Huge sucrose rockets

[Ray(in England)]

Please inform me if this calculation is anything near correct.

Task:To accelerate 2000kg. 'plane to ramjet thrust velocity along run-way using sucrose rockets.

Method: Needs 356,000 Newton-seconds of thrust.
Thanks ,Ray.

[Peter Hanely]

You didn't really give final velocity. was it perchance about 182.5 m/s? That's a bit slow for a ramjet.

1 Ns will accelerate 1 Kg to 1m/s, so mass * final velocity, assuming mass ratio is small.

Also, with time or distance we can also figure thrust requirement.

[cudabean]

182.5 m/s = 657 k.p.h., which is pretty fast in my book. I think you could probably get usable thrust out of a ramjet operating at 200 k.p.h. which is still suitable for runway speed. It won't be running efficiently, but you are developing thrust.

Another consideration: In the U.S., aircraft operating below 10,000 ft are limited to 250 knots unless other specific authorization is given.

cudabean

[Ray(in England)]

Thanks for reply,Peter.
Well, in my unlearned way, I can't recall exactly what formula I used to get 356,000 Ns.
I must have used F=ma
F=2000 x accel.
accel.= final vel.-initial vel./time
a= 72 m/s (assumed ramjet 'start' vel.)- zero/15secs.
accel. = 4.8ms^2
Meaning, F=2000 x 4.8
Giving, F= 9600 Newtons.
Thrust = 9600 x 15s.=144,000 Newton-seconds.
Which is a lot less than my 356,000 Ns., so I must have used a higher ramjet start velocity assumption.
Which do u think is more accurate?.
Thanks,Ray.

You didn't really give final velocity. was it perchance about 182.5 m/s? That's a bit slow for a ramjet.

1 Ns will accelerate 1 Kg to 1m/s, so mass * final velocity, assuming mass ratio is small.

Also, with time or distance we can also figure thrust requirement.

[Ray(in England)]

Thanks for that ramjet start velocity,Cudabean.
If I use your usable thrust initiation velocity of 55.55m/s., then I get
111,100 Newton-seconds of thrust required from my sucrose rockets.
Which I fear isn't feasible,although I've not researched their capabilities.
Ray.

182.5 m/s = 657 k.p.h., which is pretty fast in my book. I think you could probably get usable thrust out of a ramjet operating at 200 k.p.h. which is still suitable for runway speed. It won't be running efficiently, but you are developing thrust.

Another consideration: In the U.S., aircraft operating below 10,000 ft are limited to 250 knots unless other specific authorization is given.

cudabean

[Stephen H]

[quote="Another consideration: In the U.S., aircraft operating below 10,000 ft are limited to 250 knots unless other specific authorization is given.

cudabean[/quote]

That is from memory about 425 knp... correct me if im wrong knot= 1.7kph ?

Stephen

[Tom]

this is an interesting point. is there a limit in the uk? as if i was to build something that flew (quiet those sniggereing at the back) how fast could i go? would i be arrested for going too fast? there is a nearby airfield :-\

Tom