Why An SSTO IS A Good Idea

What if the rocket launcher is the payload and launches itself?

Author:  Joris Luypaert, February-12-2017.

Concepts for Single Stage To Orbit vehicles have existed since the beginning of the space-age

At the start of the rocket age, we have chosen more conservative designs because some of the required technologies were untested. Since a couple of decades now, this is no longer the case.

Take a quick look at this 12 meter high demonstrator that transformed our thinking about Single Stage To Orbit Access. It was built-in the 1980’ies, and flown in the early 1990’ies, when it became apparent that the then one decade old Space Shuttle was a design compromise gone too far and would never deliver on its reusability promises. Total project cost: USD 60 million (1991).

YouTube channel for AP Archive: Shows the DC-X SDIO Delta Clipper [1] , an in depth 17 minute introduction to the concept is posted below [2].

Later this program was taken over and then infamously ended by NASA due to lack of funding and the desire to fund an alternative NASA-originated program called X-33 and X-33 Venturestar which ultimately also got cancelled.

Some of the designers of the Delta Clipper are now on the pay roll of Blue Origin and are helping that company to develop and fly their reusable suborbital and reusable orbital vehicles.

Our organisation is heading in the same way, but contrary to the configurations chosen by SpaceX and Blue Origin, our vehicle more closely resembles the Delta Clipper while offering another leap in versatility, operational cost reduction and capability.

Structural weight is not your enemy

In most cases, a reusable SSTO loses some margin in what it can lift to orbit compared to a standard single-use rocket. Industry however knows of more powerful engine configurations that can eliminate loss of that margin. Thanks to modern advances, we can build our reusable SSTO.

We also argue and found that, if you think of the versatile vehicle as the most important part of the payload to lift to orbit, than the rocket equation would suddenly make a lot more sense. And why not? Once in orbit it becomes a deep space ferry, it keeps our crew alive for a long time, and returns them from planetary surfaces. The structural mass of an SSTO no longer is your enemy, it becomes your useful payload. You now can focus on making it more robust and durable in an iterative design cycle.

Versatility as your design philosophy

The Space Shuttle has become a text book example of how not to do reusability. SpaceX demonstrated that reusability can be done in a sensible way: rapidly and without hardly any refurbishment. They showed the way, we evolved a more efficient engineering  and profit solution with versatile growth capabilities far beyond the limits of their approach. Our approach, which has a lot of payload growth potential, is designed to outperform their reusable interplanetary Big Falcon Rocket design on cost.

An SSTO to our design can function as a habitat, a temporary space station, an artificial gravity research station, a planetary lander and a planetary ascender for cargo and crew. Today these capabilities are spread out over a multitude of vehicles, specialized to the task but needing a separate rocket to lift them into orbit. Our vehicle combines all of those functions. It dedicates a larger portion of its mass to build in the required safety, durability margins, and margins needed to safely support a crew, while taking advantage of decades of advances in building light weight and thermally stable, high performance space structures. We take the best from Shuttle, SpaceX mix it together with our own proprietary solutions to create a more versatile and capable package.

Once you get it into orbit, it still has enough internal volume to be outfitted with large inflatable volumes, science gear or any type of mission hardware needed. Commercial space is actually asking for more destinations to send their hardware, or crew, and the hardware of their clients too, while retaining a payload ferry capability, as the crew and payload opportunities on the International Space Station (ISS) are saturated.

Micrometer thick films

We also need to thank miniaturization of heavy components and systems -like bulky electronics, sensors, science packages, avionics, solar power systems and even some advanced propulsion systems- to mere micrometer thick films.

This allows us to shrink and even decimate the mass that used to be required. And now, with the advent of the multi launch of cheaper small sats, we no longer need to orbit very heavy satellites, to deliver a cargo with the same profit margins. All these advances combined, we get the same capability in a lighter package or more capability added for the same structural mass.

A marriage of capabilities

We have finally reached the point where we no longer have to make an unfavorable compromise between the mass that an SSTO would be able to lift, and the capabilities we desire. And we have figured out how to do this with mere chemical propulsion.

We cheat: A gradual transition from a stage-and-a-half to a single stage

Today we build rockets where the lower stages are heavier than the upper stages, with regards to their expendable structure. We found a way to reverse this. More structure will get lifted to orbit and less structure will be dropped as a first stage. More engines will lift to orbit and less engines will fall down. We avoid dropping engines by putting the propellant tanks below the engines.

This seems illogical. Wasn’t the point to be as light as possible? Yes, indeed. But if what you drop are light weight propellant tanks and maybe a single engine out of your entire bank of engines (to make the first stage reusable) than you still end up with a light upper stage and more payload to boot. This configuration, a combination of a propulsion stage with drop tanks, is called a stage-and-a-half system. So we cheat. When lifting of from the Moon or Mars, our vehicle is indeed a SSTO vehicle. It is only on Earth that it requires the extra propellant in drop tank and becomes a Stage and a half.

But that simply means we are the first to come closer than ever to the ideal, with all the advantages this entails.


As time goes on, we will start to lift the entire first stage drop tank into orbit, just as was possible on the space shuttle. Our propellant tanks are designed from start to be re-purposed as a habitat or corridor.  Using our advanced engine concept, we have a vehicle that has the growth capability to become a full single-stage-to-orbit, not requiring drop tanks. Instead of 1% of payload to orbit, we will be closer to 10% (excluding the wet or dry weight upper stage) than any launch vehicle ever before.

We invite you to help us realize our vision and find out more on our project pages (pre-demo, demo), but also the full scale vehicle page and the deep space version).


[1] ABOUT THE DC-X: The DC-X was the first prototype vehicle developed by the SDIO, than BMDO’s (Ballistic Missile Defense Organization, now known as the MDA, Missile Defense Agency) SSRT (Single Stage Rocket Technology) reusable launch vehicle program. The DC-X was a one-third-size experimental vehicle, built by McDonnell Douglas under a 22-month, $58 million contract. The DC-X prototype’s goals were to verify vertical takeoff and landing, demonstrate subsonic maneuverability, validate airplane-like supportability and maintainability and demonstrate the rapid prototyping development approach. The Delta Clipper flew a total of 12 flights, eight under the McDonnell Douglas test program and four under the auspices of NASA as the DC-X/A.

The first flight of the DC-X from the “Clipper-Site” was on August 18, 1993, at Northrup Strip, now known as White Sands Space Harbor, on White Sands Missile Range, New Mexico. [2] An in depth 17 minute introduction into the DC-X, Delta Clipper program: