The Return of FalconV

In the last several weeks two companies have landed boosters that have been to space. The boost back RTLS with VTVL is now established as a demonstrated capability. What’s next?

The boost back gets the upper stage(s) to space with some horizontal velocity and returns the booster to the original launch site and has a substantial performance penalty in return for this capability. An expended lower stage of the same size puts considerably more mass in orbit, though at considerably higher cost.

I would suggest that a logical next step would be for the various companies to do a parallel staging of a full first stage booster with RTLS capability along with a derated first stage booster with the upper stage on to of the derated one.

falcon 5A Falcon Five Nine configuration is an obvious early entrant. The fourteen engines burning at launch is just over half the thrust of the FalconH in development. With cross feed, the Nine will stage at a similar velocity as last Mondays’ launch and RTLS. The Five continues on until upper stage separates and then tries to reach a seaborne recovery. The upper should have a payload of about half that of the FalconH. This is 25-29 tons of payload in the DeltaIV Heavy class.

This would give a capability above that of the expendable Falcon9 for the expenditure of  six Merlins instead of ten. The possibility of recovering the Five still exists and a development path similar to that taken with the Nine could be pursued. This concept is to bridge the gap between the light payload of an RTLS Falcon9, and the large payload of the FalconH.

Since capabilities spread through any competitive industry, we could expect to see Vulcan Two One, Antaries Two One, and a Blue Origin entrant within the next several years. Not to mention the other configurations by various other companies.

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johnhare

johnhare

I do construction for a living and aerospace as an occasional hobby. I am an inventor and a bit of an entrepreneur. I've been self employed since the 1980s and working in concrete since the 1970s. When I grow up, I want to work with rockets and spacecraft. I did a stupid rocket trick a few decades back and decided not to try another hot fire without adult supervision. Haven't located much of that as we are all big kids when working with our passions.
johnhare

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21 Responses to The Return of FalconV

  1. Pingback: Just Space News / The Return of FalconV

  2. Paul D. says:

    Overshadowed in the excitement of the stage 1 recovery was the use of subcooled propellants in this launch. As I understand it, the LOX was chilled to 67K and the RP-1 to -5 C. I think this was the first use of subcooled LOX in a launch to orbit.

    I wonder what the best hydrocarbon mix will be for the methane-fueled launcher SpaceX is building, if they want to subcool it. Methane’s freezing point can be depressed by adding other hydrocarbons (ethane and/or propane, for example). (See, for example, US Patent 3380250, April 1968.)

  3. johnhare johnhare says:

    That is part of my reasoning that they had to go to extreme measures to get an RTLS even with a light payload. With an additional staging event, it might be a bit easier to make that maneuver.

  4. Christoffer says:

    Or why not launch in Texas and recover in Florida. The boost back will be changed to a minute inclination adjustment, propellant will be needed mainly for reentry and landing reducing the mass to orbit penalty.

  5. johnhare john hare says:

    That may eventually be used for some missions that have the right inclination and payload. The problem that has come up when discussing it it that there are a very limited number of orbital inclinations available if using one recovery site. Unless using Canaveral, it would entail developing and building one or several recovery sites that might see limited use. The IIP (Instantaneous Impact Point) would be over land during a good part of the flight if going for Canaveral or another east coast site. And so on. It might happen eventually, but probably not soon.

    An alternative is a recovery barge in the Gulf to capture the various inclinations and launch energies, but that begs the question of why is the Gulf better than the Atlantic? IMO the sea state might be better, or jack up barges might be more feasible, but neither of these are slam dunks.

  6. Martin K says:

    That seems to be pretty much what the Falcon Heavy is already sized for. According to spaceflight101.com its 53T to LEO figure already assumes all of the current set of upgrades. I had wondered why SpaceX was going for such a large payload, since there is no existing or near-term market for that mass. Obviously, in the long term 53T is aimed at Dragon-to-Mars, but I couldn’t see how he could justify it commercially in the here and now.

    However, when launched in max-reuse min-cost mode (2 boosters back to land, core to barge or possibly land, no crossfeed) you end up with that magic ~25T payload figure. Just enough to match ALL of its competitors, for a fraction of their costs. Crazy like a fox.

