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RocketSlinger@SBCGlobal.net
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This
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Using the Astron Omega 1 Engine as a Compressor
and Using COPVs and Inflatables as Aircraft Structural Elements
Abstract
This
sub-page to www.ResearchGate.net is duplicated
at www.rocketslinger.com
also. Here, we briefly add corrections,
comments, and additions to what was described and discussed at https://www.researchgate.net/publication/365964188_Propulsion_Designs_Using_Novel_Nested_COPVs_and_the ,
with the full title
being “Propulsion Designs Using Novel Nested COPVs and the
Astron Omega 1 Engine”. This new
paper (here) then discusses how COPVs and inflatables could be used as
structural elements in selected parts of an airframe. COPVs could double up as not only structural
elements, but also as compressed-air sources for filling a
to-be-launched-from-the-aircraft orbital rocket, or other rocket, with chilled
or liquefied air or oxygen as a propellant and oxidizer. This could be called a “poor man’s
air-breathing rocket”, with the liquid air (or oxygen) having been harvested at
higher altitudes, reducing the weight of the aircraft (plus rocket cargo) at
take-off. If the aircraft is powered by
liquid hydrogen or liquid methane (for fueling otherwise-mostly-conventional
jet engines), then a large on-board super-chilled liquid hydrogen (or methane) tank
could serve as a “cold-source” for chilling compressed air (or oxygen). Would the added mass of required support gear
(to include or possibly to include air compressors, oxygen concentrators or
generators, regulators, valves, pipes and hoses, refrigerators, and
heat-exchange devices) be so large as to negate all of the takeoff-mass-savings
to be gained by filling the rocket in-flight with harvested liquid air or
oxygen? This hard-to-answer question
isn’t answered here. What is described
in a fair amount of detail, is this: What design
elements could be used in an aircraft, to dual-use COPVs, not only as
compressed-gas sources, but also, as structural elements, to make these tradeoffs
more attractive, here.
Much-lower-pressure
inflatables (“gas bags”) are also briefly discussed here as structural elements
for aircraft, as well as buildings. They
could also be used as parts of “adaptive structures”.
Contents
Preamble, and Bits of Boilerplate
Additions and Corrections to 1st COPVs Document
An Overview of “Log Cabins in the Sky”
The first (or preceding) document in this series is at https://www.researchgate.net/publication/365964188_Propulsion_Designs_Using_Novel_Nested_COPVs_and_the and at http://www.rocketslinger.com/COPVs/ (Same document, 2 locations)… So now, for the remainder of this document, I
can just hyper-link to 1st
COPVs Document when needed, and cut clutter. Hopefully, I will completely document all my
new ideas (and newly-found sources) on this 2nd go-around, but who
knows, I may need to write more later…
As before, as with
other sub-pages of www.rocketslinger.com, the intent here is to “defensively publish” propulsion-related
(and “misc.”) ideas, to make them available to everyone “for
free” (sometimes called “throwing it into the public domain”), and to prevent
“patent trolling” of (mostly) simple, basic ideas. Accordingly, currently-highly-implausible
design ideas (usually marked as such) are sometimes included, just in case they
ever become plausible, through radical new technology developments (often in
materials sciences).
Dear Reader, excuse me as I will often slip out of
stilted formal modes of writing here. I
have no boss or bosses to please with these “hobby” writings of mine, so I’ll
do it my way! I’ll often use a
more informal style from here on in, using “I”, “we”, “you”, etc. “We” is you and me. “You” are an engineer, manager, or other
party interested in what’s described here.
Let’s thwart the patent trolls, and get ON with it!
In descending order of importance (as ranked by Yours Truly, of
course), here are the major changes, corrections, and embellishments that I
would like to address here:
‘1) The 1st COPVs Document I wrote while
assuming that compressed air would be saved in a wing-mounted assembly, never
having even dreamed of the idea that COPVs could double up as structural
elements of an aircraft. See Figure #10
in said previous document for a sample of my previous thinking. Most of the document below will concern the
details about just HOW one might integrate COPVs (pressure vessels in general)
into the structure of an aircraft.
‘2) The 1st COPVs Document I wrote with
the idea that stored compressed (in-flight-harvested, chilled, possibly
liquefied) air would be used to propel the rocket-launching aircraft, the
entire aircraft, to a higher altitude (above the normal service ceiling) for
launching the rocket. I now think that
it makes MUCH more sense to add harvested air (or more-pure oxygen) TO THE
LAUNCHED ROCKET ONLY (or at least primarily), in the name of efficiency. More details (not many more, about this) are
discussed further below.
‘3) Before, I wasn’t
aware of “oxygen concentrators” and “oxygen generators”, or nitrogen-oxygen
separators. Now that I’ve learned about
such things, I suspect that it might make sense to add such things to the
“load” carried by the rocket-launching aircraft. These could be used to purify the oxygen (v/s
simply compressed air) to be loaded to the to-be-launched rocket, of
course. I (sadly) have no ideas to add,
here, about how to scale such devices up, for our needs here, while keeping
them (these devices) lightweight. I also
don’t know which is our best choice. So I’ll provide some links, and leave it at
that. See this grab-bag of links; some being
more relevant than others… https://www.atlascopco.com/en-us/compressors/products/oxygen-generators and https://eurasiantimes.com/equipped-with-on-the-go-oxygen-chinese-soldiers-look-to-outdo/ and https://www.aviationconsumer.com/industry-news/editorial/o2-concentrators-inogen-aviator-is-tops/ and https://en.wikipedia.org/wiki/Oxygen_concentrator and https://en.wikipedia.org/wiki/Nitrogen_generator#Membrane_technology . Note that as far as I know, you have only 3
basic choices: Oxygen “concentrators”,
oxygen “generators”, and nitrogen generators (this last one produces oxygen as
the main “by-product”).
‘4) Much of the previous document (1st COPVs Document of
course) concerned
the use of borosilicate “pressure domes” (or pressure arches) inside (or used
as a part of) pressure vessels, as a weight (mass) savings. I then examined the idea in more detail, and
tore it to shreds, as being a BAD idea!
All this while I was NOT aware of a NEW development in materials
science, which is described here: https://phys.org/news/2022-12-toughest-material-earth.html “Say hello to the toughest material on Earth” From there, "The toughness of
this material near liquid helium temperatures (20 Kelvin, -424 Fahrenheit) is
as high as 500 megapascals square root meters.”
