What missions could be done with Orion on Falcon Heavy?

Question

Orion is being developed in tandem with the SLS. But Falcon Heavy is scheduled to fly earlier, early 2015, and be cheaper. So I wonder what kind of missions Orion could do with FH. Could it for example do a crewed flight around the Moon?

The first test launch with Orion is currently planned for December 2014, atop a Delta IV Heavy. According to Wikipedia articles about Delta IV and Falcon Heavy, the latter will be able to lift twice as much to LEO and 50% more to GEO. Falcon 9 is underway to be human rated, and I would think that the technical similarities should mean that the FH is human rated soon after that.

Is there some show stopper for FH+Orion?

Is there any reason to launch Orion instead of Dragon?

Answer 1

SpaceX gives the LEO payload of Falcon Heavy as 63.8 tons (presumably in fully expendable mode).

Orion, fully loaded with propellant, is about 26 tons. So LEO flight is doable, possibly even with booster recovery, but probably not with 3-core recovery.

I can't find specs for the ICPS stage that's going to be used with SLS, but it's a modification of the DCSS-5 upper stage used with Delta IV:

Those modifications include lengthening the liquid hydrogen tank, adding hydrazine bottles for attitude control and making some minor avionics changes to meet the design parameters and performance characteristics as needed by NASA to meet the flight objectives.

Falcon Heavy can lift a DCSS-5 stacked with Orion to LEO, from from which point the DCSS can provide about 2960m/s of delta-v beyond LEO, which is not quite enough to reach the moon. Orion could use its service module to do the rest, but that would leave it with insufficient fuel to enter and exit lunar orbit, so that would be a flyby mission. (ICPS on the Block 1 SLS is supposed to put Orion on a very eccentric lunar orbit for EM-1; it's unclear to me if that configuration is capable of reaching low lunar orbit and returning, but that larger EUS for Block 1B certainly will be able to.)

Without a hydrogen-fueled upper stage, Falcon Heavy second stage could put the Orion into a GTO, but again Orion wouldn't have quite enough delta-v to both circularize there and return to Earth.

At this point, it's a toss-up whether a suitable upper stage could be adapted for use with a human-rated Falcon Heavy before SLS block 1 is flying.

Meanwhile, Delta IV Heavy can put Orion into LEO for development and shakedown flights, making it analogous to the Saturn 1B to the SLS's Saturn V.

Answer 2

The problem is that Orion + Service Module is very heavy. On the order of 21,000 Kilos.

This is too heavy for anything but a Delta 4-Heavy or Falcon Heavy. (SLS probably won't ever really exist).

It looks like the Falcon Heavy with cross feed offers 53,000 kilos to LEO. (Cannot find the non-cross feed numbers, since that is a better representation of initial performance). However with the coming updates in summer of 2015 to the core Falcon 9 first stage (slight stretch, Merlin 1D's at 100% not the current 85% thrust level, propellant chilling for densificiation) the expectation is to get to 50,000 kg range without cross feed. As an update in 2017, SpaceX announced that in full expendable mode, no crossfeed, Falcon Heavy after all the Falcon 9 single stick, and Merlin 1D improvements was on track for 64,000lb to LEO.

The upper stage, being a Merlin 1D is probably an issue as the ISP is not wonderful. (Great ISP of 340 for LOX/RP1 but not a great ISP for an upperstage. RL-10 has much lower thrust but better ISP by a long shot, in the mid 400 range). Thus a third stage (or else a larger Service Module) would be wanted for further out missions. With SpaceX developing the Raptor LOX/CH4 engine, it would not be inconceivable for them to construct a higher energy upper stage one day. There are many costs involved in doing that which would make it unlikely, but still a possibility if the need really arose.

Answer 3

Technically, yes. It fits the fairing and lift capacity. The reality, no. The Falcon Heavy is not rated for human transport and SpaceX announced they don't want to go through that certification process.