Generic Tankers

One of the things that I keep coming back to about EELV derived lunar missions, is that while there are a lot of interesting possibilities out there, and they are likely to be a lot cheaper than the ESAS architecture, they’re still very expensive. Compared to the price points that you’d really need to get to in order to have real cislunar commerce, even EELVs are completely unrealistic. The fairly obvious conclusion I keep coming back to is that until you have lower cost launch to orbit (ie sub $1k/lb), lunar commerce is a real challenge–maybe not impossible, but a challenge. In other words, you really need low-cost space access (probably in the form of truly reusable space transports) before most lunar business plans can be closed.

One thing that Lockheed (or Boeing) could do to help catalyze things would be to make a line of relatively low-cost propellant tanker modules for on-orbit propellant delivery. These could be as simple as a propellant tank with a standardized docking interface (and with standardized fuel interconnects), or possibly could have a small guidance package on-board. Just enough so that between the package and the launch vehicle upper stage, the propellants can either be delivered to a location where a tug can bring them in to the propellant depot, or enough to allow the generic tank module to do the rendezvous and close approach itself. Put that technology on the shelf so that any launch company that can put stuff into orbit can buy a version of the tanker module and launch it on their vehicle. Spend the money and time with ITAR lawyers to make sure that you can get at least some of the friendly international space programs (like Arianespace, and the Japanese launch companies) on board with the project.

Just by demonstrating the concept, setting a reasonable standard, and selling generic tugs (with scalable tanks depending on the launch capacity of the vehicle in question), you remove most of the technical risk for those companies to do on-orbit propellant deliveries. While that doesn’t remove all the hurdles between where we are right now, and largescale orbital and cislunar commerce, it provides a good start. Once that technology is on the shelf (or in development), it makes it easier for other people to innovate.

Maybe somebody will contract with Lockheed to have them deliver a “used” Centaur stage back to LEO after dropping off a commercial satellite. Have it refilled, and checked out at a Bigelow Sundancer station, and then turn it into a small orbital propellant depot. NASA claims they’d buy propellants on-orbit for topping off the EDS/LSAM, if it becomes commercially available. They really do need the capability, because without it, their odds of losing a mission from launch delays is pretty high, what with the LSAM and EDS only being designed for 15 day loiters before they start cutting into margins. With it, they can really boost their lunar surface capacity (possibly as much as double the cargo mission payload). And even at the crazy price that EELVs go for these days, it would be a lot cheaper to top off EDS than to launch two Ares V missions, with two EDS’s, and two landers.

Some large NASA missions (like JIMO for instance) could really benefit from being able to have their Centaur upper stage topped-off in orbit. That would allow the thing to fly on an existing booster, without having to sacrifice any capabilities.

Another potential market for LEO propellants might be if some other country wanted to do lunar missions on the cheap. Not everyone has drunk the ESAS koolaid. Maybe the Europeans, or Russia, or China, or India could become interested in licensing or buying outright the tanker modules, and then doing their own manned lunar missions using a much more affordable archetecture. You could land two guys on the moon using only two refueled centaur stages. India for instance could probably do a manned lunar mission using their own launchers. Or if they’re saavier than that, they’d build their own lander and capsule, and launch them, but then buy a used Centaur on orbit, and buy “commodity” on-orbit propellant to fuel that and their lander. If you aren’t NASA, and you’re merely trying for the most affordable way of doing a lunar mission, you’ll buy your propellant from whoever wants to ship it.

Or maybe someone could buy a “used” Centaur, and use it as a semi-reusable tug for sending paying customers on around the Moon joyrides. Use it a few times, and then discard it and buy another “used” Centaur. Judging from the medium flight-rate ticket price of an Atlas V 401, I’d be surprised if a new Single Engine Centaur stage was worth more than $15M–If you bought it used on-orbit, it could probably be had for a song. A refueled Centaur stage (stock, not Wide Body) could send 30klb on an Apollo-8 style free-return trajectory with separation after the TLI burn, and the Centaur doing a second firing to return itself to LEO for reuse.

I could probably think of other ideas, but I think that Lockheed or Boeing could do fairly well for themselves by field-demonstrating orbital propellant transfer, and developing and selling/liscensing a generic propellant tanker module.

What do you guys think?

