ICAN-II was a proposed manned interplanetary spacecraft that used the Antimatter Catalyzed Micro-Fission (ACMF) engine as its main form of propulsion. The spacecraft was designed at Penn State University in the 1990s as a way to accomplish a manned mission to Mars. The proposed ACMF engine would require only 140 nanograms of antiprotons in conjunction with traditional fissionable fuel sources to allow a one-way transit time to Mars of 30 days. This is a considerable improvement over many other forms of propulsion that can be used for interplanetary missions, due to the high thrust-to-weight ratio and specific impulse of nuclear fuels. Some downsides to the design include the radiation hazards inherent to nuclear pulse propulsion as well as the limited availability of the antiprotons used to initialize the nuclear fission reaction. Even the small amounts required by the ACMF engine is equal to many years worth of the total antimatter production at the facilities CERN and Fermilab.