Featherweight Raven 4 & GPS Specs

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jar123

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Hi everyone,

I'm looking into application of Featherweight's Raven 4 and GPS Tracker for a rocket with a threshold altitude of 100 km/330,000 ft. I have read their respective web pages and user manuals religiously, but still had a couple of questions for each.

Raven 4
  • What is its power consumption? I noticed the GPS' is 112 mA transmitting, 60 mA not, and an average of 86 mA. Just wanted to get the same information on the Raven to determine if my battery for it will provide a long operational lifespan.
  • AGL1-3 (output parameters) max altitudes are 32,736 feet. Could this be extended to 35,000? The Apo channel will already be used and will also be extremely high for this deployment. (boat tail ejection @ apo (threshold altitude), parachute deployment @ 35,000 ft)
GPS Tracker - I have found some RF-transmissible materials for avionics insulation, but they are claimed to be tested at 9.5 GHz, which is much higher than the 915 MHz the tracker and ground station use. Does anyone know if this is a significant matter (since the frequencies are both radiowaves), or of other extreme temperature resistant materials?

Thank you all =)
 

ksaves2

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The only thing I can say is don't use carbon fiber for body tube components nor use a metallic paint on the parts. A caveat to this would be that if the radiating antenna of the tracker was in a plastic or fiberglass nosecone, everything aft of there could be carbon.
Although, I would test the GPS tracking inside of a carbon fiber tube to make sure it could receive the satellite signals nominally. Easy enough to do a test though before dedicating to a build.

For insurance, one could use a second "hardened" self-contained tracker GPS or otherwise on the apogee harness for backup.

If the tubes are carbon fiber with a "stowable" tracker, I'd make sure it has a good satellite lock before launch so when ejected, it can get back to work without too much time wasted. The big issue is the transmitted Rf getting out of the rocket. It is frequency and Rf power dependent though there are no charts available that I know of for guidance.

Kurt
 

jar123

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The only thing I can say is don't use carbon fiber for body tube components nor use a metallic paint on the parts. A caveat to this would be that if the radiating antenna of the tracker was in a plastic or fiberglass nosecone, everything aft of there could be carbon.
Although, I would test the GPS tracking inside of a carbon fiber tube to make sure it could receive the satellite signals nominally. Easy enough to do a test though before dedicating to a build.

For insurance, one could use a second "hardened" self-contained tracker GPS or otherwise on the apogee harness for backup.

If the tubes are carbon fiber with a "stowable" tracker, I'd make sure it has a good satellite lock before launch so when ejected, it can get back to work without too much time wasted. The big issue is the transmitted Rf getting out of the rocket. It is frequency and Rf power dependent though there are no charts available that I know of for guidance.

Kurt
We are manufacturing the fuselage out of carbon-carbon, however the area surrounding the antenna is a different material that is RF -transmissible. I was looking at GSXP Graphite, but the only information about dielectrics I have found came from Wikipedia so soon I am going to call the company and get more info on that.

Thanks for replying Kurt
 

jar123

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I also considered fiberglass, but its max service temperature is really low for what I need (2000 deg F or greater).
 

ksaves2

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I also considered fiberglass, but its max service temperature is really low for what I need (2000 deg F or greater).
I might be wrong but I think it might have been Robert DeHate (I apologize if my recollection is wrong) who slotted an ebay so the Rf energy could radiate out from the body. I thought it interesting but the concept was way beyond my puny intellect.

I didn't test well enough two rockets flying Beeline GPS trackers in the 70cm band. Both were glass but had pretty Dutch Boy rattle can metallic paint finishes that were clear coated and hand rubbed. Still have one of the rockets.

Did a cursory range test then launched. No packets at altitude. One rocket was lost for two weeks as apogee deployment didn't occur and it augered in. The second one went to 10k with no telemetry and was lucky that some fliers got a visual on descent and was brought back to me.

GPS signals got through as the onboard memory recorded good positions and satellite lock. The Rf couldn't get out was the issue.

