Revision 3, Jack Thundram, 481 AS.
DRL/45H Linear Projectile Accellerator
Overview
The DRL/45H is the latest in heavy duty, large scale ordinance delivery. Capable of launching a 12 ton payload of any kind, from either a stationary or mobile position, it is perfectly suited for breaking up hardened targets, such as large asteroids, into workable sizes. The projectile accelerator design is fully scalable, with a theoretical projectile exit velocity close to 0.5c . Naturally, such speeds are impractical, and most common implementations call for a rail size of 40m to 200m, resulting in an exit velocity of roughly 2Km/s  to 8 Km/s, with a typical 10 ton payload. With an average rise time of 60 minutes to full capacity, crews can break up to 25 large payload targets into debris that can be processed by conventional, non-lander space mining techniques. This makes this system bridge the gap between asteroids that are too large to handle by space miners, but too small (or too hazardous) to sustain a landing party for surface extraction.
The charge cycle consist of parallel charging a series of charging one to eight banks of TRC41 capacitors to 95% capacity, then releasing the entire charge directly into the launcher system. The capacitors should retain 20% charge at the end of a launch cycle – if not, reduce the payload size or add an additional capacitor bank. It is the charge cycle of these capacitors that limits the system launch frequency.
Requirements – Recoil and lateral forces.
The system experiences severe lateral, and recoil forces upon firing. It is recommended a launcher platform be designed specifically around the weapon system to account for these forces. The weapon’s recoil is equal to its projectile acceleration, up to a maximum of 200KN. If the system mounts are unable to accommodate this strain, a reduction in weapon current can reduce the strain, at the cost of projectile velocity. Lateral strain is focused on the round. It is most severe at the projectile loading point, exceeding the recoil forces by 150%, but is almost nonexistent at the system exit.
Lateral launcher strain can be controlled by a second set of rails flanking the first, offering a counterforce. These rails do not have the non-deformation requirements of the primary rails, nor the thermal control limits. But adding a second rail set to control the lateral strain almost doubles the systems energy requirement. Since the lateral forces are extremely hard to control at launch initiation, many versions include a partial “ballast” rail near the payload loading point.
Requirement – Thermal.
The extreme electrical currents required for this system cause both the projectile and launcher rails to heat up. Partial conversion into plasma occurs along the edges of the payload – this is not considered a problem, as the plasma carries the current extremely well between the rails. It does cause extreme thermal stress on the rail itself. The rail’s external coating is designed to be partially sacrificial to accommodate the wearing this causes. Roughly every 200 launches the rail coating needs to be replaced. This routine maintenance process can be done by drones or EVA crews, and should take no more than one standard hour. Carrying a complement of spare rail coatings is highly recommended – in case of a misfire, the payload will meld with the coating, and can only be expelled by immediately replacing the entire rail coating. Naturally, this requires the rails to be easily accessible – it is recommended to mount them on the outer hull.
In order to cool the rails down to an acceptable temperature post-launch and prevent damage beyond the coating, liquid nitrogen coolant solution is recommended. Flushing the rail during, and after launch will keep the rail core within an acceptable thermal range. The coolant system can regenerate its supply of liquid nitrogen while the system is charging its capacitors – simply recover the gaseous nitrogen and recompress it. Dissipating the resulting heat should be fairly simple in the vacuum of space, simply radiate it out through the ship’s hull. On a side note, some of the weapons energy can be recovered through the nitrogen gas expanding.
Schematic overview:
The basic concept of the rail gun dates back to the 20th century of mankind in the Sol system. While the design was slowly improved upon, up to military grade anti-orbital projectile launchers, it was not until several breakthroughs in superconductor research (around 260AS, by Ageira), that superconductor rail launching systems became a feasible alternative for conventional rocket-assisted payload delivery systems.
The basic design has not changed. Two highly conductive rails, connected to a high current inducing power source, a mobile payload in between to complete circuit. The resulting magnetic field induced by the current propels the charge up the rail, into immense velocities. The exit velocity is limited by rail length, friction, and current induced. The details of the design however have changed greatly. Replacing the rail design with a superconductor core and copper shell allowed for a sharp increase in the current, and energy efficiency as less energy was lost in material resistance.

A minor sacrificial contact material is added to the payload sides, to connect the rails to the charge itself. This material is set to partially convert into plasma with superconductive capabilities of itself, with the heat of the copper rail wall sustaining the plasma as it moves along the rail and evaporates. Naturally, the payload needs to tolerate extremely high surface temperatures. Typically the payload consists of either a dense, inert slug (using sheer impact force to vaporize the shell on impact and releasing the resulting energy on contact, explosively) or a strongly shielded explosive charge, typically with a copper alloy shell. No coolant is provided in this system for the payload itself; however, upon leaving the launcher, the payload usually cools rapidly in the vacuum of space. Note, while used in nebulae temperature will often increase, rather than decrease. Range is also impacted due to particle friction.
The utilized current in the superconductors is of a relatively low voltage (in the order of several hundred volts depending on the payload). Arcing around the superconductors to the ship’s hull will not occur.
Design schematics:
The exact implementations of the system may vary, but the following components make the primary loop:
- Two to ten pairs of SL/T33 superconductor bars (20M length). Recommended maximum is for practicality, longer is possible to use a lower launch current, however, and would rapidly become a waste. For each doubling of the length the current can be halved.
- One to eight TRC41 high-capacity energy buffers, in parallel switching, individually connected to the bus bars by separate superconductive conduits. More are possible, but again, impractical (unless an excessively long launcher is used, and thus a longer discharge time is required). These buffers should be discharged to no less then 20% during a launch cycle. 
- For each SL/T33, 10 SL/T33CC ablative copper coatings. These will lock around the insides of the bar and carry the current from the superconductors to the payload.
- A SSI334 Solid State Switch, to interrupt the current while the system is cycling or the payload is being loaded. Optionally, a SSH334 manual circuit interrupter can be installed.
- A CRG20S liquid nitrogen coolant system.
- Any payload certified to be launch able by the DRL/45H launcher system. 

A typical configuration has the rails anchored securely at about a one meter separation. A payload entry system is placed at the base of the rails, with about 10cm clearance, an allowance for the rail’s recoil. The loader designs vary, from a simple piston to push the desired payload onto the rail, to a robotic grapple. When used in a zero-g environment a grapple is recommended.
The liquid nitrogen coolant system is connected to the copper coating’s edge, using the copper’s thermal conductivity itself to guide the heat of the firing sequence away, and prevent the coating from melting. Both superconductor and coating need to be individually supported along the entire length of the launcher, requiring significant modifications to any vessel requiring this system – it is safe to say that implementing it to vessels not specifically designed to carry the DRL/54H would be at best costly.
The muzzle of the launcher is recommended to equip a series of insulators to prevent plasma arcing, which can reduce accuracy.
Conclusion
When it comes to short-to-mid range solid payload delivery, the DRL/45H more than exceeds the capabilities of standard torpedo-based systems, in terms of accuracy, range, and penetration. Capable of penetrating a standard silicate based asteroid to a depth of 1000 meters, the system can be utilized to shatter medium sized asteroids of up to 6000 meters in diameter, more than double what torpedo-based systems can handle, without requiring the risk of sending out an EVA crew to deploy a surface drill and charge.