This is an alloy made of chromium, cobalt, and nickel (CrCoNi). Also, “CrCoNi is a subset of a class of
metals called high entropy alloys (HEAs).” Perhaps HEAs of the future will serve as
NAKED (needing NO composite over-wrap?) pressure vessels? These would MUCH speed the exchange of
thermal energy across the walls of the pressure vessel!
I don’t off-hand know what
the strength or “toughness” of these HEAs might be at higher temperatures. However, these HEAs just MIGHT be able to
make the idea of the borosilicate “pressure domes” in the walls of a pressure
vessel become viable (as a costs savings for the presumably high costs of the
HEA materials). See Figure #4
(“flattened view”) of the 1st
COPVs Document as being (most likely) FAR more
viable than the other illustrated ideas concerning elongated “pressure arches”,
which would MUCH complicate the ends of the pressure vessel, as well as inducing
problems concerning HOW do we keep the whole thing from flying apart, from
internal pressures?!?
In
any case, if we kept the borosilicate pressure domes SMALL and widely spaced,
they just MIGHT serve well, in conjunction with HEAs or other new, strong, advanced
materials. This also assumes not using
ANY composite overwraps. Small
borosilicate “windows” could perhaps also have advantages (I have no clear
examples to offer) whereby optical observation of the pressure vessel’s
contents, from outside, via human eyeballs, cameras, or other optical
instruments, would be of value. I still
doubt that this whole idea is very practical.
But… Just now it is just a wee tad more well-documented!
‘5) Search the 1st COPVs Document for
the search-string “trash gas”, to see where I documented the idea of filling a
COPV with a combustible gas, purging it with an inert gas (like nitrogen), and
then filling it with pressurized
air. This is an inferior idea as
compared to what is documented here: https://steelheadcomposites.com/combined-propellant-pressurant-vessel-cppv-concept/ See the sliding piston here inside the
pressure tank, which can keep gasses strictly separated from one another. Fill one side with one kind of gas while
purging the other side! Yes, now we are
cooking with gas!
‘6) Search the 1st COPVs Document for
the search-string “mattress”, to see where I documented the idea of shaping
low-pressure airbags with internal restraints.
In more detail, the quote from there is: “If one is worried
about distortion in internal space-layers between the layers of our air-tight
bags (Kevlar or other-material-based), as we fill them, then think of your
mattress, with internal tie-back strings and button-dimples (buttons being
“washers”, if your will, like on bolts), holding layers in restraint,
preventing too much bulging.”
Well,
now I know more. I know of a source with
more details about this sort of thing! See
https://www.researchgate.net/publication/235213999_Air-Inflated_Fabric_Structures ; especially their heading “DROP-STITCHED FABRICs”, which
concerns the equivalent of the internal string inside your mattress, tied to
buttons (“washers”, load distributors) on the outsides of your mattress…
The rest of this (above) document is somewhat relevant here,
or is good “FYI” material. I suspect
that relying much on this kind of assembly for aircraft structural material
isn’t viable, for concerns about strength and reliability. More on this later (further below). However, it (the above) says “Fabric air beams
are examples of air-inflated structural elements that are capable of
supporting a variety of loads similar to conventional beams. To date, seamless
air beams have been constructed using continuous manufacturing methods that
have produced diameters ranging
up to 42 inches.”“
Also it says… “The air beam has a cylindrical
cross-section and its length can be configured to a straight or curved shape
such as an arch.” Also… “Woven structures
are generally designed to operate at pressures up to 20 psi while triaxial
braided and axial
strap-reinforced braided
structures are generally capable of higher inflation pressures.”
Before diving into the details of HOW we could do these things,
let’s go through a reasonably long summary of where we’re going to go to. Let’s think of COPVs (and gasbags) as long,
cylindrical “logs”… Now we’ll build ourselves (at least partially) a flying log
cabin out of these logs! Much of the
focus (further below) will detail how we join the “logs” together. In older, more primitive days, mosses,
lichens, and mud (whatever was at hand) were used for “chinking” the logs. See https://www.weatherall.com/blogs/log-home-blog/the-history-of-chinking ... OK, let’s not get
side-tracked! Much further below, we’ll
address “chinking” (more like mounting or securing, or mortaring) our COPV-logs
together.
Our rocket-launching
aircraft may launch its rocket(s) in one or more styles. Dropped off of the wing-bottom of a single
fuselage like “Cosmic Girl”, or off of the common wing-bottom between two
fuselages of a “catamaran of the sky” such as the Stratolauncher, AKA ”Roc”, or
out of the rear (in the style of a C5 Galaxy or a C130), or out of the bottom
like a bomber (B52, for example). These
choices are somewhat relevant to just WHERE we might like to build PARTS OF the
aircraft out of our COPV-logs.
Where would using COPV
“logs” as part of the aircraft structure clearly be a BAD idea? The entire undercarriage,
for the entire length of the aircraft.
The nose section (cockpit etc.). The tail section and
control surfaces there. The wings and their support structures. These are all OUT! If the wings are mounted low to the fuselage,
we MIGHT safely use our “logs” for the walls and the roof (ceiling) of the
fuselage in that (wings-mounting) area.
If the wings are mounted HIGH to the fuselage, then COPV-logs should be
excluded around the entire fuselage (in a ring-shape) around that entire area.
I don’t know just HOW MUCH
COPV storage space might be needed, for this entire set of ideas to be
practical (or if it is even practical to begin with). I suspect that we would NOT need to press
into the margins, but an available margin MIGHT be between the strong
undercarriage, and a flat internal floor of a working space, say, 1/3 or so up
from the bottom of the cylindrical fuselage-cavity. Call this the “sub-floor” (or “below deck”
area), perhaps. Depending on the
internal load to be carried, I think this is generally a bad idea to locate
load-carrying COPVs here. So this leaves
us with large sections of the walls and ceiling (roof) of the fuselage, where
we could double-use COPVs as structural “logs”.
I suspect that this should be plenty enough space!
