While not the topic of the games, as you know setting up the 1-km racetrack has been somewhat of a difficult task… Here’s a brief video showing the way it is done, and perhaps capturing the scale of the climb…

The line, btw, is a 3/16″ steel cable, 4300′ long, and weighs about 300 lbs.

Extra credit goes to Michael Keating (Tetherman), Keith Mackey (Heloman), and our fearless super-pilot, Doug Uttecht of Northwest Helicopters in Olympia, Washington.

More videos coming soon, including laser-tracking videos, which are a lot more exciting since you can see the laser beams that are making it all happen.

Following the successful low-altitude test two weeks ago, we re-assembled this past weekend for another round of testing – this time to full altitude, and integrating all steps of the operation.

Just like last time – everything worked straight out of the box. Set-up was quick (less than an hour) and we were ready for the helicopter. Doug Uttecht was flying for Northwest Helicopters again, and he seems to have been practicing this in his mind over the last two weeks, since we were able to dive right into it.

First flight was a warm-up flight, duplicating last week’s flight, just to make sure we haven’t forgotten anything since then. We additionally rehearsed radio commands so that we will later be comfortable positioning the helicopter.

We then practiced climber pick-up and lay-down, which are now a bit more complicated than they would have been with the winch-based design. This is done with two simple tools that allow us to handle the cable without really getting uncomfortably close to it.

We next performed a series of measurements in order to correlate helicopter positions and lasing angles. The trick is to have the climber within the allowed 15-degree lasing angle throughout the climb, while at the same time maintaining its separation from the helicopter. Not-too-steep, not-too-shallow, and actually, we need to drift the helicopter during the climb since there’s no single position that satisfied all conditions. Given the practice we’ve had, this was almost trivial to do, and what’s more important, since wind conditions  will likely be different during the games, we know we can adjust in real time to different cable sags.

Finally, we did an end-to-end test with battery powered climbers. Only USST and KCSP had climbers ready to go, and KCSP suffered from control related issues and did not have their van full of spare parts with them, so to Brian’s endless misery, they were out of the game. USST was the last climber standing, and on their second try, they put the pedal to the metal and completed the 1 km climb with no problems. Meanwhile, Lasermotive who were out with their beam director, confirmed that tracking was feasible within the 15-degree cone I mentioned.

Not much more to say then – the vertical raceway is now ready and waiting for the teams. More information on the upcoming schedule coming your way soon.

The results of this test flight were nominal – just what we wanted. Happiness is three taut chains!

• GPS position keeping worked flawlessly, with the pilot maintaining a horizontal envelope of <40 m irrespective of flight altitude.
• Virtual Bob, in all configurations, worked exactly as intended, keeping the altitude to within several feet, controlling cable tension, and damping the whole structure.
• Deployment off of the figure 8 was smooth.
• Workload on the pilot was reduced significantly, with heads-in operation proving completely feasible.

In all honesty, this should not have been so difficult to do, but the best laid plans, etc.

A big part of getting it right was finding the right crew:

Doug Uttecht and John Peden of Northwest Helicopters

Our next step is to follow up with a high altitude flight to validate the end-to-end procedures. We need to work on a technique for graciously retreiving the climber when folding the pyramid, and we need to decide on whether cables will be reused once laid on the ground.

If all goes well, we’ll be able to do this flight in two weeks, and then turn our attention to running the games.

Linear Bob, single-stranded

The apex with breakaway link

Single-Strand Bob, full view

Implementing Bob turned out to be very easy, an exercise in “junkyard engineering”. After looking at the weight and strength requirements, we chose to forgo the thick cable in favor of  steel chain, and place it only at the bottom end of the pyramid. We thus connected three 3/16” steel cables (same as the climb cable) directly to the breakaway link, and added 100 feet of 3/8” drag chain at the end of each. The total weight of the chain us 400 lbs.

The dimensions of the chain were chosen based on the rate of mass-accumulation we want to achieve – for example, if the chain weights 2 pound per foot, than as the helicopter rises one foot, it lifts 3 lengths of chains, 1.4 feet each, plus a bit of sag – a total of about 4.5 feet, and so is accumulating mass at a rate of 9 pounds per foot.

