# MAWD's max altitude

### Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

#### ben_ullman

##### Well-Known Member
So I know the MAWD can't go over 25k feet but what happens if it does? Is it going to get thrown in a tail spin and fire all the charges? I was going to use my standard ARTS, MARS, and MAWD combo in the board I make for my new rocket but it may clear 25k. Will the MAWD just display a max 25k flat line in the data capture?

Ben

So I know the MAWD can't go over 25k feet but what happens if it does? Is it going to get thrown in a tail spin and fire all the charges? I was going to use my standard ARTS, MARS, and MAWD combo in the board I make for my new rocket but it may clear 25k. Will the MAWD just display a max 25k flat line in the data capture?

Ben

According to the supplier, the MAWD is good to 26,500 MSL (plus or minus 400 feet). If it reaches that altitude, the drogue channel will fire at that time. The reason is that the altitude algorithm saturates such that there is no increase in measured altitude above that point, even if the actual altitude is increasing. This is interpreted by the logic as apogee, and the drogue fires. The main channel will fire normally. The altitude graph will show a flat spot above 26,500.

Jim

According to the supplier, the MAWD is good to 26,500 MSL (plus or minus 400 feet). If it reaches that altitude, the drogue channel will fire at that time. The reason is that the altitude algorithm saturates such that there is no increase in measured altitude above that point, even if the actual altitude is increasing. This is interpreted by the logic as apogee, and the drogue fires. The main channel will fire normally. The altitude graph will show a flat spot above 26,500.

Jim

ok looks like ill leave it disconnected! Don't need 2k pounds dissasembling itself at 26500 feet!!

Ben

2k pounds? 25000 feet? Making an S motor or something?

2k pounds? 25000 feet? Making an S motor or something?

No, don't worry about it. There will be a website and debut soon enough.
9 motor mounts total 24" in dia.

Ben

P.S. I do have plans to make an R and or S motor though.

No, don't worry about it. There will be a website and debut soon enough.
9 motor mounts total 24" in dia.

Ben

P.S. I do have plans to make an R and or S motor though.

P.S. I do have plans to make an R and or S motor though.

Troj said slow down... Troj is right...

Justin

Troj said slow down... Troj is right...

Justin

I didn't say anytime soon. Its kind of on my 10 year goals. Next to getting a sallaried job and a college degree

Ben

According to the supplier, the MAWD is good to 26,500 MSL (plus or minus 400 feet). If it reaches that altitude, the drogue channel will fire at that time. The reason is that the altitude algorithm saturates such that there is no increase in measured altitude above that point, even if the actual altitude is increasing. This is interpreted by the logic as apogee, and the drogue fires. The main channel will fire normally. The altitude graph will show a flat spot above 26,500.

Jim
Jim brings up a good point here. There are barometric pressure sensor limitations with any altimeter. Altimeters using high output level MEMS barometric pressure sensors will flat line at some altitude, typically corresponding to between 25 kft to 45 kft altitude depending on on-chip and external electronics. It not the MEMS pressure sensing element that cause this limit, but the internal IC amplifier circuit that was poorly designed several decades ago.

The sensing element itself is good to 100Kft.+ (130 kft as an apogee sensor) and several vendors, including Adept, build their own log amplifier circuit to take advantage of the large dynamic range of the unsimplified MEMS sensor. Using an external amplifier circuit is more expensive than the high level sensor, and not required by most folks, but if your going higher than 45Kft, your apogee detection options are limited to external amplifier MEMS pressure sensors, GPS, or inertial sensors.

Also there are two choices that can be made by logic when a sensor flat-lines: fire or do nothing until you determine you are really on the way down. The problem with the second option is that if you go way over the limit, you're coming in too hot to deploy anyway so.... More expensive units like the R-DAS, ARTS, Parrot could be programmed to use the barometric sensor in concert with an accelerometer and a time to deploy under more than one condition, and indeed the R-DAS (an probably the others) use the accelerometer at the apogee detector, and use the barometer only to fire the main.

You should buy what you need to fly. The higher you go, the more complicated and expensive it becomes.

Bob

Jim brings up a good point here. There are barometric pressure sensor limitations with any altimeter. Altimeters using high output level MEMS barometric pressure sensors will flat line at some altitude, typically corresponding to between 25 kft to 45 kft altitude depending on on-chip and external electronics. It not the MEMS pressure sensing element that cause this limit, but the internal IC amplifier circuit that was poorly designed several decades ago.

The sensing element itself is good to 100Kft.+ (130 kft as an apogee sensor) and several vendors, including Adept, build their own log amplifier circuit to take advantage of the large dynamic range of the unsimplified MEMS sensor. Using an external amplifier circuit is more expensive than the high level sensor, and not required by most folks, but if your going higher than 45Kft, your apogee detection options are limited to external amplifier MEMS pressure sensors, GPS, or inertial sensors.

