orion drive

Sketchy Orions

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Hello, and welcome once again to Truly Awful Whiteboard Pictures season, as I present to you the basic workings of a nuclear-pulse Orion drive, Empire-style. Or at least Empire-of-the-Spaceflight-Initiative-Era style. Mostly so that I can refer to it later and y’all’ll know what I’m talking about.

Behold ye first (and note that I’m not really getting into explaining the Orion drive itself at this point: for that see here, which should give you an idea of what I’m riffing on) an exceptionally crude and simplified illustration of the mechanics of the drive itself:

A crude diagram of the mechanics of the Empire's nuclear-pulse drive.

The way this works as part of each firing cycle is approximately this:

  1. A pulse unit, taken from the magazines, is fed by the loader into the breech/spinner and magnetically suspended there. The “spinner” spins it up for the purpose of spin-stabilization, as later in the process, it will be vitally important that the coaxial firing laser be able to lay a beam on the lens at one end of the soda-can-sized pulse unit.
  2. The irises (both the primary one built into the pusher plate, and the secondary one at the end of the coilgun, snap open to let the pulse unit pass.
  3. The coilgun throws the pulse unit out and down towards firing position.
  4. As the pulse unit reaches firing position, the firing laser delivers an ignition pulse to it (right down the now-empty bore of the coilgun). The pulse unit does its prompt critical thing.
  5. Immediately afterwards, before the plasma from the pulse unit detonation can reach the pusher plate, the primary and secondary irises snap closed to protect the firing mechanism from the detonation.
  6. And repeat for the next cycle.

As for the pulse units themselves, they look like this. Very roughly, as I’m eliminating all the complexity that goes into making them Happy Fun Shaped Charges as well as streamlined, spin-stabilized projectiles. Conceptual only:

Crude sketches of fission and fusion pulse units for 'verse Orion drives.

The upper one is the old-style fission-based unit. Basically, it’s a laser-triggered fission bomb. The firing laser hits the beamcatcher lens, which splits the laser impulse into many beamlets proceeding along optical fibers, which are set up so that the laser impulselets reach the various explosive lenses surrounding the pit at the same moment. Implosion, prompt criticality, and fission pulse proceed to happen.

The lower one is the new hotness fusion-based unit. It’s a laser-triggered pure fusion bomb. In this case, the beamcatcher lens focuses the considerably more powerful laser impulse onto a parabolic mirror and needed secondary mirrors (not shown), for the purpose of delivering the laser impulse to all sides of a fusible pellet at the same time, even as the mirrors themselves are busy vaporizing. Fusible pellet hits inertially-confined criticality, and fusion pulse proceeds to happen.

The important thing to note here is that as much of the complexity as possible has been offloaded from the pulse units to the drive, inasmuch as you might want to knock a quick thousand pulse units out in the field with a relatively crude shipboard machine shop, which is not something you would expect to be able to build the drive.

Bigger and Uglier

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DROPSHIPS: EMPIRE OF THE STAR

This supplement to the current edition of Naval Warships presents an update to the infamous Flapjack– and Flapjack II-class cavalry dropships. The Imperial Navy has recently adopted the Waffle-class vehicular dropship – also designated the Flapjack I (Block II) – as a phased replacement for the Flapjacks currently in service.

The Waffle resembles the older Flapjack in most ways, inasmuch as it too is based on the disk-type hull form, and makes use of a pair of laser-fusion nuclear-pulse drives to perform a high-velocity descent followed by a “suicide burn” deceleration. However, unlike the Flapjack, the Waffle does not land to disembark vehicles.

The main body of the Waffle, between the pusher plates, replaces the cylindrical garage of the Flapjack with a bunch-of-grapes packed between the central core and the sidewall armor. These “grapes” are the payload: tanks, IFVs, and chariots – any vehicle type equipped with a vector-control core – enclosed in a protective armor clamshell oversprayed with ablative foam.

As the Waffle performs its suicide burn, it dumps angular momentum from its core gyro, spinning the entire ship up. At the terminus of the suicide burn – typically no more than 2000′ above ground – the ship explosively discards the sidewall armor and severs the retaining structure which retains the “grapes”, causing them to be jettisoned along with a large swarm of decoys, chaff, and hunter-seeker antidefensive missiles.

At this point, the basic dropship structure is abandoned, and the vehicles, lightened by their vector-control cores, are scattered over a wide area, discarding their clamshell protection immediately before landing.

Thus, the Waffle eliminates the core disadvantage of the Flapjack, the requirement for rapid disembarkation and dispersal from a single landing site. Additionally, the psychological effect of a cloud of fireballs raining armies from the sky should not, in this author’s opinion, be underestimated.

– Naval Starships of the Associated Worlds, INI Press, Palaxias,
supplement to the 433rd ed.

