Every now and then interplanetary missions have been proposed which are are both exciting and innovative and yet, regretfully, still do not make the cut for funding. One of these was an ambitious plan to fly a rocket-boosted glider on Mars. For despite NASA winning overwhelming plaudits for its innovative landing and operation of its Mars Curiousity Rover, it went back to a more conservative approach for its next Mars mission and chose the the Mars Atmosphere and Volatile EvolutioN (MAVEN) Mars orbiter which is due to be launched end of the year.
In selecting this mission, NASA passed up the opportunity to execute an ambitious plan to fly a rocket-boosted glider though the atmosphere of the planet Mars dubbed Aerial Regional-scale Environmental Survey (ARES).
Artist’s concept of ARES rocket boosted glider in operation. Courtesy: NASA
While hypersonic gliders for planetary entry have long been considered in relation to Mars exploration (unlike for Earth entry, the heating from Mars atmosperhic entry at interplanetary speeds can be dealt with), other scientists were more interested in flying in Martian atmosphere at a more sedate speeds using gliders and powered aircraft.
Low speed gliders and sail planes, have of course, been used seriously for pilot training and sport purposes since the 1920s and they have had some famous aficionados. Test pilot and moonwalking astronaut, Neil Armstrong was also a prize winning glider pilot in his spare time.
Of course, gilders have not just been used for peaceful purposes. During World War 2, medium and heavy lift gliders were developed to carry troops and equipment behind eney lines during miltary operations and invasions, most famously used at Crete by the Germans in 1941 and later by the British and Americans in D-Day invasion of Normandy in 1944.
In fact, in a surprising way, gliders may have been responsible for a key turning point in the D-Day battle and perhaps even the war. For as German 21st Panzer armoured forces finally managed to find a way through to the Normandy beachhead, imminently threatening to roll up the entire allied D-Day landing sequence, the last wave of British troop and artillery carrying Airspeed Horsa and General Aircraft Hamilcar gliders swept overhead to land in the area behind them. As they watched these gliders fly over late in the daylight hours of D-Day, the commanders of the German Panzers feared that they might get cut off by these new glider-borne forces and ordered a retreat.
D-Day: Final wave of Hamilcar gliders landing in Normandy, France, during 6 June 1944. They carried light tanks and 17-pounder anti-tank guns (backing up the 6 pounders carried in on Horsa gliders) to help airborne forces hold off German armoured vehicles trying to recapture key bridges taken earlier in a surprise attack by allied glider-borne soldiers. Courtesy: IWM
Nazi Germany had itself earlier examined using medium and heavy lift gliders for its own planned but never executed invasion of Britain. It belatedly came up with the Messerscmitt Me 321 Gigant - a design similar th the British Hamilcar but which was later converted into the more effective six-engine powered Messerschmitt Me 323 transport aircraft. While it lost out to the conventional-looking Me 321 Gigant in the eventual selection, the Gigant’s main competitor, the Junkers Ju 322 Mammut (Mammoth) was an even larger glider of 62m wingspan,
While it had structural problems during its development, its revolutionary wing-body configuration was very advanced for its day and its planform is very reminscent of the ARES Mars glider configuration. The unmanned ARES is, of course, much very smaller at around one tenth of the Mammut’s wingspan.
Junkers Ju 322 Mammut wing/body glider design. Courtesy: German archives
The idea was for ARES to be carried folded up inside a planetary entry vehIcle before unfolding from its protective aeroshell in flight. From there, with a rocket boost (officially the propulsion system had not been settled) a flight of one hour would be made with the craft making observations and measurements of the planet’s atmosphere andmagnetic field, transmitting them via a relay spacecraft as it went.
ARES (sometimes dubbed Mars Eagle) glider/powered aircraft in plan view showing a single booster rocket nozzle. Later designs iterations have three bipropellant rocket thrusters - with two continuously firing. Courtesy: NASA
While the ARES Mars rocket-boosted glider came closest of all the proposed Mars glider and aircraft designs to come to fruition as part of NASA’s Mars Scout Programme, in the end, as already mentioned it sadly lost out to the more conventional MAVEN orbiter mission for selection. Nevertheless, Mars gliders continue to have a major following and have been seriously proposed to NASA for missions to Mars since 1999. Their time may soon come.
Earlier concept: Mother Goose Mars glider design. Courtesy: eisci.com/mothergoose
Proponents of Mars gliders and powered aircraft point out that while Mars has a very thin atmosphere, it is made mostly of heavy-molecular weight carbon dioxide. That is, at any given pressure, carbon dioxide is denser than the air on Earth. Aerodynamicists preduct that the low Reynolds number for such a passage through the Martian atmosphere would promote laminar flow over the wings. These factors increase a wing’s lift. The low gravity on Mars, also reduces the wing loading on an aircraft, allowing it to fly with less lift.
Apart from rocket boosted gliders, aircraft using very large specially designed propellers have also been proposed for Mars aircraft to use. Now that solar powered heavier-than-air aircraft such as the ultra-long range Solar Impulse craft are flying in Earth’s atmosphere, it can be envisaged that a similar design could one day work in the atmosphere of another planet for flights lasting very much longer than the ARES’ endurance of only one hour.
So while ARES was not selected last time round, it, and its powered successors, may yet have a chance to soar through the skies of Mars. We look forward to that day.
For more information on the ARES plan go here: http://marsairplane.larc.nasa.gov/platform.html