Missile Velocity

[TheMoose]

Swingkid. I’m glad to see you back. Your knowledge was and will always be welcome.

 

But I have a quickie question for you. Off topic I agree. Sorry guys, I’m just too curious. Are you really still under windows 98?

[TucksonSonny]

Interesting. Can you take it up to 80,000 feet?

 

Any indications of drag and/or thrust?

 

The same test at 80000ft (24384m) is even worse: maximum speed in Mach is about Mach 4.4 (even less than Mach 4.5 done with 40000ft)

 

Missile first accelerate to Mach 4 after 4.2 km after this decelerate to about Mach 3.6 at 10.6 km then restart to accelerate to Mach 4.4 at 14.7 km and next decelerate until finish…

(this strange behavior doesn’t exist at 40000ft)

 

This behavior is also a result of the different loft behavior at different altitudes.

(Preprogrammed loft with minizap is anyway 45 deg)

 

@The Moose,

 

Me too I still have an extra standalone Windows98 pc running for surfing on risky websites…

[S77th-GOYA]

Do away with loft at 80,000.

 

Welcome SK. :thumbup:

[Yellonet]

Quote:

Originally Posted by S77th-GOYA

A lightyear is not a measure of speed. Or time. And it is not relevant to whether a missiles top speed is truly cumulative.

 

Speed and distance is measured in lightyears in space it's the offcial measurement, Go check if you dont beleive me. I've already stated I beleive there would be a combined speed of approx mach 5.5-6 at angels 80.

A lightyear is a distance, the distance the light travels in one year.

 

Distance = velocity * time

Lightyear = the speed of light * 1 year

 

It's not a velocity.

 

Velocity can be measured compared to the velocity of light but the term lightyear is not used when talking about velocity.

[Yellonet]

I believe it's like this:

 

The missile will gain extra speed from being launched from a fast moving aircraft, how much however depends on the air density.

It can be easier to understand if you think of it the other way around, which would be more correct, the engine of the missile is what gives it the extra speed, the speed from the aircraft is there from the start. So how much extra speed the missile will achieve over the initial speed of the aircraft depends on air density.

 

 

Now imagine standing on a field, the wind is still and you throw a ball with as much velocity as you can. Let's say just for the sake of argument that you got it up to 50 km/h.

 

Next you're riding in a cabriolet going 100 km/h, you stand up and throw the ball, you should be able to throw it 100 km/h + 50 km/h = 150 km/h right? Wrong! If the wind is still you will have a 100 km/h wind against you slowing down the ball very fast as soon as you throw the ball, even if it was a missile it would struggle with the increased drag and thus would not achieve a A+B velocity.

If you're riding on an aircraft high up with lower air density however you might be able to throw the ball 50 km/h or even faster, but it can be hard to imagine as most of us never tried that ;)

[tflash]

Lets put it this way: the amount of energy needed to accelerate a missile, given a certain altitude, from Mach 1.0 to Mach 4.0 is probably not sufficient to accelerate that same missile at same altitude from Mach 1.5 to Mach 4.5, so the gain in missile speed will not be linear.

 

Inertia is working for you (this explains that there is a gain); drag is working against you (this explains the gain is not linear).

[golfsierra2]

I know it sounds crazy, but it applies to anything that is being removed from the aircraft or launched from it.

 

So, take a bullet from an on-board cannon, for example. If the aircraft is traveling with an oncoming wind speed greater than the maximum velocity of the fired bullets, the bullet will slow down once they enter the airstream.

 

Well, I think I know what you are trying to tell here, but have to point out that anything launched or fired will slow down when the thrust source is gone due to the drag induced by the air.

 

Even fired from a stationary aircraft on the ground, a bullet from the cannon will slow down as soon as it has left the barrel. Any missile will slow down as soon as the booster is exhausted.

 

The additional drag induced by the airspeed of an flying aircraft enforces this effect, but is not the reason for it. :smartass:

[SwingKid]

But I have a quickie question for you. Off topic I agree. Sorry guys, I’m just too curious. Are you really still under windows 98?

 

Yes, but only for my Lock On/Flaming Cliffs computer. ED software is unique in making disproportionate demands from the graphics card, which I was always careful to keep upgrading.

 

All icing, no cake.. *sigh*

 

-SK

[SwingKid]

Do away with loft at 80,000.

 

Correct - loft is optimized for a max-range flight profile, NOT max speed.

 

Select the AIM-120B,

set both gravity factor and preprogrammed loft to zero (to eliminate any drag from control surfaces)

set Launch Speed to 1 km/h (to minimize frontal drag),

and hit "Launch".

You'll see that the maximum obtained Mach was 2.65 M.