Also there are two choices that can be made by logic when a sensor flat-lines: fire or do nothing until you determine you are really on the way down. The problem with the second option is that if you go way over the limit, you're coming in too hot to deploy anyway so.... More expensive units like the R-DAS, ARTS, Parrot could be programmed to use the barometric sensor in concert with an accelerometer and a time to deploy under more than one condition, and indeed the R-DAS (an probably the others) use the accelerometer at the apogee detector, and use the barometer only to fire the main.

Thank you for the explanation. I wasn't sure about some of the logic. You have one hell of a brain dude :eyepop:

You should buy what you need to fly. The higher you go, the more complicated and expensive it becomes.

Bob

Well, we have 4 MAWDS since 2 were the first ones we bought them we lost one, bought another and found the rocket.

4 MAWDS
2 ARTS
2 CO Pilot
1 missileworks mini
1 MARS
Every Xavien timer

We have plenty to get the job done!!

Ben

Jim brings up a good point here. There are barometric pressure sensor limitations with any altimeter. Altimeters using high output level MEMS barometric pressure sensors will flat line at some altitude, typically corresponding to between 25 kft to 45 kft altitude depending on on-chip and external electronics. It not the MEMS pressure sensing element that cause this limit, but the internal IC amplifier circuit that was poorly designed several decades ago.

The sensing element itself is good to 100Kft.+ (130 kft as an apogee sensor) and several vendors, including Adept, build their own log amplifier circuit to take advantage of the large dynamic range of the unsimplified MEMS sensor. Using an external amplifier circuit is more expensive than the high level sensor, and not required by most folks, but if your going higher than 45Kft, your apogee detection options are limited to external amplifier MEMS pressure sensors, GPS, or inertial sensors.

Bob

You're correct about the choices currently available in analog-output sensors.

I originally chose to use a low-voltage-output sensor combined with an external instrumentation amplifier for the Parrot so that I could run everything at 3.6V, rather than 5V+. As a side benefit, the sensor can output valid readings down to a vacuum (100 kft+). The calibration range is selectable at calibration time to be either 0-32kft ASL (with about 2.5 ft resolution at sea level) or from well below sea level to a vacuum, which provides about 5 feet sea level resolution. At 100kft, the resolution is over 400 ft/count because the pressure changes so slowly with altitude in that range.

There are now also a couple of viable digital-output sensors that I'm using for the next generation of Featherweight altimeters. One of them provides valid output up to about 100 kft. The advantage of these sensors is that the calibration is done very accurately under multiple temperatures at the chip factory, and the built in A/D resolution is 15 to 17 bits, so the accuracy and resolution are both very high. One altimeter based on a digital-output sensor is currently competing to be selected for TARC, and a full-featured version, the Raven, is about to start beta testing. Another simpler dual-deploy model, the Wren, will follow after that.

I didn't say anytime soon. Its kind of on my 10 year goals. Next to getting a sallaried job and a college degree

Ben

Your gonna get bored at some point, your starting out too fast. That college degree will cost less then your S motor and rocket.

Me, I'll take things slow, start a savings build myself a triple T motor cluster.

Beside that, I'm limited to an I motor, it's not fair.

Dont cluster all 3 of them, double cluster staged to a single

Dont cluster all 3 of them, double cluster staged to a single

Or maybe 3 T's staged to an S?

That would break 100 miles.

I didn't say anytime soon. Its kind of on my 10 year goals. Next to getting a sallaried job and a college degree

You're entirely missing the point, Ben. If you're talking about it, and planning a website, then you're way ahead of yourself.

Tell us about success with 15 - 20 motors in the 54mm - 75mm range that you entirely mixed yourself. No help, no mentor watching over you, no cookbook of someone else's numbers.

Then step up to 98mm and do a dozen or so that all work properly, with the same thing.

Then you have business starting to talk about larger motors. If you haven't proven knowledge and experience with the smaller stuff, on your own, then you haven't demonstrated the knowledge and experience to step into larger things.

If that doesn't make the point, let me put it to you in simpler terms... The people who make our motors for our group projects? They've demonstrated they know what they're doing over a variety of sizes.

No way, no how, would I ever fly a motor made by someone who hasn't first proven their knowledge through repeated success, flying their own motors, in their own rockets.

As I've told you before, your enthusiasm is a great thing. But you need to control it, show some maturity and take steps. You're jumping from step 1 to step 5. Your results from LDRS should have you taking a step back and figuring out you need to slow down and work your way through the progressions.

I know that's not what you want to hear, but it's what you need to hear.

-Kevin

Replies
21
Views
963
Replies
19
Views
2K
Replies
10
Views
2K