More Thoughts on Technologies for Spacefaring Societies (Part One)

I have to admit that I’m rather impressed and surprised with the amount of response my earlier posting on that topic received. Due to some misunderstandings, I realized though that I probably need to add and clarify a bit.

First and foremost, the list I came up with wasn’t supposed to be a wish-list of all the technologies it’d be wonderful to have at some point in the future. It was an attempt (albeit a bit feeble) at trying to list which technologies we would need to master before we could become a truly spacefaring society. An important corallary to that is that though we need to eventually master all of those technologies and techniques, the transition to becoming a spacefaring society is likely going to be a gradual, evolutionary process. I’ll come back to this in a second.

The second point I’d like to make is that there are a lot of cool and interesting technologies that I really don’t consider neccessary for becoming a spacefaring society. A lot of commenters discussed tethers or space elevators. While I think they’re interesting, I can easily envision a future where it turns out that we just couldn’t get CNTs strong enough for a space elevator, but tens of thousands or millions of people live off-planet anyway. Even if tethers work perfectly, you’re still going to have to do lots of normal rocket propulsion too, and if we haven’t figured out how to store or transfer propellants–we will not really be a true spacefaring society even if we have a dozen space elevators.

The third point goes back to the corallary of the first point. In transitioning from being a space-visiting society to becoming a spacefaring society, some of those technologies are more neccessary than others, because they enable others. Take water recylcing or space tugs. It’s possible to have a space tug at ISS, and have complete water recycling capabilities while still not becoming a spacefaring society. If we’re still launching all of our payloads on expendable boosters, it’s only going to make a marginal difference. A moonbase that is being built by single-use transportation modules that can’t be refueled and have to be launched on one or two big launchers will never be affordable regardless of how good your Extraterrestrial navigation skills are, or how good your closed-loop life support system is.

If I had to pick three of the technologies that I think are the most critical, the soonest, I’d have to say reusable launch vehicles, on-orbit propellant storage, and on-orbit propellant transfer. The reason why I feel these are the most important is that all of these strike at what I think is the key piece of the puzzle–transportation. When transportation is cheap, frequent, reliable, and flexible, everything else becomes easier. Here’s an example of what I mean:

Let’s take aerobraking for instance. Right now, almost all “aerobraking” that is done is either in the form of aerocapture where you only bleed off enough energy to enter an elliptical orbit, and then over several weeks or months you use propulsion and successive passes to bleed more and more energy off. What you really want to do, especially if you have people, or time-sensitive cargo, is to be able to take as much energy off as possible in a single pass, so that a small propulsive burn is all that is needed to leave you in your final orbit. The problem is that the drag medium (the atmosphere) isn’t constant. Its density changes quite a bit over time, and if you go too deep, you’ll burn up or reenter, but if you go too slow, you’ll bounce off and have to take several passes. We need to learn how to accurately measure the densities in the atmosphere (preferrably from sensors mounted on-board the aerobraking body), so that we can safely navigate through the atmosphere at the right angle and trajectory, in order to maximize the delta-V savings while simultaneously remaing safe. In order to do that (and in order to get enough practice and experience with doing that, so that new pilots can be trained, procedures developed, etc) you really need to actually fly. Research, CFD, wind tunnels–they’re all great, but utterly insufficient. You really want to build, test, and fly lots of small, cheap prototypes. Throw dozens or hundreds of aerobrakers at the problem until you’re so utterly familiar with the right way of doing it that it can becomes natural, until you’ve gotten it to the point where the same aerobraker can fly the mission succesfully ten or twenty times in a row without damage, need for refurbishment, or requiring excessive propellant use to reach its destination. The problem is that that will not be possible until you have regular, low-cost access to orbit. Which really requires reusable vehicles. If the aerobrakers can be designed to be reusable, and if you can recover and refuel them and try again, the total cost of learning how to do that goes way, way down.

I could give other examples, but that’s one that’s been floating around in the back of my mind long enough that I had to let it out.

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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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10 Responses to More Thoughts on Technologies for Spacefaring Societies (Part One)

  1. Pete Lynn says:

    Finding the lowest cost enabler for space settlement means finding the lower cost trigger technology that switches humanity onto a self perpetuating evolutionary pathway that leads to becoming a space faring society. It is not desirable to fund that entire pathway up front, just the switch event that gets humanity onto that set of tracks.

    So what is the lowest cost trigger event? Obviously it has to tie into some kind of self sustaining market that requires people living in space. Hence reusable vehicles and other such tech candy alone, will not be sufficient.

    Although this may seem strange at first glance, one such low cost trigger event might be the development of a large hanger and workshop in LEO. This would pretty much provide a market for the development of everything else required to become a space faring society, and it might only cost a few hundred million dollars.

    A hanger and workshop in LEO would quickly become the general store of space, where most every mission stopped to be checked out. It also justifies the presence of people and gives them the means to incrementally improve their home – a space faring essential. Repair work, upper stage and satellite recycling, (perhaps a hundred ton available every year), science missions, commercial assembly work, hotel construction, etcetera. I do not think this would need reusable launch vehicles, although I expect it would soon prompt their development.

  2. Kirk Sorensen says:

    The devil is in the details when it comes to the value of a “LEO space hangar”. It sounds nice on paper, but in reality you have to plunge into the issues of differential nodal regression, atmospheric drag, atomic oxygen, eclipse periods, orbital inclination and overflight issues, communications, radiation (yes there is some), and debris.

