[Cincinatus]

"Collins said the most likely market for the heavy-lift Delta 4 outside the Air Force is NASA's new space exploration initiative, which is targeting manned missions to the moon by 2020 and eventually missions to Mars. "As NASA looks toward their exploration initiatives, here's a heavy-lift vehicle that will be flight proven," Collins said

The problem is that the Delta-IV, as cool as it is, only carries 13 metric tonnes to LEO (compare with 15 mT for the Shuttle). For even a simple human lunar mission, we'll need something on the order of 100-150 mT in LEO and we would need up to 500-1000 mT for a human Mars mission. That's a lot of Delta-IV's!

In contrast, the Saturn V could place 120 mT in LEO with one launch. We need to develop a real heavy lift vehicle; a Shuttle-derived heavy lift vehicle could put 50-70 mT in LEO using existing hardware and launch infrastructure.

[hopespringseternal]

The problem is that the Delta-IV, as cool as it is, only carries 13 metric tonnes to LEO (compare with 15 mT for the Shuttle). For even a simple human lunar mission, we'll need something on the order of 100-150 mT in LEO and we would need up to 500-1000 mT for a human Mars mission. That's a lot of Delta-IV's!

For any meaningful activity in space, expendables are a dead end. Besides that, expendables are just plain stupid, an example of continuing to do things wrong simply because you didn't have time to do it right the first time.

But the aerospace companies love expendables because they get to sell a whole new rocket for every mission. For that reason alone, letting them develop anything reusable is the fox guarding the henhouse.

[Paleo Conservative]

The problem is that the Delta-IV, as cool as it is, only carries 13 metric tonnes to LEO (compare with 15 mT for the Shuttle). For even a simple human lunar mission, we'll need something on the order of 100-150 mT in LEO and we would need up to 500-1000 mT for a human Mars mission. That's a lot of Delta-IV's!

There have been lots of proposals to build an unmanned cargo version of the space shuttle launch system. It could carry a mass equivalent to a loaded space shuttle and leave it in orbit. Such a system would be pretty cheap to develop, because it would used hardware that already exists.

A full-scale mock up of a Shuttle C concept sits at the Marshall Space Flight Center in Alabama in this 1989 image.

Boeing artist's concept for the Shuttle C, an unmanned cargo-only launch vehicle studied during the 1980s.

An artist's concept from the early 1980s shows a Shuttle-C cargo element in Earth orbit carrying the Galileo probe to Jupiter.

Cargo-Only Shuttle Still Possible in NASA's Future

[r9etb]

The problem is that the Delta-IV, as cool as it is, only carries 13 metric tonnes to LEO

Not to LEO -- to GTO. (The satellite's upper stage takes it the rest of the way to GEO.)