Space

Space Tech Bleg

29 Comments

Has the US ever done an unmanned rendezvous and docking? I can’t think of one, but of course that doesn’t mean it hasn’t happened.

[Update a while later]

Here’s a sort of related bleg. Did Mike Griffin testify to Congress recently that the Chinese could get to the moon with a multiple-launch architecture? Or am I imagining that?

29 thoughts on “Space Tech Bleg”

  2. The Orbital Express team did a great job and their separation between the systems was hundreds of miles.

    Now the DART mission, that is another story…..

    I would also claim that the Apollo lunar missions did rendezvous autonomously as it was the radar system that guided the vehicles into proximity.

    It is not really that big of a deal to do, just uninformed people claiming such.

  4. The Soviets did unmanned rendezvous and docking before they did it manned, with Cosmos 186 and Cosmos 188 in 1967, so it shouldn’t present any major hurdles. The ESA’s automated transfer vehicles use it, as would a proposed vehicle for service the Hubble Space Telescope.

  5. Yeah, ASTRO and NEXTSat aka Orbital Express would be it. They separated to very large distances.
    Unfortunately DARPA mission log pages seem to be now offline, it was fairly interesting. Youtube still has some videos of dockings and orbital ops.

  8. Hard dock is a perfect example of how space technology never develops.. even though everyone knows ramming two spacecraft together is a crappy way to go about things, they still keep doing it. There’s zero innovation.

  10. I typed it up quickly as its amusing:

    Slightly inane Q: I know chinese long march five rocket is in development , i wondered if you could compare that to anything in the American inventory of what we have.
    When its built is it really larger than anything that we have ? And why do you think that the Chinese are building such a large rocket ?

    Griffin A: Well, the Long March 5 is comparable in scale to todays Delta IV Heavy or to the Ares I crew vehicle which we were going to build and which was cancelled. So its on the order of, and of course until it flies regulary we wont actually know, but its on the order of 25 tons of payload to LEO. So it’s not in the class of say, the Saturn V or the new SLS.
    But it’s a very significant capability and in fact by launching and rendezvousing four of those in LEO it would be possible for the chinese to construct a manned lunar mission with no more than that rocket and no more than Apollo technology. And i have in fact in the past written up how that mission would work from an engineering perspective.
    So with the Long March 5 the chinese inherently possess the capability to return to the moon should they wish to do so.

    Q: And you are saying that we do not have anything comparable to that other than that what had been talked about

    A: We do not. Well, we have nice viewgraphs. ( laughter in the background )

  11. Well, other than the Delta IVH, which they did talk about, but continued to ignore. Guess the American-built liquid fuel engines disqualify it from serious consideration.

  12. Yes, I used to enjoy doing the calculations to figure out how to do a lunar mission with the Falcon 9 and Dragon.. then Falcon Heavy was announced, with 53 tons to LEO, and that game was over – it’s just too damn easy now.

    What I find especially annoying is that I did all those calculations for the Falcon 9 / Dragon with the assumption that only storable propellants were available (isp in the 312 to 320 second range), and it all seemed to close. Yet, all the propellant depot advocates continue to advocate liquid hydrogen / liquid oxygen cryogenic propellants.. they want the 400+ seconds of isp, and are unwilling to considering the massive disadvantage of boiloff and the years and years of development time required to prove that in space. There’s no urgency, so who cares if it can be done faster and cheaper with storable propellants or just docked together modules.

    1. Exactly. ISS is utilizing, well actually depending on storable propellant transfer right now and seems to be doing just fine.
      Plus, there are numerous deep space rated propulsion modules available around the world capable of utilizing said storable propellants.

      1. One thing that Ed missed from his list of everything depending on storables, was Apollo LM, that landed on *gasp* storable propellants.

    3. It’s almost if they don’t want to see a large and fiercely competitive propellant launch market and exploration as soon as possible. To paraphrase Augustine of Hippo: Lord, grant me RLVs – but not yet.

    4. While storable propellants are generally quite toxic, corrosive and have a lower Isp, they’re a well proven technology. There are satellites that have operated for well over 15 years using storable propellants for their propulsion system. As others have noted, the ISS uses storable propellants and routinely accomplishes propellant transfers. In addition to avoiding the boiloff issue, hypergolic propellants are much more dense than cyrogenic propellant LH/LOX combinations. This reduces the size requirements for the propellant depot.

