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Designing and Deploying a Shuttlecock-Style Re-entry Vehicle to Use Lifting-Body Principles



Pre-Summary This sub-page to is a companion or supplementary document to other documents found at Research Gate. As previously documented, conventional (existing) satellite-deployment fairings could be modified and subdivided into (an ideal number being postulated to be 4) powered-hinge-attached fairings segments renamed to be "petals", as they open (like a flower) for satellite deployment, and thereafter serve as the "feathers" in a badminton-style shuttlecock, for descent (re-entry). As these "feathers" degrade in re-entry-generated heat and pressure, they evolve into embedded grid fins. The powered hinges and hydraulic energy management used to accomplish this have already (albeit incompletely) been described. Here, we add additional design elements, notes, and drawings to emphasize that the highest-velocity phases of re-entry could be substantially prolonged (therefore prolonging the exchange of kinetic and momentum energy in exchange for heat energy, AKA reducing "heat flux", and reducing overall thermal stresses to vehicle structures) by using lifting-body principles for the highest-thermal-stresses phases of the re-entry process. The shuttlecock elements (and flight modes) earlier described aren't entirely negated here; they are more-so (much!) improved upon. Also important is this: What is described here is a "punctuated equilibrium" of flight of a lifting body, where the vehicle periodically rolls by 180 degrees. "Belly" and "back" of the vehicle are periodically reversed, to absorb and shed heat more equally, across all surfaces.
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Designing and Deploying a Shuttlecock-Style Re-entry
Vehicle to Use Lifting-Body Principles
Abstract / Pre-Summary
This sub-page to is a companion or
supplementary document to other documents found at Research Gate. As
previously documented, conventional (existing) satellite-deployment fairings
could be modified and sub-divided into (an ideal number being postulated to be
4) powered-hinge-attached fairings segments re-named to be “petals”, as they
open (like a flower) for satellite deployment, and thereafter serve as the
“feathers” in a badminton-style shuttlecock, for descent (re-entry). As these
“feathers” degrade in re-entry-generated heat and pressure, they evolve into
embedded grid fins. The powered hinges and hydraulic energy management
used to accomplish this have already (albeit incompletely) been described.
Here, we add additional design elements, notes, and drawings to
emphasize that the highest-velocity phases of re-entry could be substantially
prolonged (therefore prolonging the exchange of kinetic and momentum energy
in exchange for heat energy, AKA reducing “heat flux”, and reducing overall
thermal stresses to vehicle structures) by using lifting-body principles for the
highest-thermal-stresses phases of the re-entry process. The shuttlecock
elements (and flight modes) earlier described aren’t entirely negated here; they
are more-so (much!) improved upon. Also important is this: What is described
here is a “punctuated equilibrium” of flight of a lifting body, where the vehicle
periodically rolls by 180 degrees. “Belly” and “back” of the vehicle are
periodically reversed, to absorb and shed heat more equally, across all surfaces.
Introduction / Basics
Dear Reader, per my usual convention, let’s (mostly) depart from stilted,
formal ways of writing, and slip into familiar mode. In BOMs (Bills Of Materials)
lingo, the “parent” BOM calls a “child” BOM, where the child is a sub-assembly of
the parent. This document (right here) is now a grandchild!
like_Design and (same document, 2
locations) is now the grandparent document for brevity here, and
_Energy_While_Re-entering_an_Atmosphere_Using_a_Shuttlecock_Design and
(same paper) is now the parent document
for brevity here. I’ll try to minimize repetition from those papers. Obviously, if the
content here becomes muddled (confusing), one might want to at least skim the
first 2 papers.
Speaking of muddled… Dear Reader, I’ll take the blame that I deserve! It
was only after I posted the parent document up on Research Gate (1 day later)
that I realized that my thinking was seriously sub-optimal. I described a
“corkscrew” flight path as complementing a slow and continuous “rotisserie roll”,
for spreading heat across all of the surfaces of the re-entry vehicle. This, I now
realize, is highly likely to be much less optimal at reducing heat flux (heat
absorbed per unit of time) during the early phases of re-entry, than a “lifting body”
approach would yield.
