SR-71 continued from lunar hoax forum .

[SAMU]

First a couple of points further comparing SR-71 to Atlas rocket:

The liftoff weight of the Atlas being 200,000 lbs with a thrust of 300,000 lbs gives 200,000 lbs to maintain status quo flight (hover) with 100,000 lbs thrust to effect acceleration. With 200,000 lbs mass accelerated with 100,000 lbs of thrust yields a 1/2 g acceleration at launch. As the tank empties the same thrust is applied to a lighter vehicle resuling in in increase of acceleration to (reportedly) 6 g at staging.

The SR71 maintains status quo flight by being supported by the air through which it passes so most of its thrust can be used for acceleration with altitude maintained as a side effect of its speed through the air. With a reported weight of 140,000 lbs and a (reported) thrust of apx. 65,000 lbs also yields an acceleration of just slightly less than 1/2 g. Like the Atlas, as its fuel burns it also gets lighter for the same thrust and so its acceleration also increases.

Additionally the SR-71 "launches" from 30,000ft at 600 mph above 75% of the aptmosphere after midair refueling whereas the Atlas launches from sea level at zero mph. Atlas has to burn an enormous amount of fuel just to get to where the SR-71 starts fully fueled with nearly 3 times the effective fuel load and nitrogen reaction mass on its side.

As to the question of lack of control rockets you are mistaken. All of those ultra high altitude aircraft do have control rockets as there is not enough air for the airfoil control surfaces to work at those altitudes. I guess you didn't see them because you weren't looking for them or they didn't have those compartments open when you looked.

Regarding ramjets as used for orbital flight the principle works like this: The SR-71 has a bypass duct to take the ram air past the turbofan at high speed. as the speed increases more air is ramed into the engine without the turbofan getting in the way. The more air the engine has the more fuel it can burn, the more fuel it burns the more thrust it has and the faster it goes, the faster it goes The more air the engine has the more fuel it can burn, the more fuel it burns the more thrust it has and the faster it goes etc... to the limit you can pump fuel into the combustion chamber. The idea of the hypresonic air breather is to achieve most of its orbital speed and burn most of its fuel while it is still in the aptmosphere in one big spurt and then to coast on the rest of the way out of the aptmosphere into orbit. Surely some early designs did contemplate using airbreather/rocket combinations but the ideal and the current designs are pure airbreathers.

Finally, as I couldn't find the performance envelope of the SR-71 only the speed of quoted of 2200 mph is not quoted using the standard nomenclature ASL (at sea level) If we assume that its speed as reported is 2200mph ASL then at performance altitude of 85,000 ft it is above 90% of the aptmosphere so its ground speed would be ten times more than its air speed thus 22,000 mph which is orbital speed.

Additionally its range at 2200mph ASL for (stated) endurance of one hour gives a range of only 2200 miles. The range as stated from various sources I have seen has been anywhere from 2200 (official) to 10,000 (unofficial but reliable) miles. If 10,000 miles is true then it is certainly suborbital.

<font size=-1>[ This Message was edited by: SAMU on 2002-08-21 21:41 ]</font>

[overrated]

Hey, samu, could you restate the original point in question?

[SAMU]

The original topic was "A plea for a change in nomenclature.
http://www.badastronomy.com/phpBB/vi...009&forum=3&26

from the luanr conspiracy forum.

Although it was only meant to illustrate an opposing viewpoint to the point of that thread. It got off topic by others opposing details of what was only meant to be an illustration. Further illustration was supplied by me to that thread untill it was mentioned that I had hijacked that thread. So I moved it here as an away from the main stream topic.

[overrated]

Oh.

[Bozola]

The liftoff weight of the Atlas being 200,000 lbs with a thrust of 300,000 lbs gives 200,000 lbs to maintain status quo flight (hover) with 100,000 lbs thrust to effect acceleration. With 200,000 lbs mass accelerated with 100,000 lbs of thrust yields a 1/2 g acceleration at launch. As the tank empties the same thrust is applied to a lighter vehicle resuling in in increase of acceleration to (reportedly) 6 g at staging.

