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Student Aerospace Challenge 2015

(WP3 – Main Propulsion)

Alexis LEFEVRE - Antoine LEFEBVRE - Moutassem EL RAFEI - Laure DURAND -

Mohammed ALI SAAFI (avec la contribution de Thibault DE BRAS DE FER et Matthieu FLORIN)

ISAE-ENSMA - Chasseneuil-du-Poitou (Futuroscope)

The Idea

How could the space industry and tourism

develop itself, if the cost/kg it takes to reach space

is so high?

If we imagined space launch via suborbital flights

(interesting thanks to the reuse of the shuttles =

lowering the launch price and the passenger ticket

price), how come 5.4 tons over the 11.6 tons of

the vehicle are designed for propellants? Whereas

these propellants are mainly liquid oxygen, which

could be taken from the surrounding atmosphere,

during the major part of the flight!

The Technology

The hybrid engine called SABRE, for Synergistic

Air-Breathing Rocket Engine, developed by

Reaction Engine Ltd. recently proved to be able to

cool incoming atmospheric air to 120 °K in 20 ms,

before injection in the rocket engine, and is

progressing toward a full scale demonstrator.

The Issue

Having in mind the dimension of a suborbital

vehicle, would it be possible to use the SABRE

engine as primary propulsion? What kind of

design and flight path should we consider?


Designing a vehicle for manned flight (+5.4 G

max, Mach 3.8), with existing technologies, while

ensuring the total reliability, and maximal

reusability in order to reduce maintenance costs.

Application to MSV

The SABRE engine was studied in order to be

scaled down for our manned suborbital vehicle

(MSV). It delivers a thrust of 150 kN, having an

ISP around 5189 s in air-breathing mode, and 441

s while working as a rocket engine. Trajectory was

optimized under constraints, for the SABRE, to

minimize the propellant consumption.

Distinct phases of the flight emerge: a climb to 20

km altitude followed by an acceleration to Mach

3.5 in air breathing mode. Then the rocket engine

takes over during 59 s, helped by significant

aerodynamic forces to rise the shuttle to 55 km

and start a parabolic flight in zero gravity of 3 min

11 s, for a total consumption of 2.4 tons of


The aerodynamics, the combustion chamber, the

nozzle, the air inlets and the tanks have been

studied in order to meet the requirement of this

concept of suborbital vehicle.


A concept of MSV achievable within the next 10 to

15 years, provided funding, was established. The

propulsion efficiency of the SABRE engine,

applied to suborbital flights, enables to reach very

good performances, and paves the way for its

application to other areas such as transcontinental

and orbital flights.