Bit of an odd question

[Dave]

I'm doing some theoretical work (as an alternative to doing yet more revision) on model rocketry again, and I'm wondering about the effect of rapid acceleration on computer hardware. What I'm currently thinking is that the only (?) things are likely to be affected are things with lots of moving parts.

 

Obviously mounting a hard drive in there is completely out of the question. At the moment I'm considering mounting some kind of mini ITX motherboard into the rocket chassis, then using some kind of usb flash device to boot linux (my os of choice) from.

 

(If anyone cares, I'm doing this as a challenge to maybe get some kind of flight management system on board a rocket without the hassle of having to deal with embedded systems too much).

[blike]

I don't really know off hand. How many G's are you talking about? My first video rocket (using the onboard memory camera) only underwent around 5 Gs and it worked fine. My last video rocket underwent around 21.8 G (max), and the hardware failed. I'm pretty sure the failure was due to the impact during recovery, but I can't rule out that it failed during takeoff. I don't think you'll have a problem with non-moving parts (as long as the forces aren't too extreme). Anything that is connected to another piece via pins or ports need to be secured.

 

I'm sure you've thought of this, but the recovery can be just as turbulent as liftoff in some cases. For my last rocket, I ran a piece of elastic from the nosecone to the body tube, and then attached the parachute in the middle of this elastic. That was a very bad decision because the whole assembly came down spinning so violently that the fins broke off the body tube when it hit the ground.

 

What sort of flight management are you planning?

[Dave]

Nothing too ambitious really. Maybe some kind of simple altimeter setup at first just to record how high the thing goes and to get the parachute out at a sensible altitude. However an entire linux system for just that would probably be (a) expensive and (b) stupid. I'm trying to make it into a joint model/electronics project for the summer (in which I have 3 months to kill), so I'm just looking at various possibilities.

 

My original ambition was to have some kind of small camera attached to the side, then pipe the feed directly into RAM storage (flash data transfer rates aren't that good, specially not for video transfer) so I can view it later, but it's definately too ambitious for a first flight.

[blike]

There are manufacturers who sell altimeters with onboard capacitors [for ejection] for around $120. You still have to design your own ejection system [charges, segmentation, etc], but it takes care of discharging at a specified altitude. They are also programmable to disarm around mach1 until the pressure wave passes. I'm going to purchase one as soon as possible, but I don't have the cash on me at the moment.

 

I just purchased a 2.4GHz wireless camera and receiver for around $100. The range is only 500-700ft in open air, but with a 24dBi grid dish, I should be able to clear well over 5000 feet. I just finished building the rocket and installing the camera. I'm just waiting on some cash to buy the antenna and the necessary hardware to record the video feed onto a laptop during launch.

 

My long term plan for this rocket is to modify it to accept H or I class engines. These would boost it well over a mile high [and maybe over mach1]. The rocket is 39 inches high and 2.6 inches in diameter. It's designed for E, F, and G motors. I'm going to do a test launch in about a month to around 2100'.

 

I was thinking about doing onboard movie storage again, but that obviously requires recovery of the rocket, which isn't guaranteed. Plus, the actual camera is only around $39, in case the rocket were to CATO. How many rockets have you launched before? I take it you've flown a few. If not, you might want to build some and test fly them with various centers of gravity. One thing you're going to want to do (especially for video) is eliminate rocket spin. That will cut down on the forces experienced and make for a better video.

 

How big is your field, and how big is the rocket you plan on launching?

[Dave]

I'm not building huge rockets since primarily I don't have a car yet and it's a bit awkward to get around without my dad's car (which isn't around too much). I'm just planning to build a couple of tester rockets to get me started, and I've also been thinking about the wireless transmission on the video (although it's a pain to get them over here).

[felinlasv]

Hehe, you both seem to have a little more aspirations then me.. Good luck with it and you definitely have to show pictures.

[blike]

What do you pain to get them? Do you need a special license or something? I almost bought a hi-power transmitter, but the FCC over here requires that you have a HAM license, which I don't feel like getting. So I just ended up buying the low power one and some big receiving antennas

[Dave]

It's not such a big deal getting them, it's just the laws of transmitting things over here is pretty strict - although I have seen a 2km 2.4GHz microwave transmitter that I rather like the look of which I also think is legal to use.

[Dave]

On a sidenote I did make the schematic for my firing box last night which was nice. Gonna try and make it this weekend, so I'll post some pictures when I'm done.

[blike]

What are your rocket specs and what motors you plan on using?

[Dave]

Currently looking into getting a kit - not sure of which type, so any advice would be appreciated. Something with a bit of oomph (but not too much) would also be nice.

[blike]

I doubt you'll want to use a low power kit (A-D) to boost up electronics, because you probably wouldn't get very high. It might get off the launch pad, but with a struggle. I used a D12 engine on an "Estes Blue Ninja" to boost my first rocket. It only reached maybe 200ft (60m) max. [as a general rule, the thrust of an engine doubles with every letter. i.e. B is twice as powerful as A].

 

I would recommend using an aerotech midpower kit. They're a bit more expensive, but they're also a lot stronger and are designed for E-G engines. You can see their rocket lineup here: http://www.aerotech-rocketry.com/customersite/products/kits/kits_index.html

 

You've probably already seen it, but here's my rocket launching on a G-40 engine.

 

I don't know the laws where you live, but here in the states, you have to be a certified member of a rocketry association to buy any engine over G-class. To get certified you have to successfully fly and recover a high-powered engine in the presence of two other certified members. I believe you can purchase one highpowered engine without being certified.

 

If you want to get up to around 2500 feet, this rocket will get you there on a G-class engine. The nice thing about it is that it comes with a payload bay. Otherwise you're going to have to make your own so that the hot ejection gasses don't damage your hardware (I put mine in the nosecone). However, you're limited by the diameter of the rocket. If you need larger diameter, you're going to have to sacrifice some altitude [unless you go highpower].

[Dave]

Been reading up on it and the laws are much tighter over here. Anything over a D class requires a license to get (which is a pain) and another license to keep it (which is another pain). So I might just go for a simple starter kit for now just to get myself used to it. There's also the problem of finding somewhere to fly it - there's not a hell of a lot of big open fields that I can use over here.

[Thorin]

Thanks for the link! Where can I find G-class engines?

[Dave]

A lot of hobby shops will probably stock them. I'd think a quick google would turn up some results as well.

[Cap'n Refsmmat]

Probably E-Bay. E-Bay sells everything.

[Dave]

Yes, but don't necessarily assume that eBay traders are going to be 100% trustworthy. You could get a dud rocket motor, which could be quite bad when you come to ignite it.