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WP3 – MAIN PROPULSION
Study of a turbojet and ramjet propulsion system
(WP3 – Main Propulsion)
Thomas ELIA - Henri FERIEN - Mathias GHESTEM - Antoine MOSNAY
Ecole Nationale Supérieure des Arts et Métiers - Châlons-en-Champagne
Objective
Works on the primary propulsion system of
a MSV launched from a carrier aircraft are
generally based on the study of rocket
engines. Due to security reasons linked to
the storage of propellants, take offs from
public airports are not authorized. Motivated
by the innovative spirit of the challenge, we
decided to work on a new propulsion mode
that would make the MSV autonomous,
allowing it to consume kerosene from civil
aircrafts, to take off from regular airports
and without needing to be launched from
another aircraft. Thus, we have decided to
combine a turbojet with a ramjet, and will
approve the viability of this solution.
Overall Approach
Pre-sizing an aerobic propulsion system
requires knowledge of all the parameters
that have an effect on the flight, as well as
the loops that need to be considered:
These loops allow us to highlight the strong
coupling between the parameters.
First, we study the ballistic phase, to
determine the engine performances that
need to be reached: Mach 4.1 at a 32000
meters altitude and with an 80° incline.
Then, choosing a NACA wing profile, we
design the MSV, inspired by the Lockheed
SR-71 and the Concorde.
We estimate the aerodynamic coefficients
up to Mach 2.5, with an empirical approach
used for fighter aircrafts. For bigger Mach
numbers, we rely on numerical simulations
with Star CCM+.
Then, we implement a pre-sizing algorithm
using the aerodynamic results, the
calculation of the atmospheric parameters
and the detailed study of the engine
equations. We proceed by iteration to
converge towards the required air inlet
section
to
reach
the
expected
performances. The step by step integration
of Newton’s second law gives us the flight
profile. Our initial approach consists in
working with a rectilinear trajectory with a
constant slope during the propulsion phase.
After the pre-sizing, we propose a global
optimization method of our MSV. This
method causes the MSV’s geometry to vary
and uses a corrected specific impulse taking
into account the drag, thus affecting the
flight plan and the fuel consumption.