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Jonathan Goff

Jonathan Goff

President/CEO at Altius Space Machines
Jonathan Goff is a space technologist, inventor, and serial space entrepreneur who created the Selenian Boondocks blog. Jon was a co-founder of Masten Space Systems, and is the founder and CEO of Altius Space Machines, a space robotics startup in Broomfield, CO. His family includes his wife, Tiffany, and five boys: Jarom (deceased), Jonathan, James, Peter, and Andrew. Jon has a BS in Manufacturing Engineering (1999) and an MS in Mechanical Engineering (2007) from Brigham Young University, and served an LDS proselytizing mission in Olongapo, Philippines from 2000-2002.
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One Response to Generic Tankers

  1. Habitat Hermit says:

    In my opinon you’re on the right track. I have a few points I’d like to make but I hope it’s not too obvious and dull (I’m sure any engineering undergrad could easily put me to shame). Some of this echoes your points but since I take it you’re thinking more of refueling stations than tank swaps I guess it will point out similarities rather than anything else.

    While I would like to see true/advanced orbital refueling it seems to me it shouldn’t be the first step. Getting “simple” tankers would be and I think these tankers should be able to fulfill both a use as interchangeable “tank swap” stages from the get-go as well as provide the starting point for advanced refueling later on (I think a debate pitting the two different techniques against each other is a false one: both will have their strenghts and weaknesses and both will provide know-how that is applicable to other problems or for that matter even each other). The rest of this reply is just airing some views on such “tank swaps” and interfaces.

    I do not think the following should neccessarily be only in the domain of the large aerospace firms; it could be perfectly viable for much smaller entities (and rockets). I think it should scale down (or up) reasonably well but I have no way to back that assertion up.

    Please remember that these are uneducated ramblings of no value unless a lot of educated work and effort is added to them (and even then some of this would probably be plain wrong) 🙂

    My thinking went like this; a rocket has several “natural” modules:
    A – payload
    A2 – payload navigation & control, fuel, and propulsion
    B – navigation & control systems
    C – fuel
    D – propulsion (combustion chambers etc.)

    I am aware that this is a highly idealized and simplified schematic 🙂

    As I see it the minimum requirement for utilizing “tank swaps” would be to make use of an _openly published and freely implementable interface_* either between (A, A2) and (B, C, D) (a split that is already made for almost all launches) or (A, A2, B) and (C, D). Once again it’s not an either-or situation; one of them would fit payloads with seperate A2 and the other would fit payloads which have integrated A2 and B.

    * that is a lie actually but making the interface open and freely implementable could drive adoptation and widespread use which would be likely to benefit all companies involved as well as the customers.

    “Tank swaps” could possibly be much more efficient than that depending on how easily one can break and create clean interfaces for the other parts. Considering that the “swap tank” would likely need to be more than just a simple tank I’m not sure whether or in how many scenarios it will be worth it. To a certain extent it depends on how advanced an interface makes sense.

    Any of this would require autonomous or telecontrolled reassembly.

    For the simplest tank swap and interface above (A, A2 – interface – B, C, D) you only need a structural interconnect at a bare minimum though you would likely want control interconnects as well (to control and utilize subsystems like small positioning thrusters etc. as one system). For the second simplest you also need those and other control interconnects in the interface.

    A few additional notes:
    There are likely to be standards in differing sizes but for each size the following might be interesting (i.e. some, all or additional ideas might be incoperated in the standard).
    – permitting different tank sizes somewhat independent of the interconnection size (ideal for getting relatively small payloads to remote locations or other “mis-matches”)
    – specialized interfaces on the tank side of the interface allowing multiple tanks (submodularity or even branching) while keeping the non-tank side of the interface standardized (can be good for increasing competition across size boundaries as well as providing levels of redundancy)
    – a standard interface that allows for different (tank-independent) flowrates to the propulsion element (might make sense for more advanced interconnection standards where the propulsion (combustion chambers etc.) is seperated)
    – a standard interface that allows for different fuels or with submodular fuel connections and/or likewise for other needs of the interface (can provide elements of economics of scale in the production and utilization of the interfaces itself)

    There are two things that stand out in my opinon as things that should be as generic as possible:
    – communication channels required between the modules (likely to be cheaper in the long run if everything is included (or easily added later on) in all interfaces)
    – structural interconnects (might not be as simple as they can seem since they will likely play a big role in the assembly, as well as possible disassembly, of the modules)

    Apologies for any boredom-induced deaths – I could go on but I’ll stop now 😉

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