You’re as capable of “Googling” as I am, so I won’t call up links about
“lifting bodies”. I would like to bring to your attention, the following two articles:
in-the-air/ No One Can Explain Why Planes Stay in the Air”, and If I may glibly
summarize these two articles for you (they ARE good reads for the details), then
I say, Newtonian action and reaction is true, and Bernoulli is correct about the
Bernoulli Principle” as well. And yes, we’re talking atmospheric re-entry, at
hypersonic and supersonic speeds here, not airplanes. SOME of the same
principles still apply. OK, one more link, and then let’s move on.
navigation-is-everything/ is a good read… Yes, navigation is very important for
re-entry! This is a good read, but more about navigation details is beyond my
scope here. I want to focus on providing aerodynamic control surfaces, far more
Expect no profound words from me about Navier-Stokes equations, or
Euler equations either. I haven’t the expertise required to do that. My focus here
is combatting “patent trolling” of fairly simple ideas. I will describe some more
ideas (hardware and flight modes), some of which may work, and some of which
may not. I will “brainstorm”, in other words. “Throw the ideas into the public
domain”, or “defensively publish” them, as I have before. (As a side note of
interest, some pretty “out there” ideas have been patented, even! See the “Thoth
Tower”, for example. Count me among the sceptics).
So, in the parent document I tried to write of “up” and “down”, top and
bottom, as the rocket stays (more or less) in the same orientation during ascent
and descent. Rocket engines down, fairings (payload) end up. This time around,
I want the rocket-engines end to be elevated as the “fore” end, and the payload
(shuttlecock-feathered) end down and “aft”, during the highest speeds of re-entry,
to create our lifting body. So think of “fore” and “aft” from here on in, for the most
part. What was previously called a “spoiler”, will now be a “lifter-spoiler”. The
old, previously-described mode (slow, continuous roll) may still be desirable
closer to Earth, in thicker atmosphere, where the path would be more vertical
(orbital speed having been completely shed). There (lower down), the “lifter-
spoiler” would still be just a spoiler.
The classic airplane terms lift, drag, and thrust, and pitch, yaw, and roll all
apply here, except “thrust” can be replaced by sheer kinetic energy and
momentum remaining from orbital speed. This energy will take a long time to
shed. What is new here compared to the parent document is that we’ll introduce
hardware for the specific purpose of controlling “roll”. We will then describe a
sort of “punctuated equilibrium” where the re-entering vehicle travels for (?) 2 or 3
minutes “belly down” (absorbing belly heat, shedding back heat), and then rolls
180 degrees, going “belly up”, inverted, cooling what was the belly (now the
back), and vice versa. Rinse, repeat! I have never seen this idea described, so
here (below) it is!
Note that descending rocket-engines-first is no new idea. Space X does it
with their Falcon boosters (albeit not from orbital speed), and “Stoke Space” may
try that from orbital re-entry. See
stakes-claim-launch-202145047.html Stoke Space stakes its claim in the launch
industry’s rush to fully reusable rockets”. From there, “’Our entire profile will have
the acceleration vector along the center-line axis,’ Lapsa said.” That leaves
some room for ambiguity, but I interpret it to mean that they will re-enter “engines
first”. In any case, I assume here that it can be done. However, building engines
to withstand re-entry (or somehow placing a heat shield in front of them for re-
entry) is outside of my scope here. I have no relevant ideas concerning that.
That seems to me to be a reasonable introduction, so let me provide an
orientation (literally!) drawing, and then we can move on.
of Mass
Lifter /
Basic Orientation Diagram
Figure #1
The “fore” (rocket engines end) belly lifter-spoiler pushes approaching air
down, lifting the nose up. If we look at the parent document research, we see
that the windward side (belly here) has a pressure about 100 times that of the lee
side (back or top side here). That means that the position of the back-side lifter-
spoiler isn’t really going to matter all that much, assuming it is much smaller than
the petals. The “petal” on the belly aft end is in a fairly neutral attitude, not
making much of a difference (adding a wee tad of lift as is shown above). The
large “petal” on the top-side aft end, though, pushes air upwards. Being to the
rear of the center of gravity, this will push the aft end down, maintaining our
“angle of attack”. The belly side being at a pressure of roughly 100 times that of
the top (back) surface, of course, tells us that we get plenty of lift!
Diving Right In!