A log
cabin is probably a bad analogy, but I couldn’t pass it up! Our COPV-logs might be better regarded as the
siding, and the drywalls, of a “balloon frame” building. The siding and drywalls carry SOME, but not
ALL, of the structural loads. A wooden frame
carries the rest. Similarly, for what I
describe here, there should be metal (aluminum most likely) periodically
interspersed (in hoop-shapes or semi-circles) between (or among, supporting)
the COPV-logs, to add extra strength and rigidity. These hoops should be located such as to span
from undercarriage up through one wall, across the ceiling, down the other
wall, and then back down (firmly mounted) to the undercarriage. Alternately put, hoops prevent our “logs”
from rolling or sliding out of place.
This
below drawing may not be needed for most readers, but is provided for clarity
anyway.
Figure
#1
So
that’s a preview or over-view of our flying log cabin structure, with the fine
details reserved for further below. What
is the “big picture” of why we’re doing this?
Where are we going with this?
The 1st COPVs Document clarifies
a lot of this, but not all of it. Some
of what wasn’t made clear there is spelled out briefly in the first few items
under “additions and
corrections” above. Another item which definitely deserves a few
more words is this: The “Sabre” vehicle
under development can be regarded as a “rich man’s air-breathing hybrid
vehicle”, while we’re (here) trying to develop a “poor man’s air-breathing
hybrid vehicle”. Here is a repeat from
my last paper:
Concerning
“Reaction
Engine’s Synergetic Air Breathing Rocket Engine (SABRE)”, we have this: https://physicsworld.com/a/air-breathing-rocket-engines-the-future-of-space-flight/ . From there, “The precooler can cool high mass-flow
airstreams from temperatures above 1000 °C to ambient in less than
50 milliseconds, within a compact and low-weight design. It is formed from
over 42 km of tubing, the walls of which are thinner than a human hair –
thereby providing an enormous area for heat-transfer between the air and
cooling medium.”
What I
would now like to plainly state is this: I’ve never
been able to verify this at any web site, but the Sabre space-plane MUST be
getting its “cooling power” (transferred via helium) from its large tankful of
super-cooled liquid hydrogen fuel. I see
NO other possible choice! So for our
“poor man’s version” of this, the jet engines of the (relatively) slow-speed airframe
that launches the rocket, should be modified (or designed) to run on hydrogen
or methane. See https://www.reuters.com/business/aerospace-defense/rolls-royce-successfully-tests-hydrogen-powered-jet-engine-2022-11-28/ and https://www.dgc.dk/sites/default/files/2021-06/Liquid_methane_aircraft2020.pdf
. This large fuel tank full of
bitter-cold liquid fuel could then power the entire aircraft, while ALSO
serving (as this fuel warms up before being used) as a “cold source” (heat
sink) for super-cooling in-flight-harvested compressed air (or oxygen).
I
don’t have the expertise required, to discuss details about how this heat transfer
(from compressed air to being-warmed liquid fuel) would best work. Nor do I want to research these details… It
isn’t my focus here. It is just a useful
ingredient to help make the entire idea here become possibly-practical. If “Reaction Engines” Sabre-jet can make it
work in-flight, we can make a lower-tech version of this work! Yes?
Enough said about that!
The
same large tank of liquid hydrogen or methane can also be used to power a
(fairly large?) number of on-board Astron Omega 1 engines (for compressing air
and-or other gases, generating electrical power, and running an assortment of
“whatever” other gear). The 1st COPVs Document
describes in some detail, how one would best create a good high-performance compressor
by modifying the Omega 1 design… Search
for “Omega 13” in that document, and NOTE that this is my VERY cultured
reference to the movie Galaxy Quest!
The
Omega 1 is supposed to be able to run at “high altitudes”, but I’ve never been
able to ascertain just HOW high such “high altitudes” might be. Some varieties of oxygen-nitrogen separators
are also altitude-limited. The bulk of
the “cargo bay” inside our aircraft will be next to impossible to securely
pressurized with our “log cabin architecture” (I am near certain of that), and
so, SOME sub-sections will best be pressurized.
This may be as simple as a large rigid door (for getting gear and
possibly also people in and out), or double doors and an airlock, perhaps,
even, for holding in a fairly low pressure, inside something not much fancier
than a pressurized kids’ “bouncy house”, with a high-volume low-pressure
electric air pump for keeping it inflated.
***IF*** people are needed in-flight, inside the cargo bay, for
attending to “persnickety” gear and-or the rocket and its cargo, they could be
restricted to pressurized areas, and-or, wear oxygen masks, or even pressure
suits. If any fuel-burning engines are
used inside these pressurized areas (Astron engines for example), we’ll clearly
have to constantly be bringing in fresh, new air, for getting rid of waste heat
and waste gasses, as well as bringing in oxygen.
Getting
back to the super-chilled tank(s) of liquid hydrogen or methane, now, please
note that we know for sure that the Astron Omega 1 engines can run on these
kinds of fuels (presumably after turning them to gasses!). So, even without cutting-edge new jet engines
to burn such (gasified) liquid fuels, we could at least carry SOME smaller amounts
of super-chilled liquid fuels, to serve for SOME of our heat-sinking needs,
while fueling the Aston engines. If the
cutting-edge new jet engines aren’t affordable, or spend too much time in
development, we’ll need, perhaps, to rely on conventional petrol-based fuels
instead (JP-4, JP-8), for the jet engines.
We now have no giant heat sink any more, and emphasis would shift to
on-board refrigeration, for cooling compressed, harvested gasses. For links concerning refrigeration, go
towards the bottom of the section (here in this paper) at the “Adaptive Structures” section.
First, we’ll speculate as to what the optimum dimensions of the
COPV “logs” might be, and then we’ll discuss how to secure them together. We’ll consider conventional (existing as of
now) styles of COPVs, first. Then we’ll
consider customizing the COPV designs, primarily for our structural purposes. That’s a quick preview.
In my
research, the longest COPV design that I’ve seen is at https://static1.squarespace.com/static/5ca8e523ebfc7fd95c0c4fc1/t/5fb2cbbe44ad9171878b4010/1605553092670/COPV_Design_Report.pdf , where figure
4.18 (page 93) shows an 18-foot-long COPV design, but according to my reading
of this source, it has never been built…
For reference, https://steelheadcomposites.com/composite-pressure-vessels/ offers diameters
up to 17 inches, and lengths up to 102 inches = 8.5 feet.
