines, hydrolox has a lot to recommend it.

The downside of Hydrolox is the blasted hydrogen. Its performance comes from hydrogen’s low molecular mass--about the smallest anything can get and be legitimately called a molecule--but that also means it has to be incredibly cold to be liquid, at about 20 C colder than liquid oxygen. That’s troublesome for long duration storage, making “boiloff” the word of the day. Heat will get to your hydrogen any way it can, and before long, you won’t have any left. Even once kept liquid, the density is incredibly poor. That means heavier and physically larger tanks for the same performance. Even with hydrogen’s improved specific impulse, the Hydrolox Delta IV lower stage had to be five meters in diameter to lift the same payloads as the 3.8m Atlas V, since Hydrolox has about a third the mixed density of Kerolox.

==Worked Example(s)==
Planned to go here:

*RL-10 expander
*J-2S gas-gen
*SSME
*Maybe M-1 massive gas gen?

==Additional References==
GRAB SHUTTLE DECISION LINKS

Hydrolox Engine

2021-09-17T21:02:35Z

Highscore: Fixed first sentence.

[[File:Common Extensible Cryogenic Engine.jpg|left|300px]]

Since the early 1960s, hydrogen/oxygen rockets have been the practical pinnacle of high performance for space-borne maneuvers where you can afford its tradeoffs. Other higher performance engines, from nuclear thermal to the Fluorine or tripropellant mixtures get measured against Hydrolox. Lower performing combinations like methane or kerosene/oxygen had to justify lower performance for orbital applications by making up for some of hydrogen’s drawbacks.

The drawbacks for that performance are serious though: liquid hydrogen is one of the hardest of common cryogens, requiring extensive cooling and thermal management, and its low density makes for heavier tanks. Even so, some of the best-performing stages for interplanetary launches have been Hydrolox, among them the Centaur and the Saturn V’s S-IVB.

Hydrolox is well suited for near-future rockets that can’t or won’t use nuclear thermal, or for cislunar maneuvering vehicles where Hydrolox has a dry mass advantage over heavier nuclear options. It is poorly suited to long-duration spacecraft that need performance above 500 seconds and mission durations measured in years.

{| class="wikitable"
|+Engine Performance
|-
|Name
|Hydrogen-Oxygen Chemical Rocket
|-
|ISP or Exhaust Velocity
|459s <-> 4500 m/s (vacuum)
|-
|Thrust
|1,000,000 N
|-
|Efficiency
|98%
|-
|Drive Power
|2205 MW
|-
|T/W
|102
|-
|Energy Source (Fuel)
|Hydrogen + Oxygen at 6:1 ratio
|-
|Propellant
|Water exhaust
|-
|Reactor
|Combustion chamber
|-
|Power Density
|2205 kW/kg
|}

==Introduction==
Since the early 1960s, hydrogen/oxygen rockets have been the sin qua non of high performance for space-borne maneuvers where you can afford its tradeoffs. Other higher performance engines, from nuclear thermal to the spicier Fluorine or tripropellant mixtures get measured against Hydrolox. Lower performing combinations like methane or kerosene/oxygen had to justify lower performance for orbital applications by making up for some of hydrogen’s drawbacks.

Hydrolox is well suited for near-future rockets that can’t or won’t use nuclear thermal, or for inter-orbital transfer vehicles where Hydrolox has a dry mass advantage over heavier nuclear options. It tends to be associated with total burn durations measured in minutes for Hohmann least-ΔV trajectories. It is poorly suited to long-duration spacecraft that need performance above 500 seconds and mission durations measured in years.

==Design and Function==
Hydrogen-oxygen engines are, like most chemical engines, fairly simple. You get some hydrogen, you get some oxygen, you pump them into a chamber, you introduce a spark or other ignition source, and steam comes out the back glowing with a very pretty clear flame, sometimes with varying minor coloration. They are essentially universally fuel-rich (since you want more hydrogen in the exhaust anyway) and hydrogen’s such a great coolant that there’s minimal temptation to use oxygen for regenerative cooling. Ablative or radiatively cooled nozzles exist, but regenerative cooling is pretty standard. The big decision is powering your pumps. The J-2 used a gas generator, having a secondary burner to power the turbopumps. The J-2S cut that, by tapping off a portion of the main chamber gas flow, and avoiding a separate combustion chamber. You can get more complex, like the multi-stage booster pumps the SSME used to get to nearly 3,000 psi (more than 200 atmospheres!). Alternately, you can go dead simple--the expander cycle cleverly manages to harvest all the pumping energy it needs for low-pressure vacuum engine operation from the hydrogen used to cool the chamber and nozzle bell, meaning the turbine inlet gas is in the realm of kitchen appliance, not even a car turbopump, and the rotor can be made of aluminum! Literally very cool.

==Performance / Capabilities / Applications==
The main benefit of Hydrolox is its performance: even a moderate pressure engine with a vacuum nozzle can break 440 seconds of specific impulse. No other engine type in present-day service can reach those levels of performance. At the same time, hydrogen is a ''fantastic'' coolant, more than an order of magnitude better than any other fuel, meaning it’s possible to build some incredibly clever engine cycles without problems like turbine temperature or propellant “coking” of hydrocarbons. As an example of the cleverness this allows, the turbine inlet temperature on the expander cycle RL-10 is below the boiling point of water, more like a ''kitchen appliance'' than the complex high-temperature turbomachinery needed in other fuels. Similar endurance and robustness was seen with the J-2 engines for Saturn. The ''Space Shuttle Decision'' by T A Heppenheirner quotes Rocketdyne's Paul Castenholz, one of the engineers managing J-2 development. "We never wore out an engine of the J-2 type. We could run it repeatedly; there was no erosion of the chamber, no damage to the turbine blades. If you looked at a J-2 after a hot firing, you would not see any difference from before that firing. The injectors always looked new; there was no erosion or corrosion on the injectors.” As Heppenheimer reports, this was inspired by examples like a single test engine which ran for 103 starts and 6.5 hours without overhaul. Higher performance Hydrolox engines like the Space Shuttle Main Engine (SSME) have a more complex reputation, though more recent tests of the AR-22 variant demonstrated 10 firings in 10 days with no major overhaul. With good performance from even relatively simple engines, it’s no wonder that rocket pioneers like Werner Von Braun were swayed to the Cult of Hydrolox from initial skepticism. For more than half a century, it’s been the propellant of choice for upper and sustainer stages for most American launch vehicles from Atlas to Delta to the Space Shuttle. For that reason, if you want performance with near-term engines, hydrolox has a lot to recommend it.

The downside of Hydrolox is the blasted hydrogen. Its performance comes from hydrogen’s low molecular mass--about the smallest anything can get and be legitimately called a molecule--but that also means it has to be incredibly cold to be liquid, at about 20 C colder than liquid oxygen. That’s troublesome for long duration storage, making “boiloff” the word of the day. Heat will get to your hydrogen any way it can, and before long, you won’t have any left. Even once kept liquid, the density is incredibly poor. That means heavier and physically larger tanks for the same performance. Even with hydrogen’s improved specific impulse, the Hydrolox Delta IV lower stage had to be five meters in diameter to lift the same payloads as the 3.8m Atlas V, since Hydrolox has about a third the mixed density of Kerolox.

==Worked Example(s)==
Planned to go here:

*RL-10 expander
*J-2S gas-gen
*SSME
*Maybe M-1 massive gas gen?

==Additional References==
GRAB SHUTTLE DECISION LINKS