Diving right into the atmosphere, and the details here, let’s move right
along, while also, from time to time, plugging various holes that were left in the
parent document. The above drawing should be enough to illustrate the control
of “angle of attack”, or “pitch” (unlike in airplanes, the two are about the same
thing, here). I’m not really completely sure what the aft belly petal should be
doing (exactly how it should be adjusted). The below drawing is easy enough to
provide, so here it is.
Difficult to Do
Not Much Sense in This!
Adjustment of Belly Aft Petal
Figure #2
The belly-aft petal adjustment which I personally believe is best, is shown
in brown. It’s partly the best because it’s easily attained! The dotted black line is
possible (and easy to attain), but would offset the whole idea for why we are
raising the back-aft petal (for forcing a good “angle of attack” for getting lift).
Doing the dotted-black-line “thing” here, it seems to me, adds drag, and kills lift.
The dotted-RED-line “thing” here would be nice to be able to do, but our
vehicle geometry makes it very hard to attain! It COULD be done, but not without
some prices! The simplified drawing above doesn’t show it, but if you work your
way through both the grandparent document and the parent document, you’ll see
that the base of the petal (where it meets the “deck”, or floor of the payload bay)
is curved towards its outer edges, where it meets the next petal. Closing the
petal-hinge to be “more closed than normal” (normal is payload secured for
ascent) means that the outer edges of the petal-base bang into the deck (we
can’t go there). We could grow the true hinge, to span the entire base of a given
petal. If we did that to all 4 petals, we’d have a very ugly (and un-aerodynamic)
square “hammerhead fairings” design… Possible, yes! Wise? Probably not!
We could go to 5, 6, 7, or more segments of petals, to get this polygon
(where many fairings segments meet the deck, at hinges) closer to being a circle,
reducing the “ugliness” (for lack of a better word) of the hammerhead fairings
(aerodynamics on ascent) situation. While having the true hinge span the entire
base of each petal, of course. I don’t think that the extra complexity is worth it.
Just my opinion, though… No mathematical proofs will be given here!
We could possibly re-design the hinges to shove (the true hinge) upwards
from the deck, and-or outwards (away from the center of the deck), in some kind
of compound action. In light of all of our (especially heat tolerance) materials
constraints (see the parent document), AND our needs for strong, robustly
powered hinging action, I simply don’t think this is practical at all.
Perhaps most plausibly, we might be able to design the (edges) parts of
the bases of the petals (the areas that “want to” bang into the edges of the deck)
to degrade and fall away quickly, early on, during re-entry. THEN we’d be able to
“close the petal” more-closed than normal, when needed, for the rest of the
If we DO chose to do any of the above, to petals at belly-aft and back-
aft… Keeping in mind that the vehicle will “roll” 180 degrees periodically for
punctuated-equilibrium heat-spreading rotisserie rolls… We only need to take
extra trouble with the “12 o’clock and 6 o’clock” petals (which trade positions).
The “3 o’clock and 9 o’clock” petals will also swap positions, but need never be
“asked” to “close the petal” more-closed than normal. So at least the design here
allows us this small slice of grace and forgiveness!
“Pitch” control has now been fairly thoroughly discussed. Let’s move on to
“yaw” control, which is fairly simple. For simplicity, the below drawing looks
straight down the rocket-engines (fore) end, ignoring our “pitch”. Number of
engines is arbitrarily set to 4… It could easily be some other number. “4” looks
pretty in the drawing!
12 o’clock Petal
6 o’clock Petal
3 o’clock
9 o’clock
Fore-End View
Figure #3
Yaw control is simple and intuitive. As we look into the above drawing,
extending the 9 o’clock petal and pulling in the 3 o’clock will swing our nose to
the left, and vice versa. Done! (The lifter-spoilers were omitted in this drawing,
but they would be in front of the 12 o’clock and 6 o’clock petals, in the above
Moving on to “roll control” (not discussed or diagrammed in any detail so
far, in earlier papers), let us imagine two plates that push out or retract, just like
the lifter-spoilers (on Bifrost hinges with the hinges on the “fore” edge), except,
instead of flat plates, they are curved “snowplows of the air”. A tilted propeller-
blade-like thing, yes, but that doesn’t (connotation-wise) catch the strength
(robustness) required. Let’s call it a “variable-engagement air-plow”, or maybe
just a “roll control device”. The below drawing tries to capture (with a sequential
fore-end view) such a (somewhat complex in 3D) device slowly being deployed.
