Virgin Galactic/Rolls-Royce Mach 3 SST

[djfawcett]

Oh c'mon...
The point is to assess if yes or not it's mission critical for such a private business jets...
Obviously, no. Aero heating of the LE won't prevent such design.

Oh c'mon yourself. Nobody. nobody is going to use ablative technology on a commercial aircraft. And you are the one the tied One to the mach 3 vehicle, when in fact there is no commonality - you were making the point that Spaceship One didn't need titanium to fly mach 3. You are right, it needed ablative technology. Talk a look at the thermal map of an SR-71. That is the aero heating that will be encountered. And last but not least, there is no way to hide from the aero heating in a mach 3 cruise condition.

 

[TomcatViP]

It might not have made through thanks to my sorrow English but my point is not to say that ablative tech will be used. My point was to show reader how the usage of ablative tech is a minor problem by pointing at the tiny amount of mass used.
Then it's perfectly understandable that they could come around another solution given that it won't be critical for the design (mass wise).
Remember that flight profiles suggested here are very different from what a Blackbird or a Valkyrie would do. Those are air-breathing cruisers.
IMOHO there could be another way to have a dash speed of Mach3 for a bisonic aircraft with an hybridized airframe adopting different flight profile.

 

[sferrin]

Oh c'mon...
The point is to assess if yes or not it's mission critical for such a private business jets...
Obviously, no. Aero heating of the LE won't prevent such design.

They'd just make them out of titanium or stainless if it was an issue. (Maybe even some BMI could handle the task.)

 

[Zoo Tycoon]

While there’s numerous aircraft types that can fly at Mach 2 or above, probably there’s well less than ten types can truly sustain that speed beyond the heat barrier. So what’s the minimum time that must achieved to call it sustained super sonic? Well it’s the time when thermal equilibrium has been reached ie heat generated equals heat rejected.

By way of an example, please consider the Stainless Steel Bristol T188 which was designed to investigate sustained high Mach number flight. In typical British penny pinching style it specified the minimum time to achieve thermal equilibrium. It was just 12 minutes at Mach 2.5 i.e at the end of 12 minutes the temperatures would be the same as those at Mach 2.5 for an hour.

Spaceship one entire flight duration was less than 12 minutes(best info 7-8 mins) with a time above Mach1within dense air not over 3 minutes.

 

[TomcatViP]

a time above Mach1within dense air not over 3 minutes.

That...

 

[djfawcett]

This gives a fairly good idea what the airframe temperatures will be cruising around Mach 3.

 

[uk 75]

Spindrift | sci-fi-air-show

www.scifiairshow.com

As usual the future takea a lot longer than we thought.. .

 

[sferrin]

This gives a fairly good idea what the airframe temperatures will be cruising around Mach 3.
View attachment 639825

Resins for the Hot Zone, Part II: BMIs, CEs, benzoxazines and phthalonitriles

Next-generation aerospace programs demand higher temperatures for structural and hot-section components, fostering advances in thermoset resin chemistry.

www.compositesworld.com

" CYCOM 5250-4 BMI resin from Cytec provided a high rate of reproducibility by RTM in nearly 400 high-strength, tight-tolerance composite components on the F-22. Cytec has invested considerable effort in BMI formulations, including CYCOM 5250-4HT, which reportedly has a glass transition temperature (Tg) of 630°F/343°C. This represents a 100°F boost in Tg over CYCOM 5250-4. Cytec says its service temperature is 400°F/204°C. CYCOM 5250-5 BMI is designed to offer ease and consistency of processing comparable to epoxies, but with the Tg/service properties of 5250-4. Toughened CYCOM 5261 BMI prepreg pushes the toughness envelope achieved with high-toughness epoxies, but again, to the 630°F Tg of CYCOM 5250-4. "

This was over a decade ago.

 

[djfawcett]

Being very familiar with composite materials, including BMI, and their use in aerospace design (that is what I have done for the past 30 yrs), published numbers and design allowables are two different worlds. A 1.5 safety factor is generally accepted when considering thermal stress. That being said, the above stated material would not be acceptable anywhere on the SR-71 airframe (what is shown in the above picture). Obviously, there may be areas internally where it would be acceptable. Additionally, as an industry standard, Tg is normally reported as a single number when in fact Tg is a range. The reported number is usually in the middle of the range. This complicates the design process along with any discrepancies that may arise during fabrication, hence the application of safety factors.