And https://astforgetech.com/composite-overwrapped-pressure-vessels-copv-ultimate-guide/ says that “AST can manufacture forge
and spin tooling for any diameter and lengths of up to 120 inches.” That’s 10 feet!!!! For type 3… From there… Type 3
COPV… ”COPVs with advanced fibers
and metal liners are classified as type 3 COPV’s. Type 3 COPV’s from Advanced Structural
Technologies, Inc (AST), in particular, feature a thin
and lightweight 6061 aluminum liner, fully overwrapped with carbon fiber
composite. The composite materials carry the structural loads.” (Emphasis mine). Also… “AST
specializes in high capacity, high-pressure storage solutions up to 27” (69 cm)
diameter and 120” (305 cm) in length.”
“Winging it”, then, for our design purposes (compromising
between many factors), we might settle on COPVs 10 feet long, or slightly
less. As possible “fillers” (if we want
to stack or over-lay them in an interleaved order like bricks), we might also
want to have some of them be “half-bricks” at 5 feet long, or slightly
less. 27 inches (a tad over 2 feet)
sounds like TOO thick for an aircraft wall!
Maybe we should settle for 12 to 18 inches or so, for the diameters of
our COPV “logs” here, IMHO (In My Humble Opinion).
The
above idea concerning an interleaved or stacked brick-like arrangement may or
may not be valid (optimal), depending on (possibly among other factors) how the
“bricks” or “logs” interface to the metal “hoops”, as have been previously
mentioned. This isn’t an avenue which I
care to delve into, in detail.
As far
as is concerned, HOW do we secure the COPVs, and fasten them to one
another? We do NOT want to rip or tear
the composite over-wraps, so we must proceed with utmost caution! I am thinking that we should tightly jacket
them with a harness. Think of a harness
in the style of fishnet stockings, but with far bigger gaps or voids… Or like “chicken wire”, with far larger
voids. The jackets (harnesses) could be
made of any suitable type of rope or cables.
If metallic cables are used, they would most certainly have to be coated
with plastics or artificial rubber, to prevent harsh surfaces from abrading the
surfaces of the COPVs. In my mind, the
BEST option would be to fashion the harnesses from tightly stretched flat
artificial rubber “bungee cord”-type material, similar to the following type: https://www.uline.com/Product/Detail/H-3601/Cargo-Control/Rubber-Tarp-Straps-15?pricode=WA9585&gadtype=pla&id=H-3601
. Using such a harness will be of great
help in holding the COPVs in place, without adding too much mass, and without
adding too much insulation, either. Too
much insulation will prevent the COPV from shedding the heat generated by
freshly-compressed air, or compressed gasses in general.
Shock
and vibrations will “jostle” our COPVs!
We’ll want to prevent them from shifting around, and from spinning
(rolling) around. Cross-ties of rope
(from one COPV and harness) to another will help, as will ropes tied to the
metal “hoops” as well (as were discussed further above). I am thinking ROPES here, not nuts and bolts,
or other harsh, aggressive, metallic fasteners, in order to NOT abrade the
COPVs, of course.
This
will appear “jury rigged” or “unprofessional”, but who cares, or SHOULD care,
so long as it is FUNCTIONAL? I must now
momentarily digress, and tell a “war story” on myself. As an EE test engineer, I often built test
equipment that, um, didn’t look too pretty, at times. As in, I would resort to the use of “epoxy
putty”, such as “Gapoxio”; see http://aplusbputty.com/ , for
securing parts together, in an emergency.
When accused of being “unprofessional”, I would simply ask, “Is ANY
customer EVER going to say, ‘Well, I like the costs, performance, reliability,
and even the appearance of this computer or other electronic gear, here, but I
will NOT buy it, because I hear that it was tested on some UGLY looking test
equipment’? Methinks NOT!” (End of digression.)
Under
severe or prolonged shock and vibration, COPVs might STILL shift around, or
spin, inside their harnesses. Tests
and-or computer simulations might best be used to clarify these issues. ONE possible option might be to (very
cautiously) attach (glue) a “glue wart” at at least one carefully selected
location on the COPV, with holes in the “glue wart”, which can then be tied to
the harness.
A “glue
wart” could be fashioned as follows: A cup-like hollow container (of any shape)
made of artificial rubber (or similar non-aggressive,soft material) has voids in it, through which small
pipes span from wall to wall, through the walls. Pipes could be made of thin aluminum, or
moderately-heat-tolerant plastic, because the pipes will shortly be subjected
to the (self-heating or exothermic) heat of curing epoxy “potting
compound”. Keep on reading…
This
“glue wart” is now filled with epoxy “potting compound”, to be slightly
over-flowing (being thick, the compound will hold a good “meniscus”). See https://www.henkel-adhesives.com/us/en/products/encapsulants/potting-compounds.html
... To save a few dollars, the potting
compound could be “cut” (diluted) using plastic pellets (AKA “nurdles”), in the
same style as concrete is “cut” using gravel or rocks. The near-overflowing glue meniscus (ideally
not TOO polluted at the top layer, with TOO many “nurdles”) is now held
upright, while mated to the (coming down from above) COPV, for over-night (or at
least multi-hour) curing. After the
curing process, the protruding pipes are cut off, and “reamed out” (especially
if metal pipes are used) to prevent harsh edges from abrading our ropes (or
strings). Many “glue wart” pipes at many
angles will allow us many choices on how to tie the “glue-wart” to the harness.
This
(gluing the glue-wart to the COPV) may or may not be optimal. Tests and-or computer simulations should
illuminate this matter. If gluing is NOT
optimal, there’s another simple variation of this idea available to us: Form a (or form several per COPV) “glue-wart(s)”-like
soft-surfaced conformal “warts” that are NOT glued into place, but are simply
held tightly in place by the tightly-stretched (rubbery) harness. My personal bet is that this is probably the
best choice (use no glue). Solid-state
lubrication power (such as chalk), or other lubrication, between so-called
“glue warts” and the COPV surface may be desirable, to prevent abrasion of the
COPV surface.