Dude. Ummm. Where do you get your data from?

http://www.ast.lmco.com/launch_atlasFacts.shtml

Length:
Atlas IIA, IIAS - 155.5 ft (47.4 m) with large payload fairing
Atlas IIIA - 170.2 ft (52.8 m) with large payload fairing
Atlas IIIB - 174.2 ft (53.1 m) with large payload fairing
Atlas V (400) - 191.2 ft (58.3 m) with large payload fairing
Atlas V (500) - 204 ft (62.2 m) with 5.4-meter payload fairing

Diameter:
Atlas II and III - 10 ft (3.05 m)
Atlas V - 12.5 ft (3.81m)

Atlas booster length:
Atlas IIA, IIAS - 82 ft (25.0 m)
Atlas IIIA, IIIB - 95.1 ft (29.0 m)
Atlas V - 106.2 ft (32.4 m)

Centaur length:
Atlas IIA, IIAS, IIIA - 33 ft (10.0 m)
Atlas IIIB - 38.5 ft (11.68 m)
Atlas V - 38.5 ft (11.68 m)

Mass at liftoff:
Atlas IIA - 408,800 lb (185,427 kg) large fairing
Atlas IIAS - 515,333 lb (233,750 kg) large fairing
Atlas IIIA - 486,500 lb (220,672 kg) large fairing
Atlas IIIB - 496,908 lb (225,392 kg) large fairing
Atlas V (400) - 734,850 lb (333,320 kg) extended large fairing
Atlas V (551) - 1,191,250 lb (540,340 kg) Contraves Short

The Atlas II booster propulsion system, the Rocketdyne produced MA-5A, provides a total sea-level rated thrust of 490,000 lb (2,180 kN). Atlas IIAS uses four additional strap-on Castor IVA solid rocket boosters, each 37 feet (11.3 m) long and 40 inches (101.6 cm) in diameter, providing an average thrust of 112,000 lb (498 kN). The solid rocket boosters fire two at a time. The second pair of solid rocket boosters fires during flight after the first pair burns out.

The Atlas III family builds upon the pressure-stabilized design of Atlas II with the use of a new single-stage Atlas main engine, the Russian RD-180. RD-180 is a two-chamber version of the flight-proven, four-chamber RD-170 engine built by NPO Energomash of Russia. The RD-180 is a throttleable engine fed by liquid oxygen and kerosene propellants, providing a total sea-level rated thrust of 860,200 lb (3,826 kN). With Atlas III, the stage-and-a-half Atlas II booster design is eliminated with a resultant improvement in producibility, operability, and reliability.

[Peter B]

On 2002-08-21 21:13, SAMU wrote:
If we assume that its speed as reported is 2200mph ASL then at performance altitude of 85,000 ft it is above 90% of the aptmosphere so its ground speed would be ten times more than its air speed thus 22,000 mph which is orbital speed.

Er, is this right? If the atmosphere is 1/10 as thick as sea level you can go 10 times as fast as you can at sea level?

I ain't no aeronautical engineer, but it doesn't sound right to me.

[Bozola]

If we assume that its speed as reported is 2200mph ASL then at performance altitude of 85,000 ft it is above 90% of the aptmosphere so its ground speed would be ten times more than its air speed thus 22,000 mph which is orbital speed.

Bzzzt. Wrong. Wrong. Way wrong.

DON'T ASSUME!

It's speed is measured typically in two ways:

as a Mach number (Mach 3.2 according to NASA) at X altitude (usually above 85,000 feet. When you see a MPH/KPH value from a Mach number, it's been converted to compensate for altitude.

as a time between two ground points. This requires no conversion.

http://www.sr-71.org/blackbird/records.htm

27/28 July 1976
Crew: Capt. Robert C. Heit and Maj. Larry A. Elliott
Altitude in Horizontal Flight: 85,068.997 feet

27/28 July 1976
Crew: Capt. Eldon W. Joersz and Maj. George T. Morgan
Speed Over a Straight Course: 2,193.167 mph

27/28 July 1976
Crew: Maj. Adolphus H. Bledsoe, Jr. and Maj. John T. Fuller
Speed Over a Closed Circuit: 2,092.294 mph

1 September 1974
Crew: Maj. James V. Sullivan and Maj Noel F. Widdifield
Speed Over a Recognized Course - New York to London
Time: 1 hour 54 minutes 56.4 seconds
Average Speed: 1,806.964 mph

13 September 1974
Crew: Capt. Harold B. Adams and Capt. William C. Machorek
Speed Over a Recognized Course - London to Los Angeles (5,645 mi)
Time: 3 hours 47 minutes 35.8 seconds
Average Speed: 1,435.587 mph

6 March 1990
Crew: Lt. Col. Ed Yeilding and Lt. Col. Joseph T. Vida
Speed Over a Recognized Course - Los Angeles to East Coast (Coast to Coast, 2,086 mi)
Time: 1 hour 7 minutes 53.69 seconds
Average Speed: 2,124.5 mph

