HPR X Wing - T70

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Aquaman33
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Re: HPR X Wing - T70

Postby Aquaman33 » Fri May 21, 2021 9:16 pm

I was just going through NSWRA archives and found this image from April 2008.

Image

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SpaceManMat
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Re: HPR X Wing - T70

Postby SpaceManMat » Sat May 22, 2021 9:17 pm

[youtube][/youtube]On Sunday I finally got to fly the X Wing on its first trial flight.

Preparation went well, packing the chute proved to be the difficult part which was expected.

Boost was perfect, proving that the stability was spot on.
Image
X Wing T70 Trial Flight - Liftoff on Flickr
Thanks Fud Pucker for the photo.

Image
X Wing Trial Flight on Flickr

Things however went dramatically wrong at burnout. Crom’s footage of the flight captured the moment better than mine.

The high speed chute deployment was recorded at 88G by the Raven altimeter, resulting in one of the fins being broken off and the chute protector ripped off. Also in the video the X Wing can be seen bouncing on landing, this resulted in the rear bulk head cracking.
Image
X Wing Trial Flight - Broken Wing on Flickr
Image
X Wing Trial Flight - Aftermath on Flickr
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

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SpaceManMat
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Re: HPR X Wing - T70

Postby SpaceManMat » Sat May 22, 2021 10:48 pm

The flight log from the Raven altimeter tell a very interesting story, I’ve not seen this before.
Image
X Wing T70 Trial Flight - Altimeter on Flickr

What is key here is the altitude data (from the barometer) starts at 0 feet and descends to -32 feet at burnout. Unfortunately when burnout was detected by the Raven the pressure was still increasing in the avionics bay and at that point all the conditions were met for the apogee deployment channel to fire. Once the chute is out and everything calms down we can see that the altitude returns to a reasonable value, peaking at around 310 feet.

I’m pretty sure there’s a joke in there somewhere about making sure you launch you rockets pointy end down when flying in the Southern Hemisphere.

A comparison of the altitude based on the barometric data vs altitude based on the accelerometer data shows the issue clearly.
Image
X Wing T70 Trial Flight - Baro vs Accel data on Flickr
Note that the violent deployment causes the issues seen in the velocity at that point. This will cause inaccuracies in the altitude based on the accelerometer data from that point on.

So the big question is why was the avionics bay being pressurised?
I believe this is due to the location of the vent and the unusual shape of the nose. My thought is that the step that is behind the vent causes air to pile up in front of the step, the increasing pressure then flows into the vent.
Image
Nose cone - vent on Flickr

I’d be very interested to hear other people’s thought on this matter as well as if you have experienced this before?
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

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SpaceManMat
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Re: HPR X Wing - T70

Postby SpaceManMat » Sun Jul 25, 2021 9:53 pm

The rebuild is well in progress
I have cut and beveled a new wing which is always painful.
The broken wing has been removed. I also used a heat gun to remove the retainer and rear bulkhead that was cracked.

Image
Disassembly on Flickr

I am waiting of a replacement fibreglass bulkhead that should prove more resilient to hard landings.

To fix the early deployment issue I am going to relocate the air vent to the rear of the nosecone, the shape there is pretty much the same as a normal nosecone so should not cause the pressure anomaly I saw previously. The launch rail won’t be in the way as the X Wing nose does has a reasonable gap to the rail. As an added precaution I will lower the Mach lockout setting to 100 feet/s just in case this does not resolve the issue. I checked over my previous Raven flights and apogee typically occurs less than 50 feet/s so this seems quite reasonable. The last flight peaked at around 230 feet/s, so it would have given plenty of time for a reasonable coast after which the issue with the increasing pressure if it reoccured, should resolve itself. If anyone has experience or concerns with doing this I’d like to know.

Another issue was the high decent rate, I currently have a 28 inch circular chute. I don’t think I can fit the next size chute in which is 36 inch. I had the thought that I might be able to put the nose on a separate 18 inch chute. I’ve never tried returning a rocket with 2 chutes, does anyone have experience or recommendations with this technique?
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

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SpaceManMat
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Re: HPR X Wing - T70g

Postby SpaceManMat » Sun Aug 01, 2021 6:06 pm

Canopy rebuild, added balsa frame to stop it being dented in.
Image
Canopy New Frame on Flickr

Image
Canopy Rebuild on Flickr

I’ve ordered a long 2.5mm drill to build the nosecone vent. The plan is to remove the switch and reassemble the nose, then insert the drill in the existing vent and use the brass tube as a guide to drill clean through the underside of the nose. This will ensure I proper alignment of the new vent. Then I’ll epoxy up the existing vent. Hopefully I’ll be able to collect my order soon.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

SammiMD
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Re: HPR X Wing - T70

Postby SammiMD » Mon Aug 16, 2021 4:17 pm

SpaceManMat wrote:

So the big question is why was the avionics bay being pressurised?
I believe this is due to the location of the vent and the unusual shape of the nose. My thought is that the step that is behind the vent causes air to pile up in front of the step, the increasing pressure then flows into the vent.
Image
Nose cone - vent on Flickr

I’d be very interested to hear other people’s thought on this matter as well as if you have experienced this before?


Without simulating the shape of the “airfoil” of the nose cone, my guess would be you are creating a dense high pressure region at the rear of the nose. Similar to the effect of a bow wave seen in aircraft wings when flight speed approaches the speed of sound, you may be creating a pressure pocket behind the nose cone that is giving false readings to your altimeter.

Just my two cents, and may be completely wrong.


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