Such
“glue warts” (with or without glue bonds to the surfaces of the COPVs), with
holes through them for tying them to the harness, can be tied, mortar-style, to
form flat surfaces between one COPV “log” and another. “Glue warts” could ALSO be tied to rigid
members spanning from one COPV to another, to help prevent “log-spinning”
(COPV-spinning). It’s about time now for
another drawing, then…
Figure
#2
The
anti-spin cross-bar could simply be rope-tied to the harnesses at both ends,
and I’m not sure if they’d actually-really be needed, or not. Tests and simulations should help clarify
such matters, of course. If the COPVs
spinning inside of their harnesses is a REALLY serious
problem, then the cross-bars could be secured to glued-down “glue warts” at
both ends, for quite firmly solving the problem. This step might risk damaging the over-wrap
if the airframe takes a severe jolt, though.
The
harness should be installed with tension in the web of ropes (or, preferred in
my mind, rubbery flat “bungee cords”), to constantly squeeze the COPVs. However, this “squeeze force” should leave
plenty of safety margin for NOT crushing the COPV when the COPV is weakest,
which is when the COPV is empty.
The
tied-to-the-harness “glue warts” (whether or not they are actually glued in
place) between the COPV “logs” (in the place of joining mortar, if you will)
are, in my mind at least, vitally essential.
They spread the loads at these contact points, to include loads arising
from shocks and vibrations (jostling of the entire airframe). As previously mentioned, they may or may not
be glued to the COPVs (I suspect it is best to NOT glue them). I also suspect that they should run the
entire lengths of the COPVs. ALSO NOTE
that there might be troubles with the COPVs sliding end-for-end within the
harness. An appropriate “fix” for this
(not illustrated) is to place a doughnut shape (torus) at the “shoulders”
(ends) of the COPVs, like a horse’s collar, with the harness tension holding
each “collar” in place. These
end-collars should be made of pliable materials, of course, like what I’ve been
calling “glue-warts” here.
Some
fraction of the COPVs could be replaced by identically-sized-and-shaped
low-pressure inflated airbags. Doing this might help prevent a sort of “dominoes effect”, whereby
too many too-heavy and too-hard COPVs ALL slosh around together (with
accumulated “sloshing” forces) if or when the airframe takes a severe jolt. Interspersing a few softer and lighter
inflated airbags (as “dampers” of you will) may, for this reason, be a good idea. Again, test and-or simulations should help to
illuminate this matter.
What
materials might be used for such low-pressure airbags? I now repeat a short segment from my previous
paper: Sierra
Nevada makes inflatable habitats; see https://www.space.com/sierra-nevada-inflatable-habitat-moon-gateway.html , which says “The
outside of the prototype LIFE habitat is comprised of a urethane pressure bladder,
a nylon liner and a woven Vectran fabric restraint
layer.”
It is
now time to move on, to making some modifications to standard off-the-shelf
designs of COPVs, to examine what sort of design modifications we’d like to
make, in order to optimize the dual-use ideas here (storing compressed gasses,
while also using the COPVs as structural elements). Note that so far, in my descriptions here,
I’ve not addressed how we might (most likely, or most often, end-on-end) “gang
together” standard COPVs, into one common gas-storage space. High-pressure hoses (and standard tank-ports)
should do fine, I suppose, for linking standard COPVs together. “The Google Which Knows All Things” can help
you with high-pressure hoses, so I’ll not even bother to provide links about
these.
Now
suppose that we want to join COPVs end-on-end for both structural and gas-storage
purposes, at the one and the same time, while not adding much mass. See https://steelheadcomposites.com/hydrogen-storage/ , which shows
“…large-port enables variable fittings and in-tank regulators” The port end here (in this case) of a
COPV is a substantial size-fraction of the COPV diameter. It’s not much of a stretch of the imagination
to imagine that an outer thread could be added to the large port there, and
that COPVs could then be coupled end-to-end, to join the COPVs into a common
tank, both structurally and for holding their contents in common. Male threaded parts on the tank-ends, females
on the couplers… One could even use
reverse thread on half of the ends of both the males (tanks) and females
(couplers) as an option to avoid the need for spinning the entire tanks while
assembling them end-to-end. Ports could
be simplified to simply be openings to permit fairly high-volume gas-flow, from
one tank to the next. If the female
couplers are made extra-long (with a gap between the threads), a port (or ports
plural) could be added there in the middle of the coupler, for interfacing to high-pressure
hoses, as well. The female-female
coupling could be turned into a “T” joint (fitting),
that is.
If shock and
vibration is too dangerous for mechanically stressing this mostly-rigid
threaded joint between the tanks, then the mechanical load could be spread out
a bit. I can provide drawings if needed
(email me at RocketSlinger@SBCGlobal.net if needed), but I
am hoping that a verbal description here will be enough. Create, in your mind’s eye, a
conforming-shaped doughnut (torus) with soft padded surfaces where it contacts
the COPVs, and spans the gap between tanks.
The hole in the torus accommodates the male and female threads, and the
female coupler. The torus’s OD (Outer
Diameter) should NOT exceed the diameters of the tanks being joined. Now cut the torus in half, with the cut-line
being parallel to the coupler length.
Shave off maybe1/2 inch or 1 inch of torus-material along the cut-line,
to make sure we have some split-torus compression space available. Deburr and round the edges of the cut, of
course. Or just build the two halves
separately, and don’t make a cut!
To fasten the
(presumably light-weight but strong) split torus to the coupled tank-ends, we
could ‘A) most simply leave some grooves in the outer surfaces of the torus-halves
for tightly wrapping the halves together with rope or cable. Simple!
Or we could ‘B)
insert (firmly mount) metal pipe in one half of the torus, and inside-threaded
pipe in the other. Bolt the halves together! Other options may be possible.
The assembled
torus (if tightly installed) now spreads mechanical loading more widely across
the tank-ends, reducing mechanical stresses on the threaded tanks-ends. With such port-ends on both ends of the
tanks, as many tanks as are needed, could all be strung together, both for
gas-contents and for structural purposes.
