Dominant Logistics
Gunning for Space
Gun-Based Launchers
Years ago, scientists tinkered with the idea of using large guns for launching satellites into space. Jules Verne appears to have dreamed up the original concept for a space gun in Hollywood. The famed Gerald Bull actually developed and built a space gun in the 1960s that was able to put a payload into space using standard gunpowder. Even with the limited technologies of the time, these guns showed substantial promise but were abandoned in favor of expensive and risky rocket-based systems. It's high time to take another look at the gun option.
Whether we use a chemical-driven gun or a pneumatic gun, this approach offers tremendous advantages over any other option. It is the safest option available for launching satellites because it doesn't involve humans in the launch process and there are very few things that can go wrong with a gun. It is also cheaper than any other option because it requires fewer parts and support requirements than any other design. Virtually every part of a gun-based system can be constructed of conventional materials and is reusable. It is also the only all-weather option for launching satellites.
Gun-based launchers can also be located in a greater variety of locations. A gun launcher can be placed up in the mountains to take advantage of higher altitudes and thinner air to increase payload capacity. And unlike other designs, the supporting land doesn't require the ability to withstand tremendous forces like other launch concepts.
By developing and fielding a small number of space guns, we could easily and affordably field the capacity to safely launch one satellite per day without any real difficulties. In a crisis situation, we could surge that launch capacity to around four launches per day assuming the use of four space guns. No other approach can even come close to this level of capacity and the other designs cost far more money for less launch ability.
Modular Satellites
The greatest advantage of the gun approach is that it allows us to develop modular satellites that will dramatically lower the costs of space payloads along with our lower launching costs. We start by developing a standard space frame. The space frame would be a very simply section that would include thruster jets for maneuvering, couplings for adding additional sections, and basic fuel, power, and computing systems. There would also be room for adding solar panels to the frame for additional power requirements. The space frame would serve as a core around which the complete satellite would be built. Most satellites would use the space frame allowing for something approaching mass production of the frame.
Power modules would be delivered as a separate load in a second launch. These may be batteries, nuclear power cells, or even fuel cells. These would also include the same basic fuel, power, and computing systems for maneuvering that the space frame uses. The power module would be launched and then maneuvered to link up with the space frame in orbit.
Payload modules would consist of the major systems used by the satellite. These may be optics packages, communications systems, GPS transceivers, or any other useful satellite system. As with the other modules, it would include basic fuel, power, and computing subsystems for maneuvering in orbit to dock with the space frame and other modules.
With this approach, instead of reinventing the wheel with every technological advance and developing entire satellites, you only worry about particular modules. If new GPS units are needed, you simply send up the payload modules, disengage the old modules and chuck them back to burn up in the atmosphere, and link up the new payload module. You can also put spare space frames and power units into higher, unusable orbits so if a satellite fails or is taken out, all you have to do is send up a new payload and bring the spare back to low Earth orbit. The same advantage applies with the ability to refuel satellites in orbit - instead of losing the satellite entirely, you can simply send up a new fuel module.
Specialty payloads could also be developed with this approach. For example, an armor package for the satellites could be developed to protect them against attack with the system being added to the satellites no differently than adding any other module. You could also use varying combinations of modules to build a more capable satellite. Another good option would be to field a temporary satellite designed to go up and retrieve debris from previous launches. A serious problem today exists with the ever increasing volume of space junk orbiting the Earth. This space vacuum could snatch up the junk and bring it back down or move it to allow it to burn up in the atmosphere.
Perhaps the most critical advantage of this approach is that it would make manned flights far more safer and capable. Resupply modules could be sent up to an orbiter to allow for more work to be performed or to allow the crew to stay up longer. For missions into deep space, an orbiter could include a variety of coupling points so that the orbiter can be sent up and then the huge volume of supplies necessary for the extended mission could be sent up after it. We could also field a satellite to scan orbiters before re-entry to determine whether or not they are ready for the incredible stresses of coming back to Earth. With the enormous volume of junk orbiting Earth, this role becomes more critical every year.
The Gun System in Practice
We need to start by choosing two suitable locations where facilities can be built to support these operations. Each facility would possess two guns and ideally would be located in a region of relatively high altitude (10,000 feet or more). The gun tube would be a long, multisection barrel of about four feet in diameter or so (I'll let the scientists sort that one out). Projectiles would be breach loaded and any of a variety of approaches could be used to generate the launch force including chemical reactions or pneumatic systems. The gun would have a limited ability to traverse to allow for variations in orbits but elevation would be fixed.
