One of our members has been struck down with the severely disabling illness M.E. which can leave him stuck in bed for months. Other symptoms include the inability to stand or sit upright due to changes in blood circulation.
He really wants to get into space, and why shouldn’t he? In weightlessness a lot of disabilities disappear.
So we were tasked with the challenge of designing a suborbital craft that could loft him safely into space and back down again, whist keeping him flat on his back during the accelerations of launch and re-entry.
And so we conceived the ‘Spacedare’; so-called because after re-entry the bed flips over to have him lie on his stomach to glide gently home in the manner of the venerable ‘Dan Dare’ British comic strips of the 1950’s.
‘Spacedare’ is a one-man ultralight (microlight) spaceglider (boost-glider) that has the pilot lying flat. Lying flat allows healthy people to withstand up to 20 gees of acceleration, so someone with M.E. should easily be able to withstand the 4 gees during rocket ascent and the 5 gees of re-entry.
It is launched from a large hydrogen balloon at 35 Kilometres/115 thousand feet (near-vacuum conditions).
Modern European hydrogen ballooning is safe.
Falling vertically from an apogee of120 kilometres, our design and simulation software says that we need at least 1.0 square metres of drag area for every 45 kilos of spacecraft mass to keep the re-entry gees below five.
As the cockpit rotates, it will cause sideways lift forces. The airbrakes on the upper and lower surfaces can be moved independently to aerodynamically counterbalance this lift force to prevent the craft pinwheeling.
General post-re-entry steering is done by electrically-actuated elevons on the wingtip fins. The pilot shall then be flying ‘VFR’ (visual flight rules) which means he has to steer clear of cloud and fog. Turbulator strips on the leading edges of the wings counter the effects of flying at really high altitudes (low Reynolds numbers) which can otherwise cause the airflow over the upper surface of the wing to separate.
To allow the pilot to get the best view when in Space, small compressed-gas ‘RCS’ thrusters at the nose and wingtips jet him into the correct orientation.
For landing, there are one or more stainless steel skids/skis mounted on shock-absorbers. Tyres could melt, and there’s no need to take off again.
This picture shows the Spacedare on the way up to Space. Our pilot is lying inside the lozenge-shaped capsule lying flat on his back looking skyward, as a not very large rocket (shown in yellow) pushes the craft from below. The wings are vertical underneath the pilot, hitting the airflow at the angle of attack that generates no lift force (zero degrees, as we chose a symmetrical aerofoil).
The metal bar-like thing above the yellow nitrous oxide tank is a linear aerospike, which is a device that significantly reduces the aerodynamic drag on the tank and cockpit at supersonic airspeeds.
Here are the nitrous hybrid engine parameters:
Vacuum Specific impulse = 270 seconds
Launch altitude = 35 Kilometres
Apogee = 120 Kilometres
Gravity loss = 0.49 km/s
Drag loss = negligible
delta-V required = 1.77 Km/s = Mass ratio of 1.8
Total Impulse requirement =844 kNs (T-class)
Upon leaving the atmosphere, the yellow engine splits from the yellow tank to free the glider, and both are recovered by parachute.
On the way down to Earth, an electric motor slowly rotates the cockpit 180 degrees about the pilot’s middle so that he is still facing skyward. But the wings are now above him.
Now the drag of the sideways cockpit is a help rather than a hindrance, its area adds much useful drag.
There are many shapes of supersonic parachutes. Rocketeer Charles Pooley described the use of big airbrakes (barn-doors across the airflow) to slow a spacecraft, based on the X15 airbrakes.
Four large airbrakes deploy using electric motors to create lots more drag during re-entry, and to make the craft auto-stable like a shuttlecock: the pilot doesn’t need to touch the controls, instead he just lies back and takes the five gees.
The underside of the cockpit has a heatshield employing a high-temperature spray-on ablator.
Post-re-entry: At subsonic speed, the cockpit rotates 90 degrees so that the wings and pilot are both aligned (he’s now lying on his stomach in a harness), and the craft becomes a simple delta-wing glider which gently descends to Earth to land on a beach or grass runway.
The glider would be fibreglass and carbon-fibre with high-temperature resin. A sandwich construction with a honeycomb core.
With this acreage of ‘parachute’, re-entry is performed very high up in the atmosphere (re-entry will be finished well before descending into busy airspace), so although the craft will come in at Mach 3.3, the spacecraft will only feel as if it’s flying at 117 knots at sea level, which will soon settle down to a leisurely glide home at 55 knots as if at sea level.
A rocket-powered test vehicle was launched to test the concept at subsonic airspeeds: launches and ascents were stable with no oscillations despite the draggy capsule, and the Spacedare separated from its booster at altitude and descended in a stable manner.
