My crazy idea

[prowlerguy]

Well, never let it be said that I am constrained by 3FNC type rockets. I'm a firm believer that a rocket is a rocket, and if someone has ridden a full scale version, he/she is obligated to have a model somewhere sitting around. Since the good folks at Martin-Baker were good enough to let me try out one of their's, here I go.

Since there seems to be a dearth of information about my type of rocket, I am truly starting from ground zero and testing everything. Therefore the first prototype is only intended to test three items: basic stability and flight path, engine size requirements, and the use of a drouge to deploy a full-sized chute.

I just started today, so I will add construction pictures as I go. Here are the basic airframe parts:

 

[prowlerguy]

My victim. He is named Jim, after Jim Hall.

 

[prowlerguy]

The assembled bucket. Tab and slot assembly was accomplished by using a Dremel tool to cut the slots. That black dust went everywhere!

 

[prowlerguy]

A test fitting for Jim. Man, her sure has wide shoulders! I think he would lose his arm on the canopy rails going out!

 

[prowlerguy]

My attempt to create an adjustable motor mount so I can test thrust vectors needed to create a realistic flight profile.

 

[prowlerguy]

That's all I got done today. I'll post more as I go. Many thanks to Jim Flis for the most excellent material for my prototypes.

In case you haven't figured it out, this is what I am going for (sort of): https://www.ejectionsite.com/project90.htm

 

[Ryan S.]

woa very cool and unique. let us know how it flies. are you flying it at the 45 degree angle or straight up with the guy's seat kinda tilted back

 

[prowlerguy]

I'm not sure. That's why I am building the motor mount so that I can adjust the angle. My goal is to have the seat translate forward in a realistic flight path. Whatever angle is needed for that is what I will use. Drogue chute deployment and drag will also be a factor in the flight path.

 

[Justy]

Originally posted by prowlerguy
Since the good folks at Martin-Baker were good enough to let me try out one of their's, here I go.

I think that after saying something like that, a man is obliged to share the story. I note with interest that Martin-Baker Mk.7 ejection seats were used in the EA-6B Prowler, and your username could be seen to imply that you flew such a beautifully ugly craft...
(beautiful in function, but sleek and sexy, it is not.)

 

[Austin]

Looks great man...thanks for the pics and I wanna see a launch report.

Carl

 

[Micromeister]

Too Cool this should be a fun flying day! can't wait to hear the flight report!

 

[prowlerguy]

Justy:

Short version - Post Maintenance Check Flight out of NAF Atsugi, JP. Nugget (me) in back. Nice flight. Master Warning Light, right Engine Fire Warning Light! Full loss of hydraulics. BANG! Dang, the air is cold! Dang, the water is even colder. Arm's a mess, back is hurting. Big swells, 1.5 hours, JMSDF P-3 finds us, JMSDF helo gets us.

Long version available for the price of a beer or soda at TRF 2004.

All you guys wanting launch reports:
Why do I get the feeling that you older experinced guys know that this is going to turn out badly? In my paranoia, I can almost hear you guys popping the popcorn now, waiting for the show. you->:kill:<-me Oh well, we'll find out in fairly short order.

 

[Micromeister]

Na! it ain't so... We're with ya all the way... As long as we're a long way off
Actually; I truely think this one has a much better chance then the 3 D-12 clustered Foam Toilet that was attempted a few years back.. Reached the end of the 6 foot rod Spun wildly for a terrorizing, what seemed like minutes...flew into pieces and crashed to the ground. hopefully your test WILL come out much better.. now where did I put my Hardhat???

 

[Papa Elf]

Originally posted by prowlerguy
Short version - Post Maintenance Check Flight out of NAF Atsugi, JP. Nugget (me) in back. Nice flight. Master Warning Light, right Engine Fire Warning Light! Full loss of hydraulics. BANG! Dang, the air is cold! Dang, the water is even colder. Arm's a mess, back is hurting. Big swells, 1.5 hours, JMSDF P-3 finds us, JMSDF helo gets us.

I'll be there... I want to hear the long version!

So, what happened during the debriefing?

 

[jflis]

Originally posted by prowlerguy
A test fitting for Jim. Man, her sure has wide shoulders! I think he would lose his arm on the canopy rails going out!

this is a very cool design!

I only see one possible problem...

To increase stability, you may have to add nose weight. Based on the photo's, "jim's" nose isn't big enough for any weight so if you have to add weight, you may have no choice but to fill his head with lead.

Not really a problem, but if you do that, then he isn't military anymore... ...put that much lead in his head and he becomes a politician... (that, or an ATF agent)...

but, hey, whatever makes it fly...

 

[graylensman]

Prowlerguy

You absolutely HAVE to call me so we can schedule a launch I can attend... I want to see this in person.

Is it okay if I leave the kids in the car to watch?

 

[Papa Elf]

You should tune that for D13's

 

[prowlerguy]

I'm pretty much done with this prototype. Here is a detail of the engine mount and adjustment mechanism. It is hinged at the top using a dowel/launch lug hinge arrangement. During testing, the lower assembly will be held in place with copious tape, and will be epoxied once the proper angle is determined.

