Why not Vulcan Heavy?

[Kibble]

It seems to me that developing a three-core Vulcan Heavy launch vehicle topped by Centaur could be easier than developing ACES, and would also give better performance! After all, the Delta IV 5 meter cores are already built for that, and so is all the launch infrastructure.

[CptRichardson]

It seems to me that developing a three-core Vulcan Heavy launch vehicle topped by Centaur could be easier than developing ACES, and would also give better performance! After all, the Delta IV 5 meter cores are already built for that, and so is all the launch infrastructure.

Well, why not go for a five-core Vulcan Heavy?

[Kryten]

It seems to me that developing a three-core Vulcan Heavy launch vehicle topped by Centaur could be easier than developing ACES, and would also give better performance! After all, the Delta IV 5 meter cores are already built for that, and so is all the launch infrastructure.

ACES is designed for distributed launch architecture, Centaur is not. Also, it would likely be much more expensive.

[fredinno]

The extra cores would probably generate too much performance compared to ACES. What about designing Vulcan to use 10x SRB, making some of them air-startable (like on Delta II, so that only 2 fire at any one time (3 for 1st SRB burn if there is an odd number of SRBs)? Keep the core throttled down to increase its burn time and lower TWR (assuming BE-4 is throttleable.) Later upgrades could use up to 6x Delta II Core LRBs (since the tooling already exists), and then a Vulcan Heavy configuration with even greater capability as a 'final evolution' (possibly with propellant cross-feed)

- - - Updated - - -

What is a distributed launch structure?

Also, I'm not so sure adding 2 more RL-10s and a larger upper stage would be less expensive than other upgrade options- RL-10s are expensive as ..... Though ACES does not need to use RL-10s, not doing so would also add to the R+D cost. I prefer MOAR! BOOSTERS!

- - - Updated - - -

That could be a "Phase 2" upgrade....

[Kryten]

Later upgrades could use up to 6x Delta II Core LRBs (since the tooling already exists)

RS-27 production was shut down years ago; even if AR managed to scrape together the means to restart it, you'd have to replumb the launchpad to allow two separate booster fuels.

What is a distributed launch structure?

Use of depots.

Also, I'm not so sure adding 2 more RL-10s and a larger upper stage would be less expensive than other upgrade options- RL-10s are expensive as ..... Though ACES does not need to use RL-10s, not doing so would also add to the R+D cost. I prefer MOAR! BOOSTERS!

The other options are BE-3U, which Blue are developing anyway, and a new XCOR engine ULA have been funding for a considerable time already. Even if they aren't chosen, RL-10 aren't 'expensive as ....' enough to out-cash an entire booster stage.

[fredinno]

Well, if they use the Atlas pads for Vulcan, the RP-1/LOX infrastructure will already exist anyways... (Likely, since the Vulcan is more Atlas than Delta Derived...)

Either way, other LRB options exist, like Atlas V Core boosters (but would leave the problem of Russian Engines...) or a shorter Vulcan Core.

Edited September 2, 2015 by fredinno

[Kibble]

RS-27 production was shut down years ago

It was? How many RS27s are left?

[Kryten]

It was? How many RS27s are left?

Excluding those already reserved for launches, one.