No separate pressurising system was included; the tanks were simply left with an ullage space, which was then filled with gas to a few hundred psi.

Because of the narrow tubing, the bulkheads between sections could be simple plates, instead of domes like virtually all other rocket stages.

The use of ablative cooling, high-pressure steel construction, and large "empty" spaces meant that a CRPU was heavy, with relatively low performance.

Meanwhile, the low cost of each CRPU, after the economies of scale gained by producing hundreds or possibly thousands of them per year, would have still left the vehicle cheaper than its contemporaries.

[citation needed] Larger vehicles and capacities would be achieved with greater numbers of CRPUs, possibly including several hundred per flight for a heavy launcher.

The company forecast that CRPUs would eventually be so cheap, recovering and refurbishing a launcher would be no better than simply building more units.

Small, 4-unit vehicles were built and tested in Shaba North, Zaire and Seba Oasis, Libya, where heights of 20 to 50 kilometres were reached.

After really going over the trades and details with Lutz, I am quite convinced that this is the lowest development cost route to significant orbital capability.

The individual modules are less complicated than our current vehicles, and I am becoming more and more fond of high production methods over hand crafter prototypes."

-- June 2006 Armadillo Aerospace Update[7]ARCA Space Corporation have also been inspired by the OTRAG rocket for the design of the EcoRocket Heavy.