Kurt
 

gtg738w

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I also considered fiberglass, but its max service temperature is really low for what I need (2000 deg F or greater).
What makes you think you need a 2000F material?
 

jar123

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I might be wrong but I think it might have been Robert DeHate (I apologize if my recollection is wrong) who slotted an ebay so the Rf energy could radiate out from the body. I thought it interesting but the concept was way beyond my puny intellect.

I didn't test well enough two rockets flying Beeline GPS trackers in the 70cm band. Both were glass but had pretty Dutch Boy rattle can metallic paint finishes that were clear coated and hand rubbed. Still have one of the rockets.

Did a cursory range test then launched. No packets at altitude. One rocket was lost for two weeks as apogee deployment didn't occur and it augered in. The second one went to 10k with no telemetry and was lucky that some fliers got a visual on descent and was brought back to me.

GPS signals got through as the onboard memory recorded good positions and satellite lock. The Rf couldn't get out was the issue.

Kurt
Just to clarify - by "glass" I'm assuming you mean fiberglass?
 

DAllen

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330k? Where are you flying this and how are you getting FAA approval?
 

gtg738w

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Our threshold altitude is 330,000 feet, so the avionics needs to be protected from reentry temperatures.
So what are you ejecting at apogee...?
 

jar123

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330k? Where are you flying this and how are you getting FAA approval?
We're launching at White Sands Missile Range, NM. We have a PDR (prelim. design review) with the USAF tomorrow.
 

jar123

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We're launching at White Sands Missile Range, NM. We have a PDR (prelim. design review) with the USAF tomorrow.
Also, launch isn't expected for a while, so we will likely be working with the FAA in the near future.
 

mikec

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AGL1-3 (output parameters) max altitudes are 32,736 feet. Could this be extended to 35,000?
I know that Featherweight has a special-purpose high altitude build that extends some of the ranges, but I don't think these. You might consider some other way to do what you want, like a simple timer.
 

jar123

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I know that Featherweight has a special-purpose high altitude build that extends some of the ranges, but I don't think these. You might consider some other way to do what you want, like a simple timer.
Another possible option could be a combination of velocity/accelerometer/timer parameters, but using that might subject the charge to pre- or postmaturity.
 

ksaves2

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I know that Featherweight has a special-purpose high altitude build that extends some of the ranges, but I don't think these. You might consider some other way to do what you want, like a simple timer.
Ditto on the timer if one wants to keep things simple. At that altitude, things are pretty rarefied. I have seen some videos of high altitude balloons that were above 100k and when their balloon bursts, the parachute rapidly "fills" with an upward looking camera. With balloons, the payload is simply held (hangs) from the apex of the parachute where the apex is connected with a line to the lifting balloon. As opposed to being packed in a rocket.

I originally thought the chutes wouldn't fully open until they hit the lower atmosphere but I didn't think of one thing, speed. They are probably falling extremely fast and the few air molecules fill the canopy and make it "open". It's still falling very fast though.

I then surmised that with the canopy already opened, once the air becomes more dense there would be a gradual slowing of the balloon payload as it descends lower. I think that would be more than ideal to prevent shock of the payload as it descends.

Now 330k is a lot higher than 100k and I wonder if there are any low (relatively speaking) altitude temperature profiles that deal with the altitude in question as far as friction heat on descent for 330 to 100k? Why go through some PITA heat protection if it would be superfluous? Heck even the ARCAS sounding rocket I heard worked with a clockwork timer for deployment and it hit 200k!

Another thing. Heat transfer at altitude is very slow. Heck it's pretty cold up there. The balloon guys had more trouble keeping their electronics and batteries warm to function but they of course were trying to maintain altitude for hours. I remember one group flew a bottle of booze to 100k. They got a good track and saw the chute coming in on recovery. They got to the booze and it was still ice cold. (Was some sort of liquor so high alcohol content.)

The rocket isn't going to be at altitude as long as a balloon and with a near straight up and down flight, is re-entry heat going to be that much of problem?

