Skipping into the Future (TFN)
Theoretical Future News is a work of fiction.
December 14, 2024
DARPA and NASA have announced a new design competition, code-named “Stone Skip”, that will have startups and established aerospace companies competing to create a new class of space-based workhorse. The name Stone Skip was chosen to crystallize the competition’s goals in the eyes of the public. Teams need to create a spacecraft capable of docking with one or more smaller vehicles that are already in orbit. After docking, the spacecraft will then change its orbit so that the spacecraft can skip off the Earth’s atmosphere and change orbital inclination*.
“Our goal with Stone Skip is to catalyze the next generation of space innovation. We see a future where satellite operators around the world treat the life cycle of their spacecraft in a new way. Instead of needing dozens of global launch facilities to continuously fill Low Earth Orbit with new microsatellites in slightly different inclinations, companies can launch from a single location and hitch a ride with Stone Skip.
X-37 B preparing for Launch
The other market we believe will develop with the ability to readjust orbital properties is the creation of secondary markets of still orbiting satellites. Today satellites that are still functional but no longer cost-effective to operate are only able to be sold to groups who’s needs almost exactly match the previous owners. Not too many tomorrows from now a spacecraft based on designs tested in Stone Skip will allow governments and private enterprise to hand off vehicles with far more regularity and garner much longer useful life from the satellite.” From DARPA Strategic Technology Office Project Director Colonel Robert Bettinger’s presentation**
The competition’s announcement has been met with its share of controversy. Both the Chinese and Russian space programs have voiced concerns that the technologies developed for Stone Skip will be used to prevent the open use of space as a global resource. According to sources the belief is that the United States might use fleets of Stone Skip space-craft to aggressively limit what can be done in orbit, from simply not working with non-American aligned aerospace firms on satellite repositions, to more hostile moves such as changing orbital inclinations against the wishes of the satellite owners to full-on de-orbiting of spacecraft. Several draft resolutions working to define what technologies developed during Stone Skip are actually able to be used for began floating around the United Nations within minutes of the NASA announcement.
At the time of writing Boeing, Space-X, and Sierra….
Follow Up
May 22, 2025
Frontrunner Boeing and their X-37B have met some unique outside competition in the form of Space Disk a student-led team out of UCLA. While the X-37B has obvious heritage shared with the old Space Shuttle, Space Disk appears to have very little commitment to legacy innovations. Their most current prototype looks like the frisbee that the team claims was the source of their design innovation.
“We see Space Disk as a way to potentially deploy half a dozen or more of TAV (Trans Atmospheric Vehicles) from a single Falcon Heavy launch, while still leaving room for other spacecraft/equipment…”
Back to the present.
This project was a lot of fun for me to look into as I had only generally heard about orbital inclination changes and skipping off the atmosphere before researching. For those who are less familiar, here’s a little background.
Orbital inclination is the angle of your space-ship’s orbit, relative to your planet’s equator. On planet Earth that means an inclination of zero, would have your ship orbiting around the equator. As your inclination increases the higher the latitude your space craft would see. So if I had an inclination of 60 degrees, my space craft would eventually fly over parts of Alaska and the tip of the Antarctic Peninsula. Changing orbital inclination is pretty fuel-intensive the point where most satellites/spaceships are currently only able to make relatively minor corrections. A big reason for needing all of that fuel comes from the fact that there is so little air resistance in space. Many times when you maneuver a spacecraft you need to burn fuel twice, once to start the process and another time to end it (generally speaking). The other is momentum rapidly changing direction while running is hard because your body “wants” to keep going the same way it was earlier. The same happens in space, but in this space, you’ve got a lot more momentum to fight because of speed. (for those who are curious the FAA has a handy guide on maneuvering in space)
Six Space Disk Base Units packed into a standard Falcon 9 Fairing. The red volume can be debo
An alternative version of the Space Disk Design that uses an Elliptical Disk, the design increases the skipping surface area of the Space Disk while slightly reducing the number of tugs that can be transported per fairing.
The ability to drastically change inclination could impact aerospace industry. Rocket Labs, a startup I’ve written about before, which sends small spacecraft into orbit, has the large client list that they do because their customers are guaranteed that when their satellite launches from Rocket Labs the satellite has the exact inclination that they wanted. If I make small satellites and launch them on something like a Space-X Falcon 9 I have to wait or hope that I can find a company that is launching into the inclination that I want, or as close as I can get. If you have a space tug that makes it easy to change inclination, things get interesting, you could imagine the creation of depot/warehouse orbits. A spot where you stockpile space-craft components and when you have all the parts a space tug would take you to where you need to go. If changing orbital inclination is cost-prohibitive then a depot/warehouse orbit would be a terrible idea, why would I stockpile stuff in an inclination that isn’t useful***.
In my research, I found a cool Ph.D. paper by Airforce Captain Robert A. Bettinger (now a Major) where he investigated the use of atmospheric skipping to change orbital inclination. From what I understand of the paper it sounds like atmospheric skipping makes sense when you want to change your inclination more than about 15 degrees. In the paper Captain Bettinger notes that the X-37B would be a viable option for this kind of maneuver and also mentions that any shape with a lift to drag ratio of 6 to 1 should be capable of performing an atmospheric skip. (At one point I thought I read a paper that indicated that a frisbee shape would be capable of the necessary lift to drag ratio, at this time I can’t seem to find it, but since the frisbee is fun I’m keeping it. Edit Nov 26 2019 I think I found the paper I thought I was referencing and it looks like the best case for frisbees isn’t quite 6 to 1 that being said the tests are also being done at way lower velocities than the space disks would operate at)
Major Bettinger’s paper even talks about the legal complexities of skipping off the atmosphere.
Current laws on the use of space assume that you are high enough in altitude that any kind of aerodynamic influences are negligible. During an atmospheric skip, it is possible that your spacecraft would legally become an aircraft for a short while, and if you performed the maneuver over another country’s airspace there would be a chance that they could decide to shoot you down and be within their rights.
I hope this was interesting, any feedback, questions are welcome.
*orbital inclination is the angle of a spacecraft’s orbit relative to the equator. An orbital inclination of zero would line up with the equator. An inclination of 90 degrees would be what is referred to as a polar orbit
**currently Robert Bettinger is a Major in the US Airforce and I thought it would be cool to use someone who’s research was so helpful for this post,
*** Technically you could have multiple warehouse orbits at several inclinations, but I don’t like that idea for whatever reason. I mean yeah at some point the volume of spacecraft in orbit might make this make more sense, but the near-ish term I think a small number of depots would make resource management easier.