Hermes well the 100km version has two stage engines.
No. That is not true.
As far as I can work out the Hermes missile is a two stage missile but the second stage does not have an engine at the moment... There is the solid rocket booster to get the missile up to a speed of 1.3km/s and then a small light narrow low drag coasting stage that is not powered or perhaps has a gas bleed motor that just overcomes or reduces drag in flight.
When fired from a ground vehicle it is angled upwards and lofted towards the target in a fully ballistic trajectory.
When fired horizontally from a helicopter its range is closer to 15-20km
If you look at this current page:
http://www.kbptula.ru/en/productions/multi-service-weapon-systems/germes-a
Note to the right of the image of the helicopter there is a list headed System composition.
Click on the link Containerised Hermes guided missile and it will bring up a small box with the detailed information about the helicopter launched missile.
You will see the missile is smaller... the ground launched missile has a 210mm calibre booster that accelerates the missile to 1.3km/s, while the helicopter launched mode the booster is 170mm calibre and accelerates the missile to 1km per second and is fired more directly at the target... it is a bit like the difference between a tank gun firing at targets 3-5km away and an artillery piece using the similar ammo over much greater ranges lofted into the air.
In both cases the missile is a 130mm calibre missile with a warhead of about 30kgs.
The coasting stage needs to be light so the actual coasting stage will not be much heavier than the warhead... I have seen listings showing the second stage has a 27kg HE warhead and the entire second stage component is 30kgs... which is damn impressive.
The ground launched missile is 130kgs in the launch container and the helicopter or aircraft launched missile is 110kgs in the launch container... so the difference is 20kgs of solid rocket fuel in the different sized solid rocket boosters.
[quote]"The caliber of 207 mm taken from "Hermes" will not change either." if you click on that image 100km Hermes missile is used with a 3.5 meter length tube and 210mm caliber. So if the ramjet which of course will be the 2nd stage engine will mean that length wise it would be longer with a little more weight because article did say same caliber with folding wings so by bigger you mean longer length?[quote]
The article is about a new version of Hermes where the second stage has a proper ramjet sustainer engine... where before it either had nothing or a very low thrust gas bleed rocket motor to overcome drag... if the stage was sitting on the ground and this rocket was running it wouldn't actually move the rocket, but when the missile is flying through the air the low thrust rocket greatly reduces the drag of the rocket in flight so it maintains its high flight speed for much much longer... they could put a high energy rocket in there but it would only burn for a few seconds and only increase speed a little and then when it burned out the missile would rapidly slow down because drag is increased by increased speed. By using a very low thrust rocket motor the motor can burn for several minutes, and while it wont speed the missile up in flight it will make it retain speed much better which means it will travel much further by travelling faster.
This is used in artillery shells where a low power rocket motor is located in the rear of the shell and it blows gas out the back of the shell in flight to reduce drag... it is called base bleed in artillery shells and greatly increases range by helping the projectile to maintain a higher speed.
All your calculations are interesting, but the original Hermes... either with no engine in the second stage or a base bleed rocket motor in the second stage relied on a big heavy solid rocket booster for its flight range. The ground launched one got extra range by being lofted into the air up to thinner colder air at altitude where drag is less and the missile can fly faster with lower drag, while the aircraft launched model seems to be launched directly towards a target... remember that information about that new missile for the Mi-28NM that had a 25km+ range and used an IIR seeker and datalink turned out to be Hermes...
Well this is talking about adding a ramjet motor to the second stage... now a ramjet motor is flexible.... you can operate it in low thrust to counter drag and it would be much more efficient than any base bleed rocket motor because it is scooping up air as it moves so even a very small fuel burn will generate useful levels of thrust to maintain speed over enormous distances... and you can increase throttle to climb to thinner colder air where the missile can move faster because of lower drag.
The point is that the missile probably needs to move at between 1km/s and 1.3km per second to reach the different ranges it reaches, but with having a ramjet there you can use fuel to accelerate to and maintain those speeds much more efficiently than using solid fuel.
A solid fuel by weight is three quarters oxygen production and one quarter fuel to burn in that oxygen.
So say the solid fuelled rockets weight 70kgs and 90kgs, and the final stage missiles would therefore weigh 40kgs for the air launched model and the ground launched missile would also be 40kgs because they are the same missile.
So the shorter direct fire air launched missile (170mm calibre) is 70kgs + 40kgs = 110kgs, and the ground launched missile (210mm) is 90kgs + 40kgs = 130kgs.
Both 40kg missiles are 130mm calibre, but the launch tube calibres are determined by the solid rocket booster sections... both tubes are 3.5m long.
This new missile they are talking about... the missile stage will be heavier and larger calibre because it does not need to be a narrow low drag dart... it has its own motor and fuel and does not need to be accelerated to top speed by the solid rocket booster.
It is clear they are using the 210mm calibre... and they say they will use the ground launched Hermes bigger 90kg 210mm calibre booster rocket motor, so the tube will be 210mm so it would make sense to use that space for the second stage... they mentioned the weight of the new missile will not exceed 150kgs, so that means the new missile will weigh 60kgs... but with a 57kg HE warhead we have a problem...
The thing is that with a ramjet motor in the missile, they don't need the full length full power solid rocket booster as used in the ground launched model... in fact I would argue that they could halve its length and weight to perhaps 45kgs and still get enough thrust to accelerate the second stage to a useful speed and distance where its ramjet could take over...
90kgs of solid rocket fuel means about 68kgs of material that just generates oxygen, with the remaining 22kgs being actual fuel burned in that oxygen rich environment.
Cut it to 45kgs of solid rocket fuel and that means 34kgs of oxygen generating material and 11kgs of fuel, but it means you can then carry 45kgs of ramjet motor and fuel and guidance equipment.... say 2kgs for the ramjet motor itself... which is mostly titanium to resist the heat and empty space... another 15kgs of guidance stuff including control surfaces and motors, which leave 28kgs of fuel... which means it carries 39kgs of actual fuel and for the solid rocket motor it carries 34kgs of oxygen generating material, but with 28kgs of ramjet fuel and it will scoop up the 49kgs of Oxygen to burn that fuel in flight.
Most importantly it has energy management... it can climb to altitude and coast in a low engine thrust setting maintaining speed all the way and then a full throttle dive on the target.
But why are they doing this?
The key is the ramjet motor... they don't want a simple artillery shell type missile that is lofted towards the distant target and basically finds its target as it falls and then steers straight into that.
They want a high speed manouvering target that is difficult to shoot down so they need an engine on the second stage.
When it reaches its target area it does not matter if it left the tube and accelerated to 800m/s at solid rocket booster burn out or 1,300m/s... because it has a ramjet motor and can then climb and accelerate to much higher speeds if it needs to...
With the older missile the faster it was fired the more energy it had to reach the target, but with a ramjet motor it can use the fuel much more efficiently and effectively.
Nice development.
Home
Latest images
Register
Log in
dino00
A hypersonic drone?
