Ram Jet Question

[dy031101]

Silly question here- are ramjets afterburning by default?  Or do they come with both afterburning and non-afterburning varieties just like any other jet engines?

[Jeffry Fontaine]

Silly question here- are ramjets afterburning by default?  Or do they come with both afterburning and non-afterburning varieties just like any other jet engines?

Ram Jet Images courtesy of WIkipedia



You are invited to learn about the basic principles of Ram Jets at the following links:
Wikipedia Entry for Ram Jet
NASA Glenn Research Center entry for Ram Jet
PRACTICAL SUBSONIC RAM JET DESIGN
Ramjet.com entry
Practical Ram Jet Design by William T. Decker, Decker Engine Works, Plasterco, Virginia

[Ed S]

When you think about, an afterburner is simply a ramjet stuck on the back of a regular turbojet engine.  So a ramjet wouldn't need an afterburner.

Ed

[tinlail]

I suspect that the issue of if it is an afterburner depends on if it is in front or behind the nozzle.

[dy031101]

Something I'd like to be sure- diametres of intake, combustion chamber, and exhaust, is there a rule as to which one should be larger than others?

Thanks in advance.

[jcf]

Something I'd like to be sure- diametres of intake, combustion chamber, and exhaust, is there a rule as to which one should be larger than others?

Thanks in advance.

There is it seems some flexibility:
http://www.onera.fr/conferences-en/ramjet-scramjet-pde/
http://www.pulse-jets.com/ramjet/ramjet.htm
http://www.grc.nasa.gov/WWW/K-12/airplane/ramjet.html

A very cool APR Bonus on a ramjet powered X-15 derivative:
http://www.up-ship.com/apr/extras/serjx15.htm

APR is published by Scott 'Orionblamblam' Lowther, do yourself a favor and subscribe.

[dy031101]

Relatively well-known ramjet-powered aircraft, like Leduc designs, D-21, and Griffon, seem to all employ one big nose- or belly-mounted intake......

(It appears that the only ramjet-powered item in my knowledge with more than one intakes is the Meteor AAM......)

Why are things this way?  Is there any ramjet aircraft featuring two or more lateral intakes?  Was designing such an intake arrangement practical in the time period between 50s and 70s?  Why or why not?

(Okay, I ought to just say that I found the Republic AP-75 to be asthetically-pleasing and am wondering if this cross between the XF-103 and the F-105 could have been fitted with the turbojet-ramjet of the Thunderwarrior while perserving the intake design of the Thunderchief......)

Thanks in advance.

[PR19_Kit]

(It appears that the only ramjet-powered item in my knowledge with more than one intakes is the Meteor AAM......)

Why are things this way?  Is there any ramjet aircraft featuring two or more lateral intakes?  Was designing such an intake arrangement practical in the time period between 50s and 70s?  Why or why not?

While not an aircraft per se, the French ASMP cruise missile, as carried under the Mirage IV and Mirage 2000N, has twin lateral intakes for its ramjet sustainer engine. They are shaped just like mini-Foxbat, Tornado or F-15 intakes.

[dy031101]

While not an aircraft per se, the French ASMP cruise missile, as carried under the Mirage IV and Mirage 2000N, has twin lateral intakes for its ramjet sustainer engine. They are shaped just like mini-Foxbat, Tornado or F-15 intakes.

Forgot that one...... and the Lippisch P.13b (which, granted, was never built).

Why were ramjet-powered items with lateral intakes so rare though?

[Hobbes]

I suspect that the issue of if it is an afterburner depends on if it is in front or behind the nozzle.

The term 'afterburner' implies that there are two 'burning' processes going on. In a jet engine, the amount of combustion is limited by the temperature the turbine stages can withstand. In a ramjet, there's no such problem so you can inject all the fuel you want at the main stage, and there's no advantage to installing a separate afterburner.

I suspect lateral intakes are rare because it makes the design more complex (you have to carefully balance the airflow down the two intakes).

[chrisonord]

Right then Mr. dy031101, are you going to let people in on your secret???
You are going to scratch build a ram jet and stick it to the rack on your push bike arn't you 
A pulse jet would be easier as you wouldn't need to pedal like the clappers to get it going right
Chris.

[Weaver]

(It appears that the only ramjet-powered item in my knowledge with more than one intakes is the Meteor AAM......)

Why are things this way?  Is there any ramjet aircraft featuring two or more lateral intakes?  Was designing such an intake arrangement practical in the time period between 50s and 70s?  Why or why not?

While not an aircraft per se, the French ASMP cruise missile, as carried under the Mirage IV and Mirage 2000N, has twin lateral intakes for its ramjet sustainer engine. They are shaped just like mini-Foxbat, Tornado or F-15 intakes.

Also, the Soviet SA-6 Gainful was powered by a very interesting solid fuel ramjet. It had a fuel-rich solid rocket grain, with just enough oxidant to make it burn, which delivered it's gas to a combustion chamber where compressed air from four lateral intakes joined it, producing LOTS of thrust. There was a booster inside the back of the combustion chamber which got it upto ramjet speed first.

The fact that thrust went up sharply (booster) then dropped (ramjet ignition) then picked up again (ramjet on full chat) meant that it followed a peculiar "kinked" climb path, which the IAF learnt to exploit when trying to bomb the launchers during the Yom Kippur war. Basically, they dived on it very steeply, and the missile involutarily "kinked" out of it's way and then couldn't turn hard enough to hit it.

[dy031101]

Right then Mr. dy031101, are you going to let people in on your secret???
You are going to scratch build a ram jet and stick it to the rack on your push bike arn't you 
A pulse jet would be easier as you wouldn't need to pedal like the clappers to get it going right

Just thinking of building a ramjet-powered version of the Republic AP-75 in my garage with my 3D Studio Max, that's all.