    The astrodynamic disadvantages alone of LEO are voluminuous. You can’t just go to the Moon or Mars any old time you want from GEO. Here’s a good paper on the subject.

  3. Monte Davis says:

    I hope you keep pursuing this rich vein, Jon. Push farther into the chicken-and-egg mutual dependencies, e.g. that between reusable TPS and aerobraking.

    What’s the state of the art in testing candidate TPS solutions? I could be wrong, but it’s my understanding that there is still no facility combining hypersonic flow and heating (plasma torch?) on a scale big enough to test realistic shapes with realistic transients, as opposed to 6″x6″ samples for very short periods.

    I’m reminded of the smart@ss comments that surrounded shuttle RTF: “All this time and money and they haven’t fixed the freaking FOAM for once and all?!?”

    Well, no, actually — because the requisite combination of weight, insulation and mechanical strength is in fact hard to do. TPS is a lot harder, and reusable TPS that doesn’t require Shuttle-level labor between flights is harder still. So your try-and-try-again scenario for aerobraking (which makes sense to me) presupposes either (1) a pre-existing TPS solution, or (2) willingness to lose some unknown number of testbeds before you get it right.

  4. James Antifaev says:

    Jon, your discussion reminds me of one I just had with my fellow project managers this morning on how many people don’t easily grasp the concept of “critical path”.

    I would be interested to see a “critical path” technology document for a spacefaring society, including the technologies you discuss. A graphic, rather than just text – a tech tree, I guess. I know something like this probably already exists, but doing one on the web would provoke a lot of interesting discussion.

  5. Pete Lynn says:

    Self sufficiency in space first and foremost requires the capacity to evolve and develop in space increasingly independently of Earth. The current critical path to this is gaining workshops in space and there is no real getting around it. The long term development of space can not be performed from Earth, this would be like trying to design a completely new type of car 10,000 mile from the nearest road, and would just lead to developmental stagnation. As many here know only too well, fast onsite testing is incredibly critical to any new development – space is no different.

    Yes ideally one wants multiple hangers in different orbits, and I am sure that would quickly come. A hanger or five is an obvious attachment for any space station, and Bigelow seems to have basic space stations in the works already. With regard to hanger drag and radiation issues, these should be if anything less than for a comparable space station – larger volume modules have greater wall thickness and proportionately less surface area.

    Hangers probably need to be no less than five metres in diameter, going up from there, with the capacity to unclip an end cap for access, (some hanger standardization might be possible). Three approaches suggest themselves for construction and launch; inflatable, rigid and a SSTO wet tank design. Converting a Shuttle ET is priced out of the market from the start.

    The large Falcon 9 payload faring is 5.2 metres in diameter by perhaps 15 metres long, perhaps a rigid hanger of this shape would be the cheapest way of getting the first one up there. An inflatable option is probably the cheapest and easiest long-term with the capacity to go to much larger diameter. A larger diameter Falcon 9 wet tank SSTO design would also be interesting, perhaps less than a 100 million to develop and say 20 million a pop there after. Either way, 100 million should be enough to start this particular ball rolling.

  6. kert says:

    A graphic, rather than just text – a tech tree, I guess. I know something like this probably already exists, but doing one on the web would provoke a lot of interesting discussion.
    I think i saw something like that on NSS website some time ago. I’ll try dig it up later.

  7. bh says:

    The effects of long term radiation and micro/zero-g on the human body are the largest barrier to becoming a true spacefaring civilization. We may not know the exact health curve, but we know it’s real bad.

    Closing the water loop and ISRU would seem to be the next major issues.

    I like the XPPS idea.

  8. bh says:

    And I have to agree with Pete Lynn. As far as everything else, I think it’s more a matter of financial viability over ability. My point is the “trigger” will be commercial opportunity. Only when one can “make a living” (profit) there, only when the moon has its own economy will thousands of people live there. And like all frontiers, the real drive behind it will be exploitable/profitable resource(s). At the moment, the cost/pound ratio of launch is prohibitive. Dropping that cost will be good. However, scarcity of resources on Earth may change that equation sooner than we think.

    Oh, 1st timer here. Great site. Great thread.

  9. qwerty182764 says:

    I myself don’t see RLVs as being much of enabler. (Especially SSTO’s which require magic structural lightness that can somehow withstand repeatedly re-entering, and magic engines that can somehow survive more than 10 flights without extensive inspection and overhaul).

    The cost of a spacecraft has almost nothing to do with the material costs, or the fuel costs. You can easily afford to lose a tank, to lose the structure and fuel associated with it.

    The cost mainly comes from having the standing army of engineers required to maintain the thing. Launch rates/engineering and inspection hours are the main cost drivers, IMO.

  10. Randy says:

    qwerty182764 wrote:
    >magic engines that can somehow
    >survive more than 10 flights
    >without extensive inspection and

    RL-10. They are of course not ‘perfect’ for any advanced design being ‘optimized’ for upper stage use. They HAVE been used for ‘lower’ stage use with a ‘cut-down’ version for the DC-X/XA program and didn’t ‘require’ any extensive maintenance OR overhaul during the program.
    (Point though, the ‘cut-down’ versions from what I understand were really even close to ‘optimul’ for use on something like the DC-X or an SSTO of any type. A ‘new’ design would be a lot better performing AND operating)
    But that DOES show we knew and could build high-use low maintenance engines as of 30+ years ago.


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