Timers and Altimeters

[cwbullet]

It should be ok as long the rocket is facing up. If it is not, you might a get little expense you are not expecting.

[CarVac]

Why is there a problem with putting your whole budget into one device if both cheaper ones, whose prices sum to more, might be up in the sustainer anyway? It would be hard to have a separation charge for clean staging along with ignition from the booster.

[cwbullet]

Why is there a problem with putting your whole budget into one device if both cheaper ones, whose prices sum to more, might be up in the sustainer anyway? It would be hard to have a separation charge for clean staging along with ignition from the booster.

Inwould discuss it woth your father. The only problem is when the device you choose does not have the all the safety features you need. Read Adrian's post above and consider the possible bad outcomes. If the rocket ignites a second stage or air starts whenthe rocket is facing down or horizontal, the out come could devastating. MIf money is the reason, $100 can save you $1000 if you avoid taking out a house or car. I agree with adrian, you would be better with a raven, but if you can't afford it, you need to know the risks.

[MountainRocketeer]

I agree: Talk to your father and then save the money for a Raven. The Raven (which does the whole job) may or may not be more expensive than price of buying a cheaper altimeter AND a cheaper timer. But the risk of loss or other much greater expenses is much lower with the Raven--and a Raven recovered is worth a lot more than two others lost in the bush! By using the Time vs. Altitude parameters (and I use vs. Velocity, too), you are much more likely to get a straight, vertical boost.

With a stand-alone timer, there is a real possibility of the sustainer (with your electronics) igniting at a less-than-vertical angle and flying off a mile or two into the woods or scrubland where you never see it again. You will be worse off then than if you paid extra for a Raven but got it back because the flight computer recognized there was a poblem and aborted the sustainer ignition.

Worse yet, your rocket might arc all the way over, then ignite the sustainer. Hopefully, the altimeter would deploy, resulting in a shred insted of an air-to-ground missile. But some altimeters do not arm until they reach a few hundred feet AGL. If your booster catoed, lost a fin, or got hung up on the rail, the altimeter might never detect liftoff, so you get no deployment. The sustainer, ignited by an independent timer, would be free to fly at full speed in any direction, including toward people. The cost of dealing with even a minor incident of that nature would vastly exceed the extra cost of the Raven--and the cheaper altimeter and timer would likely be out of commission, anyway. A Raven, used correctly, can pretty much eliminte those possibilities.

I love airstarts and staging; almost every rocket I build can be staged, clustered, and/or airstarted. The one I flew at the last launch was clustered, airstarted/parallel staged, and vertically staged, all in the same flight. But I would not attempt any one of those without the Raven or a Tiltometer. The risk reduction and pece of mind is worth it.

[MountainRocketeer]

Another aspect of the Raven that makes safe flight and recovery more likely is the excellent interface program. Consider: 1. You are programming a single device, rather than two. 2. You can see your settings, not just count beeps and jumpers. 3. You can review detailed post-flight data, especially on off-nominal flights, making it more likely that subsequent fights will be safe AND succesful. 4. You can actually post a screenshot or configuration file so others can review the settings and make sure you did not overlook something. We can't count beeps, switches, clicks, or jumpers for you very easily.

[MountainRocketeer]

Finally, if your father is concerned about you losing electronics (or even if he is not), you want to put tracker in your sustainer. That should ease his mind about the likelihood of expensive items disappearing.

Yes, a tracker is an added expense--but if you are going to fly multiple motors, multiple cases, multiple airframes, and multiple chutes, and burn at least two reloads every flight, the cost of tracker is not nearly so significant. And it should pay for itself.

In rocketry, as in many other things, doing it with the cheapest materials may not really save you money, and will cost you aggravation and heartache. It is often better to wait until you can pay for better materials and all the pieces to do a quality job.

[CarVac]

Extremely well put. I had forgotten about the interface benefits.

blackbrandt, you must beware of the planning fallacy: most people make time and money budgets as if everything runs right, forgetting the costs of failure.

[cwbullet]

Finally, if your father is concerned about you losing electronics (or even if he is not), you want to put tracker in your sustainer. That should ease his mind about the likelihood of expensive items disappearing.

Yes, a tracker is an added expense--but if you are going to fly multiple motors, multiple cases, multiple airframes, and multiple chutes, and burn at least two reloads every flight, the cost of tracker is not nearly so significant. And it should pay for itself.

In rocketry, as in many other things, doing it with the cheapest materials may not really save you money, and will cost you aggravation and heartache. It is often better to wait until you can pay for better materials and all the pieces to do a quality job.

Very well put. It is a much better option. I would save some money up and buy a raven and a tracker. If you know some one with a tracker, borrow it. I consider good electronics insurance also.

[blackbrandt]

OK, I should look at a raven. Anyone have one?

[dixontj93060]

OK, I should look at a raven. Anyone have one?

Uh, I have three; but not selling any.

[blackbrandt]

Uh, I have three; but not selling any.

Meanie.

[dmorey]

blackbrandt,

I see you are in Apex, NC. I am in Durham, NC.

Come out to Bayboro and fly with us in September: www.ncrockets.org.

I fly a lot or airstarts and can show you how to do it reliably. I agree with the posters above, get a Raven2 or Raven3, new or used. The alternative is a cheap Perfectflite timer and the cheapest DD altimeter you can find, but the Raven is better/safer IMHO.

Dave Morey

[blackbrandt]

I have heard of your name before... where have I heard it?

[dmorey]

blackbrandt,

Don't know where you heard my name before. Astronomy Days, TARC mentor, nc-rockets mailing list?

Do I know you?

Dave

[blackbrandt]

Astronomy Days.