Pre-deployment, and when otherwise retracted, yes, a weird-shaped void will be
left in the side of the rocket body. And a small tip of the “plow” may always be
protruding, as a space saver. These small offenses against aerodynamics can
be tolerated, in the name of the benefits that we really need.
Roll Control Device, Fore-End View
Timed Sequence Deploying
Rocket Body
Implied Far-
Away End }Implied
Near End
Figure #4
Unlike the lifter-spoiler, the true hinge (part of the Bifrost hinge assembly)
should NOT lay flush with the surface of the rocket body (for the roll-control
devices here), but should be buried (recessed) underneath the surface. The
dotted blue lines in the above drawing are meant to show a strong embedded-in-
the-plow “spine” of a column shape, to cut the strong wind. It might be blunt, or it
might be sharp-edged, this wind-splitter (I don’t know what’s best for that). But
this spine is tilted away from the viewer. Poking out a tiny bit perhaps, even when
not yet deployed at all. It rises towards the viewer at the tip, erected ever more
vertically towards the viewer, as the “air-plow” deploys more fully. The more it
deploys, the more plow-blade it exposes behind it, and the more air it pushes to
the left (as shown above), imparting more and more clockwise “roll” to the
vehicle. A mirror image of the above should be deployed 180 degrees out from
the above, to provide variable-deployment counter-clockwise “roll”.
The below fore-end view ignores pitch (the same as we did when
diagramming yaw control). This time, though, to cut visual clutter, we omit the
petals, showing only the lifter-spoilers and the roll-control devices. The roll-
control devices (“rollers” for very short), just like the lifter-spoilers, should be
located not far behind (“above”, if conventionally-oriented) the rocket engines.
12 o’clock Lifter-Spoiler
3 o’clock
9 o’clock
Fore-End View (Focus on Rollers)
6 o’clock Lifter-Spoiler
Figure #5
The 3 o’clock roller can give us variable counter-clockwise roll, and the 9-
o’clock roller can give us variable clockwise roll. So far, so good! However,
notice that (as shown above) the more that either or both of the rollers is
deployed, the more lift that we get at the “fore” end (as air is deflected
downwards). After we invert (don’ forget the periodic 180-degree inverting roll for
heat-spreading in a “punctuated equilibrium” version of the rotisserie roll), 9 and
3 o’clock rollers trade positions, and now they can both deflect air UP, killing our
fore-end lift!
What this means (depending on the relative sizes and strengths of the
lifter-spoilers v/s the rollers, and possibly some other variables as well) is that, as
shown above, both of the rollers could be near-fully deployed in the mode shown,
leaving just enough spare adjustment room (with safety margin added) to
perform constant, fine control of “roll” attitude. In this mode, the two rollers could
provide enough lift, such that the 6 o’clock lifter-spoiler could be reduced in size,
or perhaps eliminated entirely.
In the 180-degrees-out inverted mode opposite what is shown above, the
rollers should be nearly completely retracted, so as to not kill the lift on our “fore”
end here. What is (in this mode) the newly-relocated 6 o’clock lifter-spoiler (was
3 o’clock as shown above) may be far more essential now!
A variation from the above is shown below. We double up on the rollers,
and eliminate the lifter-spoilers.
3 o’clock
9 o’clock
Fore-End View, 4 Rollers)
Figure #6
The bottom 2 rollers (regardless of which mode we are in, belly-up or
belly-down) can now serve as lifters for the “fore” end, while the top 2 rollers can
be reserved for actual roll-control. We have now restored symmetry! This
symmetry makes it easier to write flight-control software. Also, of course, we
have eliminated the lifter-spoilers, and in so doing, we have reduced
(consolidated) the numbers of places where control surfaces have to “invade” the
rocket body. Such consolidation should also reduce the total number of avionics
circuit boards, batteries, and hydraulics elements such as tanks and
accumulators, “heat walls”, and possibly other components as well. That is, two
closely co-located “rollers” should be able to share many types of components.