In operation, the barrel would be set to the desired position for firing and a self propelled pig (like that used to inspect the Alaskan oil pipeline) would be sent up the barrel to test for strength, seal, and straightness, and also to clean any debris that may be in the barrel. Once the pig is finished, the projectile is mounted to the launch chamber and the assembly is mounted to the breach. Proper seal would be tested and when ready, the projectile would be launched.
Depending on the payload, once in orbit, the projectile would be maneuvered by radio controls into the appropriate orbit to mate with another module, orbiter, or even the International Space Station. The chamber would be removed from the gun and inspected while the pig takes another run up the barrel in preparation for the next launch.
The gun option is not a replacement for manned space flight - it is a complementary system that can assist manned flight but is specifically designed to support and maintain our military abilities. It allows us to engage in rapid and affordable upgrades of our space infrastructure while increasing our capacity to deal with potential future threats to our assets. It also gives us more options for countering future threats to satellites by allowing for increased use of spares and the addition of physical protection to the systems while in orbit.
Other Technologies
As with any other technological issue, there is more than one way to skin a cat. Perhaps the most intriguing method proposed today is the Sky Ramp concept. This system would use a rocket sled riding on an inclined track to propel a space vehicle to speeds of over Mach 2 along a track of 2.5 miles in length at an incline of between 45 and 80 degrees. In theory, this design would physically throw the space vehicle to a substantial altitude (estimates are as high as 50,000 feet). In theory, this would allow us to replace most of the fuel required to reach this altitude and momentum with additional payload. Frankly, this idea appears to be the future of space launching, particularly launches involving a human cargo. But there are some substantial challenges that the designers of the concept will need to address and this will likely stretch out Sky Ramp development for a considerable length of time.
One of the biggest problems that I see is with the idea to build the ramp up the side of a mountain. At first glance this appears to be a great idea - until we remember how those mountains got there. Mountains are made either by geologic plates pushing against each other and pushing upwards or by volcanoes pushing molten rock up and out. Neither of these events is a happy thing for a location to mount a track to carry a Mach 2 rocket sled weighing hundreds of thousands of pounds. Think Mount St. Helens (for the younger readers, this was the long dormant volcano out West that exploded in the 1980s).
We can still use the tunneling option the designers mention but this is far more difficult than Sky Ramp designers care to realize. They mention the hundreds of tunnels and shafts that have been dug larger and deeper but leave out one critical detail - none of these tunnels is dug on an incline of between 45 and 80 degrees. All of these large-scale tunnels are either completely vertical or close to horizontal. To grasp the problem ahead, take a drive around the neighborhood you live in and check out the roofs on the houses and buildings. Imagine yourself having to replace the shingles on these roofs. How difficult is it to see that doing this very simple task would be far more difficult on a really steep roof than on ones that aren't? While the challenge is by no means insurmountable, building this tunnel in the length they are talking and having it able to withstand the forces it will be required to endure will go down as one of the greatest engineering achievements in history.
Along with the geological issues comes a related problem - subsidence. Any substantial structure that is built on land with settle into that land over a period of time. This will especially be an issue given that the proposed track will be on a incline (weight is more concentrated over a smaller area that is less stable) and will occasionally be subjected to extreme force (the launch vehicle/sled combination will weigh in at hundreds of thousands of pounds). The problem is that for this type of application, the track has to remain relatively level and even throughout its length of 2.5 miles. At high speeds and with as much weight as is involved, even minor undulations in the track could be catastrophic. Each launch will require that an extensive inspection of every inch of the track and its supporting systems and occasionally adjustments in the track are going to be required. But with the track on a major incline, this is no longer a minor task. It is going to be very labor intensive and very time intensive unless we are willing to cut corners.
Other challenges exist but I need to emphasize that none of these are insurmountable by any means. When all factors are taken into account, this concept is far and away the best option for the future of manned space flight. The point that needs to be made, however, is that while the technologies used in the concept all exist today, this isn't simply a matter of throwing the thing together and off we go. There are MAJOR hurdles that must be overcome and its going to take considerably longer than the designers probably realize. And even once we have the system in place, it is going to take considerable maintenance and testing to get the system functioning to a level sufficient for high volume use.
In the interim period, upgrades to the existing shuttle concept can be made if there is sufficient need to be putting men in space. Traditional rockets and future gas gun designs can handle the bulk of our space needs but if we must put men in space, the following modifications should be made to the existing shuttle concept:
With the amount of money we currently spend on NASA, there is no reason that all of these options could not be addressed simultaneously. The problem with NASA isn't a lack of money - it is a lack of open minds.