The aim of this motor appears to be absolutely minimum impact on the ignition of the ramjet, so i would expect very little residuals/tailoff
this other video has a couple of firings with 2 angles, idk if it has been shared before
A quick google search seems to be indicating to me that ISP of ramjets vary from 1200 to even up to 1900 depending on the fuel - and the altitude, so 1600 might not be a dumb assumption
Edit : this is from a research paper on potential performances of different engines in Martian atmosphere. The J1 value for earth should be between 5 and 10 from my understanding
indeed.
are those ramjets solid fueled like the meteor? that can change the isp a lot
Ah no? They seem to be liquid fuel, so yeah it might make a difference, good catch
this is what i found related to isp from a nato training presentation
This is not ISP, but probably ejection gas ve.
ISP = ve/g, g being the gravitational constant, so basically
ISP = 10000/9.81~1000s
my bad, should be around 610 ISP up to around 1020 isp
No its not, because the gases are not ejected at mach 30…
Thats the specific impulse of the motor.
Where specific impulse is ISP * g * ln(initial mass/final mass)
where final mass is initial mass - fuel mass - giving:
dV = ISP * g * ln(initial mass/(inital mass - fuel mass)
An ISP of 10 000 just isn’t realistic for a chemical powered engine.
And gas ejection is indeed that formula :
Ve=ISP*9.1 (on earth), so they do are ejected at insane speed.
That’s literally the second law of newton. How do you get a hundreds of kilograms heavy rocket to go Mach 5 with only a fraction of the weight in ejection gaz ? By having said ejection gaz going at a much higher speed
It isn’t, because you only need 20-30kg of propellant to mix with >>>kg of air, to give very high total amounts of energy
ISP =/= dV, this is saying a dV for the motor section of 6000-10,000 is possible
If we say the ISP is… lets say 2000.
then for a 50kg motor with 20kg of stored solid propellent. We get nearly exactly 10,000m/s…
More realistically, lets say 1400ISP.
a 60kg motor and 25kg of propellent.
Gets you a deltaV of 7400m/s
I don’t think you understand the implication of an ISP pf 6000, let alone 10 000. This would completely revolutionize the aerospace kndustry.
Typical ISP for the most efficient air breathing engines (such as turbofans) varies between 3000 (low altitude) and 7000, 7500 at high altitude at a maximum. And that’s using the most efficient tech for air breathing engines currently.
Also, here is NASA giving the Ve formula I used above
https://www.grc.nasa.gov/www/k-12/airplane/specimp.html
For reference, the formula still stands for non bypass engines (ie, ramjet). With an ISP of 1000, the ejection gaz speed would not be Mach 30 but Mach 300…
Also, even with an ISP of 10000, the Mach of the ejecting gaz is not really Mach 30, since their composition is highly different from air. It probably more along the line of below Mach 10 (before slowing down and mixing with the air)
Again its not saying the ISP is 6000-10,000
DeltaV, a measure of impulse per unit mass, sometimes called a specific impulse.
for reference r-77s solid fuel ramjet had an isp of 700s.
feel like a specific impulse of 1500s is absurd for meteor
Using what fuel?
Meteor is an air breathing engine. ISP for such technologies is higher than rocket engines.
one more image related to the meteor from the same source. it focuses on the software talked in the pdf and is meant to train personnel, but covers a lot of different topics for a2a missiles so i guess it’s worth sharing
NATO S&T AVT-321 Technical Course
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