A price that we’ve paid is that we’ve increased the “aerodynamic ugliness”
(especially during ascent), in that we’ve doubled up on the weird-shaped voids
outside of the “air plows” in the plows-retracted mode. We COULD try to
temporarily (during ascent) plug these voids with some sort of material (foam?)
that quickly degrades in the heat of re-entry. Or degrades under some sort of
triggered action (pyrotechnic devices sounds rather heavy-handed to me, for
this). Such a temporarily void-plugger could easily dislodge and fly back to
damage a petal. Space Shuttle Columbia’s 2003 accident (foam strike) comes to
mind, so I’d not like to recommend this idea. Maybe there’s a safe “fix” (for what
I regard to be a fairly minor problem), but I sure don’t know what it is!
As we roll from belly-down to belly-up modes and back, at the aft end, the
6 o’clock (becoming 12 o’clock) petal will need to be extended, and vice versa.
At the same time, one roller will need to retract while another extends, to give us
“roll”. I can’t see any preferences here… Roll in the same direction each time,
alternate, or flip a coin! Well, more honestly, if we happen to already be slightly
rolling in one direction… Fine roll-maintenance-mode never being perfect…
Then whichever way we are already rolling, “roll with it” makes sense! Be
efficient! The results might end up looking rather random, then. At the end of a
roll-inversion, we’ll need to reverse the rollers-actions momentarily, to kill the roll-
inertia of the just-now-induced roll, and then go back to stability-maintenance
mode. As mentioned previously, each such stability-maintenance-mode time
period is a “heat soak” for one side, v/s “heat shedding” for the other side. I have
no idea how long these time periods should be. 2 or 3 minutes is a wild guess,
but longer might be better. How much lift do we lose during each roll-inversion?
I have no idea!
To me, I think this is a fairly complete description of applying “lift body”
principles here. Oh, one more minor idea: At the 3 o’clock and 6 o’clock
positions, we might want to add short “fins” running from right behind the rollers,
all the way back (“up”) the rocket-body flanks, all the way back (“up”) to the petal-
hinges (or some significant fraction of those routes). At the expense of a wee tad
of drag (including during ascent), we’d get a bit more lift during descent, in lift-
body mode.
Also note that after we’ve absorbed a bunch of heat during the worst of re-
entry, and we enter the lower atmosphere, we may want to cool down the entire
vehicle. Orbital velocity is now all gone, and we can spiral downwards, vaguely
like a maple-tree seed. This is where we can go back to a slow, stately,
continuous “rotisserie roll” mode as was previously described in the grandparent
document and parent document alike.
Plugging Some Holes
The previous documents left some holes. I’ve not been able to gather any
expert advice about hydraulics. What are optimal approaches to hydraulics?
See the questions summarized at the end of the parent document for those. I
have no new answers. If I get some, I will post them as updates (or addendums)
to this document right here. I can’t foresee a 4th document in this series (I could
be wrong). In other words, I highly doubt that I’ll gather enough additional ideas
to justify yet another paper on this topic!
The parent document mentioned steamboat-style paddle-wheels as being
superior energy-harvesting devices. I forgot to mention some plausible methods
of reducing how much power a paddle-wheel extracts from passing airflow. Too
much force, too much power, and the wheel spins too fast, and falls apart! To
more thoroughly thwart any possible patent-trolling here, I now list some options
here: Shorten the vanes (paddles), put holes in them, or flip them 180 degrees,
with these blade-vanes not opposed 180 degrees to the wind, but edge-on
instead (similar to a hammermill). Or flip the blades to some intermediate angle.
Or delete the blades, and just use spikes instead. Anti-patent-trolls micro-
mission now completed!
After more research and just plain old soak-time-in-the-brain, I no longer
believe that a lifter-spoiler, or a petal for that matter, being extended against a
stiff wind, makes much sense here as serving for much of a power “accumulator”.
Yes, there is potential mechanical energy available there, in that, as we retract
such a surface, it pushes strongly against us, and we could harvest that push-
power. Send it, for example, to pressurize a hydraulic accumulator. I seriously
doubt that it’s worth the trouble. We can harvest plenty of power from the
Also, since the paddlewheels will be spinning rapidly, harnessing their
power via electrical generators (not hydraulic pumps) makes sense. Routing
power around via power wires (not hydraulic pipes) should be more robust and
heat-tolerant. The parent document (Figure #14) shows hydraulic lines, for
example. I take that back! Electrical power wires are better for system-wide
power distribution. I was heavily biased in favor of hydraulics, but I no longer am.