The 1st COPVs Document ,
at Figure #8, shows a drawing which, for your convenience, will now be repeated
as Figure #3 here:
Figure
#3
One
could mentally make minor modifications to the above, to understand my next set
of ideas here below (as before, please email me at RocketSlinger@SBCGlobal.net if needed, for
more drawings or details). The only
differences between what I now propose, and the just-now-described slight
modifications to the “large-port” tanks at https://steelheadcomposites.com/hydrogen-storage/ , is that I would
propose the use of steel only at the port-ends of the tanks, and aluminum
liners along the lengths of the rest of the tanks (as a weight or mass
savings). Also, we could get even larger
ports, most likely, and do away with the half-tori for mechanical
load-spreading at the port-ends. Total
maximum gas-pressures retained may take a hit, here, but the trade-offs might
be worth it. See more (text) details
around Figure #8 in the 1st COPVs Document
concerning joining aluminum and steel, and leak-proofing the tank (especially
around areas where steel and aluminum join together), in this context. Those details won’t be repeated here.
In your mind’s eye, take the above
drawing and throw away all but the innermost of the “nested tanks” (keep the
bottom of the drawing, and discard the top).
Take the “inner threads” and scoot them inwards
(closer to one another) on the innermost, remaining tank, to well inside the OD
of this inner tank. Round
the steel shoulders of this remaining tank, bringing the green (over-wrap) around these tank-shoulders,
right up to the steel threads.
This will much improve our ability to properly over-wrap this (above-shown)
assembly, to include diagonal wraps. The
brown
(presumably steel) port-end might (perhaps best) be “married to” (be part of
the same structure) as what is shown above in purple
above, as a “steel collar”. This would
simplify our construction, eliminating some bolts. Make the port-hole significantly larger than
what is shown. That’s it!
Now we can use these hybrid
steel-and-aluminum COPV tanks, strung together in a manner nearly identical to
what I previously described as the use of slight modifications to the “wide
port” steelheadcomposites COPVs. Our gas pressures contained MIGHT not be as quite
as high as the more-off-the-shelf design, but we’d likely be able to dispense
with the “split torus” mechanical load-spreaders.
Just
for reference, sticking to standard threads might be best. See https://en.wikipedia.org/wiki/National_pipe_thread , which goes up
to 24 inches. As mentioned before,
though, making half of the threads be reversed threads offers some advantages,
in avoiding the need for spinning the entire tanks, when stringing them
together.
So
then I’m envisioning that the inside surface of our ugly-looking, “kludged”
assembly of tied-together COPVs (and possibly airbags as well) “logs”, plus
metal hoops, will remain naked and ugly.
There’s no need to “prettify them up” with cover-panels, which will do
nothing functionally for us, other than get in the way of thermal exchanges,
and block access for gas-flow (pipes and-or hoses) and structural-maintenance
purposes. Let them remain naked, at
least on the inside! This is highly
similar to common practice in civilian airliners v/s military aircraft. Airlines use cover-panels to keep things
looking “pretty”, and to keep nosey passengers out of the plumbing and
wiring. Military aircraft generally
don’t bother with such panels.
Now
how about on the OUTSIDE, where the COPVs (and possibly airbags as well) will
be exposed to what, 500, 600 mph of airflow speeds? This may be dangerous! Just HOW dangerous, I don’t know! HOW MUCH do we need to shelter these elements
from the relative winds? Versus, how
much should they be EXPOSED to the winds, for cooling freshly-compressed air or
oxygen? I just don’t know, and I am
humble enough to admit it! (I am also
PROUD of my utterly astounding humility, but let’s not go there right now).
For
starters, maybe we could start with high-tech, tightly stretched fabric coverings,
appropriately perforated perhaps, in a compromise between cooling airflow v/s
protecting the COPVs from excessive high-speed winds, such as (repeated from
earlier on), see https://www.space.com/sierra-nevada-inflatable-habitat-moon-gateway.html , which says “The
outside of the prototype LIFE habitat is comprised of a urethane pressure
bladder, a nylon liner and a woven Vectran fabric
restraint layer.”
We wouldn’t need the pressure-bladder urethane material, but the rest
might be useful.
Now what about covering this fabric
with airflow-friction reducing materials?
It seems to me that biological evolution has pre-solved these kinds of
problems for us, at least in water! See,
as possibly a bit relevant, the following grab-bag of links: Low-friction dolphin skin? https://www.delftex.com/ is vaguely
relevant but not of much help. https://www.researchgate.net/project/Dolphin-skin-and-hydrodynamics-of-dolphins is certainly
helpful. So is https://www.sciencedaily.com/releases/2004/05/040517072242.htm .
However,
put “sharks” and-or “airplanes” into your search-strings, and THEN you can
holler, “Bingo!”.
See low-friction airplane surfaces at https://cen.acs.org/business/specialty-chemicals/BASFs-AeroShark-low-friction-film/100/i8 for “BASF AeroShark”, and then see https://www.basf.com/global/en/media/news-releases/2021/05/p-21-204.html . THIS is the type of surface material that we
might want to use in our (perforated?) outside coverings for our “flying log
cabin”!
Another
possibility is that the COPVs (and possibly airbags) could be covered, starting
from the rear of these areas, with overlapping (rope-attached or string-attached?)
fish-scale-like, light-weight, but somewhat air-permeable scales, made of
lightweight materials, and then covered with this “BASF AeroShark”
material. An alternate name for our “log
cabins in the sky” might then be the “flying fish”! Goodbye (for now), and thanks for all of the
fish!
Now to conclude this section, “for grins”, I will list
inferior ideas that I collected along the way.
Perhaps a reader or two might want to pursue avenues that I have
dropped? Possibly for
distantly related purposes? One
idea was to encase (entirely or partially) our COPVs within rubber tires
(creating a “tugboat in the sky”?), or similar low-pressure inflatables. This, IMHO, would be too heavy, too
expensive, and-or, add too much thermal insulation to an already-bad situation,
as far as is concerned, the ability of COPVs to shed the heat of recently-compressed
gasses. However, an interesting link
that I scared up is here: https://www.heuver.com/knowledge/otr/tyre-pressure-and-solid-rubber-tyres says that 9.0 bar is attainable! In truly giant tires, that is, when carrying
a load. Unloaded giant tires might carry
significantly higher pressures, safely.
But I can NOT see any kind of good “fit” for this, for the uses
discussed here.
Let’s now see how this might all come together, for an
operational flight. Some elements here
(such as throwing relatively pure oxygen into the jet engines to shorten the
take-off) are repeated from the 1st COPVs Document … But let’s get ON with it!
