* Posts by Poor Coco

327 publicly visible posts • joined 31 Oct 2009

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LOHAN spaceplane project starting to shape up nicely

Poor Coco
Boffin

Asymmetric thrust

Thrust asymmetry can mostly be solved with trigonometry: as mentined above, four engine4s firing away from the folded wingtips at a shallow angle providing the upward oomph, with two engines firing at a larger angle from the centreline in order to clear the folded wings and balance the thrust. A single combustion chamber with multiple nozzles would need custom manufacturing and would be extremely difficult to make, especially given weight constraints.

The tricky part will be ensuring simultaneous ignition; this can be addressed by having highly charged supercapacitors for the igniters. They will provide a REALLY high-current pulse which should be enough to fire all 6 igniters within a millisecond or so of each other, especially if the igniters are all wired in parallel (the first igniters burning out will result in even more current through the laggards, triggering near-instantaneous completion of ignition).

Poor Coco
Boffin

Freeze-proof controls

You can make R/C control surfaces that are immune from binding by avoiding discrete hinges entirely. Instead, stitch the control surface to its mounting point using monofilament line in a figure-8 pattern, viewed in cross section. This should work well even at extremely low temperatures, as monofilament is really tough stuff — but of course, a trial is required.

Poor Coco
Boffin

Good post!

I agree with the launch angle idea but, given the short duration of the burn — only about 5 seconds, even with a 12-engine 2-stage cluster — a 45° initial angle seems like a good idea, with the flight angle increasing to 75° or so while the engines burn in order to maximize altitude.

The exhaust gases burning the foam is definitely an issue, which is why I suggest a skin of thin strong plywood (1/64" birch aircraft grade is available) coated with aluminum foil for thermal protection (shiny side out).

Ejection charges can be nullified in a couple of ways. The simplest is just to apply a layer of epoxy over the forward end of the engine, which turns the ejection charge into a little blip of forward thrust. Another alternative is to have plugs in the engine holder tubes, so the ejection charges eject the engines (thus reducing the mass by throwing out the engine cases). But, given that the burn time for Aerotech E15s is 2.6 seconds and the delay periods available are 4 and 7 seconds, using E15-7s for stage 1 and E15-4s for stage 2 would mean near-simultaneous firing of all the ejection charges — which may be useful for ripping the booster tower off the plane (or completely apart) at apogee.

I'm glad you like the folding wing. I initially considered an F-14 style swing wing but rejected it due to weight and complexity. The Skua 1500 (which this plan uses) does use elevons, and there should be no need for a V-mixer since the autopilot should be a µcontroller with servo-compatible PWM output available — the V-mixer can be in software.

I totally agree with cameras galore. Having a camera on the rocket pod feeding data to flash memory on the plane until the moment of tower jettison would make an insanely cool video!

— Murray Pearson

Poor Coco
Boffin

I know the boost-glider you refer to...

...and it works really well in the low-power low-weight regime but will not function so well for this. Why not? Because the payload listed by El Reg will be a significant fraction of a kilogram, compared to maybe 150g total launch weight for the Estes swing-wing boost-glider.

Simple hinged wings can be accomplished with piano wire inside nylon tubes, which should become looser when chilled because the thermal coefficient of the steel wire is greater than the nylon tubes. The deployment force can come partly from aerodynamics (position the elevons in a drooped position to start it) along with, say, some mousetrap springs. I don’t recommend avoiding the folding wings entirely, as the triangular wing configuration will provide lateral stabilization and nullify net lift during the boost phase.

— Murray Pearson

Poor Coco
Boffin

Mechanically, folding wings shouldn’t be a problem...

...as long as the hinge mechanism is one that tends to loosen up rather than tighten up in cold temperatures. A nylon tube with a steel piano wire is an example of this, with simple devices like mousetrap springs to add opening force along with aerodynamic forces.

— Murray Pearson

Poor Coco
Boffin

Simultaneous ignition: solved.

If the igniters for one stage are all wired in parallel and triggered by a high-current SSR, then dumping the energy from highly-charged supercapacitors will result in essentially simultaneous ignition. Any slight asymmetry on launch can be corrected by aiming the engine pod with 2 servos.

— Murray Pearson

Poor Coco
Boffin

Pendulum fallacy

That is actually a new one for me. However, there are important differences in my LOHAN design; I think this will compensate. It would also not be impossibly difficult to have the top of the tower be a universal joint with servos that can alter the net thrust angle and guide the rocket-plane on its desired path.

