Missile Velocity

[Guest PKM]

How can you suggest that a rocket (or anything for that matter) can travel at ANY Mach number in space?

 

Since Mach is the measurement used for an objects velocity in ratio to the speed of Sound and sound can only travel through a medium such as air, water etc. Can you tell me how sound can travel through a vacuum? Quick Answer - it can't.

 

Speed can be measured in space (usually Km/h), acceleration (in G's) can be measured, but not Mach number.

 

 

 

oops, beaten to it. :megalol:

 

Is it KMH/MPH I thought speed and distance in space was measured in lightyears, Did not know you could measure G's in space. ;)

 

Anyway back on topic....

[Guest PKM]

Mach is the speed of sound. What is the speed of sound in a vacuum?

 

The equivelant of mach 1 in a vacuum is exactly 0.000001134 lightyears. ;)

[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.

[Force_Feedback]

To me it seems like drag in not proportional to speed in lomac (decelleration wise), but that's just a eyeball mk. 1 observarion, nothing proven.

[Guest PKM]

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.

[TucksonSonny]

I recently read a debate on whether or not a real life missile's speed can simply be added to the launching aircraft's speed to give the actual top speed of the missile. An example of a theoretical launch of an AMRAAM from an SR-71 at Mach 3.3 and an altitude of angels 80 was given.

 

One side argued that yes, you simply add the velocities and the 120 has a speed of ~Mach 7 at engine termination.

 

THe other side said that no, the 120 would reach a terminal velocity where thrust equals drag at Mach 4, saying that is a design limit.

 

To me, without knowing the thrust of the missile's engine and the drag coefficient, one cannot confidently choose either side of the argument. Obviously the thrust is quite large compared to the mass but at speeds around Mach 7, even a missile with very small drag coefficient would be experiencing strong drag forces. But without better data, I can't say.

 

Anyone have any thoughts on the matter?

 

Result from little test with minizap:

Trajectory maximum speed of Mach 4.5 is reached after 14.6 km.

After 152.2 km speed is still Mach 2.95.

I am still trying to find Mach 7 with no result! :D

Missile Parameters

------------------

Missile Selector : 02 AIM-120B AMRAAM

Body Length : 3.581 m

Body Diameter : 178.0 mm

Wing Span : 533.4 mm

Wing Area : 0.06472 sq. m

Launch Mass : 150 kg

Propellant Mass : 49 kg

Specific Impulse : 230 s

Boost:Sustain Thrust : 2.60 ratio

Boost Burn Time : 0.7 s

Total Motor Burn Time : 11.0 s

Controlled Flight Time : 150 s

Maximum Turn : 30 G

Skin Drag Factor : 1.00

Lifting Body : yes

Rounded Nose : no

Safety Maneuver : no

Preprogrammed Loft : 45 deg

Simulation Controls

-------------------

Step Rate : 10 Hz

Maximum Step : 3600

Step Delay : 0 ms

Minimum Missile Speed : 1.27 M

Gravity Factor : 1.00

Loft Glide Logic : no

Intercept Controls

------------------

Target Aspect : 180 deg

Launch Altitude : 12000 m (+/- 40.000ft)

Target Altitude : 10000 m

Launch Speed : 3.30 M

Target Speed : 0.83 M

Launch Loft Angle : 0 deg

 

 

:thumbup:

[Guest PKM]

Result from little test with minizap:

 

Trajectory maximum speed of Mach 4.5 is reached after 14.6 km.

After 152.2 km speed is still Mach 2.95.

