9 ms·

You are completely missing a point of this. It is a propulsion system, not a power generating one. Chemical rocket engine doesn't generate any electrical power

You are completely missing a point of this. It is a propulsion system, not a power generating one. Chemical rocket engine doesn't generate any electrical power either. Main factors in propulsion is specific impulse and reaction mass and this idea promises a huge impulse - basically once in orbit, it could ferry between Earth and anywhere-where-solar-power-is-sufficient because it doesn't need tonnes of fuel, only relatively small load of pellets would get the job done. Of course there is the issue of getting it and it's payload into orbit, but I'd say Skylon will take care of that

lutusp 14y ago
> You are completely missing a point of this. It is a propulsion system, not a power generating one. To represent an advantage over an ion thruster, it must be both. And the NASA documents that describe the project specify a fusion power gain > 1: http://www.nasa.gov/directorates/spacetech/niac/2012_phaseII_fellows_slough.html http://www.nasa.gov/directorates/spacetech/niac/2012_phaseII... Quote: "an in-depth analysis of the rocket design and spacecraft integration as well as mission architectures enabled by the FDR need to be performed. Fulfilling these three elements form the major tasks to be completed in the proposed Phase II study. A subscale, laboratory liner compression test facility will be assembled with sufficient liner kinetic energy (~ 0.5 MJ) to reach fusion breakeven conditions." The phrase "fusion breakeven conditions" means the reaction must produce more power than is requires to start it. This is a requirement to justify the project over other approaches.
- acomar 14y ago
  As other posters have noted, ion thrusters don't generate very much thrust.
- emp_zealoth 14y ago
  It is not even supposed to be used to generate electrical power. Citing from the site itself: "Virtually all of the radiant, neutron and particle energy from the plasma is absorbed by the encapsulating, metal blanket thereby isolating the spacecraft from the fusion process and eliminating the need for large radiator mass" No radiators implicitly mean no electricity generation, because it creates waste heat that has to be utilised. http://en.wikipedia.org/wiki/Fusion_rocket http://en.wikipedia.org/wiki/Fusion_rocket Proposed concept is a direct drive, and it actually claims they fixed the problem with neutrons (they are caught by the compressing metal) As for breakeven conditions they merely state that the power that the fusion generates must be at least equal to power used to start/sustain it. http://en.wikipedia.org/wiki/Fusion_energy_gain_factor http://en.wikipedia.org/wiki/Fusion_energy_gain_factor Theoretical limits of efficiency of heat engine is around 70-80% (roughly) http://en.wikipedia.org/wiki/Thermal_efficiency http://en.wikipedia.org/wiki/Thermal_efficiency and you have to use those to convert heat generated in controlled fusion into electricity. To actually achieve net power generation in a power plant, you have to generate a lot more heat that electricity, while for propulsion you merely care about actual raw (so to speak) power. Ion thrusters have their own issues, while their ISP is considerably better than chemical rockets, maximum thrust is abysmal, but it is hard to argue about that due to the lack of data on FDR. However, with ion thrusters there are other issues (for example:wear, charge imbalance)
  - lutusp 14y ago
    > As for breakeven conditions they merely state that the power that the fusion generates must be at least equal to power used to start/sustain it. Yes, but (apart from stars and weapons) this has never been achieved anywhere, ever. This is a big issue, bigger than most people realize. https://en.wikipedia.org/wiki/Fusion_power https://en.wikipedia.org/wiki/Fusion_power Quote: "As of July 2010, the largest experiment by means of magnetic confinement has been the Joint European Torus (JET). In 1997, JET produced a peak of 16.1 megawatts (21,600 hp) of fusion power (65% of input power) ... Fusion powered electricity generation was initially believed to be readily achievable, as fission power had been. However, the extreme requirements for continuous reactions and plasma containment led to projections being extended by several decades. In 2010, more than 60 years after the first attempts, commercial power production was still believed to be unlikely before 2050." My point is if this project creates a net gain > 1, it will address a lot more than the problem of getting to Mars.
schiffern 14y ago
s/Skylon/SpaceX/
- vectorjohn 14y ago
  That's what I was thinking. They're actually already doing something. On the other hand, their not-yet-developed Falcon Heavy can "only" lift 53 tons, about a third of the weight of FDR. Hopefully they can come up with a way to lift it in stages, or we still need a bigger rocket.

