SSTT - Single Stage To Tether

Single stage to orbit makes weight a premium, so materials need to be extra light. A vehicle that can re-enter the atmosphere and be reusable must be extra strong. It is difficult to make a vehicle both light and strong. With today's materials it may not be possible to make a reasonable reusable single-stage-to-orbit (SSTO) vehicle. Many people think it will be 2030 before building an SSTO is reasonable.

However,using a Single Stage To Tether (SSTT) rocket to go halfway to orbit makes things much easier. Weight and re-entry are no longer major problems. It would be easier to develop a Single-Stage-To-Tether (SSTT) rocket than an SSTO. The X-15 was reusable more than 40 years ago.

We propose an SSTT that is launched from a jet. After delivering its cargo to the tether, the SSTT would land on the Earth.

Since kinetic energy varies with the square of the velocity, the energy for an SSTT is 1/4 as much at half the velocity.

Air resistance is much more of a problem for a small ground launched rocket than a large one. The total energy of the rocket is determined by the amount of fuel, which goes up with the volume of the rocket, or the cube of the dimensions. The air-resistance is going up with the cross-sectional area, which goes up with the square.

The same cube-square issue that makes airlaunch so important for a small vehicle makes slowing down in the atmosphere much easier for a small vehicle. The thermal protection system (TPS) can be cheaper and more reusable in a small light slow rocket.

Another way to look at this is that the SSTT rocket is doing about half the delta-V normally required to get to orbit. Its size is very much like the second stage of a 2-stage rocket with the same payload capacity.

An SSTT has the advantages of the single stage of a simpler rocket design, only one engine, one set of tanks, but not the challenge of pushing the rocket technology so hard.

How many stages?

The term Single Stage To Tether (SSTT) was used back at least as far as 1995. However, as we started 2003, Google only found the term in the above URL and on

SSTT is a good name because there is only one rocket stage and it goes to a tether. But to be precise there are sort of 3 stages in that we have a jet (to launch the rocket), the rocket, and a tether. Rockets are expensive and hard to make re-usable. By allowing the rocket do less work, it is easier to make it re-usable. Once all parts of the system are re-usable, expenses will be less.

Reusable needs

A RLV needs a shape that can handle the heat of reentry, some sort of parachute and a landing method.

RLV Links

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