The long nose tower holding the rockets a safe distance from the plane will shift the CG forward a fair bit — probably 20–30 centimetres, I’d estimate — which will convert the gliding configuration into a stable boost configuration. After engine burnout, wing deployment and tower separation, the glider will naturally adjust itself (eventually, given the extreme altitude) into gliding mode.

Poor Coco
Boffin

Not straight through the CG!

If the centre of pressure is directly through the CG then the rocket will be neutrally stable, i.e., it will keep going in whatever direction the nose is pointing at all times and will not be controllable. A JATO takeoff works because the airplane's tail is far back, allowing control.

Passive aerodynamic stabilization makes the CP fall behind the CG. Mounting the rocket pod (with cameras, etc.) far ahead of the aircraft will shift the CG forward, resulting in stability — the folded wings and vertical stabilizers will cause a stabilization CP aft of that point.

— Murray Pearson

Poor Coco
Boffin

Electronics isn't the problem...

...weight is. Active swiveling nozzles, especially for the 8–12 engines I imagine for LOHAN, would be really bulky and heavy. However, servos providing two-axis pivoting of the entire rocket pod could compensate for the asymmetric thrust and also provide guidance in concert with the elevons on the folded wings, without much weight penalty.

— Murray Pearson

Parmo v poutine: Your cut-out-and-keep pdf guide

Poor Coco
Thumb Up

It’s official...

...the proper type of gravy for poutine is awesomesauce.

So, LOHAN: What's it to be?

Poor Coco
Boffin

Concept plan

Here is a rough sketch of my aforementioned concept with a drop-off thrust tower, a foamy folding wing and a “personal massager” fuselage design. Comments?

http://media.jetboyrockets.com/LOHAN_001.pdf [warning: 212 KB PDF]

Poor Coco
Boffin

Oh, also...

...I have drafted up some rough plans for a design concept; starting with an R/C foamy flying wing (1500mm span), saw it in half and insert a cylindrical body which bears an uncanny resemblance to a “personal massager” (for obvious reasons) and which contains the avionics. This connects at the nose to a carbon-fiber mast to a pod containing cameras (which will be lost, so they record onboard the plane) and either four, six or eight Aerotech E15 ammonium perchlorate composite rocket engines (details at http://www.jetboyrockets.com/motors/detail/23/) in a conical configuration. The wings will be hinged at midspan with a passive elastic tensioner that will deploy them after the engines burn out; there will be aluminum covers over the leading edges that will protect the servos etc from the engine gases and which will fall off as the wings unfold. This means the wingspan is only 600mm or so while the engines burn and 1650mm after unfolding. If you’d like to see a .dxf, email LOHAN@jetboyrockets.com and I will send it out.

Poor Coco

Skip “Low Orbit”...

...because we’re not doing anything like orbiting, we’re strictly aiming for altitude, not horizontal speed. However, the craft (on liftoff) will be lighter than air:

Lighter than

Oxygen

High-

Altitude

Namesake

Or, aiming for more 1337 points through recursion:

LOHAN,

Our

High

Altitude

Namesake

(“Navigator” also works, but “Namesake” is a nice wink at the recursion.)

Atlantis blasts off on last shuttle mission

Poor Coco

Nothing is guaranteed...

...but there is little reason to view this as the closing of Kennedy Space Center. SpaceX’s pad is there, and when the Falcon 9 Heavy flies that will be a show and a half.

El Reg to unleash rocket-powered spaceplane

Poor Coco
Boffin

More thoughts of rocket boost-gliders

I did a quick look around and spotted the Wowings Skua 1500 (http://tinyurl.com/wowings-skua-1500) slope-glider. It has certain attractive properties; it’s designed to be fast; it has the stabilizers at mid-chord; it looks really cool.

It would be nice if the wings could fold or swing back for the high-speed fight and then pop out just before the mast blows off, after the engines have burned out and some coasting time has elapsed. This would further reduce the frontal area; the wings could be locked back and then snap into place with a bungee cord or similar once the engines have burned out and the dynamic loading is low enough. Here’s another opportunity for explosive-bolt technology. :-)

The more I consider the engine-mast idea the better it sounds. It could even be a mounting point for small, cheap video cameras feeding back to Flash storage on the plane (you can reasonably expect to lose the cameras along with the engine pod). The wires might have to pass right past, even wind around, the explosive charges to ensure they don’t foul the separation. BUT DAMN WHAT A VIDEO THAT WOULD MAKE!