  7. johnhare john hare says:

    Accepting your points as accurate, this concept would then be for the 10-13 ton range. It all depends on the economics of course. Quoting someone from years ago, “The rocket equation makes for a good start, but the economics equation makes for a better finish.”

  8. Martin K says:

    Musk is on record as wanting to minimise the number of different vehicles they have to design, build, certify, update, etc. Both F9 and FH are assembled from the same three components – the F9/FH booster, the reinforced FH core and the common 2nd stage.

    You would be adding two more to this list, as well as brand new problems such as asymmetric thrust between the 5- and 9-engine parallel boosters, weight shift between the two sides (your cross-fed 9-engine stage drops from 400T to maybe 50T at separation or 25T dry).

    If you really, really want some sort of new high-medium-class launcher, you might be better using two short F5-type boosters on a standard FH core and 2nd stage. But don’t forget that SpaceX has just upgraded the F9 to 17T LEO. Surely that adequately covers the 10-13T range assuming land or barge recovery, and the full 17T with none.

  9. johnhare johnhare says:

    If F9 were capable of 10-13 tons with recovery, then F9H would be at 30-40 tons with recovery. Also, I only added the F5 stage as the 9 and upper would be the same.

  10. Chris Stelter says:

    I must confess I don’t see the point in this. Just use a Falcon Heavy. That way, you’re only expending a single Merlin engine and a single small upper stage. Or, go the other way and use an expendable Falcon 9 full thrust, which should have performance to LEO surpassing an Atlas V 551 and Proton-K.

  11. johnhare john hare says:

    Whether or not there would be a point to this depends on a number of assumptions I made, which may or may not be valid.

    I assumed that there will be a non-trivial cost in turning around each F9 core that RTLS, This would cut those in half for payloads in this category compared to the F9H. That building the F5 core would simply involve shorter tanks on the same tooling and leaving off 4 engines from the basic F9. That recovering far at sea will be an issue for the foreseeable future and that the F5 core would be considerably cheaper than an F9 core. That the shorter core has a better chance of seaborne recovery. That aerial recovery is more likely with the lighter core. And so on.

    Another point is that I enjoy speculating on future possibilities.

  12. Jim Davis says:

    I think if SpaceX decided it needed something between the Falcon 9 and the Falcon Heavy (whether expendable or reusable) the way to go would be to remove one side booster from the Falcon Heavy but retain cross feeding between the two remaining cores. No new hardware.

  13. johnhare johnhare says:

    You may well be right. My assumption is that the F5 would be an F9 with less barrel sections and fewer engines making it simpler and cheaper. This assumption may or may not be valid.

  14. Paul451 says:

    Christoffer,
    “Or why not launch in Texas and recover in Florida.”

    Distance between the Texas launch site and the Florida landing site is over 1000 miles. (1600km.) The down range for the F9 first stage is about 250 miles (400km) and usually less than 200.

    John Hare,

    Small aside: The F9 (and F5) core is 3.6m wide. The F9 payload fairing is 5.2m wide (internal 4.6m) to allow full diameter commercial payloads. Your version would be limited to a 3.6m payload fairing and maybe 2.8-3m payloads. How are you going to make use of that 25+ tons?

    (But it’s the asymmetry that is the killer. Jim’s alternative wouldn’t work either.)

    Hmmm, if you had an FH style triple core, but used that short F5 as the centre core (with cross-feed) so that the upper-stage is snugged down in the gap between the two taller boosters, and the tops level. That lets you use a triple-wide hammerhead fairing. So 12.4m wide, 5.2m “thick”. (11.8×4.6m internal.) With up to double the height, given that you are starting where the upper-stage starts on the true FH. Simultaneous 4-6 commercial payloads, or a super-large custom 25-35 tonne payload.

    Same boosters as FH. Same upper stage. Only the F5 is new, and that will piggyback on the cross-feed manufacturing used for FH core stage. (Plus the new payload fairing, of course.)

    Ascii:

    HHH
    XUX
    XFX

    If that makes sense? HHH is the hammerhead fairing. U is the upper-stage. Two X’s means F9, one F means F5.

