Cray
02/11/03 02:39 PM
147.160.125.185
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Gee, I guess using the term "jump fighter" in AT2 might provoke the wrong image. For the record, I mean V/STOL fighter, not "KF-drive equipped" fighter.
LOSTECH AND THE BIRTH OF THE RAVEN
Anyway, the Raven Shuttle and Raven Jump Fighter are vehicles with a common origin in the Hindu Collective, a region within the Crucis March (or maybe Capellan) of the Federated Suns. Back in the Day, before the First Star League, the Hindu Collective was a prosperous group of stars settled by (gasp) India-ethnic Hindu settlers. It stomped the heck out of one of the FedSuns Civil War factions in the 2520s who thought to run through the unaligned Hindu Collective Worlds. Later, the Hindu Collective joined the FS and gave the Suns a useful economic shot in the arm.
The Succession Wars were not kind to the industrialized worlds of the Collective.
The Star League Memory Core was a chance for the worlds of the former collective to bootstrap themselves up out of the 21st Century level of technology they had sunk to. With the same degree of organization and industriousness that had made the Collective great by the 2500s, the people of the former Collective worlds set about rebuilding. First targeted were "enabling" technologies that would make other technology easy to recover and support. Besides advanced water filtration technology (and supporting chemical and mechanical industries), fusion technology received a lot of attention. With more research groups than copies of the Star League Memory Core, some research into recovering lost technology was bound to stray into new areas ignored by the Star League.
One of these was fusion rocketry, fusion air breathing jet engines, and fusion jump jets for mechs. In the course of developing a "reaction chamber" for a domestically produced jump jet for domestically produced battlemechs, the firm of Kandla Atomics Ltd. had to start from scratch due to the inability to license existing jump jet designs. With only partial records from the Memory Core, it set about designing the reaction chamber. With no preconceptions of how to design the system, the engineers involved recognized that this system would also be useful for airbreathing fusion engines if a continuous-feed air compressor could be attached (as opposed to the burst-feed compressor of jump jets). This would let the chamber be used in the much broader market of civilian aircraft - airlines would sell (someone's) first born children to eliminate fuel costs. And it would be easy enough to close off air intakes into the chamber and just pump in an alternate reaction mass (which the jump jets would need to do anyway, if they were to be of any use for mechs in a vacuum), like hydrogen or mercury.
Since the jump jet contract was real while aerospace markets were just speculate, Kandla finished up the jump jet project and watched happily as its jump jets went into locally-built Griffins and Stingers. Its marketing execs began soliciting airlines and aerospace firms for interest in fusion-powered aircraft that could operate entirely on air. The airlines were distinctly interested, but they would have to replace (not refit) their current fleets of twenty million C-bill airliners. That wasn't something to be casually or quickly, especially not when the technology was unproven. (And, some more educated airline executives pointed out, this was a real sticking point because this technology hadn't been developed in the Star League. Fusion-powered jets back then had used reaction mass. Did Kandla actually think it could something the Star League hadn't?)
Kandla, however, wasn't the only company interested in this technology. Kandla built fusion engines and fusion-powered reaction engines. It did not build aircraft. Locmar Aerospace, a local civilian aircraft firm, did build aircraft, and was drooling over the possibility of replacing thousands of large airliners in service throughout the former Collective worlds.
Locmar, which stood to earn a lot more money from replacing airline fleets than Kandla, easily mustered the investors to fund a demonstrator. It subcontracted Kandla to build a fusion-powered reaction engine that could use air or some liquid for reaction mass.
The end result was the Raven, a shuttle capable of short jaunts in near-planetary space. It would be inexpensive enough to compete with business jets, certainly saving in the long run versus the enormous fuel costs of IC jets. Just to emphasize the opportunities opened by fusion power, the Raven would be a VSTOL aerospacecraft.
While Locmar played up the Raven as being named after an animal iconic of wisdom and foresight, the choice of the name came from the hull of the Raven, which was black. The aligned crystal steel and ceramics of the hull were black for best heat radiating performance during re-entry. With a large mass budget and no need to humor military procurement boards eager to get the last drop of performance out of the Raven, Locmar aerospace engineers gave the Raven large, generous delta wings, with large vertical winglets at the tips. With the advanced materials of the day, the Raven could also have sharp, low drag leading edges. If it chose an unpowered re-entry, the Raven would be able to brake gently and slowly in the upper fringes of the atmosphere, imposing low G-forces on the occupants and low thermal burdens on the heat shield. The low hypersonic drag enabled by the sharp leading edges would allow the Raven to steer (during re-entry) great distances off its original orbital path without using reaction mass. Its stall speed would also be low, enabling a reasonable landing speed - without using its VSTOL features.
