Rocket-Boosted Orbital SR-71 Derivative

[KJ_Lesnick]

Lee,

Thanks! Just curious... if the Blackbird was constructed out of Beta Titanium that could take 1,000 to 1,200 C max... isn't that pretty close to the re-entry temps for the space-shuttle?

While the metal wouldn't likely reach incandescence at those temperatures... wouldn't the air itself glow like the fireball around the shuttle when it re-enters the atmosphere?

What factors would other than aircraft temp cause the air around a plane to glow or not glow?


KJ

 

[Lee]

KJ, quoted: "...if the Blackbird was constructed out of Beta Titanium that could take 1,000 to 1,200 C max... isn't that pretty close to the re-entry temps for the space-shuttle? "

I was looking at the 'official' picture of the Blackbird that showed "550-600 deg" over most of the plance except the afterburner, which was '1100'. A static test stand picture of the J58 had the afterburner glowing cherry-red to pink. Really.




KJ: "While the metal wouldn't likely reach incandescence at those temperatures... wouldn't the air itself glow like the fireball around the shuttle when it re-enters the atmosphere?"

3,600 deg F. is more like it---at the maximum. That why the nose and TPS is ablative. The Shuttle is a lot hotter.




KJ: "...What factors would other than aircraft temp cause the air around a plane to glow or not glow?"

Static electricity in a thunderstorm? Radio transcieving is a real bear while something like this go going on. Reentry heat will do the same thing.

 

[KJ_Lesnick]

So part of the glowing is the ablation process?

 

[Orionblamblam]

So part of the glowing is the ablation process?

No. Ablation would cool the system, and thus reduce incandescence. The glow is created simply by the compression of the atmosphere so that it's temperature rises* to where it is hot enough to glow. Some portion of the heat generated by the compression is transferred to the vehicle by convection and conduction; obviously, half of the radiant energy is radiated onto the vehicle, which absorbs some, reflects some, and retransmits some.

*Usual dreary example: bicycle tire pump. Rapidly compress the air within, and it gets hotter.

 

[Lee]

Mission Control at Houston also has a problem communicating with distant probes while the spacecraft are using ion thrusters and the like. They were actually ionizing cesium or mercury, though.

I've always thought reentry heat did the same thing to radio reception of spacecraft like Gemini, etc.

 

[sferrin]

Mission Control at Houston also has a problem communicating with distant probes while the spacecraft are using ion thrusters and the like. They were actually ionizing cesium or mercury, though.

I've always thought reentry heat did the same thing to radio reception of spacecraft like Gemini, etc.

It did. On of the things that had to be addressed with the Sprint ABM was being able to communicate through such a layer.

 

[Lee]

Yes, precisely. SR-71 pilots may not have been able to radio their base if they could really go Mach 5, yes? Assuming they did fly that fast, that is.

 

[KJ_Lesnick]

Mach 5 or Mach 6 shouldn't yield a temperature anywhere near a shuttle re-entry.

The X-15 for example got to about 1,200 F, not 1,200 C. Since chinese are good at dealing with heat, I don't see any reason why the temperature would be much higher than 1,200 F for the same speeds.

 

[Lee]

Mach 5 or Mach 6 shouldn't yield a temperature anywhere near a shuttle reentry....

Okay, I see your point. Maybe I'm getting old?
I was thinking(?) the temperature for Mach 5 was the same as Mach 25, or, using Hafnium diboride/tantalum carbide impregnated carbon fiber matrices on the leading edges of wings would allow that high of temperature.
Even the second case above would be stretching things for ionization at 2000-2300 deg. C.

 

[sferrin]

Mach 5 or Mach 6 shouldn't yield a temperature anywhere near a shuttle re-entry.

The X-15 for example got to about 1,200 F, not 1,200 C. Since chinese are good at dealing with heat, I don't see any reason why the temperature would be much higher than 1,200 F for the same speeds.

"Chinese are good at dealing with heat"? What the hell is that suppose to mean?

 

[Barrington Bond]

I think he meant CHINES

...or Sweat shop factories...

 

[overscan (PaulMM)]

Given you are talking about Kendra you might want to pick a different pronoun

 

[KJ_Lesnick]

Whoops! I meant chines, not Chinese!

Kendra Lesnick

 

[mz]

It's different to spend a few minutes hypersonic like X-15 did and cruise thousands of kilometers... The shuttle that just does a re-entry has to be hooked up to a big cooling system right after landing to prevent the aluminium from taking damage from the residual heat from the hot parts - and it has those well insulating tiles and blankets that add considerable weight.
There's two ways to handle heat: a hot structure like SR-71 with titanium or insulating and using aluminium like the shuttle. I'm no expert but I think the former has a lower max heat attainable and the latter is less mass efficient.
Not only the temperature, but the duration of the flight gives challenges too.

 

[Lee]

Not only the temperature, but the duration of the flight gives challenges too.

