SS1 Technical details
Report on Burt Rutan's presentation at Oshkosh as posted on a space newsgroup by Paul Breeds.

I went to two of Burt Rutan's presentations at the EAA Oshkosh show. I thought people would like some technical tidbits from the presentations. This is all from memory, so if I introduce any errors they are probably mine and not Burt's. You should be able to contact EAA and get Audio CD's of two of his three presentations. You want the Forum recording of his private manned space flight presentations. (I ordered audio CD's while I was there)

This whole post is somewhat random, but it is in six broad topics:

Program in general
Anomalies in the first space flight.
Motor Details
Future Orbital Flight.
It is clear that SS1 was designed to enable suborbital space tourisum. The program was fixed price and > 20M$ and < 30M$. SS1 will be making many more flights beyond the X-Prize attempts. Burt showed some fantastic video, but it is not publically availible. The video will be part of the discovery channel SS1 presentation some time this fall. Mike Melville was awed by the experience, he raved about the distant horizon, the weightlessness and the whole experience.
ANOMALIES in the first space flight.
1)At around 60K ft they experienced a 50 knot wind shear. This caused a yaw motion that coubled to roll. While he did not come right out and say it I got the impression that the pilots response to this caused more deviation than the event itself. This caused a 10 degree error in the desired 90 degree vertical track.

2)As a result on the error in vertical tract Mike had to run the pitch trim to the full up position. This caused one of the elevon trim motors to hit the stop and reach thermal cutoff. When at the peak of ascent during the reconfiguration for reentry the pitch trim was reset to zero, one elevon went and the other did not move right away because it was in thermal cut off. This caused the indicated full roll trim indication. As mike was activating the secondary trim sestem the thermal cutout cleared and the problem actually fixed itself as the backup system was being activiated.

3)The Fairing collapse. The fairing was built of thin composite material much like a composite engine cowl. While an engine cowl can be two inches away from a 500C engine part, it does this in air with convection. The SS1 cowl was black on the inside and facing a black engine case that was 220C (Temperature from memory so I could be off +100C) Thus the two coupled via radiative heat conduction with no air to cool the structure, it got too hot and soft and colaped during reentry. Problem has been addressed by painting the interior white and adding some small stiffining ribs.

All boost guidance is done with aerodynamic surfaces. Maximum Q or indicated airspeed is 260 Knots. From watching the video the motor start is very abrupt. The pilots head really snaps back. The motor makes a really wild moaning sound. The sound would be right at home on the sound track for a Hollywood horror film.
Burt spent a lot of time studing the X-15 program. The 2 times the X-15 went to "Space" the reentry angle was very critical, The one X-15 fatality was caused by an error in reentry angle.

One of the primary design goals was a carefree low precision reentry.

On flight #2 or #3 SS1 reentered upside down and the feathering shuttle cock reentry worked from that attitude.

SS1 has 14 lbs of ablative thermal protection applied. The key ingredient is discussed in a current article in air and space. It was clear the this was an unintentional leak, and Burt would not repeat it. (Anyone read the article ?)

SS1 decelerates very high in the atmospehere. At the Xprize weight SS1's stagnation temperature will be 1000C, this will be above 100K ft thus little thermal conductivity so not much heat flow to the structure.

SS1 would survive reentry with no TPS applied, but it would suffer some damage.

Reentry deceleration is complete by 60K ft.

Maximum Q or indicated airspeed is 130Knots on reentry.

MOTOR Details
I've assembled a number of Motor details. From an earlier on-line article: 3000 lbs of Oxidizer and about 600Lbs of rubber.

From Burt's presentation EAC vs SpaceDev Space dev was 1 to 3% more powerful and lighter. Space dev uses a 4 holes in their core, EAC one hole.

Burt was surprised that both EAC and Space Dev succeded in building working motors.

After the presentation I asked Burt about the motor performance, and he answered my question with a bit a hesitation. So I hope I'm not giving anything away that will get him in trouble:

Ground ISP 220
Flight ISP 260
25:1 expansion ratio
Total Impulse 880K newtons.
Burt made it very clear that he is working hard on developing an Orbital vehicle. It's not clear if he is actually building hardware, but he is clearly working on a design.

He was very clear on the difference in challenges between sub-orbital and orbital.

He discussed that air launch does not add much significant energy to an orbital craft.

He discussed the energy advantages of Launching from the Equator.

He discussed the need for a orbital tourist destination and mentioned the work of Bigelow aerospace and inflatable structures.

All in all I though he had a good handle on what was needed for low cost manned orbital space flight.

After reading this post, it is long enough. Many more minor details were provided, I'll add more to follow up posts.


Audio CD's of EAA forums can be had: The 2004 forums are not listed yet, but this is the contact. The specific Burt Rutan forums are:
11:30-12:45 Friday July 30 Honda Pavilion 7 Private Manned Space Program. (The one I attended)

2:30-3:45 Friday July 30 Honda Pavilion 7 A chat with the Rutan Broters. (I could not attend this one I ordered the Audio I'll let you know how it is)

10:00-11:15 Saturday July 31 Honda Pavilion 7 Private Manned Space Program.