Whalejet
Topic Author
Posts: 105
Joined: Wed Jan 04, 2017 3:31 am

Ramjets and Aircraft Catapults

Mon Mar 12, 2018 12:50 am

Hello all,

So I'm sure many of you on this forum have heard of ramjets, which would be ideal for supersonic travel but have one drawback - they need to be accelerated to high speeds to be made efficient.

I read that a Ramjet becomes "self sustaining" at speeds of above Mach 0.5, which got me thinking. Obviously, throwing jet engines and ramjets onto one airframe would be hideously inefficient. However, what if you accelerate the ramjet up to speed on the ground - using say, an electromagnetic catapult or steam catapult like what is used on aicraft carriers? Obviously, you would need to build new runways which have roughly double or triple the length of current runways in order to make the acceleration comparable to a normal aircraft.

Basically, what do you think of this idea? Is it commercially viable? I don't really know what to make of it and I'm curious.
 
GalaxyFlyer
Posts: 766
Joined: Fri Jan 01, 2016 4:44 am

Re: Ramjets and Aircraft Catapults

Mon Mar 12, 2018 2:18 am

You’re kidding, right? The certification problem would be immense. What if there’s a failure during the launch? How do they abort at M.5 which is about 320 knots at S.L.? What if the ramjet fails after liftoff? How does it land?

GF
 
FlyHossD
Posts: 1594
Joined: Mon Nov 02, 2009 3:45 pm

Re: Ramjets and Aircraft Catapults

Mon Mar 12, 2018 4:01 pm

Whalejet wrote:
Hello all,

So I'm sure many of you on this forum have heard of ramjets, which would be ideal for supersonic travel but have one drawback - they need to be accelerated to high speeds to be made efficient.

I read that a Ramjet becomes "self sustaining" at speeds of above Mach 0.5, which got me thinking. Obviously, throwing jet engines and ramjets onto one airframe would be hideously inefficient. However, what if you accelerate the ramjet up to speed on the ground - using say, an electromagnetic catapult or steam catapult like what is used on aicraft carriers? Obviously, you would need to build new runways which have roughly double or triple the length of current runways in order to make the acceleration comparable to a normal aircraft.

Basically, what do you think of this idea? Is it commercially viable? I don't really know what to make of it and I'm curious.


Google "V1 BUZZ BOMB LAUNCH" - the V1 used a catapult ramp for just this purpose. Please note the relatively short length of the ramp; a ramjet doesn't need to be going M0.5 to launch.
My statements do not represent my former employer or my current employer and are my opinions only.
 
WIederling
Posts: 6164
Joined: Sun Sep 13, 2015 2:15 pm

Re: Ramjets and Aircraft Catapults

Mon Mar 12, 2018 5:51 pm

FlyHossD wrote:
a ramjet doesn't need to be going M0.5 to launch.


The V1 had a pulsejet engine that was started before launch.
The steam catapult then brought it to ~200 knots for stable flight.
Much like the CATO of a CATOBAR type carrier.
Murphy is an optimist
 
Andre3K
Posts: 341
Joined: Tue May 30, 2017 10:11 pm

Re: Ramjets and Aircraft Catapults

Mon Mar 12, 2018 10:17 pm

A few things. A pulsejet is not a ramjet, and a ramjet powered aircraft could not land as the speed degrades below the self sustaining threshold. Unless you want to land at 3 times the speed of a normal airliner(I'm not getting something like that no matter what).

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