 

At least two sources have suggested the aerodynamic drag in miniZAP is a bit too low, so the only way this missile could have a faster speed in real life is if I guessed its propellant impulse too low at 230. The highest reasonable number that we could put here is 270, which still only gets you to Mach 3 in miniZAP's low-drag air. I just don't see how this missile can claim get to Mach 4 above its starting speed - even in a vaccuum! Sounds a bit like "plasma stealth" to me. ;)

 

-SK

[GGTharos]

You mean loft as you programmed it, SK?

In real missiles it tends to balance range and speed (not much point of shooting it farther if the other guy's missile gets to you first, even though you fire first, or something like that)

And, just because you don't see how the missile ends up doing it, doesn't mean it's doesn't - ALTHOUGH, IIRC recent tests with NASA firing AIM-54C aircraft as test rockets has not had them accelerate past mach 3, more or less as per minizap prediction ;)

[cool_t]

Ok

 

Ill keep putting this link here untill you all understand that if your Jet is flying at Mach .01 or Mach 2.5 the speed will have an extra push for the missile.

 

Terminal velocity/V-Max/paracidic drag/temperature/wind/ ect.

 

You will not pass up a AIM 120 if your going Mach 2 your aim 120 will reach way past Mach 4 in real life. In LOMAC if your going Mach 2 you will watch your 120 creep infront of your jet.

 

PLEASE READ THE LINK.

 

HYPERSONIC

 

http://www.nasa.gov/centers/dryden/research/Phoenix/phoenixmissile.html

[Weta43]

Bit OT, but somebody might be vaguely interested:

 

United States Patent 5435503 Real time missile guidance system US Patent Issued on July 25, 1995 (basically a description of the algorithms)

 

http://www.patentstorm.us/patents/5435503-claims.html

[nellen_mellen]

wow, this thread exploded. Good thing I was building a new computer:P:D, so this makes my first post from my new Quad core machine:D

 

I was thinking about this whole question and the an idea came to me that really simplifies it.

 

But first, I think that I should clarify a few terms:

 

"Velocity" = distance/time

"airspeed" = speed of air particles moving past an object

 

This is really a question that revolves solely around what impact air resistance has on the ability of the missile to exceed its "maximum velocity".

 

The easiest way to think of this situation is to eliminate all of the extraneous factors affecting the missile and the launching craft.

 

So, lets start with a vaccum, and lets do away with gravity, i.e., lets think about a spacecraft in deep space launching a missile.

 

This is about the only case where you could simply add the launching vehicle's velocity to the velocity obtained by the missile once its launched.

 

I should add, however, that you will not be able to have a "set maximum velocity" under these conditions.

 

Since this is an "ideal" scenario of deep space, where there is (ideally) no gasses or gravity to impinge on an objects ability to accellerate under its own thrust, an object will not have a "maximum velocity" (leaving out the discussion of limited fuel, relativity and speed-of-light).

 

So, back to the earth atmosphere, where there are things that get in the way of accellerating, like air and gravitational pull (although that doesnt really apply much since were travelling paralell to the ground).

 

As your launch point moves higher into the atmosphere away from the earth, it may very well be that a missile launched at a very high altitude, where the air is less dense, will exceed its maximum velocity and "air speed".

 

But overall, I guess, its all up to the environmental circumstances to determine the maximum velocity of an object.

 

Its just necessary to remember that the density of the air is much less, and therefore the sole reason that any of this is happening is that the force imparted onto the missile by the oncoming air is less, so it accellerates beyond its "maximum airspeed", but it will never be able to exceed its "maximum drag force" without having additional thrust that can overcome that force, which will only result in a new, higher "maximum drag force", were it will stop accellerating.

[cool_t]

?

 

Here it is agian,

 

http://www.nasa.gov/centers/dryden/

 

Phoenix Missile Hypersonic Testbed

 

01.06.07

 

Researchers at NASA's Dryden Flight Research Center at Edwards Air Force Base, Calif., and the Naval Air Warfare Center Weapons Division, China Lake, Calif., are investigating the use of surplus demilitarized Navy AIM-54 Phoenix air-launched missiles as possible hypersonic test platforms or testbeds. Hypersonic flight is defined as aerodynamic flight at speeds of Mach 5 or greater, and use of surplus Phoenix missiles is one of the methods being considered to obtain critical flight data in the hypersonic regime.

 

Image Above: An inert AIM-54 Phoenix missile nestled under the fuselage of NASA Dryden's F-15B aircraft is being studied as a possible test vehicle to obtain hypersonic data.

 

These missions, to be conducted over restricted military test ranges, would involve launching a missile from a NASA F-15 aircraft flying at speeds up to Mach 2.0, with the missile then accelerating to speeds up to Mach 5.0, depending on its trajectory before fuel is exhausted. The missiles would carry experimental research payloads into the hypersonic regime, something that is currently difficult to achieve.

 

Image Above: This graphic depicts the launch and flight profile for proposed hypersonic test flights of surplus Phoenix missiles launched from NASA's F-15B research aircraft.

