Apogee Aspire + Mach 1 + Altimeter?

A few years ago I tried to go supersonic with an Apogee Aspire on an Estes G80-7T. I followed all the tips (i.e. airfoil the edges of the fins and laminate them, create fillets between the body tube and fin roots, etc.), simmed it in OpenRocket (which said 4,700 ft and 877 mph), and stuck a JollyLogic AltimeterTWO in there for confirmation.

When it came back, the altimeter was blinking at 562 mph (meaning I exceeded the G-limit of the device), and read 3,780 feet for max altitude. Later I read that I was supposed to angle the altimeter so that a corner of the device faces upward in order to not exceed the G-limit and get the true max. velocity reading.

I'm building another one now and I want to know if there's a better altimeter to use that won't break the bank -or- if someone has used the AltimeterTWO on a Mach 1 Aspire successfully, how??

Hopefully this is the answer to the second question.

https://www.apogeerockets.com/education/downloads/Newsletter293.pdf

Unfortunately, that article creates a mount that will only work in 54mm diameter body tubes, and the Aspire is a 29mm diameter rocket.

Use a barometric altimeter, like the Perfectflite APRA. No issues with Gs unless the battery comes loose.

I just used mine on a flight, it beeps out altitude and speed. Accuracy is something I can't speak to.

It says that you're supposed to shield the APRA from the ejection charge and shock from the rocket hitting the ground. How did you work around this for the Aspire, which doesn't have a payload section or a parachute?

I recommend the Perfectflite pnut altimeter. It's basically an Apra, but it's lighter and has a built in LiPo. It won't have g-shock issues.

RocketRoll said:

It says that you're supposed to shield the APRA from the ejection charge and shock from the rocket hitting the ground. How did you work around this for the Aspire, which doesn't have a payload section or a parachute?

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You could put it in a section of 18mm BT with a few vent holes and padded end caps, but I think I would just attach it to the base of the parachute. Maybe a wrap or two of electrical tape to keep the battery in place. If the wadding protect the chute, I would expect that is sufficient protection for the altimeter too. Since the parachute should be the last thing landing, it should land the softest.

Handeman said:

You could put it in a section of 18mm BT with a few vent holes and padded end caps, but I think I would just attach it to the base of the parachute. Maybe a wrap or two of electrical tape to keep the battery in place. If the wadding protect the chute, I would expect that is sufficient protection for the altimeter too. Since the parachute should be the last thing landing, it should land the softest.

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The problem is that the Aspire doesn't come with a parachute, only a streamer. And if it did, it's projected to travel over 4,000 ft... I'd be afraid of my rocket with altimeter drifting into the next state...

I would use an Altimeter 1 or 2. They will handle the g-load just fine. The Altimeter 2 will simply not give an accurate speed reading. You can get a really close speed estimate by plugging your rocket into OR or Rocksim, entering the weight exactly, and adjusting the coefficient of drag until the apogee matches what you got in the field. Then you have really close speed and acceleration numbers without having to worry about fit, or expensive high-g computers.

Tonimus said:

I would use an Altimeter 1 or 2. They will handle the g-load just fine. The Altimeter 2 will simply not give an accurate speed reading. You can get a really close speed estimate by plugging your rocket into OR or Rocksim, entering the weight exactly, and adjusting the coefficient of drag until the apogee matches what you got in the field. Then you have really close speed and acceleration numbers without having to worry about fit, or expensive high-g computers.

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How do I adjust C_d in OpenRocket?

Click on a part, then click edit, and change the surface finish one way or another. Rougher adds drag, smoother reduces it. You can stack the effect by doing multiple parts. You can also change the fin profile to rounded or squared to increase the drag there as well. Not super easy, but it works.

Why don't you weigh the finished rocket, sim it and fly it? Any added weight is going to degrade the performance and your major problem is going to be finding the thing. Believe me, I flew a sonic Aspire 3 times on G80's and used a long burn F10 3 times. Lost the rocket finally on the last flight. Each time it went sight unseen for the longest time. When I wasn't able to reacquire a visual on the last flight, that's when it was lost. Rocket was getting pretty ratty looking by then. Kurt Savegnago

RocketRoll said:

The problem is that the Aspire doesn't come with a parachute, only a streamer. And if it did, it's projected to travel over 4,000 ft... I'd be afraid of my rocket with altimeter drifting into the next state...

