Why does SS1 need the drag configuration?

The X-15 had no such ability and landed fine. Curious as to why SS1 needs the drag configuration.

Also, am i right in thinking that SS1 could never survive a re-entry from a true high orbit?

Just for fun, I posed the question to Scaled. Of course, they may be way too busy to post a reply. But we'll see.

Suprised it's never been brought-up before. Thanks for emailing them.

Some of these other guys may know the answer off-hand. But I'm certainly no real engineer. Just a software one

The only part that I know about the first bit is that the X-15 was meant to withstand much more than SpaceShipOne. The drag configuration on SS1 partially has to do with keeping the ship from overheating, because like you said in the 2nd bit, SS1 wouldn't be able to handle it. The forces that a ship would go through on reentry would propel the craft to such a high speed that SS1 would melt as it is now. The X-15 was designed (with the technology available then) to withstand those forces, and they still managed to just about burn the tail off of it at Mach 6.7... so now consider that after a full orbital reentry, the speed would be about Mach 18 and I think SS1 would have a little bit of a problem.

Doesn't answer the question about the X-15, but I though I'd post it anyway... from the Scaled Tier 1 Site:

I myself a few weeks ago sent an e-mail to Scaeld too and I got an answer very quickly - less than one day. One of my questions were the physics behand the feather-technique.

The person responding said not to be a physicist and bacaus of this not to be able to answer this question. The other questions were sufficiently answered.

Hello, eraurocktchick87,

it's very nice that you are quoting Scaled.

I did so in a german fore and a german chemist annoyingly began to try to argue away Scaled's explanation. He seems to be quite ignorant. Perhaps here somebody might explain the physics working behind the feathering.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

I'm not a physicist either, but I do have some knowledge of aerodynamics. I guess the feathered position is a controlled stall (the rudders and elevator-stabilators have still authority)

The feathered tail causes a nose-up pitching moment. However, the plane's natural behaviour is to pitch nose down; the center of aerodynamic forces acting on the plane lie behind the center of gravity.

As the plane slows down, the authority of the tail decreases, thus the pitching moment decreases. The forces acting on the plane will still cause pitching down moment. The plane will descend in an attitude where the moments cancel each other out.

F1A free flight gliders actually use a bit similar technique; at the set time (180 seconds) the horizontal stabilizer will rotate to a large negative angle, stalling the plane and bringing it down in a gentle, belly-first stall.

Which way does this cause the effect of high drag and deceleration at high altitude? As I am understanding Scaled's explanation without the feathering deceleration will occur later at lower alttitudes. The annoyingly arguing chemist didn't believe the high drag effect and the deceleration at higher altitude.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

Scaled's answer seems acceptable. However the "feathered drag" configuration would be useless for a true re-entry from a real geo orbit. I wonder if Scaled is working on a ship that can withstand a true re-entry?

*heh* All we can say to that is, "Hey, it works". And of, course, I think I would trust Rutan and his team over and above a chemist

Well, the whole $20-million project is called "Tier One"...... Unless, of course, I'm the only one who thinks that name implies other "Tiers" are forthcoming.......

SSO flips its tail up for the same reason that the Shuttle zigzags on re-entry. The heat generated by moving through the atmosphere is related directly to two factors: how thick the atmosphere is, and how fast the vehicle is moving. Increase either factor, you increase the heat the vehicle has to withstand. Thus, the quick and dirty solution to this problem is to try and avoid both: slow down while you're still in the upper (thinner) atmosphere.

Considering that both SSO and the Shuttle are designed to fly (meaning that if you move them at a sufficient speed, they'll begin to drift upwards), slowing down is actually pretty hard: since they're falling, they want to pick up more speed. There are three effective (and therefore traditional) ways for a pilot to burn airspeed: one, to pull the aircraft into a steep climb; and two, to execute a scissors, which is defined as a series of jinks, which themselves are short, sharp jerks in any direction (old fighter pilot slang there). The third is to activate the craft's mechanical air- or dive-brakes, as appropriate (if they're equipped).

Now, a steep climb won't work in a reentry, because the vehicle isn't yet generating enough lift to do more than tilt a little bit. Besides that, as you descend, you'll gain most of your airspeed back again. Thus, the Shuttle executes a long, extended scissors maneuver, swerving back and forth to use up the extra airspeed.

[hypothesis]Rutan, realizing that extra airspeed would require extra shielding (which, in turn, weighs more), decided to build divebrakes into SSO. However, the divebrakes required would be so massive that he instead turned the entire rear portion of the wing/tail structure into super-sized divebrakes.[/hypothesis] By rotating up about 60 degrees, the rear wing portion effectively kills all lift created by the vehicle, causing the tail to drop, and turning the entire vehicle into a really big parachute. Also, because the design orients itself to the proper attitude (meaning SSO doesn't need to be controlled on reentry), this system allows the pilot to relax during the single most strenuous flight period.

All in all, SSO's re-entry system is truly a work of genius.

Hey Hey

Burt Rutan took time out of his very busy schedule to answer my question, along with some others. The following reply seems to be a combined answer of several questions RE the X-15...

I like answers that come from the horses mouth. I didn't know that SS1 had a non-mettalic body. I presume it must be some sort of carbon composite then?

*heh* Yeah. Thus the company name Scaled Composites. I assume Voyager was made of the same (or similar) materials.