Kurt
 

watheyak

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First off, let me explain that I'm not an engineer, just a dumb pilot. To me, "threshold" means the beginning of a runway.

But when you say your "threshold altitude" is 330k', are you referring to the apogee?

The reason I ask is because, while that altitude is certainly impressive, the word "re-entry" usually refers to something returning from orbit, at orbital velocity.

Maybe I'm missing something here, but if it's returning from a ballistic trajectory by deploying a parachute or something similar, there will be very little friction. And no heat. Sure, it might be falling supersonic, but there's not enough atmosphere to create much heat. But I could be totally misunderstanding the situation.

I know you didn't come here to have a bunch of armchair quarterbacks re-engineer your project, but when I hear carbon-carbon and re-entry it makes me think there's something amiss. Similar flight profiles have been accomplished with much less exotic, and cheaper materials.
 

jar123

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Ditto on the timer if one wants to keep things simple. At that altitude, things are pretty rarefied. I have seen some videos of high altitude balloons that were above 100k and when their balloon bursts, the parachute rapidly "fills" with an upward looking camera. With balloons, the payload is simply held (hangs) from the apex of the parachute where the apex is connected with a line to the lifting balloon. As opposed to being packed in a rocket.

I originally thought the chutes wouldn't fully open until they hit the lower atmosphere but I didn't think of one thing, speed. They are probably falling extremely fast and the few air molecules fill the canopy and make it "open". It's still falling very fast though.

I then surmised that with the canopy already opened, once the air becomes more dense there would be a gradual slowing of the balloon payload as it descends lower. I think that would be more than ideal to prevent shock of the payload as it descends.

Now 330k is a lot higher than 100k and I wonder if there are any low (relatively speaking) altitude temperature profiles that deal with the altitude in question as far as friction heat on descent for 330 to 100k? Why go through some PITA heat protection if it would be superfluous? Heck even the ARCAS sounding rocket I heard worked with a clockwork timer for deployment and it hit 200k!

Another thing. Heat transfer at altitude is very slow. Heck it's pretty cold up there. The balloon guys had more trouble keeping their electronics and batteries warm to function but they of course were trying to maintain altitude for hours. I remember one group flew a bottle of booze to 100k. They got a good track and saw the chute coming in on recovery. They got to the booze and it was still ice cold. (Was some sort of liquor so high alcohol content.)

The rocket isn't going to be at altitude as long as a balloon and with a near straight up and down flight, is re-entry heat going to be that much of problem?

Kurt
According to Featherweight, the Apogee channel can be set to any altitude, so I'm not considered about the 330,000 ft threshold. I'm concerned about parachute deployment at 35,000 ft, because the altitude parameters cannot exceed 32,736. Hence why I mentioned utilizing a combo of velocity, accelerometer, and time.
 

kjs

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I'm looking into application of Featherweight's Raven 4 and GPS Tracker for a rocket with a threshold altitude of 100 km/330,000 ft. I have read their respective web pages and user manuals religiously, but still had a couple of questions for each.
Jar - send me an email at
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and I'll loop in Adrian for that discussion to be sure the Raven and Tracker can meet the needs. Also let me know if it would be possible for me to attend the eventual launch... :)
 

TonyL

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If you are flying out of WSMR and you have a relationship with USAF, then you have funding or a sponsor. A cube-sat GPS module would be a logical choice for such a project and would likely have all the characteristics you would want.

Most commercial GPS chips are not calibrated above 125 kft or so. Whether it is really 60 kft or 150 kft, it is well below the intended apogee, and what used to be called the COCOM limits still apply, so most of the flight up will be in GPS blackout and its performance at apogee is unknown [read: is expected to fail to lock] until one tries it, at which point one expects it to fail to lock.

When I talked to Adrian about >32kft deployment for the Raven, really there was not much to do about it beyond work with the functionality it has. The current Raven may have more options. There is only one tracker that I am aware of that has a calibrated GPS chip to the desired altitude but the formerly COCOM limits still apply.

br/

Tony
 
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