Trope-a-Day: Orion Drive

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Orion Drive: As we mentioned way back in Nuclear Weapons Taboo, Eliera was always enriched in heavy metals, including the uranium family, and low on fossil fuels; and since the first set of uses of nuclear technology were all harmless civilian applications before anyone ever thought of weaponizing it…

Well, yeah.  Orion drives, or nuclear pulse drives rather, were an obvious development, from the early days of Project Phoenix (orbital shots), for satellite launches, and on through Project Oculus (near-orbit space station) and Project Silverfall (moon shots), and on through the early days of space colonization.  And not just for orbital maneuvering; they were used for ground launch, although replacing fission bombs swiftly with laser-triggered fusion pellets, up until they were eventually replaced with gas core closed-cycle nuclear thermal rockets, and eventually with mass driver/laser ablative hybrid drives for bulk cargo and trimodal NTRs for passengers, and eventually with beanstalks.

(Of course, this wasn’t entirely without consequences.  While the name of the Bright Desert originally referred to the glare reflecting off the pure white sand, the pleasant Cherenkov glow coming off both the glass-lined craters of the Imperial Orbital Launch Reservation and the pyramids of glass ingots stacked in the Burning Brickyard – the primary planetary nuclear waste disposal site – gives it an entirely new meaning these nights. Fancy nuke-resistant fallout-minimizing launchpads weren’t invented immediately, after all…)

The Breakfast Of Champions

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DROPSHIPS: EMPIRE OF THE STAR

The final entry in this section, affectionately known to the Imperial Legions as the “Big Ugly Breakfast 1” – and less affectionately known to almost everyone else as “Good gods, what is that thing?” – is the Flapjack-class cavalry dropship (Eye-in-the-Flame Arms/Artifice Armaments). Uniquely among Imperial starship designs, the Flapjack has adopted the rare “disk” or “saucer” hull form. It does this because the Flapjack-class is equipped with not merely a single, but a pair of nuclear-pulse drives, using the relatively environmentally friendly laser-fusion or (in the Flapjack II) antimatter options, the descent and deceleration drives; the dorsal and ventral hulls of these ships are in effect simply the pusher plates for these drives. The main body of the vessel, suspended between these on hydraulic dampers, is a short, wide cylinder, heavily structurally reinforced and itself surrounded by  “sidewall” armor as thick and refractory as the pusher plates.

The intended usage of the Flapjack is orbital insertion of armored vehicles, en masse, into hot zones. To enable this, after being decoupled from a carrier in the high orbitals of a planet under attack, the Flapjack uses its descent drive to accelerate downwards through the atmosphere, minimizing dwell time within range of orbital and anti-air defenses. In addition, while the descent of a Flapjack obviously has far too bright a sensor signature to be concealed, the combination of the radiation hash from the descent drive’s thrust bombs and the plasma sheath formed by its hypersonic atmospheric transit together render it extremely difficult for weapons systems to attain successful guidance lock, and terminal guidance (especially to the fine degree necessary to insert a weapon into the narrow window of vulnerability between the pusher plates and the sidewall armor, even if the weapon is capable of surviving and maneuvering in the immediate environment of an active nuclear-pulse drive) virtually impossible.

At the end of its descent trajectory, the Flapjack uses the more powerful thrust bombs of its deceleration drive to perform a “suicide burn”; i.e., maximal deceleration at minimum altitude, compatible with lithobraking in a manner which preserves the integrity of the ventral pusher plate. This deceleration burn serves the additional functions of preparing the drop zone for the arrival of the dropship by flattening any structures or prepared defenses, and eliminating any but the most heavily armored, secured, and radiation-proofed resistance in the immediate area. Once the ground is reached, multiple armored cargo access doors with integral ramps and excavation drones permit the Flapjack to be actively discharging combat vehicles within minutes of a successful landing.

A proposal for an infantry dropship along the lines of the Flapjack, tentatively designated the Pancake-class, has been advanced by Eye-in-the-Flame Arms, but at the present time the high-radiation aftermath of such a vessel’s landing is not considered viable for personnel wearing M-70 Havoc combat exoskeletons or N45 Garrex field combat armor, the current legionary standards. While this would not be a problem for troops equipped with the specialized N45r Callérás high-rad field combat armor, its associated disadvantages and the expense of refit ensure that, for the foreseeable future, infantry will continue to be landed via drop shuttle (q.v.)

– Naval Starships of the Associated Worlds, INI Press, Palaxias, 421st ed.

1. A statistically improbable number of combat drops take place at planet dawn.

Orion Drives

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wolfkazumaru replied to your quote: “Phoenix Zero, you are blue-lighted across the”

Using nuclear drives in atmo? Tsk, tsk, that’s dangerous.

Ah, you humans and your silly fragile immune systems…

Well, considering at the time they were already using nuclear power plants, nuclear furnaces, nuclear-powered vehicles, and nuclear devices to excavate reservoirs, cut tunnels, dig canals, disperse inconvenient mountains, and so forth, no-one was really all that worried about another use for Our Friend, The Atom.

(Especially one that was being tested in the middle of a freakin’ desert many miles from anywhere stuff might fall on.)

It also helped that in their universe, no-one at the time had thought of using them on people. I mean, sure, you could theoretically weaponize a nuclear device, but what would be the point? Everyone knows they’d have no imaginable practical use in warfare, right? What possible use is there for a bomb that completely obliterates the economic value of whatever you’re fighting over?