The most important issue in space development is reducing the cost to orbit. While there are other possible ways to reduce the cost to orbit, we feel that Single Stage To Tether is the most promising approach (see flash demo).

Using a suborbital rocket of around 40,000 Kg gross mass, you could take a payload of about 4,000 Kg to the end of an orbiting spinning tether. Because of the tether, the rocket only has to provide a bit over half the delta-V of going to orbit. This makes it much easier to make the rocket a reusable launch vehicle (RLV). If the rocket is an RLV then the cost to orbit could be as low as $6/lb. This is more than 100 times cheaper than the best current launch prices of around $1,000/lb to LEO and $6,000 to GEO. This kind of savings can be had with a modest tether tip velocity of 2.5 km/sec due to a number of factors. After the tether is fully loaded with solar cells and thrusters, it could handle a 4,000 Kg payload every 90 minutes. This would require a few RLVs.

The huge potential market is tourism but there are some other markets for such a system and some problems to be worked on. Tethers have had a bad reputation and there are some reasons why tethers have not yet been used. Still, this method of reducing cost to orbit seems very practical and with far lower development cost and risk than any other method of which I am aware. I have a few thoughts on who might finance this.

The key to getting the tether system up for a reasonabl cost is bootstrapping from an initial small tether. At first you could not fly your reusable rocket with a full load, because the tether can not handle that much, but it would still be the cheapest way into space.

We are working on an initial design we call CateCATS1. From this we will try to estimate time for rollout and costs. An initial tether project could be using a lunar tether to pickup regolith and return to Earth for fun and profit. We also have a list of Future space projects that might become reasonable once launch costs are reduced. Used throughout these web pages are some bibliographic references. Simulator and Rocket Equation Applet

We are working on a space tether simulator that anyone can use for free. This simulator can also be used as a "projectile simulator", "rocket simulator", "drag simulator", "reentry simulator", "meteor simulator", "solar sail simulator", or general "space simulator" for looking at atmospheric drag and heating on projectiles or rockets. You may need to install the newest versions of the Java JRE for the applets to run right. You can also get a new Netscape or a new Internet Explorer. To try the simulator, click on "Run the Space Tether Simulator" below, then click on "Design point" or "Rocket 20km", and then click on "Start Simulation".

Dreams into Reality - Evolving and Spreading Ideas

Good ideas are recognized as such and spread. I got most of the ideas for this web site from discussions with my father, Henry Pratt Cate Jr., starting in late November 2002. He has recognized their merit from published papers, space conferences and the Internet. Some publications similar to the ideas on this site are at, paper in 1995, and one in 1982. On usenet Henry Spencer has discussed the idea. Some of the key people in spreading tether ideas over the last 10 years have been Robert Forward, Robert Hoyt and Joseph Carroll. Many tether ideas were published by Hans Moravec, Jerome Pearson, Robert Forward, and Arthur C. Clarke more than 20 years ago. Jerome Pearson is still active in tethers at Star-Tech Inc. It seems Hans Moravec heard of tethers from John McCarthy who thought about tethers in the 1950s. Some people call a spreading idea a meme (see or

I think that spreading the ideas on how we could get to the moon was an important part of actually getting to the moon. Robert Goddard said, "It is difficult to say what is impossible, for the dream of yesterday is the hope of today and the reality of tomorrow." In a 1920 report Goddard outlined the possibility of sending a rocket to the Moon. Robert Heinlein worked on the movie "Destination Moon" (1950) and Wernher Von Braun (who studied Goddard) worked on Colliers magazine articles (1952) and the TV show "Man and the Moon" (1955) with Disney. Likewise, spreading ideas for ways to achieve low cost to orbit should help us actually get low cost to orbit. I think space enthusiasts are too pessimistic right now. I am trying to publicize the ideas I like best with this web site and posts to newsgroups. If you like these ideas, and want to see this dream turned into reality, do what you can to spread the word, link to us, tell others, email someone, etc.

For more information on Space Tethers

Some other sites I like


For questions/feedback on the ideas/info/simulator/code/web-pages here please send email me at vincefour at but replace four with 4 and " at " with "@". I would like to make the information here as accurate as possible and any help is appreciated. I believe that by accurately simulating much of this project we can know what is really possible.

Copyright (c) 2002 - 2006, by Vincent Cate. All rights reserved.