6 March 1990
Crew: Lt. Col. Ed Yeilding and Lt. Col. Joseph T. Vida
Speed Over a Recognized Course - Los Angeles to Washington D.C. (1,998 mi)
Time: 1 hour 4 minutes 19.89 seconds
Average Speed: 2,144.83 mph

6 March 1990
Crew: Lt. Col. Ed Yeilding and Lt. Col. Joseph T. Vida
Speed Over a Recognized Course - St. Louis to Cincinnati (311.44 mi)
Time: 8 minutes 31.97 seconds
Average Speed: 2,189.94 mph

<font size=-1>[ This Message was edited by: bozola on 2002-08-21 23:10 ]</font>

[Bozola]

furthermore, what's with this tenfold speed increase? Where did this come from?

ASL = at sea level? Ummm, that's a bit misleading. Either you are reading IAS (indicated airspeed) or TAS (true airspeed). Altitude comes into play to figure out the IAS to TAS conversion.

It's interesting to note that the speed of sound decreases with altitude. Above 60,000 it's around down around 660 mph...so let's see if your IAS is reading 3.2 Mach then

3.2Mach * 660MPH/Mach = 2,112 MPH TAS.

[SAMU]

I guess a little basic flight school is called for here.

Airspeed at sea level (ASL) is a constant. The same as groundspeed. As altitude increases the air thins. The aircraft is traveling through less air for a given distance traveled over the ground than it would at a lower altitude. Although indicated airspeed (IAS) is one thing at sea level and the same thing at altitude, you must compensate for thinning air at altitude by increasing ground speed. If you are traveling through air at 2200 mph indicated air speed in sea level pressure of APX 14 psi then your ground speed is 2200 mph. If you are traveling through air at half sea level preasure of 7 psi with an indicated air speed of 2200 mph then your groundspeed is 4400 mph etc. While the airspeed of sound decreases slightly at altitude, its ground speed increases the same way.

One might propose that the stated (official) speed is a ground speed measurement(as its officialy stated range indicates (speed 2200mph/endurance 1 hour).) .This proposal would not work, as, if its groundspeed is 2200 mph and its altitude is 85,000 feet then its indicated airspeed would be 220 mph. Now just between you me and whoever might be reading this, the SR-71 looks to me like it can go through the air at better than 220 mph IAS at sea level and better than 220 IAS at 85,000 feet. In fact I think I could find references to some boats that can do better than that at sea level and so can you.

The atlas facts I got here:

http://www.hq.nasa.gov/office/pao/Hi...d/programs.htm

<font size=-1>[ This Message was edited by: SAMU on 2002-08-22 02:48 ]</font>

[SpacedOut]

Samu -

How did you come up with the 220 mph figure???

To the best of my knowledge, indicated airspeed does not change with atmospheric density as does the speed of sound. (as was correctly stated by Bozola)

I don’t have the time or awake brain cells to do the math right now but I believe that the actual airspeed of a plane at 85,000 feet with a measured ground speed of 2,200 mph is higher than 2,200 mph (simple spherical geometry). If I’m wrong, would someone please provide the actual math

[SpacedOut]

Double Post [img]/phpBB/images/smiles/icon_eek.gif[/img]ops

<font size=-1>[ This Message was edited by: SpacedOut on 2002-08-22 10:13 ]</font>

[GrapesOfWrath]

On 2002-08-22 07:01, SpacedOut wrote:
I don’t have the time or awake brain cells to do the math right now

Maybe next life time [img]/phpBB/images/smiles/icon_smile.gif[/img]

but I believe that the actual airspeed of a plane at 85,000 feet with a measured ground speed of 2,200 mph is higher than 2,200 mph (simple spherical geometry).

The difference due to spherical geometry is insignificant--you'd only be 16 miles above a sphere (the Earth) of radius 4000 miles.

But let me understand this, are you seriously suggesting that the Blackbird has actually flown at 22 thousand miles per hour?

[SpacedOut]

Not I – Samu has stated that he believes that the Blackbird could obtain orbital flight.

I was just questioning his calculation of 220 mph airspeed at 85,000 feet. I just thought airspeed for any given altitude would be greater than the ground speed - which is not very much according to GOW (thanks BTW).

One additional thing Samu – please look carefully at pictures of the SR71 – there are no RCS thruster ports in any of the photos – these are very visible on vehicles such as the X15 – RCS thrusters are absolutely necessary if the plane was designed for non atmospheric fight.

