Burn criteria for generic fusion reactors in space
In space, nuclear fusion reactors would face other issues than on Earth. For instance, mass, reliability, and overall efficiency become by far more crucial.
Significant differences in the choice of materials, subsystems, and working principles of the fusion reactor as such can be expected. In this context it is helpful to identify which technologies would play a key role and need to be fostered. It appears to be reasonable to follow the approach of “option reduction”, i.e. we ask which technology will probably NOT play a role.
The ACT collaborates with the Institute of Space System (IRS) in Stuttgart, Germany , in deriving generalised burn criteria for generically designed nuclear fusion reactors in space. Those fusion reactors are initially modelled bottom up on a volumetric basis, i.e. without reactor shape, size, or type. The power balance considers significant gain and loss terms including varying surface properties, energy conversion systems, and a newly derived reactor design [2, 3].
Recent model improvements  concern mostly nominal as well as non-nominal ones. The former relates to side reactions between educts, the latter between products (and educts and products). Results show indicate that side reactions can negatively impact on burn conditions significantly. However, resolution of those effects also points towards another way to optimize propellant mixtures.
Of course, the model gives total (and subsystem) masses on basis of the chosen parameters once reactor shape, size, and type are defined. First results confirm on a much more elaborated level that D-T reactors as well as He3-He3 setups are no option due to the extremely high total masses as a consequence of the heat generated in the vessel.
 D. Petkow, R.A. Gabrielli, G. Herdrich, R. Laufer, H.-P. Roeser, Generalized Lawson criterion for magnetic fusion applications in space, Fusion Engineering and Design, Vol. 87, Jan 2012, pp. 30-38
 R. A. Gabrielli, D. Petkow, G. Herdrich, R. Laufer, H.-P. Roeser, Two Generic Concepts for Space Propulsion based on Thermal Nuclear Fusion, IAC-12-C4.7-C3.5.6 presented at the 63rd International Astronautical Congress, Naples, Italy, Oct 2012
 D. Petkow, G. Herdrich, R. Laufer, R. Gabrielli, O. Zeile, and H.-P. Roeser, Comparative investigation of fusion reactions for space propulsion applications, Transactions of Japan Society for Aeronautical and Space Sciences, Space Technology, Japan, Vol.7 (2009) Pb 59 – Pb 63
 Gabrielli, R. A., Herdrich, G., Roeser, H.-P., Haid, S., Heyn, M., and Petkow, D., Effect of Nuclear Side Reactions on Magnetic Fusion Reactors in Space, 48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit and 10th International Energy Conversion Engineering Conference, 29 Jul - 1 Aug, Atlanta, Georgia, 2012