We’re
sitting on the runway. Our COPVs are
mostly filled with high-pressure cooled air and-or high-pressure cooled oxygen,
which has cooled down while sitting in the tanks (COPVs), or been forcibly
cooled. Our to-be-launched rocket(s)
is-are loaded and ready to go, minus compressed (perhaps liquefied) air or
compressed (perhaps liquefied) oxygen, to be harvested and loaded onto the rocket(s)
later, at higher altitudes. Given
clearance, we taxi down the runway and (optionally) dump some oxygen into our
jet engines, to speed the takeoff (and shorten the needed runway). There are lots of optional features
here… Mix and match! We take off and gain altitude, perhaps
hastening our departure using some of our compressed air and-or oxygen.
En route to an elevated rocket(s)-launching altitude
and location (in better weather and-or closer to the equator), we replenish the
compressed (perhaps liquefied) air and-or oxygen that we’ve expended during
take-off and ascent. The gasses pre-cool
a bit first, in our expansive fuselage-walls COPVs storage spaces, after being
compressed (most likely by our on-board modified Astron engines, for
example). Then the cooled, compressed
gasses (air or oxygen) are (optionally) liquefied by thermal exchange with the
aircraft’s super-cold supply of being-burned liquid hydrogen or liquid methane
fuel. The liquefied air or oxygen is
loaded onto the to-be-launched rocket(s).
Optionally, right before the rocket(s) are launched, the launcher
aircraft might burn some of its stored, compressed (perhaps liquefied) air or
oxygen, to exceed its normal service ceiling.
Finally, the rocket(s) is (are) launched.
Note
that pressurized vessels are stronger.
For a simple illustrative common-sense mental exercise, just think…
Would you rather drive on flat tires, or on inflated tires? So in that vein, presumably
rocket(s)-launching time (merely dropping the rocket(s) and then letting them
light themselves up) is presumably a LOT less stressful to the aircraft, than
taking off and landing. We can surely afford
to expend a lot of COPV contents (and thus weaken the COPVs) at the top of the
flight profile, and then re-pressurize (re-strengthen)
the COPVs during descent. Land with
pressurized (strong, but hot) COPVs, let them cool back down, refuel and reload
the aircraft, rest, test all systems, replace, repair, and refurbish, and “rinse
and repeat”! Done!
Just
suppose that our rocket(s)-launching aircraft (through an emergency need, pilot
error, or sheer accident or bad luck) finds itself in a horrible windstorm,
and-or severe wind shear. Automated
systems (to include structurally-embedded strain gauges, for example) could
even detect such things, to be computer-automated, and blended with pilot
commands. In an emergency, rather than
losing the aircraft, the inflated structural airbags (if used as interspersed
with COPVs) could be rapidly deflated.
This would allow airflow to flow THROUGH the body of the aircraft,
decreasing structural loads to the body of the aircraft. Areas (of the aircraft body) subjected to
such semi-sacrificial, aircraft-saving uses could be carefully selected to
minimize damage (especially water damage in wet weather) to the contents of the
aircraft. But…
Rather wet than damaged or destroyed! (I
just hope that the lawyers will permit this!).
In
passing, let me note that similarly, “semi-sacrificial floors” could be added
to buildings. Rather than having the
building be toppled in (for example) a hurricane, vent (deflate) some
structural airbags! The
“semi-sacrificial floors” could be thoroughly waterproofed (floors and ceilings
both), and contain (hopefully water-protected) infrastructure, such as pumps,
air handlers, water heaters, air conditioning units, heat pumps, and so
forth. Such floors COULD even contain
low-cost, lightweight, but high-capacity pressurized-air COPVs for energy
storage! In passing, please note that
some of the Old-Order Amish (in workshops to include wood-working shops) use
high-pressure air, instead of electricity, as a power source for power tools,
for religious and-or cultural reasons.
High-pressure air, then, is sometimes called “Amish electricity”. See https://artdiamondblog.com/archives/2013/06/_source_kelly_k_18.html for
example. Long live compressed air power!
Getting
back to our semi-sacrificial sky-scraper-floors, and their contents possibly
containing compressed-air
energy storage, the following is HIGHLY relevant: See, in the popular press, https://www.pv-magazine.com/2023/01/06/storing-solar-power-with-compressed-air-storage-air-conditioning/ , which then links to https://www.nature.com/articles/s41598-022-26666-1 , “Cooling potential for hot climates by utilizing thermal
management of compressed air energy storage systems” , which is also accessible
at https://www.researchgate.net/publication/366470877_Cooling_potential_for_hot_climates_by_utilizing_thermal_management_of_compressed_air_energy_storage_systems . When emptying out the compressed air storage,
for energy recovery, the cooling power of the expanding gases could be used to
assist air conditioning, is the fairly straightforward idea here.
Here’s
a concluding grab-bag of perhaps-vaguely relevant links. Note that some of them have to do with
cooling (refrigeration), which could be relevant to our possible in-flight
needs for cooling and-or liquefying air and-or oxygen. Precisely HOW would we use such things? I really don’t know!
Such
links are at https://www.researchgate.net/publication/245529080_Some_issues_on_the_design_and_analysis_of_pneumatic_structures and https://www.researchgate.net/publication/286173742_Comparative_parametric_modelling_of_composite_tubes_and_composite_overwrapped_pressure_vessels and https://www.inceptivemind.com/new-more-environmentally-friendly-air-conditioner-uses-solid-refrigerants/25926/#:~:text=One%20class%20of%20solid%20refrigerants,%2Dto%2Dsolid%20phase%20change. Also https://www.sciencedaily.com/releases/2022/08/220822130431.htm Note that many of these “barocaloric” materials work at ridiculously high pressures. That means that they’re off limits for our
practical uses. For example, see https://www.researchgate.net/publication/332510202_Colossal_barocaloric_effects_near_room_temperature_in_plastic_crystals_of_neopentylglycol 0.25 GPa
here… GPa convert to bar
= 2,500 bar is too high for us!
See https://www.unitconverters.net/pressure/gigapascal-to-bar.htm for a handy
converter. The root page here (https://www.unitconverters.net ) links to MANY
handy converters, by the way.
