Half-Scale Apache, Flying Solo

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OverTheTop
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Half-Scale Apache, Flying Solo

Postby OverTheTop » Thu Aug 17, 2017 8:10 pm

Half-Scale Apache, Flying Solo

Time to Fly!
In the interest of proving the sustainer of my half-scale Nike Apache, the Apache is to be flown on its own.

Full build thread here if you are interested: viewtopic.php?f=6&t=5019

After waiting many months (bad weather, fire season, bad weather, other commitments) it is finally time to fly this bird.
It had been prepped since last year, so I basically just needed to check the LiPo batteries and load it onto the rail. Packing the car was more hassle.
It was do be flown at the June launch of Tripoli Rocketry, at Serpentine. Weather was perfect. 15deg and sunny, with a gentle breeze.

Prepresize.jpg

AtPadresize.jpg


After some issues with the GSE (power inverter stopped working, laptop almost flat) finally everything was sorted and the button pushed. Motor (CTI M840) was a bit slow to ignite but finally roared to life and burned for the designated nine seconds.
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Flight pics thanks to Lamp

Telemetry was good and strong, but curiously indicated quite a quick sink rate after arcing over. As it was getting towards 2k’, where the main was set to fire, my telemetry antenna spun around and I lost signal. Luckily it was in the same paddock so there were lots of eyes on it. Data would later show a descent rate of 288 km/h. Main charges fired and the chutes did their job as planned. Interestingly there were reports from observers of something detached from the rocket can coming in ballistic. Fake news I’m afraid. I had engineered the rocket so that if it broke it would all be held together by design. It worked to design, and the only thing that may have possibly come in ballistic (no evidence was found) may have been a stray crow or something similar. It also could have been a case of mass hysteria.

Viewing the landing site showed the transition had suffered a brittle failure (z-axis weakness in the 3D print) at the expected location. I had designed that part to accept all the boost forces of any motor capable of being installed, but thinking about it a couple of months ago I realised there was a weakness across the transition. In this case it was not strong enough for deployment forces, especially going from 80m/s to 9m/s as the chute snaps open. I was expecting around a third of that for the nominal descent rate.
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Basic Flight Data
Altitude: 16906’ (5153m)
Peak Speed: 362m/s (Mach 1.05, 1187fps)
Peak Rotational Rate: 191 deg/s
Sink rate (drogue): 60-80m/s
Sink rate (main): 9m/s


Examining the data and pics it shows that the descent started off a little slower but then sped up. Seeing the landing layout, I surmise that the rocket went a little nose-down after apogee, and with a little windmilling on the way down the wound the NC harness along the airframe, with the NC tucking into the lew of descending airframe, ending up just past the fins to the rear. This resulted in the rocket coming in in a low-drag configuration at 80m/s.

The main chute deployed at 2000’ as programmed, giving a 24G jolt to the airframe. The rotational acceleration (from nose-down to nose-up) of the airframe snapped the transition, and a contact with the NC during the flip (ding visible on NC) cracked that as well.

The flight was a success, even though a couple of parts were cracked due to unexpected behaviour. The fin construction (using the isogrid with CF skins) held up perfectly, although going just supersonic was not a particularly heavy burden for them. The maximum spin rate of 191deg/s was a good demonstration of the build quality of the fins and can.

Simulations were a bit off, due to the stepped airframe I believe. Original results suggested 19200’ and Mach 1.2.

Being able to monitor the battery voltages on the main altimeters through the telemetry was great for confidence at launch. Loss of these signals also indicates NC ejection. Well worth doing IMHO.

So future refinements include improving the GSE, more drogue area on the NC end.

She will fly again, with a newly printed transition, and a repaired NC.

Stay tuned for the next flight report :D
TRA #13430
L3
"Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

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Re: Half-Scale Apache, Flying Solo

Postby SpaceManMat » Thu Aug 17, 2017 10:07 pm

Looks like a great shake down flight 8) 9 sec burn would have been impressive to watch :!:

How cleanly did the cable disconnect? Any sign of stress on the plugs.

What's the plan for the next flight?
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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OverTheTop
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Re: Half-Scale Apache, Flying Solo

Postby OverTheTop » Fri Aug 18, 2017 7:29 am

Cable disconnect was instantaneous on all four channels. It is really good knowing exactly what those other altimeters are seeing before the button is pushed. Cable was a little worse for wear, but still serviceable for the following flight. It is a consumable so I will make more as needed. The contacts in the cable and the avionics were kept from contamination by a liberal coating of contact grease before assembly so they won't degrade with the corrosive BP residue.

Love the long-burn motors.

It has flown since this flight. Report to follow :D
TRA #13430
L3
"Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

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OverTheTop
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Re: Half-Scale Apache, Flying Solo

Postby OverTheTop » Fri Aug 03, 2018 6:25 pm

I have been a bit slack getting this post happening. I just got busy and missed that I hadn't posted it :(

The Apache flew again at MARS Attacks in early August 2017. Entirely nominal. 13k' on an M1770. Mach 1.1. Landed 1.9km downrange.

Apache1aresize.JPG


Apache3Resize3.jpg


Apache2resize.jpg


Here is the rocket at 20m away :shock:
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Finally reasonably visible at 3m away
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TRA #13430
L3
"Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

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CATO
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Re: Half-Scale Apache, Flying Solo

Postby CATO » Tue Aug 07, 2018 10:24 am

Nice flight.... :)
"In thrust we trust"

AMRS 21 L3
TRA 07459 L3

Impulse:
2018: 14,767 Ns (44% N)
Ns 17: 5,973; 16: 34,558; 15: 35,955; 14: 6,016; 13: 10,208
PB - Gorilla N2717WC, H: 10,260', S: 1.14M


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