lutusp 14y ago

> You are completely missing a point of this. It is a propulsion system, not a power generating one. To represent an advantage over an ion thruster, it must be both. And the NASA documents that describe the project specify a fusion power gain > 1: http://www.nasa.gov/directorates/spacetech/niac/2012_phaseII_fellows_slough.html http://www.nasa.gov/directorates/spacetech/niac/2012_phaseII... Quote: "an in-depth analysis of the rocket design and spacecraft integration as well as mission architectures enabled by the FDR need to be performed. Fulfilling these three elements form the major tasks to be completed in the proposed Phase II study. A subscale, laboratory liner compression test facility will be assembled with sufficient liner kinetic energy (~ 0.5 MJ) to reach fusion breakeven conditions." The phrase "fusion breakeven conditions" means the reaction must produce more power than is requires to start it. This is a requirement to justify the project over other approaches.

acomar 14y ago
As other posters have noted, ion thrusters don't generate very much thrust.
emp_zealoth 14y ago
It is not even supposed to be used to generate electrical power. Citing from the site itself: "Virtually all of the radiant, neutron and particle energy from the plasma is absorbed by the encapsulating, metal blanket thereby isolating the spacecraft from the fusion process and eliminating the need for large radiator mass" No radiators implicitly mean no electricity generation, because it creates waste heat that has to be utilised. http://en.wikipedia.org/wiki/Fusion_rocket http://en.wikipedia.org/wiki/Fusion_rocket Proposed concept is a direct drive, and it actually claims they fixed the problem with neutrons (they are caught by the compressing metal) As for breakeven conditions they merely state that the power that the fusion generates must be at least equal to power used to start/sustain it. http://en.wikipedia.org/wiki/Fusion_energy_gain_factor http://en.wikipedia.org/wiki/Fusion_energy_gain_factor Theoretical limits of efficiency of heat engine is around 70-80% (roughly) http://en.wikipedia.org/wiki/Thermal_efficiency http://en.wikipedia.org/wiki/Thermal_efficiency and you have to use those to convert heat generated in controlled fusion into electricity. To actually achieve net power generation in a power plant, you have to generate a lot more heat that electricity, while for propulsion you merely care about actual raw (so to speak) power. Ion thrusters have their own issues, while their ISP is considerably better than chemical rockets, maximum thrust is abysmal, but it is hard to argue about that due to the lack of data on FDR. However, with ion thrusters there are other issues (for example:wear, charge imbalance)
- lutusp 14y ago
  > As for breakeven conditions they merely state that the power that the fusion generates must be at least equal to power used to start/sustain it. Yes, but (apart from stars and weapons) this has never been achieved anywhere, ever. This is a big issue, bigger than most people realize. https://en.wikipedia.org/wiki/Fusion_power https://en.wikipedia.org/wiki/Fusion_power Quote: "As of July 2010, the largest experiment by means of magnetic confinement has been the Joint European Torus (JET). In 1997, JET produced a peak of 16.1 megawatts (21,600 hp) of fusion power (65% of input power) ... Fusion powered electricity generation was initially believed to be readily achievable, as fission power had been. However, the extreme requirements for continuous reactions and plasma containment led to projections being extended by several decades. In 2010, more than 60 years after the first attempts, commercial power production was still believed to be unlikely before 2050." My point is if this project creates a net gain > 1, it will address a lot more than the problem of getting to Mars.

schiffern 14y ago

s/Skylon/SpaceX/

vectorjohn 14y ago
That's what I was thinking. They're actually already doing something. On the other hand, their not-yet-developed Falcon Heavy can "only" lift 53 tons, about a third of the weight of FDR. Hopefully they can come up with a way to lift it in stages, or we still need a bigger rocket.