Tuesday, May 31, 2011

Space Travel in The Black Desert: Practical Considerations for STO Transport

         And here we are again, ready for another week of hard science-y goodness, RocketFans!

         I've spent the weekend working out some ideas on the practicality of commercial spaceflight.  Being a RPG designer, my main concern must of course be getting PCs around my setting in a practical fashion.  As a Hard SF aficionado, my concern is to make such an unlikely situation seem remotely plausible.  The two rarely go together.

The desire
         Realistically, the idea that there will be a great number of of private spacecraft owners is completely bogus.  If we look to the incidence of real-life aircraft owners, the analogy is obvious - I mean, how many people do you know that own their own planes?

The reality
         Another consideration is the cost and practicality of using crewed spacecraft at all, or spacecraft with independent propulsion.  My L-Drive concept is all well and good (if a little unrealistic), but the conventional Light Craft, which has the laser system on the ground, is more practical for 90% of orbital transportation needs.  Add to this the sad fact that when all is said and done, the idea of launching a fully fueled spacecraft that will not use this fuel for the all important boost out of Earth's gravity well is not very practical at all, and it seems to me that a little modification and/or clarification is in order.

         Relax.  This is where the fun begins.

         First of all, the L-Drive itself is only plausible as a propulsion system under certain circumstances.  For flying around like a conventional aircraft, it works great, no fuel cost, no problem!  For actually attaining orbital speeds and altitudes, there are a few caveats.  The L-Drive spacecraft must launch without the propellant it will use once in space on board.  This is a hard necessity; the weight of the propellant is 75% of the rocket's total mass, and launching all that dead weight from surface when you aren't going to use it is simply too impractical to consider.  Don't panic; a rocket can carry enough fuel for orbit changes the same as the Space Shuttle does, and if you need to leave orbit for points West you can gas up in space, with the cost of said propellant already factored into ticket costs.

Right idea, wrong Airline.
         Second, spaceplanes are more practical than tail landers.  I don't like this one either, but the constraints of the propulsion system make it so.  The lifting body design of a spaceplane will let the L-Drive spacecraft accelerate slowly, probably over several orbits.  The orbits will be low- to medium-altitude (where aircraft fly) in order to feed the most dense atmosphere into the L-Drive's bells.  This kind of launch is unheard of in conventional rockets, which attempt to punch through the atmosphere as fast as possible in order to prevent gravitational drag from pulling them back down.  Spaceplanes, which can defy gravity by virtue of their wings, overcome grav-drag enough to make the slow launch work, which means that their L-Drive systems will not require as much power.  Additionally, the spaceplane designs can make use of linear catapults, which further reduces the power requirements on the spacecraft itself at launch. Tail landers can use catapults, but it requires orienting them sideways, which is, if not impractical, at the very least a pain in the ass.

Most common of all...
        Third, L-Drive powered spacecraft will not be nearly as common as "conventional" Light Craft.  The majority of commercial orbital flights will, in my opinion, involve drone craft launched up through the use of a ground-based laser.  These Light Craft will rendezvous with stations in geosynchronous orbits to allow passengers and cargo to be transfered to other stations in orbit or to spacecraft heading to Luna or the great beyond. There may be some stations that have orbital laser capable of pushing Light Craft out into space, but these will most likely be heavily regulated, since these lasers are powerful enough to vaporize lesser rockets and fry targets on the ground.

That's no moon, it's a gas station!
        Lastly, there will be massive propellant depots in orbit.  These will be supplied either by Light Craft carrying water up from Earth, or from Iceteroids at the LaGrange points that manufacture propellants from the cryolith.  Which method is used will depend on whether or not a particular depot is owned by a Terran nation that has extensive water resources on the ground, extensive orbital resources, or both.  It all depends.

        As the week continues, we will look more at these idea, culminating with an example traveler going from Terra to Mars, and changing planes along the way.  Until then, have a good one, RocketFans!

Note: Caption links go to the websites where I found the pictures.  This is meant to give credit, not as additional information to the post.


  1. I own an airplane...

    Anyway, great article. I have always found laser propulsion interesting.

  2. I have owned more than one airplane. Light aricraft are not STO shuttles. What you really need to think about is something roughly the size of a C-5 or An-225. I have always thought that laser propulsion made more sense than conventional rockets, if only because it makes them safer.

    Using a induct-trac linear accelerator also makes sense in reducing the onboard need for propellant. Also the combination of laser/induct trac would give a robustness needed for commercial operations.

    Becasue of the proliferation of commerical airports, having a spaceplane that could land at any airport on Earth makes sense. Tail landers will rip up tarmac if they were to arrive at an unprepared field. This also gives an ability for safe abort should the laser fail during boost phase. The spaceplane just glides back to either launch point or goes suborbital and lands at a convenient field overseas.

    This abort mode is also useful as a mode for high speed transcontinetal transport. Not just next day air, but this afternoon. Or this morning if you get to the airport before the next run to Bejing.

    I could see where you could use the STO spaceplane to tranfer to an IPV or Cycler. Boost to orbit, fuel up for tranfer burn at the Orbial depot, burn to interecept the Cycler, redezvous and hitch a ride outbound.

  3. Yup, that's the general idea. Space infrastucture that makes sense! Also, it's rarely tried in RPGs to make all the necessities of space travel part of the fun of the game, and not just a plot point or scene change.


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