Archive-name: rockets-faq/part6
Posting-Frequency: monthly
Last-modified: 10 October 1994
*** PART 6: Payloads
Any additions or corrections should be sent to that address]
Updates
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October '94: Updated AstroCam section with "Sticky Shutter" discussion. Updated
"Adept" section with new products. Updated "Transolve" section with
review from recent "Sprocketry".
August '94: Added "Night Flying" section. Updated hombrew still camera section
based on NARAM 36 inputs.
June '94: Added reference to "Microbats" project. Added "Alternative Boosters"
to Astrocam section. Updated some camera references.
April '94: Re-wrote section headings into "Q&A" format, minor editing throught.
Split off "Guidance Systems" into separate (new) Part.
Renumbered to "Part 5" as part of FAQ reorg.
Added table of motor "theoretical performance" in Astrocam Section.
Jan '94: Minor addition to camera introduction
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Introduction - Flying sport rockets is fun. Flying competition rockets can
be exciting in the heat of battle. Scale models (my favorite) can be as much
of a challenge to research and build as they are to fly. But if you want to
do something "real" with your rocket, you've got to fly a payload. This also
provides you with a good response to the perpetual question from the great
unwashed masses when they ask "so, what's it do?"
6.1 Camera Payloads
Cameras are the most often flown payloads (after eggs and bugs :-) because
they hit us where we live. No other payload lets us see the flight from our
rocket's point of view. The intensity of interest in camera payloads can be
seen by how early they were flown: Goddard flew them, the VfR (the German
rocket society which gave Von Braun his start) flew them and, of course,
dozens of post war sounding rockets carried camera payloads. In fact, the
very first operational (as opposed to experimental) rocket system was Alfred
Maul's photoreconnaissance rocket built for the German Army which was used
from 1912 until airplanes became more reliable.
Some of the products and techniques that have been tried and/or are still
available are:
6.1.1 Can I just go out and buy a camera for my rocket? What cameras will work?
Some commercial camera products produced over the years:
6.1.1.1 Camroc - The first purpose-designed rocket camera. Designed by Estes
and sold from 1965 to 1974. A marvel of simplicity, it was patterned after
several homebrew cameras of the early '60s (see 5.1.2). It was simply a
cylindrical body that held the film topped by a hemispherical nose that
was flattened off to accept the optical window which the forward facing
lens looked through. One shot per flight on "Astropan 400" (Kodak Tri-X)
cut into a 1 1/2" dia. round negative. Easy to process at home. The film
had to be push processed to 1200 ASA (officially, though most home
developers went to 1600). Extremely valuable on the collector market.
[Note: Don't write me asking how much your old Camroc's worth. Bob
of the Camroc: "At one time there were quite a few homebrew modifications to
the Camroc floating around. Most popular was substituting a 3-element glass
lens from Edmund Scientific for the standard plastic lens; it gave much
sharper and better color-corrected results. I have also seen a wide-angle
variation with yet another Edmund lens that required cutting the forward body
section of the Camroc down to a much shorter length. As someone pointed out
at the time, the Camroc lens was a short telephoto relative to its film
format. It doesn't make sense to send a rocket up as high as possible and
then use a telephoto lens to get a SMALLER angle of view; it's a wide angle
you really want, so you can get more in the picture from a lower, easier-to-
aim flight with a smaller motor and less risk of losing the camera. Several
people flew color slide film in the Camroc, but high-speed color films were
pretty terrible at the time; the ASA 1600 print films available today would
probably work very well in it."
6.1.1.2 Cineroc - Estes' second foray into camera payloads, the Cineroc was
*much* more sophisticated than the Camroc. This was a full bore 8mm movie
camera crammed into a package not much bigger than it's predecessor (although
more aerodynamic). Introduced with much fanfare in 1969, it lasted only 5
years before its plug was pulled in 1974. The lens looked aft via a hooded
mirror and it shot ~15 sec worth of flight time at 2X speed (30 sec projec-
tion time). At least that's what the spec says. In reality, most Cinerocs ran
in the 18 - 20 fps range which is more-or-less normal speed. The film was
a Kodak ASA 160 instrumentation film on a polyester base which was probably
adopted because it was the only daylight-balanced Super 8 film available.
