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German Aerospace Center (DLR)
in the Helmholtz Association
DLR SART Web Portal
http://www.la.dlr.de/ra/sart/projects/dsl/dsl.php.en
Date: 24-Oct-2014

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The DSL Space Transportation System

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, ยท 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

DSL - A Highly Flexible Space Transportation System

Different types of second stages can be carried in the partially open cargo bay. A configuration overview:

STS System Supersonic Carrier Aircraft
with integrated ballistic second stage (yellow) in partially open cargo bay
Expandable Second Stage Expendable Ballistic Second Stage
with different possible capsule, payload, and fairing types
Reusable Rocket Second Stage Reusable Winged Rocket Second Stage
Reusable CC Second Stage Combined Propulsion Reusable Second Stage