Hydraulic motors probably still make sense for the relatively slow (but
powerful) motions needed for all or almost all of our aerodynamic control
surfaces, as controlled by “Bifrost hinges”. However, they should (I think) be
locally powered by electrically-powered hydraulic pumps. Any more details
above and beyond that? I would need some expert advice!
Even these hydraulic motors could possibly be replaced by electrical
motors. We might be able to go purely electrical, with no hydraulics at all.
Apparently Space X’s “Starship” powers its (belly-flop-controlling) flaps this way,
off of batteries. So it could be done, apparently… At least here, we’d have the
ability to nearly constantly be “topping off” our batteries, from the paddlewheels.
Aerobraking and Aerocapture
Dear Reader, I’ll leave the “Googling” to you, here. Aerobraking, 146 K
hits; “Aero braking”, 22.9 K hits. Aerocapture, 148 K hits, and “Aero capture”, 9.2
K hits. It looks like “The Google” likes the compounded-words versions here
best, for search-strings!
The first and most obvious uses here (and the largest market) for what
these 3 papers have described, are for launching Earth satellites, and for
recovering and re-using as much of the upper stage as is possible. These uses
will involve lower re-entry speeds. However, the methods described here
(especially with future, improved materials, navigation, in-orbit refueling, and
other technologies), after refinements from using such methods as described
here, descending from Earth orbit, could be used for interplanetary journeys as
well. Human-rated? Probably not any time soon! I can imagine getting some
severe motion sickness from constantly repeated roll-inversions, for one thing!
But cargo should do just fine.
The methods described here could be used for delivering satellites, cargo,
rovers, drones, and-or balloon atmospheric probes (think Venus) to other
planets, and for returning cargo to Earth (Example: Cargo coming back from the
lunar “Gateway”, such as, for example, moon rocks). The methods described
here most certainly provide robust control surfaces for path-control! Path-control
will be critical for aerobraking and aerocapture.
For probes sent to other planets (unlike Earth-satellite-delivery runs,
where recovering the rocket engines for re-use is THE big-dollars item), we’d
typically not have to worry about damage to the rocket engines… They can be
sacrificed, there at the super-heated “fore” tip, as we enter atmosphere. With the
rocket engines destroyed, we can still make a hard landing, delivering impact-
forces-resistant cargo or probe hardware, possibly to include rovers, even. Or
we can have parachutes drag out (of the payload bay) rovers, drones,
exploration balloons, or blimps. See
exploration-mission-ideas “Mars on the cheap: Scientists working to revolutionize
access to the Red Planet”, where a somewhat similar “shuttlecock hard lander” is
described. From there, “The Small High Impact Energy Landing Device
(SHIELD) concept is part lander and part shock absorber, all rolled up in one
The astute reader may recall that, for the schemes described here to
work, we need protection from heat, for heat-sensitive components. See Figure
#1 of the parent document, and associated text. Liquid nitrogen is an affordable,
effective cooling liquid, suitable for use here. Could liquid nitrogen survive a 9-
month journey to Mars, for example? Note that boiled-off gasses can be re-
condensed, but that’s clumsy and hard to pull off in space. Not impossible; just
hard. For one thing, we have to shed excess heat in a vacuum, as part of this,
and that’s not easy to do.
But wait! See and “Gravity Probe B” was able to
maintain a supply of liquid helium for an entire 17 months, without re-
condensation, in a “dewar” (a large vacuum-walled “Thermos bottle”, if you will).
Helium boils off at -269 C, while nitrogen boils off at a (relatively) balmy -196 C
instead. So if “Gravity Probe B” could do it, so can we!
Well anyway, after we perfect the shuttlecock-style re-entry (with a phase
of a “lift body” mode operation) for Earth-orbit uses, aerobraking and aerocapture
awaits us! I thought that this was at least worth mentioning.
I have no special expertise or any more plausible ideas concerning any
associated matters here, so I will sign off at this time. This concludes my ideas
as of this time. Comments or questions (or idea contributions) are welcomed at
Stay tuned… Talk to me!