 

The Phoenix missiles used for hypersonic research will have their explosive warheads removed, and their tracking and guidance systems replaced with a smaller, more lightweight guidance system. The missiles will also be heavily instrumented to obtain and transmit test data from experiments in such areas as thermal protection materials, scramjet propulsion, guidance & control, boundary layer transition and aerodynamics at hypersonic speeds.

 

At present, NASA is performing design, analysis, and testing leading up to a Critical Design Review at the end of 2007. As part of the preliminary studies, several "captive-carry" flights will be flown by the F-15 with an inactive missile with no propellant carried on the aircraft's centerline pylon to determine the performance of the aircraft when carrying the missile. The project has not been funded to conduct actual launches to obtain hypersonic flight test data, and a decision on funding such research is not expected before 2008.

 

Image to Right: NASA Dryden aircraft and avionics technicians install the nose cone on a Phoenix missile prior to a fit check on the center's F-15B research aircraft.

When in military service, the Phoenix missile was the primary long-range air-to-air weapon carried by the Navy's now-retired fleet of Grumman F-14 aircraft. It was the first operational radar-guided air-to-air missile that could be launched in multiple numbers against different targets from an aircraft. The missile was in operational service with F-14 squadrons from 1974 through its retirement in late 2004. The Navy has no current need for the remaining supply of Phoenix missiles and is making several available to NASA for its hypersonic research efforts.

 

A Phoenix missile is 13 feet long, 15 inches in diameter with a wingspan of 36 inches. It weighs about 1,000 lbs. in its military configuration.

 

Image Above: Surplus Navy Phoenix missiles like this one mounted on the centerline pylon of NASA's F-15B research aircraft may be used to acquire hypersonic flight test data.

 

Thomas Jones of NASA Dryden Flight Research Center is the principal investigator for the development of the Phoenix missile hypersonic testbed. This testbed development effort is funded by the Hypersonics Project under the Fundamental Aeronautics Program of NASA's Aeronautics Research Mission Directorate.

 

 

 

[tflash]

Now that is some good info, cool_t!

[S77th-GOYA]

Mach 5 is normal spec for the AIM-54C.

[D-Scythe]

Mach 5 is normal spec for the AIM-54C.

 

Since when was this "normalized"?

[S77th-GOYA]

Normal meaning look around at different sites and it shows the A and B model at M4.3 and the C model at M5.0. Like the AIM-120's normal spec is Mach 4.

[GGTharos]

That is just peak velocity for some launch parameter (ie. launch at mach 2, etc) ... the average speed to target decreases as distance increases.

[dravisar]

So my question is: How much of this is modeled in LOMAC?

 

I know altitude and related air pressure are very loosely modeled, but what about this discussions topic?

[S77th-GOYA]

So my question is: How much of this is modeled in LOMAC?

 

I know altitude and related air pressure are very loosely modeled, but what about this discussions topic?

 

LOMAC's A2A missiles reach top speed very quickly during burn. It might be a little different for a lofted shot but I doubt it. Launch speed is negligible. You might get a little difference in range between a very slow and very fast launch speed.

[Pilotasso]

That is just peak velocity for some launch parameter (ie. launch at mach 2, etc) ... the average speed to target decreases as distance increases.

 

It has been demonstrated that AIM-54C average speed throughout its flight is closer to mach 3.

[Guest Cappy333]

Effect of Launch Velocity on Missile Velocity

 

I attached a picture of some graphs I created to show the effects of launch velocity on missile velocity. These graphs are qualitative not quantitative. This means that while the shapes are informative, the numbers used were arbitrary. These graphs were created using physics equations, but not data from a particular missile.

 

Definitions:

k = constant of proportionality (this number depends on altitude, and the size and drag coefficient of the missile)

Vd = Drag limited top speed of the missile (this would be approached if the missile had a large amount of fuel and time to reach that speed)

 

I have made some simplifying assumptions:

1) Thrust is constant for the first half of missile flight.

2) Thrust is 0 for the second half of missile flight.

3) Drag is proportional to the square of velocity. (D=k*V^2)

4) The velocity of the missile at launch is less than Vd. (at t=0, V<Vd)

5) The launch trajectory is horizontal

 

Depending on the missile and conditions, there are 2 possiblities with different graph shapes:

case A) The missile accelerates until it runs out of fuel, then decelerates. The missile does not closely approach Vd.

case B) The missile accelerates until it approaches Vd, then remains at Vd until it runs out of fuel, then decelerates.

 

In case A, increasing the launch speed will increase the speed of the missile during its entire flight and increase the maximum speed reached during the missile's flight.

 

In case B, increasing the launch speed will increase the average speed of the missile. It will increase the speed during the thrust period of flight, but will not significantly increase the maximum speed, and will not significantly increase the speed during the gliding period of flight.