Spaceplanes that are suborbital are mostly supersonic and feature H-tail or rather large wingtips. This looks to be similar to a H-tail configuration but I'm unsure abut how it works, which is why I say large wing tips. They focus on a delta wing and elevon for the pitch and roll and yaw seems to be controlled using this. For example look at the following spaceplanes. vss unitydream chaser NASA(Cancelled) XCOR Lynx

1. https://www.virgingalactic.com/articles/VSS-Unity-First-Powered-Flight/
2. https://www.sncorp.com/what-we-do/dream-chaser-space-vehicle/
3. https://www.flyfighterjet.com/xcor-lynx-space-flight


Most spaceplanes are aerodynamically just hypersonic airplanes. The tailless delta wing with directional stabilising fins on the tips is an optimal solution, especially if you do not want a fin on the fuselage. Directional stability can be elusive and highly non-linear, so types designed before the days of high-speed digital control systems often resorted to extra-large surfaces.

During re-entry a spaceplane cannot nosedive or it would overheat and melt or tear itself to bits. It has to kind of pancake down on its underside, keeping just enough forward speed to maintain aerodynamic control (An orbital craft needs hi-tech heat insulation even for this but for suborbital craft it is unlikely to be needed). The safe angle for this manoeuvre is really quite small with little room for error, just a few degrees either way. It was an acceptable risk for the Space Shuttle but may not be for commercial passenger flights.

SpaceShipOne and Two are a unique solution to the problem of safe re-entry. The tail configuration is known as the outboard tail or outboard horizontal stabilizer (OHS). It has been studied from time to time but never really flown (a German research prototype was built in WWII but it is unclear whether it ever flew). It was adopted for the SpaceShip series for the obvious reason that it gets the stabilizer out of the way of the rocket exhaust. It also eased the mechanical solution to their other big aerodynamic innovation, the variable-geometry "weathercock" tail. By swinging the tail up for re-entry, it stabilises the spaceplane as it pancakes back down, hugely increasing the safe zone and making re-entry almost trivially safe.

Passengers returning from actual orbit present a far greater challenge, as yet unsolved.


Dreamchaser isn't intended to be suborbital. Don't know about your 3rd picture, but the Spaceship 1 & 2 were designed by the same person/company, so it's not surprising they use the same design elements.

The designs of Dreamchaser vs Spaceship N address two different problems. An orbital vehicle has to decelerate from ~17,000 mph, while a suborbital vehicle on a ballistic trajectory (simplistically straight up and straight down) starts from zero speed at its high point, and needs to keep from gaining too much speed. So if I'm not mistaken, a main function of the H-tail is to allow the entire vehicle to act as a drag device. That wouldn't be practical for an orbital reentry vehicle due to heating & aerodynamic forces.

  • $\begingroup$ Dream Chaser worries about gaining too much speed too, especially during re-entry. Both it and Space Ship 2 want to stably slow down from space to atmosphere and glide home. The third plane is concept only, it's company went out of business. $\endgroup$ – Robert DiGiovanni Sep 26 '18 at 2:23
  • $\begingroup$ In other words, after deorbit burn, Dream Chaser, now suborbital, but with much more potential and kinetic energy, must slow down and glide as well. So needs heat shield, Space Ship 2, not as much. $\endgroup$ – Robert DiGiovanni Sep 26 '18 at 15:38
  • $\begingroup$ @Robert DiGiovanni: As I said, suborbital flights start from essentially zero speed at the top of their arc, and want to keep from gaining speed (think parachute). Any orbital reentry vehicle starts from orbital speed (otherwise it wouldn't be in orbit, of course) and slows down. The problem there is to manage the slowing in a controlled way. $\endgroup$ – jamesqf Sep 26 '18 at 18:07
  • $\begingroup$ Here's where it gets good. An object in orbit starts with 0 vertical speed as well. It's all potential energy. It does have horizontal speed, and so does sub-orb (think Redstone). The task of returning to around 200 knot glide through the air is the same, why separate them? There for Dream Chaser is qualified for sub-orb flight. Imagine how much smaller the Space Shuttle's fuel tanks would be if it were sub orb as well. $\endgroup$ – Robert DiGiovanni Sep 26 '18 at 18:24
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    $\begingroup$ @ Robert DiGiovanni: Humans - at least some of us - may use feet and miles. Wikipedia uses meters &c, and I'm too lazy to do the conversion. WRT falling straight down, SS1 would start from an altitude of 62 miles (!327K ft) or greater (that being the definition of "space" for the X-prize), and zero vertical speed. so it would take rather more than 60 seconds to impact the Earth, even if not slowed by air friction. Which slowing - coming full circle - is the purpose of the H-tail arrangement. $\endgroup$ – jamesqf Sep 29 '18 at 4:25

At extreme speed, the more symmetry you have, the better your chances are of staying straight. This is especially of concern at very high altitudes, where aerodynamic forces (indicated airspeed) are small. X15 is good example of this. Also, H type tail helps keep control surfaces away from the rocket nozzle.

Shuttle type vehicles also emphasize roll and pitch stability in re-entry. Very interesting to note the humble capsule has 360 degrees of roll stability (there for also pitch). The Soviets liked the ball, with the weight set a little low, for the same reason.

Space ship 2 has the (shuttle cock) feathered configuration. Dream Chaser (and the Air Force) has strong dihedral. These just want to come in upright and land safely.


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