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The purpose of the Aspire is to put an F10 in it, fly it, lose it, and forget it. Afterwards, believe the Apogee advertising or your simulations that said it went one mile and/or Mach 1, and brag about it at cocktail parties. Enjoy.

Once you start talking about adding an altimeter, dual deployment, and tracker all to "prove" you did it, then the Aspire quickly becomes a poor choice for your objective. The rocket is now heavier, more complicated, needs more power, and requires beefier construction techniques. Find a better starting kit, like designs from LOC, Madcow, WM, etc.

Here is some Aspire fun I had a few years ago. Great kit! Fun rocket!

[YOUTUBE]3tpF9Qhgbpk[/YOUTUBE]

Buckeye said:

The purpose of the Aspire is to put an F10 in it, fly it, lose it, and forget it. Afterwards, believe the Apogee advertising or your simulations that said it went one mile and/or Mach 1, and brag about it at cocktail parties. Enjoy.

Once you start talking about adding an altimeter, dual deployment, and tracker all to "prove" you did it, then the Aspire quickly becomes a poor choice for your objective. The rocket is now heavier, more complicated, needs more power, and requires beefier construction techniques. Find a better starting kit, like designs from LOC, Madcow, WM, etc.

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Ditto,

Assume you are going to do it 'cause the rocket is very lightweight and the sim says so:no: I purpose built a four finned 38mm MD cardboard LOC tubed, fiberglassed laminated plywood fin can rocket. Used an EggTimer TRS in an
extended upper bay. Cut the base of the nosecone off so the antenna projected up in there. Apogee blows the rocket apart and Archtype cutter releases the main when it gets to deployment altitude. Rail guide bound on the rail from dirt and the thing still hit Mach 1.25 to 8567' (that's what it said) all on a venerable J350. If it would have been an L2 attempt, depending on the certifier, might have been considered a DNF because none of the events were seen. The events obviously occurred when
they should by the behavior of the live telemetry and when I took the 1.7 mile hike to get it. Walked right up to it and carried a Yagi antenna for ground recovery and picked up the final position while it was on the ground and I still couldn't see it. Chute was obvious it deployed in time. Rocket is flyable again after prepping.

Bottom line is if you smash an Aspire to 4800' to 5000', you'll be lucky to ever see it again. First time I did a G80 at a major launch, the rocket simply disappeared. Tim Lehr asked if I used an SU motor which I had the foresight to do. Oh well, God probably admired my paint job so much, likely snatched it up to be admired!:surprised: Found out later it was found, turned in and I got it back. Put two more G80's in it and three F10 flights. Rocket landed in a road one time and cracked a fin. The last G80 flight it disappeared and failed to be sighted again. I suspect it landed in a pond nearby. I thought I saw it but might have been hallucinating. I was using the silver reflective mylar
material for a streamer but it sometimes snaps in two and comes apart. I learned to run a bead of scotch tape along the edges to make it more resilient. Fan fold the streamer 'cause the mylar can rattle loud enough sometimes so you can hear it before you see it. Your ears can tell you were to turn to look if you hear the thing coming in. Ahhhhh, I built another one but I might just stick a chute in it and fly it low and slow 'cause I did another nice paint job.

Kurt

ksaves2 said:

I learned to run a bead of scotch tape along the edges to make it more resilient.

Kurt

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WOW, that's a Great tip. My mylar streamers would get beat up and tear apart, so I switched to yellow caution tape. This may be just the solution I needed. I think the silver mylar is much more visible. Thanks Kurt!

Graduator said:

WOW, that's a Great tip. My mylar streamers would get beat up and tear apart, so I switched to yellow caution tape. This may be just the solution I needed. I think the silver mylar is much more visible. Thanks Kurt!

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It can be a pain to do but if you aren't going for records will help. Another point. Cutting the streamer. Some scissors and dull razors can leave micro transverse fractures in the edges of the mylar streamer material.
Look under magnification and if you don't see 'em, still tape the edges as they are going to fracture and break
anyways. That's how my first Aspire was further "beat up" when the mylar streamer broke in two and it came in
hotter than it should have. Kurt Savegnago

I just put an AeroTech G125-14A into the Aspire for some destructive testing. This is a fibre glassed Aspire and well..... maybe this isn't the best combo. Trying for 600 m/sec @ 2 km + altitude. Cold clear day..... tracking smoke included.