The VSTOL features, originally intended to capture the eye of execs by letting the Raven land on rooftop helicopter pads, also gave the Raven utility on airless worlds. It would eventually capture the eye of the militia.
For spaceflight and commercial use, the Raven was configured for a crew of 2 in the cockpit and 4 short haul passengers. Reaction mass tanks in the wings and the large wing roots (the Raven had a blended wing-body design similar to the Slayer) held a mere 3 tons of reaction mass. Behind the passenger cabin was a 3-meter diameter, 10-meter long cargo bay that ended in a sharp, conical tail. The tail swung up and out of the way for easy loading; the cargo bay also had classic, twin dorsal cargo bay doors. The cargo bay could either hold 5 tons of cargo (duh) or insulated tanks for an additional 5 tons of hydrogen reaction mass. (After the the Raven prototypes were tested, mounts for over-wing drop tanks were added. See AT2 errata.)
Just for giggles and to emphasize the Raven's versatility, Locmar made the Raven reasonably seaworthy. It could land and takeoff (vertically) from water. It did not have a hull suitable for horizontal water landings, and its water jet system could make about 5kph of headway in calm water.
For Ravens that would only be used in the atmosphere, the 3 tons of wing fuel and 5 tons of cargo were replaced with seating for a "platoon" of passengers (28; 3 tons) and 4 tons of presumably much denser cargo than liquid hydrogen. Executive models could also feature heavier armor.
UNDER THE HOOD (BONNET)
While a useful shuttle and business "jet", the Raven was meant to show off its engines. The core of the engine was a 180-rated Kandla fusion power plant that supplied enormous amounts of power to twin reaction chambers on either side of the body. The reaction chambers featured several types of high energy emitters: electron beam guns and tunable masers and lasers. Ahead of the reaction chambers were the powerful axial flow compressors (much like most jet engines had) that could ram air into the reaction chamber under high pressure, where the emitters would superheat the air. The compressor, unlike many conventional aircrafts' jet engines, was not driven by a turbine in the exhaust stream. The compressor was driven by high efficiency linear motors around the rim of the compressors' stages. Also, electric pumps were present to dump hydrogen into the reaction chamber when additional thrust was needed, or when the air was too thin for the compressors (or just nonexistant).
By borrowing lessons from jump jets (which usually made do with local air for reaction mass), Kandla Atomics' engine could avoid the need for reaction mass all together, at least when in thick atmospheres and at low thrust demands. This was noticeably superior to aerospace fighters, which were simple fusion rockets (no air intake, and the fuel inefficiency to show for it) and conventional fusion-powered fighters, which did mix in some atmosphere with onboard reaction mass to double their fuel efficiency over aerospace fighters.
While this was quantitatively superior to conventional fighters (outside of combat), the Raven had a much worse thrust-to-weight ratio compared to aerospace fighters. The Raven's engine was as heavy as fusion-powered conventional fighters' (10.5 tons, in this case, for a 180-rated engine). On the other hand, ASFs used pure rocket designs and thus did away with the heavy compressors and squeezed a great deal more thrust out of the same sized engine. While the 30-ton Raven could accelerate (at overthrust) at 4.5Gs, a 30-ton ASF with the same engine could accelerate at 6Gs. The difference was even sharper when it was remembered that the ASF's engine would only be 7 tons, not 10.5 tons.
The VSTOL system was a straight forward thrust vectoring system. Four ports, two in the middle wing roots and two in the stern, could pivot up to 100 degrees below horizontal (enabling not only a hover, but slow backward movement). The Raven's obligatory reaction control system for vacuum movement also doubled as stabilizing "puffers" during VSTOL movement. A superior flight control system made operation in VSTOL format extremely simple, a case of using a multi-axis control ball.
Finally, the unavoidable aerodynamic compromises necessary for the Raven to operate at any speed from a hover to orbital velocities meant the Raven had the aerobatic performance of an aerospace fighter, not that of a more agile, optimized conventional fighter.
