24 thoughts on “Reusing Falcon Heavy”

  1. Depends on what is being optimized. The only performance number that matters is $/kg. LOX and Kerosene are cheap. The closer you can approach that cost as a limit; the more flights over which you can amortize the cost of the vehicle; the more reliability you can build in so that turn around approaches that of jet airliners, the better off we are on settling Mars.

    Nothing you haven’t said yourself Rand…

  2. Interesting, given that SpaceX itself has indicated that FH center core RTLS is highly problematic.

    As for the boosters, if they’re using crossfeed, sending those back to the launch site will be far less a performance hit than a F9 launch (they’ll sep at a lower velocity, and at an earlier point in the proflile, than a F9 staging). IMHO, RTLS for the FH boosters is viable – unless you’re on a max capacity mission.

    The center core is another matter entirely. I think they could recover it with their ASDS (barge), but not RTLS – not without an enormous payload hit.

    As for the accuracy of the video… I do question why they chose to show RTLS for the center core. That makes no sense to me.

    BTW, I’m a big fan of the promise of FH, because I have long felt as Dale, above, does; that dollars per pound to orbit is the most important number in spaceflight.

  3. Bringing the side cores back to the pad, on the other hand, seems to be a very good idea, since they stage at lower delta-V than the first stage of a Falcon 9.

    1. That would essentially require it to achieve orbital velocity with the center core. Even if they could go that fast (actual speed at staging will be less than half of that speed), they’d have all the issues of reentry from orbit.

    2. I’ve heard that the Falcon 9 first stage could make SSTO with a (smaller) payload. Given that kind of mass ratio, a relevant question is what kind of payload a Falcon heavy could deliver to a minimal orbit without a second stage burn.

      Stage recovery from orbit is another issue. Transpiration type cooling of the engines?

  5. As I suggested a while back, if they shift launches to South Texas, they could do landings in Florida if they don’t want to fly all the way back. Then barge or fly back back from there.

    1. I did some rough calculations with a missile range spreadsheet. To cover the roughly 900 miles from Brownsville to the Florida coast on a ballistic trajectory, the stage would need to be going a bit over 9,000 MPH. If that number is accurate, that’s likely quite a bit faster than what the stage is going at separation. It may also be faster than what the current structures can withstand in aerodynamic and heat loads.

  7. SpaceX makes some sweet videos, and kudos to them for the last landing attempt, and I hope they score with the next one.

    But I can’t help wondering what our risk-averse Eastern Range folks have to say about INCOMING boosters. I admit I’ve been trying to watch for a discussion about this issue, but I must be missing something. Are they OK with just the FTS as protection from a wayward return trajectory? Would the RTLS site exclusion area be necessarily larger than the launch area? Just haven’t seen much on this.

    1. Those “returning boosters” are mostly depleted of propellant, and don’t pose much of a risk. Certainly no more than an airliner, and a lot less if the airliner is fully fueled.

      1. As can be seen in the recent SpaceX video of the F9R CRS 5 recovery attempt, crash and explosion. Not nearly as dramatic as the Orbital oops at Wallops.

  8. I hadn’t thought of it, but the two boosters themselves are about the only way to get great video of a returning booster, so I hope they add a camera system so each booster can track and record its mate.

    1. I hope so too. I found the ELVIS videos to be one of the most valuable tools for engineering data. The ground tracking cameras are nice, but necessarily to wide angle and far away to provide the details needed. If the Mark I eyeball is still one of the best instruments for inspecting things, then lightweight camera systems that can be placed almost anywhere are the next best. Another perfect example is David Spain’s comment above, the camera on the barge made it clear just how dramatic, or not so much, the failed landing was.

    1. Won’t a launch from South Texas have a ground track that pretty much goes right over the extreme eastern tip of Brazil? Is that far enough downrange to make center core recovery possible on land with a reasonable sized payload?

      Should we be looking for signs of Elon shopping for real estate near Fortaleza or Recife?

      1. It would if launched through the Straits of Yucatan, which is a possibility that has been mentioned. However, and only AFAIK, the usual guess is that they’ll launch over the Straits of Florida, a more northerly trajectory.

        However, Brazil is far from Texas, and to reach it the center core would have to be moving pretty fast — cf Larry J’s comment upthread about recovery in Florida.

  10. Maybe the video left out the part where the center core landed on a barge, refueled before then flying back to the cape.

  11. On the other hand. If you build out 3 more ASDSes for West Coast use. I’m not convinced that an RTLS is such a compelling win over a sea return option. It’s rocket fuel vs ships diesel. You can waste a little ships diesel, esp. If you can tow two ASDSes with a single tug. Or maybe use larger fuel tanks on the ASDS and let it power itself home. At least burning ships diesel don’t cost payload nor force trajectory trade offs.

  12. What struck me the most about the video (the first of such videos I’ve watched), was just how much it put into perspective how significant of a feat it is to return the boosters to the launch site. The flip, retro-burn, flip, re-entry burn, land sequence is a dance that is so surreal to see in a simulated video, it’s hard to believe or imagine that it’s been happening that way in reality for the last bunch of flights of the Falcon9, but it’s also very reassuring to see that something that seemingly complicated is being accomplished on a regular basis.

    I agree about the Mk I Eyeball, as well. Actual video of this sequence in action would likely fascinate many people and put to rest any notion that something like the crash on the ASDS was a “failed mission”, when it was simply a failed landing after so many other complex things going right.

  13. My understanding of the F9 return to Barge and landing is that the fuel used to do that is obtained by reducing payload. Is that correct?

    If so, is that also the mechanism of obtaining fuel for FH returns?

    thanks

  14. “If so, is that also the mechanism of obtaining fuel for FH returns?”

    I’m sure that it is. Just remember that fuel is cheap, structure is expensive.

    If John Schilling’s numbers are correct, I still think even a 75% reduction in payload would be worth it if it allowed for repeated reuse of the FH cores. Three cores’ worth of fuel is still much less expensive than one cores’ worth of hardware (the payload number for FH with flyback of all cores is equal to that of an F9 with no recovery).

    And if the cost to orbit is significantly less with full recovery of all cores, I suspect satellite/spaceship designers will find it worth their while to modularize their craft (in-orbit fueling and/or assembly).

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