For Oribital's Pegasus, about 25% (solid fuel) engines, and 25% support labour [1]. http://www.mitre.org/sites/default/files/pdf/kane_mls.pdf http://www.mitre.

For Oribital's Pegasus, about 25% (solid fuel) engines, and 25% support labour [1]. http://www.mitre.org/sites/default/files/pdf/kane_mls.pdf http://www.mitre.org/sites/default/files/pdf/kane_mls.pdf Page 7 (Rest of that paper is also an awesome read about the problem space. Although it was from relatively early in Falcon 1 development... Pegasus has gone from alone in its class, to having competition, back to being alone).