  15. johnhare john hare says:

    A meter gap between the parallel stages would allow a full 5.2 meter fairing with a bit of margin. I don’t know how snug you would want parallel stages.

    From Shuttle launches, I think the asymmetric stages might not be an insurmountable problem. Also, bimese launchers with crossfeed have been suggested by quite a number of people with more experience than I have.

    That triple wide fairing looks like a winner at first glance. I often read about payloads being volume limited rather than mass limited. Also looks like a sweet solution to lifting body orbital vehicles.

  16. Paul451 says:

    “A meter gap between the parallel stages would allow a full 5.2 meter fairing with a bit of margin. I don’t know how snug you would want parallel stages.”

    Weirdly hard to find details online. Judging by hi-res images of DIVH, and a ruler, the 5.2m cores have a 0.5m separation.

    However, if the minimum gap is set by aerodynamics and vibration, you can’t have the payload fairing wider than the cores, or it’ll close up the gap and either screw up the aero (esp. at supersonic) or damage the payload/booster through impact vibration.

    (That may screw up my hammerhead idea as well.)

  17. Paul451 says:

    Weird idea popped into my head, I thought I throw it up here before I forget it…

    Picture the standard FH, it can’t expand its payload fairing much further than F9 or it risks becoming aerodynamically and structurally unstable. (Depending on whether you go wider or taller.)

    However, add two more payload fairings on the side of the upper-stage. This gives you three times the volume

    Since F9 fairings are about the same length as the upper-stage, these fairings will reach to the side-cores, so hopefully the aerodynamics works out. The mounting points for the side-payloads would be at the top, where the current payloads attach, and at the thrust-frame for the upper-stage engine, no new attachments or forces on the sides of the upper-stage tanks, and hopefully symmetrical loads on the top/bottom frames.

    Bad ascii art again:
    (Note, the dots are just to centre the ascii, they don’t represent anything.)

    At launch:

    …H
    HUH
    BMB
    BMB

    Where the H’s are the three separate sets of fairings, the U is the upper-stage, the B-pairs are side-cores, and the M-pair is the centre core.

    After side-core staging:

    …H
    HUH
    …M
    …M

    After MECO staging:
    (The fairings also jettison. So P is for exposed payloads.)

    …P
    PUP

    After secondary payload deployment…

    P
    U

    Which allows the upper-stage to then perform a final burn just for the main/centre payload.

    In theory you could also double-length the side payload fairings. Although you’re increasing the number of different variants of fairings you need to tool for, adding cost.

    — Secondary concepts – which becomes obvious when extrapolating from side-mount and adding some of John Hare’s past toroidal-tank ideas:

    – Have a giant payload fairing going right around the upper-stage. Full length. Carry about six to eight conventional payloads, or one of two specially built giant payloads.

    – Add jettisonable side or even toroidal tanks around the upper-stage. Plus a 10m payload fairing on top (or three conventional fairings if you’re only using standard-width side-tanks.) Should allow you more fuel to put heavier payloads into GSO/GEO/BEO.

    (The toroidal tanks could come from the early work of the BFR-size tanks. Outer ring-sections are BFR, inner sections are F9/FH. Only the top/bottom caps will be unique.)

  18. Paul451 says:

    Ascii art for the toroidal upper-stage extra tank…

    Side view:

    HHH
    TUT

    Top-down view:
    (dashing are for lining up and don’t signify.)

    -TT
    TOT
    -TT

  19. Paul D. says:

    Chris (@Robotbeat) on twitter pointed out something interesting about Falcon: the reusability of the first stage can increase mission reliability by making the system more resilient in the face of engine failures. There is extra propellant that can be used to still achieve the desired orbit, at the cost of expending the first stage instead of recovering it.

  20. johnhare johnhare says:

    Interesting. I wonder if there is any possibility of returning the whole vehicle to launch site. If not, then saving the revenue at the expense of a stage
    might make sense. It would depend on rative values.

  21. Peterh says:

    I suspect the legs aren’t rated to hold the vehicle with a full upper stage and payload attached. But otherwise a return to launch site in the event of trouble early enough in launch would be a potential.

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