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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?

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  • $\begingroup$ @codesparkle Concerning the edit, I've seen F9H being used for Falcon Heavy. Compare with "Delta IV Heavy". Heavy in practice means using two common core boosters. The 9 stands for 9 rocket engines in each core. $\endgroup$ – LocalFluff Aug 26 '14 at 12:59
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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.

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  • $\begingroup$ Worth noting that Orion isn’t intended to ever pursue LLO, so that’s not really a shortcoming; Gateway makes it unnecessary and is energetically favorable - on the downside this is why every lander design is going to have to incorporate a transfer capability from NRHO->LLO->surface, and then back to NRHO closest approach. $\endgroup$ – JPattarini Jul 1 at 3:39
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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.

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  • $\begingroup$ There's some debate on whether cross-feed will ever happen. reddit.com/r/spacex/comments/31tp4r/… $\endgroup$ – ceejayoz Apr 21 '15 at 20:49
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    $\begingroup$ I agree on the upper stage ISP problem, but I betcha SLS will exist. $\endgroup$ – Rikki-Tikki-Tavi Apr 22 '15 at 1:01
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    $\begingroup$ @Rikki-Tikki-Tavi Allow me to qualify "Really exist" as, launch more than twice or three times. One launch in 2018 (still slipping), next launch in 2021 manned, then next is 2023 or 2025? You call that really existing? I would bet by 2023 that SpaceX (or somebody) will be launching something as big as SLS for a heck of a lot less than NASA. $\endgroup$ – geoffc Apr 22 '15 at 1:07
  • $\begingroup$ Non-crossfeed is 45,000kg, even with M1D+ $\endgroup$ – ReactingToAngularVues Apr 22 '15 at 2:20
  • $\begingroup$ Delta IV Heavy launched Orion just to have it crash back down again in order to test its heat shield. Could it have put Orion in LEO? How far could a Falcon Heavy launch an Orion? To Lunar orbit? To a Lagrange point? $\endgroup$ – LocalFluff Apr 19 '17 at 10:35
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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.

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  • $\begingroup$ Considering the common heritage with Falcon 9, I'm sure that the certification wouldn't cost much. If NASA wanted SpaceX to human certify Falcon Heavy, and paid for it, SpaceX would make it happen. $\endgroup$ – PearsonArtPhoto Jun 30 at 21:51

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