This is 'right on the money' (cliche, I know :). But the Germans chose a less powerful explosive for the V-2, a TNT-based derivitive, I think, because the heat load on the nose amounted to almost 1,000 deg. F during the ascent.
Acceleration of the V-2 started out at about 1 g and rose fairly quickly after that. 30 sec. after liftoff, the rather primitive guidance system forced the whole rocket into a 45 deg. angle toward England and that added to the heat on the nose instead of rising vertically.
As mz said, and I imply here, flight duration has something to do with how a aircraft/spacecraft is designed internally.

 

[KJ_Lesnick]

The X-15 reached 1,000 F to 1,200 F immediately upon reaching Mach 6? That sounds unusual as the Concorde to my knowledge doesn't reach 260 immediately upon reaching cruise-speed, and the XB-70 took some time to heat-soak after reaching cruise. Could be wrong though.

 

[Michel Van]

here some answer to X-15 at mach 5
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19710070036_1971070036.pdf
4 MB big

some picture out PDF
p.s. same thing happens to SR-71 also at mach 5

 

[Lee]

Michel Van has a partial point with his X-15 presentation: that the X-15 gets as hot as the Blackbird, but KJ (I believe) is making the point that the Blackbird remains at Mach 5 for quite a bit longer than the X-15, right?
Correct me if I'm wrong, KJ.
If that is his point, I would argue that heat stress would amount to drastic weakening of the Blackbird airframe without active cooling by JP fuel through the forward chines and then circulated elsewhere in the plane.

 

[Michel Van]

after PDF

a X-15 Mach 4 flight
stays 200 secound on Mach 4 (rocket drive) with wingspar temp over 600°F

 

[KJ_Lesnick]

Which aircraft-shape overall is better at tolerating Mach-5 or Mach-6 in terms of kinetic-heating assuming they're not the about equal?

-The A-12/SR-71 chined-shape with delta-wings?
-The X-15 blunt semi-chined, design with a thin tapered, unswept wing with a slightly blunt-nose?

I'm kind of wondering because chines can deal with heat pretty well, although I'm not sure exactly how they compare to a blunt-nose, the X-15's chines are kind of bulges, where as the SR-71's are much better blended so it would seem. The X-15's very thin tapered straight wing is actually very efficient for supersonic flight compared to a delta wing, however the trim-drag is better with a delta-wing, especially with a chine in front...

Anyone?


KJ Lesnick

 

[Michel Van]

look here Lockheed proposal for a Mach 5 plane
http://www.secretprojects.co.uk/forum/index.php/topic,1967.0/highlight,lockheed.html

by the way it use not Titanium but Inconel
http://en.wikipedia.org/wiki/Inconel
and still at Mach 5 the Inconel will be red hot.

 

[avatar]

hey isn't this there in Bill Sweetman's Aurora book as well?
if yes , i'll refer

 

[Lee]

KJ_Lesnick, quoted: "Which aircraft-shape overall is better at tolerating Mach-5 or Mach-6 in terms of kinetic-heating assuming they're not the about equal?
-The A-12/SR-71 chined-shape with delta-wings?
-The X-15 blunt semi-chined, design with a thin tapered, unswept wing with a slightly blunt-nose?"

The blunt chines of the X-15 would probably carry away heat better (so will the blunt nose) at least that's what I read in college textbooks years ago. Regardless of the shape away from the leading edge. Bottom line: equilibrium temperatures are lower with the blunt design. The sharp nose may have less drag, though.





KJ: "I'm kind of wondering because chines can deal with heat pretty well, although I'm not sure exactly how they compare to a blunt-nose, the X-15's chines are kind of bulges, where as the SR-71's are much better blended so it would seem."

Overall, the blunt design was favored most of the time. Better heat tolerance made up for other shortcomings.




KJ: "The X-15's very thin tapered straight wing is actually very efficient for supersonic flight compared to a delta wing,...

I didn't know that in general for wings. I did know that L/D ratio was better with the tapered X-15 wing. There were NACA(predecessor of NASA)reports back in the late 50s and early 60s that indicated this in test results. NTRS may have them available to the public, but I hadn't had the money to copy them off up 'til now.
However, I did find this:

Comparison Between Theory and Experiment for Wings at Supersonic Speeds
http://stinet.dtic.mil/cgi-bin/GetTRDoc?AD=A380791&location=U2&doc=GeTRDoc.pdf

This paper goes into some experimentation for wings as such, but the reader will need to decide whether or not it's explanatory enough or not.

I just saw Michel Van's Mach 5 reference aircraft while I was online. That design is more than just well known; I think it was printed in Pop. Mechanics/Science magazine. If not one of them, then as reference(s) for the SR-71(?)





KJ: "...however the trim-drag is better with a delta-wing, especially with a chine in front..."

As you say, the delta wing may actually have less trim, wave or parasitic drag. That's probably why the designers added them to the Shuttle. Also, a thicker, deeper delta wing would weigh less and be cheaper to build than an X-15/F-104 wing. I read that in textbooks and remember it to this day.

 

[KJ_Lesnick]

The blunt chines of the X-15 would probably carry away heat better (so will the blunt nose) at least that's what I read in college textbooks years ago. Regardless of the shape away from the leading edge. Bottom line: equilibrium temperatures are lower with the blunt design. The sharp nose may have less drag, though.