Stauffer, Titus. (2021). Methods of Decelerating a Spacecraft Through
Atmospheric Re-entry Using a Shuttlecock-like Design.
Stauffer, Titus. (2021). Harvesting and Managing Energy While Re-
entering an Atmosphere Using a Shuttlecock Design.
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Abstract This sub-page to is meant to describe methods for converting a vacuum rocket engine nozzle (with a large bell shape) into one that can operate efficiently and safely at sea level (with a much smaller bell shape, with today's typical design). Three primary alternatives are described… '1) One could put an array of hinged gates (NOT permitting one-way flow of hot rocket exhaust gasses into the lower-pressure ambient environment, for vacuum or low-ambient-pressure applications) into the extended areas of the bell shape (those exceeding what is needed for sea-level operation). However, the one-way-gas-gates WOULD allow ambient air to flow (at sea level or in other higher-pressure environments) inwards into the rocket nozzle, thereby reducing "back flow" of air (along the insides of the outermost rim of the nozzle, when the nozzle is "over-expanded"), which is associated with inefficiency, chaotic oscillations, and danger. '2) One could design the outermost (lower) extensions of the nozzle to be used in a vacuum environment (as in, for example, the Space-X Falcon 9 interim upper stage, formerly being design-tweaked to begin emulating the upper stage of the "BFR" system, AKA, the BF Spaceship), but to fall away (be discarded) immediately after the final de-orbit burn. This converts the bell shape from a vacuum nozzle into a sea-level nozzle, by drastically reducing the nozzle in size. '3) One could formulate the materials and construction of the outermost extensions of the nozzle to be burned away by the heat of atmospheric re-entry. This might be an especially attractive option if one uses a shuttlecock-style re-entry method with the rocket engine(s) at the "fore" end during re-entry. Options for precisely this method (rocket engines at the fore end in shuttlecock-style re-entry) have already been described (citations provided here). Designing these outermost nozzle portions to be sacrificially burned or ablated away will help protect the engines, and facilitate their re-use.
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Abstract / Pre-Summary This sub-page to is a companion or supplementary document to another document found at and at (same document, 2 locations). In BOMs (Bills Of Materials) lingo, the “parent” BOM calls a “child” BOM, where the child is a sub-assembly of the parent. This document deals with sub-assemblies of the designs described in the “parent document”, and so, it will henceforward be referred to as the parent document for brevity. Temperatures endured during re-entry (both on the windward and lee sides) are briefly examined here, as are temperature tolerances of materials and subassemblies. Then a “heat wall” design is described, which can be used to protect subassemblies from heat damage. Much of this is focused on hydraulic machinery, which will need to be used to control the “petals” (or grid fins) as were described in the parent document. Many variations of a powered hinge are described here. One of the best versions consists of a curved (arc-shaped) friction plate attached to each petal-becoming-a-grid-fin (AKA, fairing segment). The friction plate is gripped between two powered, slowly rolling funnel shapes, to create a torque-limiting device, to absorb sharp peak loads without damage. This hinge system is called a “Bifrost Hinge”, and the name given to it, is explained. To harvest energy (or power used to perform work) in a spacecraft entering an atmosphere, we could use roller chains similar to (but larger and stronger than) the chains used in bicycles and chain saws. In a chain saw, some of the plates (in the chains) are extended outwards with teeth, for cutting wood or other materials. Here, instead, some of the plates are extended outwards to “catch the breeze” during re-entry, the same as windmill vanes catch energy from the wind. The overall device, then, here, will be called a chain windmill. The vanes in such a device could possibly take many forms, but two are described here. One is a single plate per each set of chain-plates that is so equipped, which is stopped (by a hard-stop) from folding past 90 degrees, with the right angle formed to “catch wind”, and not fold further towards the lee side. However, this vane is allowed (during the chain segment’s return journey towards the windward side) to fold out of the way of the prevailing wind. The alternate (here-described) vane is a “butterfly vane set”, with twin segments that “flap” to catch wind in one direction, and fold out of the way in another direction. They can each perform a partial rotation around pins protruding outwards from each pair of roller-chain plates that is so equipped. Each of the two twin vanes (“butterfly wings”) provides the hard-stop for the other, in this design. In either form, a chain windmill is not at all an optimal solution here, for us. An energy-harvesting device could also resemble a paddle wheel on a riverboat. This approach will be far less disadvantaged by lack of lubrication than a chain windmill would be. And as will be shown, lubrication WILL be a major problem for the chain windmill (unlike the paddle wheel). Also described here is an airflow spoiler that could be placed to the windward side of the energy-harvesting device, possibly sized and located in a compromise between partially protecting the energy-harvesting device (best choice being a paddle wheel) from too much heat and strong airflow, and not getting enough airflow to harvest enough power. The spoiler is composed of a hinged heatshield-covered plate that can be thrust out into (or retracted from) the airstream. It could be activated by a (heat-walled) “Bifrost hinge”, which could also double up as a “hydraulic battery” used to store extra power. These are sometimes called “hydropneumatic accumulators”. In the design context here, the variably pressurized nitrogen in such a device could be partially or entirely replaced by the variable pressure of passing air in the airflow spoiler (which pushes on the plate). Such a design choice may have to be balanced with the other possible purpose of the spoiler, which is to partially protect the paddle wheel. The body of this document contain far more details, and sometimes-implausible variations. However, the above covers the most important basics.
