The rumors are flying
in regards to the CEV's launch vehicle, and it appears that the trade space is wide open. Each of these choices has its drawbacks and advantages that are worth considering.Ares I:
This is the current baseline. It will also require a moderate amount of new development. The five-segment SRB must be put through its paces. An all-new second stage and the mostly-new J-2X engine still need to be developed and tested. It will heavily rely on the shuttle's standing army, and will recycle much of the shuttle infrastructure (except for the MLP, which will be built from scratch
for Ares I.)
Ares I will not be "simple" or "soon," despite the wishful thinking of ATK's public affairs department. It will probably be safer, though, as it only needs a single engine on the first stage (compared to three for the Delta IV Heavy and Atlas V Heavy.) It also reduces the loads placed on a crew during a launch abort due to its depressed trajectory.Delta IV Heavy or Atlas V Heavy:
This was the baseline during the O'Keefe days, and it makes the most sense in my mind. Both of these rockets are in production, both of them have been reliable thus far, and there's the benefit of competition/redundancy in that both rockets have similar capabilities.
NASA made a big deal about man-rating both rockets, but this wasn't a showstopper with Redstone, Atlas D, or Titan II. If the avionics that detect engine anomalies are linked to the capsule's escape system, it will provide the crew with a more reasonable chance of escape than the shuttle ever did.
In addition to the abort loads problems noted earlier, it should be noted that the Heavy EELV rockets will have three engines burning on the first stage, which is inherently less reliable than a single-engine. This shouldn't be a big problem. The Atlas had three engines, the Titan II had two, Saturn 1B had eight, and Saturn V and Shuttle had five.
Lastly, the structures and infrastructure for the EELV's will need some upgrades, like a service tower for the CEV after being mounted to the booster. This is still less than the upgrades needed for the Ares I's infrastructure. However, Lockheed Martin will need to complete the engineering required for the Atlas V Heavy, which was never finished due to a lack of orders from the Air Force. This isn't negligible, as demonstrated by the Delta IV Heavy demo.Ares V:
The editor at US Space News is very fond of talking about the option of mounting a CEV atop the Ares V, sans SRB's. I don't know how seriously this concept was studied. As it currently stands, Ares V is undergoing another trade study, examining a switch to kerosene-oxygen fuels burned in the RD-180 engine. This is driven by a desire to switch back to the 8.38 meter tooling for the Shuttle ET, rather than the 10 meter tooling of the Saturn V. It's also worth noting that two new "super transporters" will be built for Ares V to replace the existing crawlers that have been in use since 1968.
This option requires a lot of new engineering (even more than Ares I,) but it will be done anyways because the Ares V is baselined for use in the lunar missions in the 2017-2020 time period. While Ares V will never achieve the economies of scale that are possible with Delta or Atlas (operating at a maximum flight rate,) it will still be used for the lunar-Mars missions.
The biggest forseeable drawback to using the Ares V will be the time table for CEV missions. It's doubtful that Ares V will be able to support a CEV launch in 2012, and even 2014 seems unlikely. It all depends on when NASA can free up development funds for the Ares V, which were supposed to be a trickle until Ares I was complete.
My recommendation to NASA is to rely on Delta IV Heavy for the initial stages of CEV flight tests. The modifications can be accomplished inexpensively, they can run concurrently with Air Force launch needs, and they could inspire Boeing to build more Delta IV's for orbital space tourism. Once Ares V development ramps up, NASA should commit to adopting a version of it for CEV launch. The manned version of Delta IV Heavy will be phased out once Ares V enters service.
And what will become of Ares I? As I've said before, throw "the stick" to the dogs. Split Ares I's development budget into three pieces and use it to man-rate the Delta IV Heavy, accelerate CEV development for a first manned mission in 2012, and accelerate Ares V development.