 

I am still trying to find Mach 7 with no result! :D

 

Missile Parameters

------------------

Missile Selector : 02 AIM-120B AMRAAM

Body Length : 3.581 m

Body Diameter : 178.0 mm

Wing Span : 533.4 mm

Wing Area : 0.06472 sq. m

Launch Mass : 150 kg

Propellant Mass : 49 kg

Specific Impulse : 230 s

Boost:Sustain Thrust : 2.60 ratio

Boost Burn Time : 0.7 s

Total Motor Burn Time : 11.0 s

Controlled Flight Time : 150 s

Maximum Turn : 30 G

Skin Drag Factor : 1.00

Lifting Body : yes

Rounded Nose : no

Safety Maneuver : no

Preprogrammed Loft : 45 deg

 

Simulation Controls

-------------------

Step Rate : 10 Hz

Maximum Step : 3600

Step Delay : 0 ms

Minimum Missile Speed : 1.27 M

Gravity Factor : 1.00

Loft Glide Logic : no

 

Intercept Controls

------------------

Target Aspect : 180 deg

Launch Altitude : 12000 m (+/- 40.000ft)

Target Altitude : 10000 m

Launch Speed : 3.30 M

Target Speed : 0.83 M

Launch Loft Angle : 0 deg

 

 

:thumbup:

 

You wont find mach 7.

[S77th-GOYA]

Speed and distance is measured in lightyears in space it's the offcial measurement, Go check if you dont beleive me.

 

It's not that I don't believe you, it's that I know you are wrong.

 

Look here: http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980211a.html

[Vati]

The real question is... is the launching plane on the conveyor belt or not?

[S77th-GOYA]

Result from little test with minizap:

:thumbup:

 

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

 

Any indications of drag and/or thrust?

[Rhen]

The real question for a pilot is the effective range of the weapon in question. Range is effectively increased by 40% (or more) when accelerating from M0.9 to M1.3 before release of the Slammer. This allows the missile enough energy at terminal maneuver to make a successful kill. We train to be high (where the Eagle likes it), and fast at release.

 

That and the optimum autopilot flight path in the Slammer guidance system allows ranges to increase significantly without changing weight, motor, or missile design characteristics. Only software (autopilot flight path) and release point are necessary to increase it's range. That's why the -120D looks the same but has a significantly increased range.

[Guest PKM]

It's not that I don't believe you, it's that I know you are wrong.

 

Look here: http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980211a.html

 

So the IAU use MPH and KMH for measuring speed and distance in space?, They use lightyears based on miles per year, The actual internationally recognised name is the Julian year, Was'nt you the one who also said that density doesnt create drag?.

 

http://en.wikipedia.org/wiki/Julian_year_%28astronomy%29

 

http://www.howstuffworks.com/question94.htm

[S77th-GOYA]

PKM, I'm done with you. You are either trolling or have a very poor grasp of these types of things.

 

Rhen, it's good to hear from you again. Can I take from that that a launch speed of greater than M1.3 is negligible as to added range? Or maybe that is reaching into classified data?

[cool_t]

Here it is again

 

Here it is again,

 

http://www.nasa.gov/centers/dryden/n...-093-DFRC.html

 

:thumbup:

[S77th-GOYA]

Bad link address

[Rhen]

Hi Goya,

 

Range increases to 50% for M1.5 and continues to increase (not gonna tell you when it begins to plateau off :noexpression:) through the supercruise ranges for the Raptor.

 

Going into the hypersonic realm is beyond my area of expertise as I don't have a need to really care at this point. :lol:

[britgliderpilot]

Hi Goya,

 

Range increases to 50% for M1.5 and continues to increase (not gonna tell you when it begins to plateau off :noexpression:) through the supercruise ranges for the Raptor.

 

Going into the hypersonic realm is beyond my area of expertise as I don't have a need to really care at this point. :lol:

 

Implying that the supercruise range for the Raptor stretches significantly above Mach 1.5? ;)

 

I hadn't heard about it being much more . . . . which is interesting . . . but not really surprising, that thing's spectacular.

[S77th-GOYA]

Thanks Rhen. Can you tell me this: When you say a percentage of range increase, what are the baseline launch parameters? Meaning if M1.5 gives a 50% increase, what speed is a 0% increase? The M 0.9 you started your acceleration from?

[Guest PKM]

PKM, I'm done with you. You are either trolling or have a very poor grasp of these types of things.

 

You said I have a bad grasp? wtf!!. Goya no offence but your full of shit.