Seattle is a good town for finding cheap chain. A few phone calls to used marine equipment stores, and there it was – a barrel of 100 m and 400 pounds of 3/8” chain, weighing about 1.2 pounds per foot. Perfect – we can use it as is, or double it up. This chain has shorter links than a standard trade chain, which means it weighs more per foot. Maybe an old anchor chain. Perfecter.

The point masses for step Bob should weigh about 500 pounds total – 167 pounds each, and should be sturdy enough to be beaten around a little bit, and cheap. Truck tires did the trick, and Tires Inc were happy to donate a few used ones to our cause. We ended up taking only three 75 lbs tires, so were on the light side. (this will show in the video of the flight)

Since the forces at the end of the chains are now very low, we used soft line to tie the ends of the chains to our cars. We deployed it on this beautiful field not far from Northwest’s HQ, hooked up the helicopter, and in no time were ready for the first test flight.

The sequence of images clearly shows how Bob works  - The helicopter picks up the cable from a figure-8 coil we set up, and after the coil is exhausted it picks up the apex of the pyramid. The pyramid “stands up” until the chain begin to rise, at which point the rate of pickup decreases and equilibrium is reached.  The pilot doesn’t have to stop the helicopter – it does it all by itself.

Double Stranded Bob	Double Stranded, Step Bob

Step Bob and Linear Bob

When looking for a softer cable arrestor device, Dryden’s John Kelly came up with the concept of Bob.

Bob is a weight that hangs at the end of the cable, lifted by the helicopter, so that once airborne, the tension in the cable is determined by Bob, independent of the altitude of the flight, which is determined by the helicopter, and can deviate considerably, as long as Bob does not touch the ground.

In order to prevent Bob from potentially becoming, well, a wrecking-bob, we would need to attach slanted stay-lines to him, limiting his motion.  The stay lines must be close to horizontal, so that possible vertical motion of Bob will not be hindered.

Of course the helicopter will now be lifting the stay lines as well, so their weight gets added to Bob’s weight. Actually, if we make the stay lines heavy enough, we don’t really need Bob anymore – the weight will be distributed along the stay lines, and no point mass will be hanging over our heads. Thus was coined the term “Virtual Bob system” – a bobless bob!

Next, we make the heavy stay lines (three of them) slant at a full 45 degrees. Since they are heavy, they will sag, and some portion of their length will lie on the ground. If the helicopter moves upwards, the amount of airborne weight increases, thus pulling the helicopter down. If the helicopter moves downwards, the amount of airborne mass decreases, and the helicopter floats back up. Since this is a very gradual stabilizing force, we call this configuration “Linear Bob”.

If we further place point masses a certain distance up the stay cables, we will give Bob a distinct “notch” for the pilot to pull against – we call this configuration “Step bob”. Ideally the point masses add up to the extra lifting capacity of the helicopter at that altitude, so that the only way it can pull them up is to bounce against the end of travel – thus giving us a very soft, resettable force fuse that is coupled to a fixed altitude – Once the helicopter exhausts its inertia, the weights come back down to the ground, resetting the helicopter’s altitude.

This keeps us with the paradigm of flying constant tension, except the system now has a large, self-correcting sweet-spot.

Following Mike Kapitzke’s suggestion, we also moved the breakaway link to the apex of the stay-line pyramid. Now, since the Virtual Bob system fully determines the position of the apex, if the breakaway link were to pop, everything will fall within the base of the pyramid, and so anyone standing outside the edges is not in the fall zone – very convenient for us.

On the right you can see diagrams of Linear Bob and Step Bob. They work well in theory – all that remains (again) is to try them in real life.

The Dynon D10-A display screen ...

... installed in the MD-500

The world’s most boring video clip

As you recall, one of the difficulties we had to solvel when designing the vertical raceway for the games was the requirement to hover over a specific point while at high altitude. The problem is that while flying up high, the pilot cannot really judge the vehicle’s location or speed – imagine looking down from a jetliner (right about the time when you’re told to fold up your food tray and return  your seat to the right up position) and seeing how everything down below is ant-sized… If you look downwards, every slight tilt of the plane, or every motion of your head, will result in very large apparent motion.