      There may be alternative propellants to hypergolics that would allow storability without the bad aspects, such as liquid methane/LOX. The boiloff temp for that combination is substancially higher than LH/LOX, so it might be easier to manage with sunshades. I’d love to read any studies on different storable propellant combinations if someone can provide some links.

      1. Storable is one of these unfortunate words. Eventually we’ll want to see LOX and LH2 become space storable – and the sooner the better – , as they would be – by definition – in a depot. Hypergolic is used similarly unfortunately. It’s not so much the hypergolicity itself that’s important (=spontaneous combustion on contact), though that is useful, but the fact that traditional hypergolics are space storable with current technologies.

        And markets should decide where to put depots and when, at what levels of traffic, and with what type of propellant, just as with launch vehicles and other space transportation infrastructure. Saying that is no more than taking the argument of demand-pull seriously, and saying less is not taking it seriously.

        But to do that, you need to create that demand first, again the sooner the better and the larger the demand the better. I’ve long argued that traditional hypergolics are the best for that, especially as they are the propellants of choice for spacecraft. But there’s no need to impose that, you could have competitive procurement of a refuelable spacecraft with initial operational capability within three years or less. I’d be amazed if the market went for and delivered a spacecraft with cryogenic propulsion as essentially no spacecraft uses cryogenic propulsion. I think it’s silly to think NASA should say it knows better than the market.

        You could argue that even the decision to buy propellant in orbit could be left to the market, but I think there are decent arguments for not insisting on that.

        1. Storable is one of these unfortunate words.

          There isn’t really a better alternative, but you could go with “nitrogen tetroxide propellant combinations”, which would cover something like 90% of related existing hardware , tankage and propulsion modules.

    5. The real problem with spending money on geptil and nitric acid is the ISRU. If you just want to avoid SLS for flags-and-footprints, then sure… If you want do more in space, then their utility becomes questionable.

      1. How so? Why do you think spacecraft invariably use traditional hypergolics?

        Why, if you left the depot decisions to the market and especially since traditional hypergolics don’t require a lot of spending? And why not go with SEP instead, what’s so magical about LOX/LH2? Involving markets is the magical ingredient we need, not LOX/LH2 or any other specific technology.

        1. To the degree specific technologies are desirable, the market will find them, at the moment when it starts to make economic sense given factors like technology maturity, practicality and levels of traffic.

    6. My focus on LH2/LOX has always been that the boiloff can be used to make water (something useful anyway) and hold station. The storables I’ve worked with have the additional mass/complexity of needing a separate pressurization system. I’ve not seen an analysis showing how prop density trades with tank mass relating to Isp. The crossover point between LH2/LOX and storables would be pretty close to the LH2/LOX side, I think. Anyone have one handy?

      1. Not that it’s a crucial consideration in my view, but hydrazine can be used to replenish lost nitrogen in a manned spacecraft, and was considered for that role for Space Station Freedom because of commonality with the RCS propellant.

        As for a pressurisation system, you’ll still need one regardless of whether it uses a third fluid.

    7. or just docked together modules

      From the point of view of near term exploration it may not make much of a difference whether you use storable modules or refuelable storable modules, but from the point of view of jump starting cheap lift and commercial development of space it makes a lot of difference. Launching prefueled modules on commercial launchers is already helpful, but freeing launchers from any size constraints other than the natural ones would be much more useful still. If storable propellant transfer still needed to be proven there would be a good case for starting with just dockable modules, but it is a mature technology.

  13. I remember being on a forum where someone was asking if an unmanned Shuttle could be launched and dock with the ISS. Somebody expressed the opinion that automated docking was simply too difficult to achieve. I then suggested that maybe a space-walking astronaut could strap themselves to the outside of a Progress, ride the progress over to the Shuttle, dock the Shuttle, and then the Progress could re-dock on it’s own, since automated docking was too difficult to achieve.

    Somebody took that seriously enough to call me an idiot. I guess I had neglected to turn on the big neon sign that said “SARCASM”.

    1. If the spacecraft and station have a means to accurately measure relative speed and location between the docking adapters, I don’t see how automated docking needs to be very complicated. Being a well understood task of Newtonian dynamics, automation should be able to do it better than a pilot most of the time.

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