A.4.2.1.4 Conventional Gun 1
One of the methods for quickly launching into Low Earth Orbit is to use a conventional gun which uses some form of a high explosive charge through a gun to launch the system. Our team looked at this type of launch system and performed a feasibility study. This configuration was not chosen in the end due to several limiting factors.
Conventional guns have been used as high altitude research launchers in the past, specifically, in the 1960’s during the HARP (High Altitude Research Program.)1 In this program, a Navy 16in conventional gun was used to fire a rocket carrying a payload to a certain altitude, at which point the rocket would fire in order to get a final boost into orbit. The program had several very attractive features that would have worked well for our project. The first would be the high turnaround rate. Some predictions are that the gun could fire at a rate of approximately once an hour, which would greatly reduce ground time and allow a high volume of vehicles to be put into orbit.
A second attractive point of the conventional gun is the relative simplicity of the actual launch vehicle. The initial launch would be using a very large barrel gun with a semi-standard explosive charge. The projectile would then be a rocket with a form of a propulsion system (most likely solid) that would fire and take the small payload into orbit. Since our satellite is so small and has a low mass, this system could be able to fit within the gun in order to be launched.
There was one main reason why this configuration was not finally chosen even with the very attractive qualities. This has to due with the inherent nature of the gun. The projectile would be accelerated at a very high rate in order to get the muzzle velocity needed to get to a high altitude. In the HARP program, estimates were that the launch vehicle would need to withstand approximately 13,000 G’s.1 This g-load was determined to be too high for our system and components. Problems arise with these extreme g’s during launch including integrity of materials, sensitivity of electronics, and cracking of solid propellant. In order to get the structure and electronics to withstand these high forces, it was determined that it would be too costly in the long run and would limit the satellites that would be put into orbit using this system. The main theme of the project is to allow groups to cheaply put small satellites into orbit, and by limiting the capabilities of the satellites that would be launched, we determined that this conventional gun was not an attractive launch type.
References:
1. Wade, Mark, “Martlet 4,” [http://www.astronautix.com/lvs/martlet4.htm. Accessed 1/12/08.]
Author: Stephan Shurn