 

[prowlerguy]

Here you can see the launch lug and the parachute container (plastic bag on back of seat).

 

[rstaff3]

Wow, this is one of those threads that somehow I hadn't been following. Big mistake! I love this kind of project and it looks like you are doing an excellent job! The adjustable mount is great.

 

[prowlerguy]

And finally the other side, showing the parachute mounting screw-eye. This is a 24mm mount, so I should be able to use a wide variety of engines in here. I plan to use a D12-3 for the first flight.

I intend for the first flight to be just me, for safety and pride preservation reasons. Once I am sure it is reasonably safe (and I have moved beyond stability testing), I will invite others to view it. And in case this design is unstable, I will add a dowel and plane setup. While this won't look like a Martin-Baker, it will look pretty similar to the Soviet S26 (or S36?) stabilizing arms.

 

[prowlerguy]

Well, I have good and bad news. The good news is that nobody was hurt and the seat survived with very minor damage. The bad news is that stability is a serious issue, to put it mildly.

I loaded up a D12-3, packed the chute, and took off for my field. After setting up and prepping the engine, I gave a countdown. At engine ignition, the launch lug bound up to the rod. The rod finally seperated from the pad, and Jim and his seat did loops, twists, and turns at an altitude of around 10 feet, carrying the launch rod like a skewer. Then, the launch lug broke free from the seat just about as the motor burned out, Jim fell the earth, and the parachute deployed after a brief pause. Well, that sure was exciting!

Possible causes of erratic flight path:
Hanging on the rod
Thrust vector not even close to CG
Unbalanced drag and weight

I will be scrapping this design, and looking to correct a few of these issue. I'll be back.

 

[jflis]

well, this is how we learn!

Give Jim a Dramamine and git back to the drawing board

 

[Micromeister]

Don't fret, the experiment was well worth the try! Great idea, design and construction work, AND you followed the safety rules for unproven designs. Would have be Super if it had worked the first time, But I'm sure many of us will be happy to tell you...Lot's of our far less ambitious projects have ended with the same spinning, wirling thud...Pop! you just experienced. Keep trying I think given adjustments and maybe a different placement of the launch lugs this seat will fly.
Great thread and report.
Thanks for sharing.

 

[rstaff3]

I'm sorry it didn't work perfectly, but what the hey. This is a very unique design and would be expected to take some experimentation. I'm sure you had fun working on it, I know I enjoyed hearing about it I'm looking forward to 'round 2'.

 

[wwattles]

Prowlerguy,

Time to skip the flight testing on the Mercury models, and go straight to Gemini! That's right, TWO seats, with TWO test subjects. Why? It makes the overall body more symmetrical. So you put a BT up between the two seats, with them back to back, and throw a lot of noseweight in, and voila! You've got a stable rocket again!

WW

 

[powderburner]

There is a great line in the movie 'Jeremiah Johnson' when JJ beds down for the night out in the snowy boonies. He mixes coals from the campfire with dirt before laying his bedding over the top. The preparations of his sleeping accomodations are observed by his new friend, an old-timer who is wise in the ways of mountain-man-dom.

Later that night when the coals burn through JJ's blanket and wake him abruptly, the old man comments that JJ didn't put enough dirt over the coals. "Saw it right off," he says.

Trying hard to resist being a smart ***, I will simply suggest that you do a bit of reconfiguring to get the motor under the seat. I know, this is difficult with the scale you have selected, but observe where the nozzles are on the real seats, and where the thrust vector is pointed. You are going to have a difficult enough time with this model, due to unconventional aerodynamics, without asking for more trouble with asymmetric thrust.

Maybe a cluster of A10T motors?

 

[prowlerguy]

Thanks for your support, guys. I've still go a bunch more raw materials to go before I will punk out on this one. Besides, everyone needs their "thing." Why, pretty soon you'll hear "Did you see that crazy SOB flying an ejection seat at XXXX '05? Darn thing almost worked, too."

ww,

You crack me up. The closest I could come would be an F-111 type ejection capsule. Hmmm. There's a fallback position, maybe.

 

[prowlerguy]

powderburner,

You are spot on. That is part of Mk1 Mod1. The challenge will be venting the ejection gasses in such a way that I can get some sort of chute deployment. Fabrication is already underway.

Clusters may come later when I have worked out other issues. For now, the engine will extend below the seat frame.

On a related topic, I have seen some say that saucer-type rockets can be launched san rod. Is that true?


Oh yeah, I almost forgot that there were some positive lessons learned, too. The adjustable motor mount held firm, so if anyone is doing some sort of science fair project (think Variable Geometry Duece), this might be useful.

 

[prowlerguy]

For information, there is a great shot of one type of rocket motor used in this application. The orientation of the fuel to the nozzle/manifod is certainly unusual. I wonder when Aerotech will be producing one of these?

https://www.ejectionsite.com/mkf7seat.htm