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Why does SS1 need the drag configuration?

Posted by: roygrif - Mon Aug 02, 2004 8:15 pm
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Why does SS1 need the drag configuration? 
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Post    Posted on: Wed Aug 04, 2004 2:02 am
Feathered drag ensures that the SS1 re-enters "belly-down", like a feather or the seeds from some plants.
The X15 did not need a similar feature because it had an horizontal impuls keeping the fuselage in the correct position.
Most other spacecraft re-entering from orbit need to be in a correct position too (heavy-duty heat-shield enters first) which is obtained using small rockets or escaping gas.
The main difference between these spacecraft coming from orbit and the former two (SS1 & X15) is the speed at re-entry.
SS1 has almost no horizontal speed, so it "gently" falls down into the atmosphere.
The X15 had a considerable horizontal impuls and therefore needed an according thermal protection.
The space shuttle re-enters at an horizontal speed of mach 25. That's why it has thousands of specially crafted protective tiles


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Post    Posted on: Wed Aug 04, 2004 3:07 am
That can fall apart if they are struck by anything on the way up, while they are in space, or on the way down... Time for some change eh?

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Post    Posted on: Wed Aug 04, 2004 11:28 am
What about the following ideas?

1. Variable angle the wings of SS1 to be fold to.
2. Controlling the angle the wings are folded to by computer based on sensor-inputs.
3. I might misanderstand all technical english explanations somehow - doesn't feathering provide drag and decelerationat horizontal reentry?
4. Feathering of wings having protective tiles.
5. Making the wings of other materials fit to survive larger forces and temperatures.
6. Controlling the shape of the wings (computer, sensors)
7. Controlling the extension of the wings

Are further technical and technological developments of the wings and the feathering impossible?



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Post    Posted on: Wed Aug 04, 2004 11:51 pm
In this day and age, very little is actually "impossible" any more. It might be impractical though. With all the modifications needed, I would think that it would be better to keep SS1 as a suborbital ship and design a new one for orbital travel.

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Post    Posted on: Thu Aug 05, 2004 12:32 am
eraurocktchick87 wrote:
In this day and age, very little is actually "impossible" any more. It might be impractical though. With all the modifications needed, I would think that it would be better to keep SS1 as a suborbital ship and design a new one for orbital travel.


It'd be the same thing: the necessary changes to make SSO into a fully orbital vehicle (and to be able to bring it back in one piece without pulling a Columbia) would require Rutan to disassemble, scrap, rebuild, and refit an entirely new airframe, not to mention the extra fuel capacity (if not an entirely new engine designed for a longer, more efficient burn). There's no real way to make SSO orbital.

This does not, however, preclude one from learning from all the myriad engineering experiments conducted with SSO, and applying them to an orbital vehicle.

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Post    Posted on: Thu Aug 05, 2004 6:20 pm
Why doesn't he just use a drouge chute?

simple, tried and tested technology. You would have to jettison it once it
had done its job but would be recoverable, and even not would come in under
the X-prize's 10% mass rule.

I don't like this feathering malarky. It seems overly complicated, hence overly
prone to failure.

What would happen if, God forbid, the pilot was unable to unfeather the
spacecraft after re-entry.

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Post    Posted on: Fri Aug 06, 2004 7:16 pm
Don't panic, Dave... the occupants of SS1 are equipped with parachutes.

A bigger problem would be what happens if the ship fails to feather at altitude... and my guess is that the ship is designed to be survivable during such a re-entry. The only issue would be dead-sticking an unpowered aircraft at Mach 3, but as many folks have pointed out, that's been done by the x-15 before anyway... and that's why Burt has experienced test pilots flying his ship.


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Post    Posted on: Fri Aug 06, 2004 8:16 pm
Dave H wrote:
I don't like this feathering malarky. It seems overly complicated, hence overly
prone to failure.


As I've said before, it works. And it seems to work very well. The proof is in the pudding...