The Cineroc used a custom film cartridge meaning that you either used the
Estes processing service or went to a custom lab. It could be developed
at home using a Kodak E-4 developing kit, but this was *much* more trouble
than most modelers would want to go.
Gary Rosenfield, now president of Aerotech/ISP, made a name for himself
by coming up with a significant hack on the Cineroc that both reduced its
diameter and increased the film capacity. As detailed (somewhat sketchily)
in the V 14, N 1 (July 1974) issue of the _Model Rocket News_, Gary took
the basic guts of the camera (lens/film gate/geneva transport plus motor
and batteries) and put them in a BT-55 tube with the mirror hood outside
as usual. He extended the tube fore and aft enough to hold 50' of film (a
full cassette worth) in random storage, i.e. no spools. The film simply ran
from one compartment, through the gate and into the other compartment.
While this made the system much more difficult to reload in the field, you
could now have the film developed anywhere, provided you bothered to
rewind it back into the standard cassette afterwards. The photo of "Wild
Man Rosenfield" that accompanies the article is probably suitable for
blackmail :-)
The official reason for its early demise, still lamented to this day, was
that the small electric motor it used went out of production. However,
in a conversation with Mike Dorffler (the designer) he revealed that the
product was killed by a combination of events that occurred over a very
short (2 month) period in early '74: the motor went out of production,
Eveready stopped making the tiny "N" batteries, Kodak changed the formula
of the film which couldn't be accommodated by the custom lab doing their
processing and, the coup de' gras, a technician dropped the mold for
making the custom lens.
Some Cinerocs are still flown today 20 years later. The size "N" alkaline
batteries, much better than the original carbon-zinc ones that Estes
supplied, are widely available now; and the new film stock (which is
available off the shelf, not special order like the one Estes originally
chose) is sharper and less grainy than the old stuff. Both of these actually
make for easier and better Cineroc results today than when it was first
introduced. You do still need a custom film lab to deal with the nonstandard
lengths of 8mm film, however.
6.1.1.3 AstroCam 110 - Another Estes product and something of a combination of
the previous two. Reverting to the still format, the AstroCam was designed
around a stock 110 cartridge. It took multiple shots per roll of 400 speed
color print film, but still only one frame per flight. The lens looked out
through a hooded mirror (like the Cineroc) but this time looking forward
(like the Camroc). Image quality was marginal due to the plastic lens and
small format, but the film can be developed anywhere (although the prints are
reversed). A very long lived product, it lasted from it's 1979 introduction
until early 1992 when, for reasons known only to themselves, Estes canceled
it. Public demand was great enough that they re-introduced an "improved"
version in early 1993. Said improvements consisted of a better lens for a
sharper image, a one stop increase in aperture (so it can use the much more
available 200 speed film) and pre-assembly of the lens and sprocket. Perhaps
the biggest improvement of all was that they dropped the price by $10 :-)
6.1.1.4 AstroCam building and flying tips - The AstroCam is the source of
continual threads on r.m.r. The following is a distillation of nearly half
a megabyte worth of AstroCam discussions I've archived:
GENERAL TIPS
* The film is quite grainy, hence a lot of people move on to 35mm cameras.
* Underexposure is a problem - the pictures are lousy if you launch in
anything other than bright sun. Of course, there's also the usual problem
of forgetting to open the safety shutter before launch.
* Overexposure is a problem several ways:
- The shutter cord can get tangled in the shroud lines, taking multiple
exposures or one long exposure.
- A hard impact can take another shot. At the least, landing impact will
close the safety shutter making you wonder if you forgot to open it
before launch.
- Problems with sun and heat on the pad make some folks drape it with
aluminum foil until final countdown.
- Adjustments on the pad are always a source of causing the shutter
to go off on the pad.
* Chris suggests advancing the film before take off and advancing it after
...
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