To solve this, our aviation consultant Keith Mackey worked with instrument maker Dynon to create a GPS based hover aid, which tells the pilot where he is situated relative to the desired hover point. The helicopter can be 5000 feet above and 5 feet to the left of the hover point, and the instrument will dutifully tell the pilot to move 5 foot to the left.

Having briefed the pilot on the instrument setup on Friday, the first task was to translate theory into practice. Understanding the instrument is one thing, but learning to fly it is another – the pilot has to train himself to properly react to the information the device is giving him – match the size and timing of the control inputs he’s making so as not to lag too much, nor over-compensate.

Luckily for us, Doug Uttecht, our pilot, is experienced in precision flying while pulling power lines, where he is constantly feeding off of instrument readings, and so was a perfect candidate for this job. Keith and Doug finished installing the GPS in the helicopter on Friday and we were all ready to go.

The first thing Keith did was take Doug for a test flight – in his car!  They drove around the helipad, learning to operate the Dynon and getting a feel for the responsiveness of the GPS needle. (This was also significantly cheaper!)

They then took the helicopter on a 10’ hover, and replicated the car exercise, flying around the imaginary waypoint and watching the needle pointing at it and flipping around every time they passed over it. Then the same thing over again at 200 feet, where visual reference is still a viable way to hold position, except by then Doug was flying completely “heads in” – based solely on instruments. 2000 feet, no problem either.

Horizontal station keeping was typically within 10 m, and within 40 m on rare occasions. Vertical station keeping was similar. 20 minutes later they came back to the helipad, saying “well that was easy – what’s next?”

During the hover, Keith recorded this video of the instrument readouts. Boring indeed, since nothing is changing – as it should be.

Dynon have stepped up and are loaning us the instruments needed for the games, and we are very grateful for that – we could not have done this without them.

We spend the last couple of weeks looking at the results of the last test flight at Dryden. First order of business was of course to sort out the sequence of events that led to the activation of the safety breakaway link.

We were able to confirm a few things pretty quickly:

• We re-tested the breakaway link and know that it pops as designed at 3000 pounds, very repeatedly and reliably. Since the helicopter was aiming to pull only 500 pounds, we are confident that the high force was a result of hitting the end of the tether at high velocity.  This is in agreement with the ground video that shows the helicopter first dropping and creating quite a bit of ground slack, and then picking it up rapidly just before the cable goes taut and disconnects.
• In the design phase, we estimated the velocity in which the helicopter has to move in order to create a snap load sufficient to pop the link when the end of the tether is reached. This was approximately 1000 feet/minute, which is in rough agreement with what see in the video.
• Based on the location of the dropped link, we know that the helicopter deviated from its prescribed hover zone. This is in agreement with the ground observations at the time of the disconnect.
• We estimate that once the helicopter deviated from its prescribed horizontal position, the pilot’s attention was diverted from keeping an eye on the tension and altitude readouts, which resulted in the behavior described above.
• The GPS hovering-aid system was not used in either of the flights, since the pilot preferred to use visual references.
• The ground winch did not pay out cable before the breakaway link separated, even though this was intended. This is a result of a combination of the bypass load being set too high (2000 pounds instead of the preferred 1000) and the inertia of the winch drum.
• We estimate that the winch can work as a slow fuse against an accidental pull by the helicopter, but is less effective against a snap load. The manufacturer now says that the setting cannot be brought down to 1000 pounds.

With these conclusions in mind, we proceeded to modify our flight setup:

• We are moving back to the original “small helicopter” model. The S-58 we used was a result of a limited choice that we had. It is heavy, and thus a) has a slower reaction time, and b) has more inertia that manifests itself as snap load once the slow reaction time causes a snap condition in the cable. We located an MD 530 (our original “weapon of choice”), and can also use s lightly heavier helicopter like a Huey H1B.
• We are working with a pilot that is experienced in doing utility power line pulling, which is similar to what we’re doing. To our endless delight, this pilot has pulled 6000’ tether spans in the construction of the recently completed Tacoma Narrows bridge project, and so is well versed in constant-tension line pulls.
• We have done away with the winch. While this is the “industry standard” way of pulling line with a helicopter, we can do better, since our cable does not have to be threaded onto power poles… more on this later, but we have created a custom “gradual arrestor” system which will mitigate snap conditions if we were to run into the same issue again.
• We are now mandating the use of the GPS hover system as the principal means for position keeping.
• At Dryden’s advice, we’ve moved the breakaway link from the top of the cable to the bottom. While still protecting the cable, the result of a breakaway now are that only a small portion of the cable drops from a low altitude, and the helicopter is left towing a long piece of weighted cable, which it can then safely deposit on the ground.
• At Dryden’s encouragement, we will perform a gradual test plan, starting out with untethered flights validating the GPS system, followed by a lower-altitude test demonstrating the system in operation to an altitude of 1000′, and then proceed to a full-height end-to-end demonstration.