 

;)

[Weta43]

Sorry guys but this discussion has to have made the hardest work possible of a simple question.

 

whether or not a real life missile's speed can simply be added to the launching aircraft's speed to give the actual top speed of the missile.

 

It didn't need minizap, or advanced physics, just a little thought experiment

 

Simple thought experiment 1 : If you launched an amraam from a hypothetical aircraft that was doing mach 10, would the amraam end up doing mach 14 ?

obvious answer - no - the amraams motor will only drive it to mach 4 (?) so it will instantly start to DECELERATE till it reaches its designed speed - assuming the motor burns that long.

 

(unless it's in space where there is no air to cause drag.

Why - For the same reason an object doesn't keep accelerating indefinately when dropped in the atmosphere, but reaches a 'terminal velocity' that falls at it moves through more dense air closer to the ground.

The missile doesn't accelerate till the motor burns out, it accelerates till the force of the motor is ballanced by the drag. The higher the launch, the less drag so the higher that terminal velocity will be, but it will still be a finite number defined by the thrust of the motor & the drag at that altitude.)

 

Does adding launch speed add range - yes.

 

the missile is already at high speed when launched & does not have to spend as much time accelerating to it's maximum speed. That means it spends more time at maximum speed & covers more distance while its motor is burning.

 

Thought experiment 2 : Think of a car at a drag strip. say you're stationary at the start line & you put your foot down & in 9 seconds you get to max speed, in 10 you cover the quarter mile. 10 seconds of motor burn gets you 1/4 mile. If you had a rolling start & crossed the start line already at maximum speed you'd get a lot further that that 1/4 mile in those 10 seconds

 

Guys - It's not brain surgery !!!!!

 

:-)

[S77th-GOYA]

Guys - It's not brain surgery !!!!!

 

:-)

 

No, it's rocket science. :smilewink:

 

You make the assumption that the missile has reached equilibrium at mach 4 rather than the possibility that the motor quits while the missile is still accelerating and under optimal conditions, the speed at motor burnout is Mach 4.

 

I have considered that even if you are correct there will still be an increase in range because the missile reaches top speed earlier in its flight. But I don't think that would substantiate the amount of increase in range that Rhen has provided. 10% range increase for 0.1 mach increase.

[Weta43]

The rate of acceleration is non linear, so the effects are also non linear, but in and of itself, 10% increase for 0.1 mach increase is not enough to describe launch conditions & so can only be true for a limited number of cases.

[S77th-GOYA]

Yes, but missile launch at M1.4 gives 40% while release at M1.5 gives 50%. Those are the figures to which I was referring.

[Weta43]

It's a non linear effect, where - at least through the middle of the range - the higher the launch speed relative to terminal velocity, the greater the effect on range, but without knowing the launch speed against which the %age increases are given - the increases sound large, & the lauch speed isn't that close to terminal velocity - but I guess if the base case speed were low enough ...

I have to go and eat, but it could be that the higher initial speed allows the missile to get to its 'lofted' altitude quicker & there are additional range increases through this.

[SwingKid]

One side argued that yes, you simply add the velocities and the 120 has a speed of ~Mach 7 at engine termination.

 

THe other side said that no, the 120 would reach a terminal velocity where thrust equals drag at Mach 4, saying that is a design limit.

 

I agree with Rhen and lean far more towards the first answer.

It obviously isn't quite as simple as a basic addition, but that seems far more correct than to say the AMRAAM reaches "terminal velocity" at Mach 4 with the engine running. I think that even the sustain motor will keep the missile accelerating all the way to its burnout, nowhere near terminal velocity.

 

On the other hand, I don't believe the implication that an AIM-120 can accelerate to Mach 4 from rest, i.e. claims of "Mach 4 plus the speed of the aircraft." Given the claimed weights of the missile and propellant, that doesn't seem to be physically possible even in a frictionless vaccuum. I suspect it should be around "Mach 3 plus the speed of the aircraft," which somehow went through a broken telephone to become Mach 4, and then Mach 4+, and then "Mach 4 plus the speed of the aircraft."

 

-SK