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Pre-Summary This sub-page to describes how payload fairings for an upper stage could be modified to remain attached to the satellite(s) deployment mechanism(s), and to one another, and also (optionally but highly desirable) to the entire interim upper stage (fuselage, fuel and oxidizer tanks, and rocket engines, etc.) as well. Whereas a commonly used design today involves the use of 2 (two) clamshell fairings, which are jettisoned before satellite deployment, the base design here envisions "N" fairing-segments, or "flower petals", or simply "petals". The petals can also be thought of as "feathers" in a feathered badminton shuttlecock. Each of 2 clamshell fairings are now subdivided (sliced) into smaller segments, with each shell-slice being vaguely reminiscent, not only of a flower petal, but also of the skin-slices of a sliced orange. For this document, "N" will be set to "4", with one (marked) exception. Each petal remains attached to the base of the assembly (ideally but not always, this assembly is the entire upper stage), at the base of the petal, by hydraulic actuators. During re-entry, the petals are sometimes more-retracted (less deployed) and sometimes more-deployed (less retracted), as one travels radially around the periphery of the bulk (center of mass) of the "shuttlecock". "N" = 4 petals is enough to control the descent path (vector), as controlled by the hydraulic (or otherwise-powered) actuators. Unlike the grid fins used by Space X on Falcon 9, these petals will not rotate on an axis that skewers the centerline of the fuselage, but rather, will be retracted to be almost vertically parallel with the fuselage when fully retracted, and nearly perpendicular to the fuselage when fully deployed. This is the "degree of freedom" which is needed already anyway, to protect the payload on ascent ("flower" is in the "bud" stage; payload = pollen not yet deployed, so to speak). The "bud" must turn into a "flower" to deliver the payload. "Petal control" is a bit complex, but highly important! Not only are the petals adjusted to control the descent path, but also, from one side of the center of mass (of the fuselage or capsule) to the other, the deployed petals are more-deployed on one side than on the other. This lop-sided deployment slowly spins around the center of mass. Thus, the (usually cylindrical) center of mass tilts, and does a slow "rotisserie roll" to spread the heat of re-entry across all of its surfaces. Each petal also gets to spend some time partially protected from the highest re-entry heat as well. A given fuselage-surface (or petal) element will slowly alternate time in the heat v/s time in the relatively sheltered slipstream. The probably-ideal flight path might best be described as a corkscrew. This will prolong the travel distance and time, providing more time to shed heat. Solid petals would gather too much force from the hot air or plasma during re-entry, requiring excessive mass (for both petals and actuators) for strength, to avoid being sheared off. This is why Space X uses "grid fins" rather than planar solids. But we need solids to fully protect the payload during ascent. "Having your cake and eating it too" is obtained here as follows: The petals are manufactured as grids, but are filled in (grid-holes plugged) by optimized plastics or ceramics (or other lower-melting-or-burning-point materials) formulated to melt, burn, and-or fall away during the heat of re-entry. This means more work for refurbing the petals before re-using them (if they are re-used at all), but this is a small price to pay for recycling an entire upper stage.