"Dholmes" wrote in message
...
The solids on Delta are very underpowered. The ones on Atlas have over
twice
as much fuel.
Delta 2 uses up to 9 I can see no reason Delta 4 could not as well.
A pair of reusable solids about half the size of the shuttles for both
Atlas
and Delta could prove interesting.
The question is would it be cheaper.
Delta's main engine makes a killer second stage for a very large rocket.
Another option would be to use slightly shortened Deltas, 3 at launch and
one as a second stage. but kerosene do seem to work best as a booster
stage.

Delta IV was not structurally designed to handle 9 solids, and can't be
refitted for more than 4 without major redesign. One "small" obstacle is the
pair of T-0 umbilical panels that occupy the north side of the vehicle.
Boeing could probably show you some studies that indicate the market didn't
require any more than 4 solids (I'm not saying they're correct, just that
they no doubt have them).

Massively clustered Delta IV CBDs with propellant cross-feed
would be technically possible, and get into heavy-lift range with
a relatively affordable mass-produced modular design.

But veeery high risk. Cross-feed propellants has been looked at by at least
one of the EELV manufacturers.

-Colonel K