Moonburner Motors Get Bent

First time I've tried to upload a vid clip.
Hope it works OK.


When I first started experimenting with making my own sugar motors, I made several decisions under their own merits which eventually lead to an epiphany. When combined, these factors
created an interesting moonburn synergy.

First, I chose to use 15/16" diameter [24mm] phenolic cases that are thicker walled, than Aerotech, being 3/4"id instead of 7/8"id. To simplify the nozzle issue, I elected to buy Aerotech nozzles instead of producing my own from scratch, though this requires that I turn down the nozzle OD to fit my cases. Like most other experimental motor makers, I still wanted to maximize the propellant fraction. I decided to pour directly in the cases, including the convergent frustrum. No casting tubes or liners required. After only a couple false steps, I tried silicone tubing as my core spindles, which works great when casting sugar propellant. The silicone spindles are longer than the motor case, and extend all the way from the nozzle to beyond the top end. A rod or dowel, as the case may be, the same diameter as the nozzle throat, but loose inside the silicone, extends through, acting as an alignment guide and throat plug. After curing, the rod is drawn out, then with a steady tug, the silicone stretches, losing contact with the core wall, and pops right out pretty as you please.

Though I started with core burners, a major goal all along was to make moonburners since I couldn't buy any commercial ones for a long time, and then when I could, only in 'J' and above.
With the old Aerotech D-G moonburners, the fuel was precast and had a drilled port to one side that you would have to blindly hunt for with a piece of 'S' bent Thermalite. Even for
someone experienced with these motors, it was tough to install, tough on the Thermalite and chuffed too often at the best of times.
Epiphany; My flexible silicone spindles need not be straight. I attached the silicone tubing to the nozzle throat with a short plug, then 'S' turned the tubing over to the case wall where
it's held in place with a suitably fashioned wire clip. This creates a smooth pathway for the ignitor during installation AND expulsion, even when using Copperheads. This 'S' turn also creates a short area of coreburn configuration near the nozzle, producing a higher takeoff spike before it settles into full moonburn mode. Perfect for a medium size 'D'-'E' bird.

Another goal of making motors was that my wife [now ex] and I had always been into clustering, especially air-starts. Estes 'D's are great for this but keep costing more and more.
I was already enamored with the idea of focused thrust [long before Flis-Kits] and wanted a way to add that feature to already existing rockets with air-start clusters. The curvy silicone core spindles work even better with the angled nozzles. Now there's only one shallow bend instead of an 'S' curve. This also reduces the coreburn section, making the motor more of a true moonburner. Since classic moons ramp up and down more gently than other motors, they are less prone to affecting the flightpath if multiple ignitions are uneven, or lacking. Focused thrust, of course, further reduces possible flightpath disturbances. I made a 10 degree angled nozzle holder for my lathe, so that I could modify the Aerotech nozzles before gluing them into the cases.












Angled lathe tooling with unmodified nozzle
installed, and a used angle nozzle motor.

Atlas 5 Updates

Atlas 5-411 Astra 1KR, Flt#8, with single strapon.
Note the vectoring main motors.


Atlas 5-511-AV010, New Horizons, Flt#7
All up with five strapons.


This illustration speaks for itself.


A special thanks to Gunter Krebs who made comment on my Atlas? 5 post. He also posted a link to the Atlas 5 info on his most excellent website; Gunter's Space Page
I had visited Gunter's sites in the dim and distant past and since then lost his address.

So it turns out that the Atlas 5 can be flown with up to five strap-ons, or as few as one [or zero of course]. This is still practically unique in the space launch industry. Aside from the two shuttle systems which are asymetric by nature, the augmented Atlas 5 is the only other one that I know of. This of course requires a robust thrust vector system and an equally capable flight control computer able to adapt to, or be programmed for, the asymetry from the moment of liftoff in addition to the usual trajectory programming, weather, and any other possible anomolies.

While the original Atlas balloon tankage was welded stainless steel, I learned that the Atlas 5 tankage is isogrid [machined] aluminum. The main motor[s] are/is a Russian RD-180. Actually a single assembly with two chambers. One more very useful link: Atlas 5 Data Sheet

Atlas? 5

I was surfing for the X37B and landed on the Atlas 5 which
is going to be the X37's launch vehicle soon. I didn't know
much about the Atlas 5 and admittedly, I still don't know
enough.  Research will continue though.  I have a few
points to make in this post, more may arise in the future.

As near as I can tell, this is practically a new vehicle, it
bears so little commonality with the Atlas that I know,
it hardly deserves the name. Atlas always had  3 liquid
rocket motors in a stage and a half arrangement. It took
off on 3 motors, then later drops the outer pair,
continueing on the center motor alone. A sweet solution.
This new bird has only 2 liquid motors.
More important than the name, L-M adds the older Atlas
launch success rate in with the new one, claiming over 600
successful launches. Most of those flights were made by
the original Convair later renamed General Dynamics.
Marketing hype that doesn't fool anybody who cares.

