Space Travel
Fair Warning: This segment and the next one of An Author’s Journey are going to wax a bit technical.
Robert A. Heinlein stated that “Once you reach Low-Earth-Orbit (LEO), you are halfway to any place else in our solar system.
Jerry Pournelle goes into much more detail on why this is a truism with his page on Getting to Space. http://www.jerrypournelle.com/reports/jerryp/gettospace.html
The bottom line is that any rocket launched from the surface of the Earth is going to need approximately 90% of it Gross Lift Off Weight (GLOW) just to achieve LEO. This means getting things to the Moon or Mars or one of Jupiter’s moons is going to be expensive until we can develop a large-scale, off-Earth presence. Right now, we are stuck at the bottom of a very expensive gravity well. It will take a lot of very expensive flights, moving small quantities of humans as well as machines to a permanent base up there, before we can consider ourselves safe from some random disaster. Right now, all of our eggs are in one basket. There are dozens of credible scenarios where all human life on our planet is wiped out. If you feel like a bit of depression, then these two links might be just the ticket.
http://www.kurzweilai.net/were-underestimating-the-risk-of-human-extinction
http://en.wikipedia.org/wiki/Human_extinction
When I mention a permanent base, I don’t mean the International Space Station (ISS) or anything in LEO. Low-Earth-Orbit is a requirement for a staging area, but we should not be sinking gazillions of dollars into building anything complex there. The reason is simple. LEO is not stable. Anything you put in LEO is bound to come back down and burn up upon reentry unless you provide a little adjustment from time to time. If we want a permanent, long-term place to build an orbital colony, then it has to be at one of the Lagrange points. The other alternative is the Lunar surface.
In order to get to any of these places, we need a truly reusable spaceship. All of our current designs use lots of throwaway segments and while this makes money for the big aerospace companies, it is not a solution. The recently-retired US space shuttle program is an excellent example of why you should not let politicians and accountants design a spacecraft. Although it was billed as reusable, there were many flaws in the design that had been pointed out by researchers long before the first one was ever built. Politics became the primary design factor and thus we ended up with solid-fuel boosters used for human flight, the Challenger disaster, and a design that required the main engines had to be totally rebuilt after every flight.
“Rebuilt?” That’s right, rebuilt. Any mechanical device, including giant rocket engines, have a power curve. If you run them at 100% of their rated power output, then the designer can give you a pretty good idea of how long the engine will last. If you run it at 80%, then it will last much, much longer. In order to make their goals, every flight of every space shuttle ran the engines at between 110% and 115% at launch. That meant that as soon as it got back, the engines had to be torn down and totally rebuilt. Which is one reason why each of these supposedly reusable spacecraft required a six to nine month turnaround time between flights.
A truly resuable spacecraft will have to be something along the lines of the Single-Stage-To-Orbit designs that have been so favored by science fiction novels, movies, and TV shows. The closest we have come so far has been the SSX program.
http://www.jerrypournelle.com/slowchange/SSX.html
In 1993, Congress, via the Air Force Chief of Staff, requested a report on what the Air Force would probably need to accomplish its mission over the following 25 years. A three-volume report titled Spacecast2020 was released a year later. Volumes two and three are still classified, but the first volume is an eye-opener. Click the link and read it for yourself.
http://csat.au.af.mil/2020/index.htm
One of the primary requirements mentioned is a totally reusable spacecraft able to move small groups of men to LEO with very short notice. Later on, a General Mitchel Burnside Clapp headed an advanced research program to develop such a craft.These links provide the details of such a craft.
http://www.ai.mit.edu/projects/im/magnus/bh/analog.html
http://www.ai.mit.edu/projects/im/magnus/bh/bh-faq.html
When Congress got wind of this project, they realized it would be in direct competition with the giant pork barrel jobs program known as the Space Shuttle, so they shut it down. From there on, the real-life story gets a bit hazy.Over the past twenty years, there have been many rumors to the effect it had become a black-box project, much like the first ten years of the SR-71,
In Omniphage and the rest of the Multiplarity Trilogy, Project Black Horse has grown up.
Anthony Stevens' Weblog 