Poor Coco
Boffin

*ahem*

First off, I demand recognition for my original LOHAN recursive acronym (http://forums.theregister.co.uk/post/1111223) even if its altitude objectives were contrary to a rockoon.

Next off, as someone with experience building rocket-powered planes (Hasegawa F-104 plastic models with black powder engines) I can give you some tips:

• The propellant you will want to use is APCP, ammonium chloride composite propellant — the stuff inside the Shuttle SRBs, for example. Its specific impulse is much higher than black powder.

• To handle the problem of a stable low-speed launch, you need a rocket that will fly stably in what’s normally an unstable configuration, one with the CG far back. To accomplish this, you need to move the engines to the NOSE of the rocket, like the abort rockets on a human-carrying capsule.

• To obtain thrust from the nose without incinerating the craft, place 3 or more engines in a conical configuration on a mast attached to the glider’s nose, with the engines firing at roughly 30° from the centreline. When the engines burn out, the mast separates (you can use explosives!) and the glider is left with an appropriate mass distribution for a controlled descent.

The RC foamie suggestion is excellent; to obtain one strong and tough enough to withstand almost anything, you can skin the foam with 1/64" (0.4mm) aircraft-grade birch plywood, which is truly an astounding material. I have a sailplane wing I built out of it which is a pure monocoque structure: no foam inside, not even ribs, just some basswood stiffeners on the flat side and air.

One person you certainly want to speak with is Tim Van Milligan of Apogee Components (http://apogeerockets.com/). He is incredibly knowledgeable about rockets and I bet he’d love the chance to work with you guys.

El Reg cuts ribbon on new Special Projects Bureau

Poor Coco
Paris Hilton

LOHAN the ekranoplan!

You should build an autonomous ekranoplan (a.k.a. ground-effect vehicle [GEV] or wing-in-ground-effect [WIG] aircraft).

“LOHAN, Our Hovering Autonomous Namesake” is an obvious acronym expansion, which is nicely recursive and has a sort of meta quality to it.

Woman with 15 IDs gets 7 years for multiple VAT fraud

Poor Coco
Happy

Ah, Verity CONNOR.

I just HAD to read this to make sure it wasn’t our fine Ms. Stob!

Fired-up eco-boffin gives it '180 per cent'

Poor Coco
WTF?

Name of the unit...

...should clearly be the, "what?"

Single-patent lawsuit hits Apple, Google, Amazon, Priceline...

Poor Coco

I know!

We could rip off Chairface Chippendale's idea and put them into a pit full of alligators and cows.

MOO! HISS! MOO! HISS!

Fukushima's toxic legacy: Ignorance and fear

Poor Coco

Safe doses of ionising radiation

You can consider the effects of ionising radiation on the body in a manner analogous to vibration or physical shock on a structure.

At very low flux rates (say, under 1 µSv/h) the effects are similar to ordinary vibration and the stresses from regular-strength wind. These create no long-term effects.

A high flux rate is like a blast of wind or a significant earthquake. The loading on the structure will cause changes: cracking in concrete, structural steel yielding and so on. This will NOT destroy the structure unless the impact is way, way past the design limits; but it will induce permanent changes in the structure and alter its vibrational characteristics a bit.

Finally, there is an energy level at which, after many large impacts or one huge one, the system fails. This is over 1 Sv, give or take, in the case of radiation dosage.

Fukushima one week on: Situation 'stable', says IAEA

Poor Coco
Thumb Down

Well then...

The moon is 2% closer than average, IN A LOCATION IT ARRIVES AT ON EVERY SINGLE ORBIT (it usually arrives there while not at full moon, which is a matter of illumination not distance from Earth). There are exactly ZERO stresses from the 'supermoon' that the Earth is not exposed to EVERY MONTH, idiot!

Poor Coco
Thumb Down

Critical *IS* safe at an operating nuclear plant!

"It is better to keep your mouth shut and look like an idiot, than it is to open your mouth and remove all doubt."

Criticality is the normal state of an operating nuclear reactor: http://mitnse.com/2011/03/18/what-is-criticality/

In other words, criticality by itself has nothing to do with danger. However, if the fuel stored at #3 loses its boronated water then perhaps the stockpiled fuel will regain criticality and THAT would be a problem. But it does not look at this time like that will happen.

Poor Coco

Oh, FFS, at least have the courage to post with a username!

1. The blown-up reactor buildings have only a superficial resemblance to other buildings that are ACTUALLY destroyed. The upper sections were only intended to keep weather out.

