Neither Fish Nor Fowl

And next in our review of less conventional starship types, we come to that odd duck, the aerospace cruiser. (And many of these remarks, naturally, also apply to its larger cousin, the aerospace carrier.)

Ever since the early Imperial Navy absorbed the old air forces into its Close Orbit and Atmospheric Command (CLATMOCOM, under the Second Space Lord), these specialized classes and their equally specialist crewers have existed in something of a limbo, engaging in practices often deemed unnatural among decent, right-thinking spacers. Such as, if I may write in hushed tones for a moment, streamlining.

In short, while normally one can rely on a comfortable dichotomy between airships – which stay down in the nice, warm, notably present air – and starships – which avoid atmosphere in the much the same way that a thirsty Leirite avoids water – the aerospace cruiser defies this. While even the interface vehicles that bridge these two realms tend to minimize their time spent in the inconvenient middle, it spends all its operational time in a realm too low for low orbit and too high for upper atmosphere, being beholden to neither.

This requires a large number of rather unsettling compromises. Let’s begin our examination with the fundamental reason why: the entire purpose of an aerospace cruiser is to provide a secure base from which atmospheric combat vehicles can sortie, and in order to let them be competitive ACVs, it is necessary not to weigh them down with large extra drive mechanisms just to enable them to get to and from the mama bird. Thus, said mothership must not operate merely in low orbit, but dipping well into the atmosphere – into the lower mesophere – at typical altitudes for lithic worlds no more than 65 to 80 km (211,000 – 264,000′) above the surface. Such altitudes are already painfully difficult to reach for dedicated air vehicles, but manageable with relatively small auxiliary aerospikes.

And yet, the implications! A non-interface starship at this altitude suffers from high levels of atmospheric drag, enough to rip any normal starship’s – one not designed for atmospheric entry – structure apart, and thus, aerospace cruisers must share the great attention to streamlining and the heavier structure required by interface vehicles, but to an even greater extent, since the aerospace cruiser must not only penetrate the entry interface, but hang in it while launching and receiving aircraft from its vomitories.

(This in turn involves various trade-offs in other starship systems, like radiators, which must be accommodated behind streamlined panels while still functioning effectively; the point-defense laser grid must be tuned to atmospheric frequencies despite the effects on performance – and aerospace cruisers are well within the practical offensive range of ground-based aircraft and anti-aircraft systems; the engines must not choke when run in atmosphere; and so forth.)

The next issue, fortunately, partly cancels out this one. While an aerospace cruiser sustaining (via continuous burn; copious fuel supplies and an oiler or two to restock them are also essentials for space-to-atmo operations) orbit at 72 km would have to deal with an arbitrarily long period of fending off the atmosphere at 8 km/sec, consider that the period of such an orbit is a little under 1.5 hours, meaning that an aerospace cruiser maintaining its “natural” orbital velocity will pass very rapidly over the battlespace and out of air range; and pilots in general, it should be said, are notably unappreciative when their mothership leaves them behind.

To avoid this, aerospace cruisers are required to operate in forced orbits, maintaining station above a particular location. This requires, of course, even more copious supplies of fuel and multiplies the required continuous – and for those not familiar with the concept, continuous here means if the drive ever stops, you fall right out of the sky and die – station-keeping burn considerably, but at least it spares you quite so much brutalization by the atmosphere and makes launching and receiving aircraft practical, not just theoretically possible.

So before we continue and look at specific types, let’s raise a glass to these low-flying, fuel-gulping, plasma-shocking, sky-hanging abominations of nature, and all that sail in them! We don’t look down on you – except literally – but we wouldn’t have your jobs for a Service pension and a nice retirement moon.

– the Big Boys’ Book of Boom