Space Fighters

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08/07/03 09:25 AM

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Once, there were only aerospace fighters. Shortly thereafter, BT introduced conventional fighters. What about fighters adapted for space only?

Why would anyone want those, other than for aesthetic closure of the air-only/air-and-space/space-only arc?

If you're looking for a role to fit space-only fighters into, do consider that:

1) It's a heck of a lot easier to blow up an invasion force in its dropships than on the ground
2) BT might be noted for technological backsliding due to the Succession Wars, but it's STILL the future, and there are quite a few important assets in space: asteroid mines, factories, endosteel refineries, satellites, etc.
3) For reasons discussed below, a space-only fighter is easier to build than an aerospace fighter, and probably simpler than a conventional fighter

A corporation with an asteroid mine to protect isn't interested in atmospheric performance, but it is interested in the bottom line. A planet with limited technological capabilities might not want to go through the trouble (see below) of developing a fighter that can perform well in air and space, and transition between the two environments. A highly penny-pinching planet might want as many fighters as possible to intercept invaders and is willing to skimp on atmospheric performance. And thus: the space-only fighter. Or space fighter. Yeah, space fighter. That sounds better.

Space only fighters are easy to build?

Well, relatively. Consider:

1) Conventional fighters have to deal with a variable environment. Between sea level and 20000 meters, atmospheric conditions shift wildly and wing designs will vary depending on intended operating altitude...and if a designer has to deal with both low altitude and high altitude operations, they'll be pulling their hair out. The military will add complications because military planes will usually be supersonic, meaning the designers will have to deal with the differing aerodynamic regimes of subsonic, transonic, and supersonic airflows. The military will probably also want all sorts of annoying things like "short field operation," "positive control at high angles of attack," "lightweight for maximum agility," "as armored as possible," "internal weapon bays here, right where you were thinking of putting that fuel tank," etc.

There's a reason airplanes are described as "a group of compromises flying in close formation."

2) Conventional fighters have life easy compared to aerospace fighters. Aerospace fighters not only need to deal with all the problems conventional fighters have (but make compromises: note aerospace fighters have lower maneuverability and fuel endurance than conventional fighters), but also have to deal with hypersonic flight, atmospheric entry, launch, interplanetary navigation, and the environment of space. Systems that work fine in the air don't necessarily work fine in space: many electronic systems on modern fighters expect to have even the thin air of 60000ft to keep cool. Mechanical systems expect air for lubrication and cooling. Heat sinks definitely benefit from having air around (note a fighter in the air can fire six times as often as a fighter in space.) Once you design systems to work in space, they won't necessarily work in the atmosphere: the US space shuttle uses several different cooling systems depending on whether it's on the ground, re-entering the atmosphere, or in orbit. Every single regime an aerospace fighter has to operate in would make the fighter "a group of compromises flying in close formation," but aerospace fighters don't just deal with one - they deal with all of them.

3) Space fighters don't have to deal with the headache of atmospheric aerodynamics. They don't have to deal with re-entry. They don't have to adapt their rocket nozzle shapes to working at sea level atmospheric pressure, air pressure at 50000ft, and vacuum. They can basically operate in a single, very constant environment. Sure, space is no picnic: there are temperature extremes to deal with, vacuum makes shedding heat difficult, life support has to be fairly self-contained, etc., but once you can get into space, relatively primitive technology can handle the issues. (I daresay 19th Century engineers would be up to the task if you told them what to expect and gave their boilerplate creation a free ride into orbit. CO2 scrubbers, liquid or compressed oxygen, evaporative coolers, rockets...quite feasible.)

So, what sort of rules are reasonable for Space Fighters?

1) Space Fighters can land, they just can't deal with an atmosphere. With the abundant thrust of BT fusion engines, landing on even large, airless worlds would be easy. Stick some bug legs on a space fighter and give the navigation systems the right software and they'll be able to pivot and land butt-first on an airless world. A Space Fighter that attempts to land in atmosphere thicker than 1% of Earth's will automatically crash unless the GM is feeling generous.
2) For somewhat more trouble, a Space Fighter can be a "Spheroid Fighter," as opposed to the standard Aerodyne Fighter. This fighter can perform like a spheroid dropship in an atmosphere (i.e., it lands, takeoffs, hovers, or crashes).
3) Cheaper. A Space Fighter is 75% of the cost of an Aerospace Fighter. A Spheroid Fighter costs the same as a normal aerospace fighter, but has normal Space Fighter benefits (below).
4) Optimized reaction control system. Using the AT2 advanced movement rules, a Space Fighter can pivot 3 hex faces per thrust point spent (keep track of fractions for fuel usage.)
5) Optimized engine nozzles. Space Fighters calculate their thrust rating with a +3 thrust point bonus rather than a +2 bonus. For example, a standard, 50-ton aerospace fighter with a 200-rated engine will a thrust of 6. A 50-ton space fighter with a 200-rated engine will have a thrust of 7.

Mike Miller, Materials Engineer

Disclaimer: Anything stated in this post is unofficial and non-canon unless directly quoted from a published book. Random internet musings of a BattleTech writer are not canon.
12/27/06 12:45 PM

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I like it. Have done up any Space Fighters with these ideas in use?

Given time and plenty of paper, a philosopher can prove anything.
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