The pics above are from the recent launch of the Intelsat
14 satelite. Reading about the flight, I found that it used
3 strap-on motors. Scrolling through the roll-out pics,  I
was struck by the sight of 2 of the strap-ons side by side.
Typically 3 strap-ons would be attached equidistant around
the booster. Further through the pics I find the third strap-
on on the other side next to an empty mounting pad for a
fourth. The Atlas 5 is outfitted for only 4 strap-ons mounted
in 2 opposite pairs. I would've designed the booster with 6
mounting pads, which would allow any balanced combo of
2,3,4, or 6.  It's a pure guess on my part that they didn't
want to rebuild the launch pad. The umbilical tower is a
bit too close to allow strap-ons on that side.

These days, strap-on motors are about as likely to have
inward canted nose cones as traditional concentric cones.
The Atlas 5 strap-ons have a cone style I've never seen
before. They are canted inward but the tip is full width
and flattened next to the main booster.
Wonder what they call it?

Such a great idea...

Such a great idea, yet even Estes doesn't seem to
want to build one. WTF?
In the 1997 Estes catalog there was a kit that never
reached production. It was a model of a fly-back booster
called Star Booster. It's based on descriptions in Buzz
Aldrin's sci-fi book; Encounter with Tiber. copyright 1996
Great book by the way. I dug it up for this post and then
read it all again.

In the book, the Star Booster is built by Boeing to take
a slide-in Zenit motor/tank assembly, built under license,
in the USA. One or two of them would be attached to a
core vehicle as a strap-on like an SRB is. After using up
it's propellants, the Star Booster would seperate from the
core vehicle then glides back to an automated runway
landing near the launch site. After each flight, the Zenit
is removed for seperate servicing. When the airframe is
ready, the next available Zenit gets installed for a quick
turn-around.
BTW; Boeing really is building licensed Zenits for the
Sea Launch commercial launch program.

The Estes Star Booster model was going to be 18" long,
with a 9.5" wingspan, parachute recovery, C motors only.
By the looks, I expected it to have a cast styrofoam
fuselage over a cardboard core tube, just like the large
Shuttle Orbiter kit of the same time period.

I've been looking at the Estes Star Booster recently  with
ideas for reproducing it. I have hot-wire foam cutting
equipment, so it's not a big stretch for me to model it at
the original size or larger.  The difficult part is that not
only do I want it to glide, I want it to glide with an unfair
chunk of reload casing inside it. In short, a realistic mission
as afly-back strap-on,  boosting a level 2 size rocket.  For
the sake of balance it needs a long thin motor case.  Either
a 29/360 or 38/480+ sized case, probably EX  and burning
sugar. The big trade-off [ya can't design anything without
trade-offs] is, to maintain balance, the bigger the  model,
the longer the motor case needs to be, and  vice-versa.   
Of course, it'll glide like a brick!

For more info see;  Fly-Back Boosters, Reprised
right here at ZZakk's Lab on Monday, May 18, 2009
These 2  posts [of 3 before long] were supposed to coincide
more closely, but I'm easily distracted.

The search for Little Joe III goes on.

Dick Stafford of Dick's Rocket Dungeon linked me to
this illustration he posted a couple years ago.
Is this the shape of Little Joe III?  
The search goes on.
It's certainly conjecture in the illustration since it shows
3 possible versions, and it shows a generic Apollo style
escape tower on the cone.
I would discount the 2 segment SRB version outright.
Even if ATK had already developed it, it would be
expensive, and offer only one performance  profile.
Version 2 with the 2 surplus Minuteman 1st stages
would be neat, and answers the above problems a
bit better.  Now version 3 with the GEM-60's, that's
the ticket!  Load'er up with however many strap-on's
needed for a particular test, and let'er rip!
Quantity discounts when ordering by the truckload.

BTW: Dick ran a stability sim on a 3"dia modroc of
the MLAS in my previous post.
Check it at: http://rocketdungeon.blogspot.com/

Shuttle Kvetch

Two possible versions of Shuttle-C.

Anyone who knows me, or who's read this blog, should
know that I love anything that flies, from paper
airplanes and match rockets to the Voyager probes
currently coasting in intersellar space.
I don't hate NASA, or the Shuttle. As those of us who
know anything about it know, the blame isn't all on
NASA's shoulders. For the sake of brevity [too late]
NASA will do for now.
Part of this first rant is going to spill onto the
International Space Station as well. More on the ISS
in the next installment.

I am mad at NASA for the way they screwed up the
shuttle program nearly every step of the way, until
it's admittedly too late to do anything about it.
What angers me most is that it's an obviously modular
system, and yet this is the most underutilized
feature of the system.

