Wednesday, December 7, 2011

A Case for Smaller Spacecraft II

A 550-meter-long Missile Craft
          A Case for Smaller Spacecraft II

      Yesterday, we began a discussion on the viability of making smaller, more inexpensive interplanetary spacecraft despite the fact that such ships would be less powerful.  Like any situation that involves humans, there are other factors besides physics that dictate a warship's design, even one that is meant to ply the deeps of space.

      We had just come to the conclusion that a smaller, less capable spacecraft may be designed due because they would be cheaper to build, require less crew, and could be built faster than larger, more capable designs.  That being said, today we have to establish whether or not a small spacecraft could actually do the mission required.

      Anyway, above is a concept for an interplanetary missile craft made using the Wings 3D program.  The missile craft is 550 meters long, has a crew of 80, carries two auxiliary craft (not shown), a company of Espatiers, two hundred kinetic kill missiles, and the same amount of laser-armed interceptor missiles.  They also have eight laser turrets for defense. These spacecraft are charged with laying siege to orbital settlements and assaulting the same. 

An IPV-Escort.
      My concept for a smaller IPV, which we'll call an IPV-E (for escort), is only 83 meters long.  It has a crew of 16, with three or so Astronaut Candidates on their training cruise.  They carry only a tenth of the armament of their larger cousins, with two lasers and forty missiles of various types.  In addition, however, they are able to employ a Fusion Torch out of both their forward and after thrusters, which unlike the big ships, are proportionately large enough to give the IPV-Es a .5g acceleration in addition to the .005g constant boost from the magnetic sails.  The spacecraft is too small to carry Espatiers, but has enough consumables and life-support to carry another fifteen people in need be.  These spacecraft, like their names suggest, are designed to provide extra defense to tactical and missile craft against rockets, missiles, other IPVs and asteroid outposts.  

      One thing about the IPV-Es that make them capable of doing their mission is the fact that there are about four times as many of them as any other class of interplanetary craft.  Usually a pair of these "tuna cans" are assigned to a larger IPV as an escort into harm's way.  They can provide extra defense by virtue of their sails, they create additional targets for attackers, and their extra missiles allow for more force to be projected.

     In addition to all of this, a triplet of the diminutive craft is at least capable of holding their own against larger IPVs and the depredations of rockets.  Because the IPV-Es are three craft instead of just one, they can attack from three directions at once.  Two of these CortDivs can completely surround an asteroid or IPV and therefore attack from any direction.  Unlike a single large craft, if one of the escorts is destroyed, the task force's effectiveness is diminished by a third, not completely neutralized.  In addition, because the IPV-Es can accommodate 30 (or even 45 if for short periods) if only one is capable traveling under their own power, they can rescue the crews of the other two.

      Because the IPV-Es are equipped with Fusion Torches, they can actually attack another IPV directly, which is not something that their larger brethren are capable of.  I was wondering if this was a viable option, since the Torches have such a short range and I didn't think they could get close enough, but it should work, because the Torches can overheat the defending IPVs just by firing into the outer layers of the magnetic sail, which is still at a range of about kilometers.  The trick is that the IPV-E can't use their magnetic sails for defense during this evolution, so they are exposed to every laser, missile and stray bit a debris.  This is why the the body of the spacecraft is so stubby; everything that is important to actually fighting the craft, with the exception of the outboard antennae, are hidden behind a twenty meter of water, composites and payload.

      Anyway, that's what I've got on the subject so far.  As always, comments are welcome.  Enjoy, RocketFans!


  1. Neat! This allows for some greater variety in craft.

  2. One more question that I'm not clear on - do the IPV-Es carry other craft with them or not? I get the impression, not.

    It almost suggests a niche - a IPV style craft whose life systems are only the carried craft.

  3. IPV-Es are not designed to carry small craft. That being said, they are supplied by Catapult Assisted Single-Stage To Orbit Rockets (CASSTORs), which are certainly small enough to carry on their docking rings. A larger rocket, like a Paladin, can be carried if it is secured with cargo cables. A Heinlein or Phoenix can dock, but they are simply to massive to be carried on the spinning docking rings. The IPV-E also doesn't carry enough propellant to service one of these Orbiter, either.

  4. Your dynamic on usable thrust will be this:

    Is it possible to use thrust to successfully evade incoming kinetics by moving laterally to their inbound vector?

    If the answer is "Yes", then craft will naturally bifurcate into "Able to dodge kinetics by thrust" and "fortress point defense."

    Smaller craft have a viable tactical role (as opposed to a strategic role as you've described in these two posts.)

  5. To quote you Ken, "Maneuverability ceases to be a tactical concern."

    Smaller craft, such as fusion powered rockets, must attempt to clear their vector by blasting their Fusion Torch along the angle of attack, while larger craft rely on their magnetic sails to project a bubble of plasma that deflects debris and lasers. These sails put huge stress on the large craft's radiators, and an assault by Torches delivered by rockets (mostly drones) can overload the system and force the sails to drop.

  6. Love the designs for these new ships. What are the vanes at fore and aft, and why are they different sizes? (Or is that just perspective?)

  7. Partly perspective but the aft vanes are indeed smaller. The vanes are the Magnetic sail arrays. They are different sizes in order to minimize the plasma plane effect building up in front of the spacecraft.


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