In late 1957 Dornberger and Ehricke at Bell sketched out a civilian passenger version of BOMI. The original concept was for a straight-winged vehicle, but the design ended up with a delta wing after much iteration. The two-stage vehicle would launch vertically, with the upper stage on the back of the first stage. Identical engines would be used, firing in both stages for 130 seconds - five on the first stage and three on the second. After exhausting its propellant the lower stage would separate and glide back to base for refueling and reuse. The second stage would continue until shutting off at 46 km altitude. It would take the passenger glider 75 minutes to cover the 4800 km planned range.