[spelling and minor edit]


<font size=-1>[ This Message was edited by: SpacedOut on 2002-08-22 10:19 ]</font>

On 2002-08-22 07:54, GrapesOfWrath wrote: To: 6:13 A.M. PST

Maybe next life time [img]/phpBB/images/smiles/icon_smile.gif[/img]

The difference due to spherical geometry is insignificant--you'd only be 16 miles above a sphere (the Earth) of radius 4000 miles.

But let me understand this, are you seriously suggesting that the Blackbird has actually flown at 22 thousand miles per hour?

|=|AY watch it? I was trying to get a level 3 density 2day

[Bozola]

Airspeed at sea level (ASL) is a constant. The same as groundspeed.

You seem to be indicating your ASL as the same as IAS. So, would your definition be true at high tide, or low tide? What about on a day with a really low pressure front moving through?

Really simplified. Purists, please forgive me.

...the SR-71 looks to me like it can go through the air at better than 220 mph IAS at sea level and better than 220 IAS at 85,000 feet....

This is a classic mistake of confusing speed with pressure. You should ask yourself "just what is that gage measuring"?

Aircraft measure their speed by air pressure - IAS is really a measurement pressure.

To the pilot, IAS (especially Mach) is more important because it tells you when you are going to stall, compress, or be happy. Stall speed is always IAS. To the navigator, TAS is more useful because they want to know position. Fortunately (in the pre GPS days) there were lots of nifty tables you could use to convert the two, based on altitude (which is another measure of pressure..[img]/phpBB/images/smiles/icon_wink.gif[/img]).

As you climb you have to keep increasing your TAS to maintain speed because as the pressure drops, your IAS drops. There comes a point in your climb where you can't increase your TAS anymore and that little IAS needle hits the rated stall speed. At this point you are no longer flying; gravity has reclaimed your sorry a**.

If the SR-71 was reporting an IAS speed of 2200mph at 85,000ft, that would be suspicious for a number of reasons.
Firstly, because (you are correct on this, though grossly misinterpretated) the aircraft would be traveling at an ungawdly TAS speed. Secondly, because supersonic aircraft report their speed as a Mach number at an altitude. Thirdly, the pressures and frictions generated by an IAS value of 2200mph would fry an aircraft (remember, IAS is a measure of PRESSURE not speed). And, finally, the TAS as cited by the time over distance records (note that there's refueling lags in those data...those guys sure can refuel quiclkly!) is incontrovertible.

When you actually examine the data, you will find that the 2200mph value is a "civilian" number converted to TAS; a value given to the great unwashed public who are used to automobiles, and only understand TAS. At no point does any data report an IAS value of 2200 mph.



<font size=-1>[ This Message was edited by: bozola on 2002-08-22 11:48 ]</font>

[GrapesOfWrath]

On 2002-08-22 10:17, SpacedOut wrote:
Not I – Samu has stated that he believes that the Blackbird could obtain orbital flight.

Oops, yeah, I meant to address Samu. Sorry.

[SpacedOut]

No problem GOW.

Links to photographs of an SR17 and X15 for Samu – Re: RCS thrusters.

Photo of a Blackbird.

Photo of the X15 at the Smithsonian Air and Space Museum. (can anyone locate a better photo?)


<font size=-1>[ This Message was edited by: SpacedOut on 2002-08-22 12:39 ]</font>

[Bozola]

http://www.dfrc.nasa.gov/gallery/photo/X-15/

[SpacedOut]

Thanks Bozola (site didn't come up with google ?!?)

This X15 photo clearly shows the RCS ports at the nose.

[SAMU]

Just a simple question for those who think they are versed in the subject. What groundspeed do you think the SR-71 could fly at sea level? You will have to extrapolate its groundspeed from what you know about the subject because it never flew at sea level. Just as I have been extrapolating its groundspeed at altitude from what I know about the subject because it never officially flew with an orbital groundspeed. While some are saying that it couldn't fly into orbit, it certainly could fly at sea level. It didn't fly at sea level but what would its ground speed have been if it had?

For those who need the conditions described to a pedantic degree; the tempreture is 80 degrees F, no wind, pressure 29.92, altitude 0 ft above sea level.

[overrated]

I've seen at least two SR-71s up close. They don't appear to have RCS systems, nor have I read of them having such systems. This bears out in the NASA fact sheet about the aircraft:

"Aerodynamic control surfaces consisted of all-moving vertical tail surfaces above each engine nacelle, ailerons on the outer wings and elevators on the trailing edges between the engine exhaust nozzles." (full article: http://www.dfrc.nasa.gov/PAO/PAIS/HTML/FS-030-DFRC.html)