2. They're not producing power because THERE WAS A HUGE EARTHQUAKE AND TSUNAMI which rendered them dangerous. Maybe you missed that point. Failure to produce power after that disaster is a trivial point.

3. None of the other sites CONTAINED highly radioactive material. Except for ALL THE OTHER NUCLEAR POWER PLANTS IN JAPAN THAT DID JUST FINE despite being also totally overwhelmed by the natural disaster.

There is plenty to celebrate in this. Get your head out of the sand.

Fukushima on Thursday: Prospects starting to look good

Poor Coco

Case study...

...The USA after Three Mile Island. They haven't built any more since then, afaik. The cost of the plants rocketed and they became instantly uneconomical.

Not that the Merkins lack nuclear reactors, that's another story entirely.

Poor Coco
Boffin

The figures are reasonable

The range in accelerations is due to the varying structural and geologic parameters at different points in the plant. No two parts of the plant will have the same local damping coefficient or elastic modulus, and so different parts of the plant will accelerate differently (and also deform differently). Unless there was only one accelerometer in the plant, which is a ridiculous idea, it makes perfect sense that a range of maximum accelerations was reported.

The amplification of waves away from the epicentre can occur for various reasons relating to soil mechanics. The 1985 Mexico City quake was awful not because of the quake itself but the amplifying effect of the sediments the area rests on.

The above being said, I haven't tried to verify his figures either.

Poor Coco

It's about the nature of engineering

This disaster — remember, there have only been 4 recorded 9.0+ earthquakes in the last century — was a larger magnitude than had been considered likely to happen in the life of the plant. And, for the first 40 years of its life, it was perfectly valid. Even now, when it was utterly overwhelmed, it demonstrated graceful failure and was thus a triumph.

However, in the light of 2011 events, I bet all Japanese plants will have to withstand a design earthquake in the 9.0–9.2 range in the future; and also perhaps an 8 metre tsunami.

As inadequacies in current design become evident, design procedures are updated. This is what China's announced it's doing, and that is a good thing, isn't it?

Fukushima reactor shell ruptured?

Poor Coco

Fundamental engineering lessons...

...are learned through failure. And the failure at Fukushima is about the safest possible failure of this magnitude. Nuclear engineers can take a lot of lessons out of this.

Here's a design revision for future plants: include a large cooling reservoir, with enough coolant to chill all of the reactor cooling systems failed, and burst-resistant (flexible?) piping. The reservoir must be elevated enough to provide gravity-flow cooling. The water inside might as well be the nice demineralized stuff, since you'll have all the time in the world to fill it.

Fukushima is a triumph for nuke power: Build more reactors now!

Poor Coco
Thumb Down

The only source?

Um, hydroelectricity doesn't generate GHG (as long as you're out of the tropics).

Fukushima reactor core battle continues

Poor Coco
Boffin

It WAS cosmetic damage.

The roof demolition was unfortunate but it occurred outside the pressure vessel designed to hold the reactor through a meltdown: the structural integrity of the important parts was not affected at all. The vast majority of "radioactive material" released was a nitrogen isotope with a half-life in seconds. This is really the most worry-free nuclear-plant accident I can imagine, and given the unprecedented size of the quake and tsunamis, it was a brilliant performance on the part of the engineers and technicians. Bravo!

Spooks' secret TEMPEST-busting tech reinvented by US student

Poor Coco
Boffin

Don't eff up other planets!

"And then we should prioritize space travel and off-world colonization as this planet is becoming filled up with human trash."

Please watch WALL•E, and consider the message of the movie. Maybe the first planet we should attempt to terraform is Earth?

Apple to Microsoft: 'App Store name is not generic'

Poor Coco
Linux

I have a solution!

http://www.system76.com/

Solved! My Pangolin Pro rocks.

Man found guilty of battery after ejaculating in co-worker's drink

Poor Coco
Stop

As Frankie once said...

"Relax, don't do it, when you wanna come."

Mac App Store: Developer godsend or Evil Empire?

Poor Coco

The App Store...

...is precisely why, after 26 years of Mac OS in various flavours, I am getting out of Dodge and never buying another Mac for computing again. Entertainment, possibly, but not for computing.

The walls will close in. I don't want to be inside them.

NASA hails 'amazing' exoplanetary system

Poor Coco
Boffin

Yes, you are missing something.