That may very well be true. But I remember seeing a chined version of the V-2 (The fins were extended all the way to the nose producing a chine)... just a proposal which would have the range to hit the US from Germany (3500 nm range), and the regular V-2 could do Mach 5 -- to get 3500 nm it would need way more speed and used stainless steel metallurgy. It didn't have titanium beta or anything and yet it's chines looked a lot like the Blackbird.

I'm wondering how much of a difference would there be between the blackbird chines and a blunt chine.

Overall, the blunt design was favored most of the time. Better heat tolerance made up for other shortcomings.

Yeah, that's what I remember for the most part. Although I've heard weirder things, such as the blunt nose somehow reducing drag under some conditions by better distributing heat. This is totally confusing because the X-43, the SHARP-spaceplane concept all currently use razor sharp noses.

I just saw Michel Van's Mach 5 reference aircraft while I was online. That design is more than just well known; I think it was printed in Pop. Mechanics/Science magazine. If not one of them, then as reference(s) for the SR-71(?)

Do you have a picture of that?

 

[Lee]

KJ, quoted: "...This is totally confusing because the X-43, the SHARP-spaceplane concept all currently use razor sharp noses."

There's a reason for that. Word was that a sharper wing leading edge made for a lot less drag, and in so doing, raised the effective L/D by, say, 100-150 %. This allows much better crossrange coverage in case of emergency; that going double when spacecraft use a lifting body to provide partial lift on reentry.





Lee, quoted: "I just saw Michel Van's Mach 5 reference aircraft while I was online. That design is more than just well known; I think it was printed in Pop. Mechanics/Science magazine. If not one of them, then as reference(s) for the SR-71(?)'
KJ, quoted: "Do you have a picture of that?"

Unfortunately, I don't have the original source, and if I did, I wouldn't have any means to upload a picture to the 'Web without my own computer, scanner and image processing software.
(I'm composing this on a borrowed computer.)

 

[KJ_Lesnick]

Hard to believe McDonnell and McDonnell-Douglas managed to come up with all sorts of ideas without blunt leading-edges and noses.

 

[sferrin]

Hard to believe McDonnell and McDonnell-Douglas managed to come up with all sorts of ideas without blunt leading-edges and noses.

And none of them flew.

 

[KJ_Lesnick]

The X-43 flew... (I don't know who built it) and it has a sharp leading edge

 

[Orionblamblam]

The X-43 flew... (I don't know who built it) and it has a sharp leading edge

Made out of a solid chunk of tungsten, IIRC. Not valid for operational large vehicles.

 

[KJ_Lesnick]

Orionblamblam,

I take it that would weigh a lot...

 

[red admiral]

I seem to recall reading that Saro had some similarly wild ideas about getting a variant of the 177 into low orbit.

Regards

Fred

From speaking to some of the Rolls-Royce rocket guys last year i didn't hear anything about this. It was thought the SR.53 could make 120,000ft in a zoom climb so the pilots were expressly told not to attempt it. Mostly from the fact that there would be no control at that height without a reaction control system. Theres quite possibly some paper scribbles with an SR.177 with RCS and increased rocket fuel storage to make it higher, but I haven't heard anything of it.

 

[Orionblamblam]

Orionblamblam,

I take it that would weigh a lot...

As well as being incredibly expensive, fragile and very likely a failure. What will survive a few seconds at high Mach is not necessarily a good indicato of what would survive an hour or more at high Mach. The X-43 needed ballasting up front, so makign the nose out of tungsten served several roles, but for an operational large aircraft, you'd want your ballast to be something more than jsut dead weight.

 

[Lee]

Orionblamblam,

I take it that would weigh a lot...

Orionblanblam, quoted: "The X-43 needed ballasting up front, so making the nose out of tungsten served several roles, but for an operational large aircraft, you'd want your ballast to be something more than just dead weight."

Lee: Several hundred pounds worth of tungsten. The manufacturer said, or implied, in an interview that if they could get around the ballast issue, flight performance would increase appreciably.

 

[KJ_Lesnick]

How would a heavy nose help ballasting?

I thought the center of pressure would go AFT on a supersonic design.

 

[Michel Van]

How would a heavy nose help ballasting?

i think is to keep the center of gravity in center of Aircraft
otherwise the planes flip over and falls form the sky, tail first or nose first down

right orion ?

 

[Lee]

How would a heavy nose help ballasting?

Michel van, quoted: "i think is to keep the center of gravity in center of Aircraft..."

Actually, to keep the average center-of-gravity(CG) in the correct place.
I'm confident that if there was a better way to maintain balance or soak up heat, the design engineers would have thought of it.





Michel Van: "...otherwise the planes flip over and falls form the sky, tail first or nose first down"

Usually nose first(especially on the Concorde). That's why there's an aft trim tank built under the vertical stabilizer of the Concorde and it's filled after passing Mach 1 or so.

Michel Van: "...right orion ?"
orion... is an engineer; he would be the one to ask.

 

[KJ_Lesnick]

Center of Pressure shifts aft at supersonic speed... resulting in nose down tendency