Advanced Space Transportation Concept

DSL is a concept for an advanced Two-Stage-to-Orbit (TSTO) Space Transportation System (STS), under investigation at the Space Systems Analysis Division of the German Aerospace Center (DLR). The main characteristics of this STS are a supersonic carrier aircraft, as the first or booster stage, and the different possible types of air-launched upper stages. The mounting of these upper stages in a partially open cargo bay on the bottom of the carrier aircraft enables a large variety of reusable, as well as expendable, upper stages to economically reach each desired orbit, · a safe separation maneuver, assisted by gravitational force, and improved aerodynamic coefficients by complete integration of small second stages (diameter less than 2.75m).

The air-breathing supersonic carrier implicitly offers higher safety and reliability than the vertically launched rocket STS. Separation at an altitude of about 20 km at a flight path angle of 12° considerably reduces the gravity-loss and improves engine performance of the rocket stages. The desired staging Mach-number range (2.7 - 3.5) has significantly lower technology requirements than those of hypersonic-staged systems. Additionally, a TSTO is considerably less sensitive to the payload mass delivered to the orbit than any SSTO. Last, but not least, there are some synergy effects to the development of a future supersonic civil transport.

DSL reference configuration data:

Separation conditions Ma = 2.7 at 20 km

Initial take-off mass of the DSL system 560,000 kg

Initial mass of the ballistic second stage 200,000 kg

Payload mass into LEO (90 km x 400 km , 28.5°) 16,100 kg

Payload mass into SSO (90 km x 895 km , 98.0°) 10,100 kg

Payload mass into GTO (200 km x 35800 km , 0.0°) 6,500 kg

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