* Posts by IWishIHadAHandle

5 posts • joined 3 Aug 2011

Microsoft begins cagey Windows 8 disclosures

IWishIHadAHandle

"Widows Live Engineering Group"

... did they have a mass culling of Vista engineers ?

LOHAN team buried under ballockets

IWishIHadAHandle
Pint

Aero feedback

... using controlled fins for Aero feedback, will also not be that easy to set up. Settings that work fine up to 10k would be totally u/s at 80k. It would need to be tested in a low pressure wind chamber, (assuming that you can find one).

Also with all rail/tube launches, there remains the issue of icing up. It is probably not feasible to have heating elements all of the way along. For simpler systems, depending on the time to altitude, you could maybe use one of those Ski hand warmer packs for a particular component.

Reg readers ponder LOHAN's substantial globes

IWishIHadAHandle
Pint

Comments and corrections

I whole-heartedly agree with the first part, and the first part of the second part.

The second part of the second part forgets however that even at that altitude there is still air resistance and it needs to dealt with/utilised - that is why there is a terminal velocity even up there. The problem as I understand it, is that it is difficult to get to a decent proportion of that speed quickly enough and stably enough before the normal control surfaces can be used. Hence a lot of suggestions for using rockets themselves or gyroscopic effects for stability during at least the initial phase.

IWishIHadAHandle
Pint

... as I think about it ...

Going on from this simple idea and my previous suggestion of dropping with a drogue, could the craft be built with a relatively large 'open backed cone' shaped front end ? (leave a small whole at the front of the cone, and the craft can exist inside it), this might allow for it to aerodynamically put itself into a vertical stance as soon as it gets up enough speed - a sort of fixed parachute. As long as the engine can overcome this deficit in height/speed then you will win even if you have to give up some height. Using http://www.cs.wright.edu/balloon/images/1/1c/SDM51.pdf for the approx. terminal velocity, and my l33t estimating skills, I would guess at about 100m/s so reachable in around 10 seconds losing 1500 ft of height. I assume that launch will occur ~80000 ft as last time the balloon popped at 90k and that is not wanted. Aerodynamic control must be established before then - if anyone can calculate exactly when then you can reduce the deficit - but 10 seconds is ample time.

The next question is, can this be overcome easily by the rocketry?

IWishIHadAHandle
Pint

I think that weight on the back might ...

Gravity acts through the centre of mass/gravity, and if there is a pivot then the system will orientate itself. So that would be the difficulty, making a reliable release mechanism that allows free movement during ascension. Of course getting it to set to 45deg is a bit different, and the whole system would add weight. (If you were going this method though, I think you just build the plane with a large rear engine. Once it is burnt the c.o.m. would naturally shift forward allowing for more glider like properties.) Either way, unless you can release absolutely smoothly, there is a good chance that the orientation would get knocked out on release - so you need to power launch from the angle if no other mechanism is being used.

I am not sure that the initial launch is actually the complex bit, I think that getting it to go where you want afterwards is. If the aim is height, then a vertical launch is preferable, so at that altitude would a simple small drogue 'chute work for vertical orientation or is there too little air? i.e. drop the rocket off with the chute on the nose, wait a second or two, then fire up, (if the chute has to be too large, then this obviously wouldn't work).

However the issue is still how to keep it in the right direction while it is accelerating; once you start on internal gyroscopic stabilisation, you are beyond my pay grade. Although it will accelerate nicely in the direction it is facing any already existing attitude changes will continue to occur. c.f. ground launched rockets don't generally move before the engine fires, and if one does, or falls over while it is firing, then much Benny Hill like hilarity ensues, because noone has any idea where it will end up.

With all of these ideas/engines, how will they work when they have ice on/in them? The advantage of a normal engine is that it is already lit by the time it gets up there - or is the air above Spain dry enough for that to be a minimal problem?

Too much rambling, too many questions and not enough answers, so I'll leave it there.

Beer because... well it's beer isn't it?

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