Ok class... who here knows that the original strap-on
boosters were supposed to be hybrid motors?
Huh, what happened? I admit I'm a hybrid proponent,
bigtime, but that floored me when I found out.
Hybrid motors are great because they are a lot simpler
and cheaper than liquid fuel boosters, and broadly
speaking, a LOT safer than liquid OR solid boosters. A
hybrid is vastly simplier than a bi-liquid system and
doesn't carry all that liquid kerosene or hydrogen that
makes such a pretty fireball. While a hybrid is more
complicated and heavier than an all solid rocket motor,
it's still safer because, if there's a problem, you can
shut them off.
Unfortumately, Hybrid tech was still very immature at
the time, it would still be a few years before AMROC
tested their big ones, and those weren't big enough.
However, there was no reason the shuttle couldn't fly
on solids initially, while Hybrid R&D was fast tracked.
Modular remember? The Hybrid strap-on boosters might've
been flying in time to avert the Challenger disaster.

After Challenger, NASA and Rockwell put heads together
and decided what improvements to make before building
a replacement orbiter. Bravo!
Of course having a large inventory of huge orbiter
components in storage helped speed construction. Endeavor
really is a B model orbiter. The other 3 orbiters received
the same upgrades wherever possible. After Endeavor flew,
and the fleet upgrades were finished, they should've sat
down AGAIN and planned an even better orbiter. Not just a
Challenger replacement, or 2nd Endeavor, but an eventual
fleet replacement, or supplement. Maybe a real departure
from the earlier orbiters, certainly more maintainable.
Modular!! As these new orbiters came on line, the older
units could be retired to museums. Read COLUMBIA!!!
If NASA had done this, the fleet would still be modern,
if not cutting edge, today. Hell, this still could've
[should've] been done when the SSTO initiative fell through.

At some time NASA had plans for Shuttle C. This would've
been an unmanned wingless cargo version. Little more than
a cargo bay with motors and guidance. Three reasons for
building it were to be able to fly heavier or larger loads
when needed, like station segments, and to reduce man hours
in space when not needed. Third would be hazardous payloads.
After Challenger, liquid fueled payload boosters were
outlawed for the shuttle for crew safety reasons, reducing
the types of missions STS could support.
Using Shuttle-C, station segments would be released in orbit
near the station, then crews would retrieve them for
assembly. Before the station was manned, they would've placed
2-3 modules in orbit, then sent up a manned orbiter, with
supplies and other components, to do assembly. Of course,
today the segments might be docked autonomously.
I always thought you could make even bigger station segments,
and attach the guidance/thruster package, and motor pack to
the segment couplers at each end, then fly it in place of an
orbiter. The flight components would be removed and saved,
eventually flying home in an orbiter cargo bay for reuse.
Of course either scenario assumes you want the STS system
involved in boosting the major station components anyway.
Read Saturn!!
The shuttle bay is dinky compared to a Skylab, and Skylab
was no strain on the Saturn V. I do not advocate resurrecting
the Saturns after all this time, they really are dinosaurs now.
I am saying we should never have fully retired them.
Incremental improvements have kept Atlas, Delta and Titan in
the air longer than Saturn's been on paper.

Plenty of folks like to second guess NASA and I'm genuinely
sorry to be lumped in with them. However I've had these opinions
for years, and even shared them with a few NASA engineers, who
happened to agree. Not just because I'm a size 2 1/2 biker
maniac either. It feels good to finally write and post this.


I'm sure this post could still use more editing, but if I held
onto it any longer it would turn into a book.

Fly-Back Boosters, Reprised

Last week, the USAF released study information concerning
lower cost, shorter lead time, access to space. I think
it's funny that the USAF was studying similar proposals
back in 1988. Amongst more familiar designs were the first
drawings I'd seen of fly-back booster systems. They add
a lot to the liftoff weight, but reusability is greatly
enhanced by not dipping the booster in salt water, like the
shuttle strap-ons. Other typical features include motor
commonality, where possible, and limited reusability.
An example would be; useing the motor[s] X number of
times in the fly-back booster, then transferring them to
the disposable core stage[s] for one last trip.

I am by no means bitching. I like these systems. However
it is somewhat amusing how history repeats itself, only at
twice the price now. There are no technical hurdles to
overcome now, and there really weren't any then either.
The Air Force isn't asking for peak performance. Larger
base capacity makes up for moderate performance coupled
with higher reliability. The difference between pro-stock
class and top-fuel dragsters or funny cars at the drag strip.

The big difference between the old fly-back system and the
new, is that with the old, it was primarily a very heavy lift
system [105,000-160,000 LB/LEO], while the new approach
is part of a fully rounded low to heavy capacity [peak 64.000
Lb/LEO] program. I like modular systems, especially when
there are enough modules to fully utilize the concept.

Stay tuned for some modular space system gripes, coming soon.