DSL is a concept for an advanced Two-Stage-to-Orbit (TSTO) space transportation system (STS). 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.
|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|
Different types of second stages can be carried in the partially open cargo bay. A configuration overview:
|Supersonic Carrier Aircraft
with integrated ballistic second stage (yellow) in partially open cargo bay
|Expendable Ballistic Second Stage
with different possible capsule, payload, and fairing types
|Reusable Winged Rocket Second Stage|
|Combined Propulsion Reusable Second Stage|