Non-conventional refrigerators have
(for some time now) been able to use sound waves. See https://phys.org/news/2016-12-refrigerator-multistage.html , which then links
to “Design and experimental
verification of a cascade traveling-wave thermoacoustic
amplifier”, which can be found at https://www.researchgate.net/publication/303598825_Design_and_experimental_verification_of_a_cascade_traveling-wave_thermoacoustic_amplifier .
See
in the popular press, https://www.sciencealert.com/scientists-just-invented-an-entirely-new-way-to-refrigerate-things and
https://hackaday.com/2023/01/06/salty-refrigeration-is-friendly-to-the-environment/ ,
which lead to https://www.science.org/doi/10.1126/science.ade1696 , “Ionocaloric
refrigeration cycle” Or see https://www.researchgate.net/publication/366529710_Ionocaloric_refrigeration_cycle for the same...
Also
(getting back away from refrigeration now) see https://www.researchgate.net/publication/304424721_Smart_Composite_Overwrapped_Pressure_Vessel_-_Integrated_Structural_Health_Monitoring_System_to_Meet_Space_Exploration_and_International_Space_Station_Mission_Assurance_Needs and https://www.researchgate.net/publication/353879171_New_Advances_and_Future_Possibilities_in_Forming_Technology_of_Hybrid_Metal-Polymer_Composites_Used_in_Aerospace_Applications/figures?lo=1 … For grins!
Also
“for grins”, see an explosion test at https://www.space.com/lockheed-martin-space-habitat-explodes-video . “Habitat
bursts violently at 285 per square- inch (psi), or more than six times the max
operating pressure.” This means that it
is rated for 47 psi or so, then…
I’ll
be the first to admit that I’m a moderately well-self-educated non-expert, at
best, here, concerning this topic.
However, in the usual interests of thwarting “patent trolls” who might
otherwise patent perhaps-obvious ideas, here goes! This concerns the rocket engine(s) for
mid-air-launched rockets, more specifically, in my mind, at least. I suspect that we have a premium, here, on
keeping things simple and light-weight. So… For whatever these ideas may be worth!
Cold
liquid fuel (perhaps cold methane or cold hydrogen, or even cold refined
kerosene) and cold liquid oxidizer (air or oxygen) might enter the combustion
chamber insufficiently gasified, still be very cold, and be hard to keep
lit. We might use a rocket-engine gas
generator (see https://en.wikipedia.org/wiki/Gas-generator_cycle ) that is
undersized, as a cost savings, or we might skip the use of such a thing
altogether, and simply spray cold liquids (or even gas-liquid mixes) into the
(top of the?) combustion chamber. In any
case, we might have trouble keeping it all lit.
So
here comes possibly-new-idea number one!
Use a derivative of the Astron Omega 1 engine, and modify it. As previously noted in this document, the 1st COPVs Document
describes in some detail, how one would best create a good high-performance
compressor by modifying the Omega 1 design…
Search for “Omega 13” in that document (end of repeated remark). The rocket, at too-high of an altitude for
breathing ambient air for the Astron engine, can breathe some stored,
compressed air instead, of course. Now
imagine that the added (extra) “compressor” stage is still added, BUT it also
adds FUEL INJECTION AT THE END OF THE OXIDIZER COMPRESSION CYCLE. The mix of hot, compressed air and burning
fuel, for this added cycle, is NOT used to expand inside the engine (thereby
extracting rotational “work”, as in the still-retained part of the original
Omega 1 engine design), it is simply expelled into the
top of the rocket’s combustion chamber.
The entire Astron engine then serves as a giant spark plug, if you
will. With a top “redline” speed of 25 K
RPM, our “giant spark plug” should have NO trouble keeping the rocket’s fires
lit!
Idea
number two here is as follows: See “Space Shuttle rocket engines” at https://en.wikipedia.org/wiki/RS-25 , which tells us
that “A second hydrogen flow path from the main fuel valve is through the engine
nozzle (to cool the nozzle).” Now
suppose that we created a hollow-walled nozzle with (for example) an outer
shell made of aluminum, and an inner wall of (for example) stainless steel (310S alloy, perhaps). The inner wall has tiny holes
drilled in it, as well as “passive thermally activated flow-switches”. To understand details of what such “passive thermally
activated flow-switches” would look like, see https://www.researchgate.net/publication/331556573_Designs_for_Passively_Thermally_Gated_Fluid_Flow_Switches , with a duplicate copy
of this document also located at http://www.rocketslinger.com/Psv_Tgt_Fsw/ .
Cold
(liquid, gasses, or mixed) fuel enters SOME of the segments of the nozzle (at
the top or small-diameter end of the bell shape), within the aluminum and steel
“sandwich”). So the combination of tiny
simple weep-holes in the inner steel layer, and passively gated flow switches
also, cools the nozzle walls, with cooling power inherently directed to where
such cooling power is most needed. The
same could be done with cold oxygen or air as well. If we slice the bell-shaped nozzle into many
vaguely triangle-shaped (orange-peel-like) pieces, alternating fuel v/s
oxidizer inside the “sandwich” slices, we can mix fuel and oxidizer somewhat
well. Manufacturing the many identical
or nearly-identical “orange peel triangle slices” might be assisted by 3-D
printing. Fasten the segments together
and hook them up! (If we chose to
sandwich-convey ONLY fuel or ONLY oxidizer, the “orange peel segmentation”
won’t be needed at all, of course.) Cold oxidizer and-or cold fuel now
simultaneously cools the nozzle wall, while also adding combustion within the
nozzle. Lengthening the nozzle (away
from all of the combustion) with a more-conventional single-walled nozzle, to
allow combustion to reach completion or near completion before exiting, would
most likely be a good idea. Also note
that this “hollow metal sandwich walls” idea could be used in the combustion
chamber only, or the nozzle wall only, or both.
There you have it! For what it’s
worth!
That’s
all that I have for now.
Stay
tuned… Talk to me! My email is RocketSlinger@SBCGlobal.net
Back
to main site at www.rocketslinger.com
References
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Titus. (2022). Propulsion Designs Using Novel Nested COPVs and the.
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Mehmet & Al-Rashid, Rashid & Yassin, Ahmad & Radwan,
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compressed air energy storage systems. Scientific
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N. & Moya, X. & Tamarit, Josep.
(2019). Colossal barocaloric
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Nature Communications. 10. 10.1038/s41467-019-09730-9.
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