The data that is now available thanks to Kepler gives us a vastly larger sampling of planetary systems and gives us an idea of what is possible in solar system formation. This is wonderful insight.

It could also simply be amazement at the wonderful devices we have now made, such as Kepler. Bravo boffins!

Canada? The computer vendor says no

Poor Coco

Wrong town, dude.

The Chinooks hit Calgary: Edmonton simply stays in the icebox all winter. I know this well, having spent a quarter of a century there. It's really not terribly surprising, the number of indoor shopping malls there.

W3C apologizes for HTML5 brand confusion

Poor Coco
Thumb Up

A suggestion

From now on simply refer to WHATWG as "WHAT Working Group?"

Official: music is a brain stimulating drug

Poor Coco

Apropos

"Turning to drugs to make you sleep

Will only lead to sleep

But sleeping is a gateway drug

To being awake, being awake, being awake again."

— They Might Be Giants, "Wearing a Raincoat"

Shocked mum muzzles foul-mouthed toy mutt

Poor Coco
FAIL

Um...

That recording was definitely NOT a "Yank accent". But I think I'll start using "bark" as a synonym for "fuck".

Harder to read = easier to recall

Poor Coco

Help Fight Crimes Against Typography!

Their methodology was flawed, because it only tried making existing documents worse. They should have also compared them with clear, professionally-designed copies; it may well be the case that the cleaner but "un-designed" one is the nadir of readability because it is neither especially clear nor is it a word-puzzle that poor reproduction creates.

Why assume a phenomenon as complex as readability is a linear function?

Enormous 1km ice-cube machine fashioned at South Pole

Poor Coco

Ice clarity

In this location, the ice is exceptionally clear and also very uniform. There is almost no silt deposition there, not surprisingly; it's surely much purer ice than exists in Greenland since there's nowhere much to bring silt from.

They are using the ice about 1000m deep because air bubbles are compressed out at that depth and the ice allows an unparalleled mass-observation device.

Poor Coco

JATO Planes

...have been used for a very long time in Antarctica. My dad surveyed part of Victoria's Land in 1962–63, and I have a picture he took of the JATO bottles being affixed to a US Navy C-47 (military DC-3) flown in to take them out at the end of the expedition.

Missile defence FAIL: US 'kill vehicle' space weapon flunks test

Poor Coco

I know why it failed!

They forgot to take off the oh-so-patriotic maneuvering-thruster caps emblazoned with freedom-loving eagles.

PARIS concocts commemorative cocktail

Poor Coco
Pint

Hmmmm....

The Knicker-Freezer

Booze From A Tube

Hypobaric Hyperglycemia

PARIS Gets Really High

Ford secrets thief caught red handed with stolen blueprints

Poor Coco
Thumb Down

The company that SHOULDA gone bust...

...Chrysler. What an abomination of a car company.

How to make boots on Mars affordable - One way trips

Poor Coco
Thumb Down

Hang on a moment...

The reasons given by this guy for colonizing Mars includes a nearby supernova wiping out life on Earth.

But if Mars has no magnetosphere, wouldn't the people there be even more fucked?

The forgotten, fat generation of Mac Portables

Poor Coco
Thumb Up

Meeeeeeemorieeeeeeessss

I used a Portable one day at my first-ever graphic design job in '89. Was impressive indeed, which tells you how now-tech WE were in those days.

But I wanted to talk about the IIfx; I used one of those in '92 to create (to my knowledge) the very first full-colour gloss magazine with entirely desktop prepress, on a IIfx. It almost killed me, but I did it.

I recall deciding that "IIfx" stood for Too Fucking Expensive, but until the '040-powered Quadras came along it was the Cadillac. I had a poster showing the labeled components in the 'fx and I noticed that they had not just one but TWO Motorola 6502's. "Why," I thought, "Those are CPU's from my old Atari 800!" (which I'd used less than a decade before that). Know what they were used for? Driving the keyboard and mouse. One per ADB plug.

Those 6502's were probably the first example I saw of the exponential growth of computing power. "A CPU reduced to an I/O driver! Oooh, ahhh, the magnificent power of the IIfx!"

DARPA fashions miracle robotic attachment from balloon, coffee

Poor Coco
Happy

All I can say is...

...that doesn't suck because it sucks!

Apple threatens Java with death on the Mac

Poor Coco
Pint

Whew!

Every day I become happier I bought a System76 Ubuntu laptop.

PARIS looking 50/50 for Saturday launch

Poor Coco
Boffin

GO GO GO!

That is all.

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