Page "Mars Direct" Paragraph 39

A modified proposal, " Mars for Less ", was developed by Grant Bonin, and has been adopted as the design reference mission for a new umbrella group of advocates, the MarsDrive consortium.

The design retains most of the essential features of Mars Direct, but uses multiple medium-lift rocket launchers that are commercially available today ( such as the Ariane V or the Delta rocket ) to launch the crew vehicles, and their propulsion, separately, and mate them in orbit.

By doing so, the multi-billion dollar development cost of a new launch vehicle is avoided.

However, the orbital rendezvous required, while potentially reducing cost, has inherent risks.