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Post    Posted on: Fri Aug 06, 2004 8:25 pm
Dave H wrote:
Why doesn't he just use a drouge chute?

simple, tried and tested technology. You would have to jettison it once it
had done its job but would be recoverable, and even not would come in under
the X-prize's 10% mass rule.

I don't like this feathering malarky. It seems overly complicated, hence overly
prone to failure.


A drogue chute that has to deploy properly at high supersonic speeds in stagnation temperatures of 1000C. I'd feel safer with the feather, to be honest :P In essence, it's a pneumatic ram which is probably mechanically simpler than the landing gear on the average commercial jet. How often do those fail?

I read somewhere that on one of its previous flights, SS1 started a slow roll at apogee and re-entered the atmosphere upside down. The aerodynamics of the feather took care of it and righted the vehicle automatically. A drogue may well have had problems deploying in such a situation.


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Post    Posted on: Sun Aug 08, 2004 3:35 pm
SawSS1Jun21 wrote:
A bigger problem would be what happens if the ship fails to feather at altitude... and my guess is that the ship is designed to be survivable during such a re-entry. The only issue would be dead-sticking an unpowered aircraft at Mach 3, but as many folks have pointed out, that's been done by the x-15 before anyway... and that's why Burt has experienced test pilots flying his ship.


Chances of that are pretty low, considering the design. SSO would be pretty likely to rip itself apart under low-altitude supersonic conditions: the fuselage simply isn't streamlined enough for that. If you look at vehicles such as the MiG-25 and the SR-71, you'll notice that their fuselages are specially streamlined for supersonic flight. The biggest difference is the fact that both these aircraft have long, sleek, narrow fuselages to help diffuse the effects of the shockwave. SSO, on the other hand, has a short, stubby fuselage.

The shockwave is probably the single biggest problem facing a high-Mach vehicle. For example, the SR-71 drags along a shockwave with the resistance of 49 deisel freight locomotives pulling against it. If SSO's structure itself didn't fall apart, the friction would generate enough heat to incinerate the vehicle -- SSO is designed to take extremely high temperatures for a short period of time, not (just) very high temperatures for a long period of time.

Of course, Rutan might have designed the entire vehicle with all these things in mind, allowing for a risky but possible last-ditch landing effort.

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Post    Posted on: Sun Aug 08, 2004 9:18 pm
Exactly. I am sure the event would ruin the ship, but I'll wager strong money that Burt has decided to rig the ship to sacrfice it's life in order to save her crew.

I actually just found a link in another thread (the "shuttle replacement" thread in general topics) about a fella who went to Rutan's appearance in Oshkosh which quoted him as saying the ship would survive unfeathered re-entry but that it would sustain "some damage"


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Post    Posted on: Mon Aug 09, 2004 12:59 pm
SawSS1Jun21 wrote:
Exactly. I am sure the event would ruin the ship, but I'll wager strong money that Burt has decided to rig the ship to sacrfice it's life in order to save her crew.

I actually just found a link in another thread (the "shuttle replacement" thread in general topics) about a fella who went to Rutan's appearance in Oshkosh which quoted him as saying the ship would survive unfeathered re-entry but that it would sustain "some damage"


Somehow that sounds exactly like Rutan.

I'll be damned if Burt Rutan doesn't get rated up there with Jack Northrop in the engineering history books someday.

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Post    Posted on: Mon Aug 09, 2004 2:22 pm
Or Kelly Johnson :)


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Post    Posted on: Tue Aug 10, 2004 4:32 pm
Dave H wrote:



I don't like this feathering malarky. It seems overly complicated, hence overly
prone to failure.

What would happen if, God forbid, the pilot was unable to unfeather the
spacecraft after re-entry.

Dave H

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Post    Posted on: Tue Aug 10, 2004 7:33 pm
SawSS1Jun21 wrote:
Or Kelly Johnson :)


Okay, the name rings a bell, but I'm not quite sure which one.... What'd he do again?

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