THE RAVEN'S CLAWS
In summary, the Raven was an inexpensive, very versatile VSTOL shuttle with enough elbow room for a platoon of infantry and several light utility vehicles (1- or 2-ton jeeps). It could deliver troops to a moon or space station in hours or less, and drop troops anywhere on a planet from a ground launch in about 45 minutes, if it took an unpowered suborbital hop. (Faster, if it burned constantly.) And to repeat, it was a VSTOL suitable for operating from rough fields, ponds, and small plots in forests.
The local militia liked that.
The Raven's core engine system and wings could easily be built around a different body, a better armored, better armed one without the roomy cargo bay.
The local militia liked that, too.
Locmar planned to produce several dozen Raven shuttles a year for corporations, and that was just using one of its smaller business jet assembly lines. If the interest and money was there, Locmar could see fit to build the Raven quite a bit faster. Or a variant of the Raven.
The local militia liked that, too.
After the Raven (shuttle) was flying and securing deals for fusion-powered airliners across former Hindu Collective worlds, Locmar invested its own funds in producing an armed variant of the Raven. This included improving the hull materials, removing the roomy cargo bay, and adding 4 laser mounts. The Raven (fighter) would be nothing but a mediocre light fighter suitable for harassing poorly escorted enemy dropships, strafing, and bombing, but it gave local militias a numerous, versatile, easily maintained fighter from local facilities.
RULES FOR AIRBREATHING FUSION-POWERED FIGHTERS
CVF = conventional fighter, ASF = aerospace fighter
*At its normal thrust rating and less, and at altitudes conventional fighters could operate at, an "airbreathing" fusion-powered fighter like the Raven does not use reaction mass. (Applies to CVFs and ASFs).
*At overthrust, and at any altitude the fighter can operate at, an "airbreathing" fusion-powered fighter uses reaction mass like an aerospace fighter. (Applies to CVFs and ASFs.)
*In space and high atmospheric altitudes (where CVFs cannot operate), an airbreathing fusion-powered fighter uses reaction mass like an aerospace fighter. (Applies to ASFs.)
*The engine weight of an airbreathing fusion-powered fighter is like a CVF's fusion engine: 50% heavier than normal. (Applies to CVFs and ASFs.)
*The thrust of an airbreathing fusion-powered fighter is determined like a CVF: thrust = engine rating / tonnage. (Applies to CVFs and ASFs.)
COMMENT
Chris Hartford, writer of AT2, has spoken unto us and said fighters always use fuel, even outside of combat, in the atmosphere, and below overthrust ratings. Yes, this applies to fusion-powered aircraft, to. If you ignore this rule and don't charge fighters fuel outside of combat, then ignore the alternate equipment set.
RAVEN SHUTTLE
30 tons
10.5 tons 180 fusion engine (airbreathing)
....Thrust: 6
....Overthrust: 9
....SI: 6
0 tons 10 SHS
3 tons cockpit
3 tons fuel
1.5 tons VSTOL
3 tons armor
....Nose: 15
....RW/LW: 11/11
....Rear: 11
4 tons passengers (4 passengers for short space flights)
5 tons cargo
VARIANTS
The cargo bay can be replaced with a slide-in liquid hydrogen tank holding 5 tons of fuel. Loading this dome-ended cylinder into the gaping stern door usually provokes rude comments from the ground crew and onlookers.
The civilian Raven isn't always used for trans-atmospheric flight. Many civilian users find zero-G nauseating and keep the Raven to atmospheric flights. Therefore, the extensive lifesupport and crew facilities for space travel are removed, leaving the standard cockpit. Since civilians have little need for the afterburner, the wing hydrogen tanks are left dry. This frees up 7 tons. Further, the engines are downrated to 175, and the "all atmospheric" Raven is left at 25 tons and with better (7/11) performance. The typical replacement for the 7 freed tons is with 28 economy-class seats and space for 4 tons of luggage and other cargo.
The military Raven fighter has a very different looking body, though its nose and wings are recognizable. It trades the current 4 passengers and 5 tons of cargo for 4 wing-mounted medium lasers (or ER MLs), 2 more tons of fuel, and 3 more tons of armor. The armor is upgraded to ferro-fibrous and heat sinks improved to DHS.
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.
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