# Meh-ga Nuke

## Motivation

Years ago, Bdale flew some [Woot](http://woot.com) screaming flying monkey dolls 
in his [L3 certification airframe](http://gag.com/rockets/airframes/Goblin10/), 
leading to some seriously amusing [videos](https://www.youtube.com/watch?v=q7C-sqdSo8M).

Unfortunately, that airframe was one of many lost in the 
[Black Forest Fire](http://www.gag.com/blackforestfire.html).

At a conference late in 2014, one of the founders of Woot approached Bdale to talk 
about the possibility of another sponsored rocket project for his new venture, 
[A Mediocre Corporation](https://mediocre.com/) and its flagship site
[meh](http://meh.com).

Bdale had already started thinking about building another "big-ass rocket" ...

After giving it some serious thought, the goal became building something bigger
than anything Bdale had built and flown before, but that would fit in with the 
"mediocre" theme somehow.  Most rocket folks start out flying "three fins and a nose
cone", so doing a simple rocket of that style seemed like a good starting 
point.  The coolest such rocket clan Garbee has ever built was undoubtedly
[Robert's first high-power airframe](http://gag.com/rockets/airframes/LilNuke/),
a [LOC Precision](http://shop.locprecision.com/) 
[Lil' Nuke](http://shop.locprecision.com/product.sc?productId=114&categoryId=12)
kit.

So .. how about a stupidly-large upscale of the LOC Lil' Nuke!  A meh-ga nuke!

## Design Details

After a bunch of playing around in [OpenRocket](http://openrocket.sourceforge.net/),
and considering the limits of the CNC equipment at hand, an airframe diameter of 
approximately 12 inches was chosen.  We can fly high on 6-inch research motors
(first flight planned to be on a James Russell research red-flame "O" motor), and
fly low and super crowd-pleasing on fast-burning M motors like the 
[CTI Pro98 M3400WT](http://pro38.com/products/pro98/motor.php) in a suitable adapter.

To achieve sufficient stability on an O motor, the nose needs to be pretty 
heavy.  Simulation suggests that turning the nose out of solid pine would work
out just about perfectly.

Because such a heavy nose cone will put significant compression load on the rest
of the airframe, we'll build internal structure to carry that load rather than
depending on the airframe material itself.  Some quick back of the envelope
calculations suggest that 3 ribs made of cheap, common 1x2 pine lumber should
more than suffice.

The fins will be fabricated from nominal 1/2 inch birch plywood, rounded, 
vacuum-bagged with one layer of carbon fiber for stiffness and one layer of
fiberglass for surface preservation and strength.  They will insert into fin
grooves cut in the forward and aft fin rings and interlocked with two
intermediate rings.  All fin to ring joints will be augmented with chopped 
fiber and/or glass fabric scraps.  Once the fin can is fully assembled, an
extra layer of fin to fin glass across the airframe will be installed to 
help keep the fin can together during landings.

The airframe will be constructed from 12-inch concrete form tubing with the
inner and outer layers peeled, wrapped with two layers of 6oz fiberglass.  A 
section of airframe tubing wrapped with one glass layer will be slit and
closed down to form a coupler so the main airframe can be built in two pieces
to ease transportation and flight prep.

Recovery will involve a 3-foot drogue parachute deployed by blowing the nose
cone off at apogee, and an ARRD will be used to release a 28-foot main chute
from a deployment bag.  For high flights, a reasonable main deploy height for
traditional "dual deploy" recovery will be chosen.  For lower flights, the
main will be deployed just long enough after apogee to permit the drogue to 
re-orient the airframe, approximating the "main out at apogee" experience.

A side-access electronics bay will be constructed in the valley between two
fins near the leading edge of the fins.  Electronics will consist of one
each Altus Metrum [TeleMega](http://altusmetrum.org/TeleMega) and
[TeleMetrum](http://altusmetrum.org/TeleMetrum) boards.  The TeleMega is
overkill, but I'm curious to see what the airframe rotation rates are like
in flight, and the gyros will capture that.  Each will use a single 850mAh
LiPo battery, and rotary switches mounted in the airframe for on/off.  Two
charge cups will be mounted on the forward ring of the fin can for apogee
deployment, and an ARRD will be mounted on the other side of the same ring
for main deployment.

The main airframe tube will contain ribs and additional structure to carry
the load induced by the nose cone, and to direct apogee deployment gasses
around the main parachute deployment bag.

Because the kinetic energy at ground impact even under the large main will
be fairly high, the ring at the aft end of the airframe will be doubled
to 1.5 inches thick for extra strength.

The airframe will be set up with 1515-sized rail buttons, and use of 
Terry Lee's launch trailer with 20 foot rail is assumed to ensure stability
for all flights.

## Construction Log

2014.04.16
Purchased 12 feet of 12 inch concrete casting tube from White Cap, they cut
it for me into pieces approximately 8.5 and 3.5 feet long.

2014.04.18
Peeled the tubes inside and out, resulting cardboard measures 12" ID, 
and 12.25" OD.  Cut two centering rings from scrap 1/2" OSB to allow use of
on-hand 3/4" copper water pipe as an axle during glassing operations.  I
ended up cutting the longer piece of airframe tubing to ease the glassing
process, such that I can "wrap normally".

2014.04.19
Realized I only have enough glass to do one layer on the coupler.  Placed
order for a full roll of 60" width 6oz E-glass.  Used West Systems 105
resin and 209 extra-slow hardener mixed in 3-pump batches to bond one layer
of glass and peel-ply to the coupler tube.  Took either 15 or 18 pumps total,
the cardboard tube is much "thirstier" than the PML phenolic tubing I've
glassed for previous projects.  Given how much cheaper the concrete casting
tube is, this is fine, I'll just need to pay attention to my epoxy stock and
order more if needed!

2014.04.20
Peeled the peel-ply on the coupler.  Looks adequate for use as a coupler, 
but there are several spots where more epoxy would have made me happier.  Will
compensate when wrapping the airframe tubes.  Given how "thirsty" the cardboard
is, I think the trick will just be to paint the tube with a thick layer of epoxy
before starting to apply the glass, then be generous when wetting each layer.