The design changes were completed on the first week of the month, and the helicopter operator, Northwest Helicopters, had an opening on the weekend of 9/10. We drew out the logistics plans over labor week weekend, shipped everything out on Tuesday, and flew out on Thursday to prepare for a Saturday flight.

Dave Horn (who organized the SE conference only a few weeks ago) and Seattle-Based team LaserMotive helped with manpower at the site.

I’ll post a little bit more on each of the components list above, and then get back to the actual test flight.

Hi Folks – As the status message on the right indicates, we’ve had a good “return to flight” weekend, with the successful demonstration of a helicopter-borne vertical raceway. This should not have been so difficult to begin with, but sometimes execution of a plan takes an unexpected detour, as was the case here.

In the next several posts I will cover what we did over the weekend, why we did it the way we did, and how it all turned out.

Special thanks to Greg Schoenbachler of Silver Stream Organics and Cattle Company for the generous permission to use their land, and to Doug Uttecht and John Peden from Northwest Helicopters for pulling extra hard on that helicopter.

In preparing the follow-up report for the test, I also found this gem in my archives – a helicopter flight video from youTube, demonstrating the basic ability of a helicopter controlling its position while maintaining a constant pulling force on a long line – this is what convinced us (almost a year ago) that in principle this operation is feasible with a helicopter using standard practices. However, as the saying goes, the devil’s in the details, and the past year was spent mostly on ironing these out.

Stay Tuned for more information, coming your way soon.

Ben

Stress tests are all the rage these days, but to engineers stress tests are old acquaintances.

It is always difficult to place your project into a stress test – you poured your heart and soul into it, and all you really want to do is protect it and treat it gently so it doesn’t break…  Which is of course silly – you should test your brakes in an empty parking lot, not in the middle of traffic. 

The difference lies in that you are not really emotionally invested in your car’s brakes…  Your project, in contrast, having consumed a fair chunk of your life (and money) over several years, is now practically your child…  So there it is – this week, the teams will be stress-testing their kids.

Spaceward’s role is a bit easier.  We’re stress-testing our helicopter-tether system, but for us it is very clear that we want everything that can possibly fail do so this week rather than in July… So as much as possible we’ll rehearse and test every aspect of the games.  Our goal is to be in a position where the July games are simply a repeat performance of the test.  This will of course not 100% possible, but we hope to get close to this goal.

Take for example the camera crews that will film the operations from nearby. Obviously we can run the tests without them, right?  Except that if we do that, we’ll have a group of people at the anchor in July who are totally unfamiliar with what’s going on – not a good idea.  But they don’t really need to shoot video, right? They can just pretend – why should it matter if they produce video? Except that the camera vans transmit in the MW band that’s awfully close to some of the teams telemetry channels. A climber might work perfectly well when the TV van is just hanging out at the anchor pretending to go about its business, but then be completely non-functional in the real games, since the TV van is now transmitting for real.

These interactions are also old engineering acquaintances, and at NASA Dryden the people are well aware of the importance of testing comprehensive systems. Once you bring the system together, there’s no guarantee that it will perform in exactly the same manner as the sum of its parts. Regrettably, life often makes the ideal test impractical – it might be too expensive, or just physically impossible. So project managers always have to walk the line, make these types of decisions, and then live with the consequences – projects that are too expensive, or tests that are never perfect.

Another complication is that while end-to-end tests are the best for detecting flaws and preventing malfunctions, component-level tests are best at providing detailed performance data.

Engineering is not a black-and-white field. The key to a successful project is to keep a cool head, always take time to think things over, and not try to “gamble” just because you are anxious to see success.

Especially in stress-test week, success lies not in flawless execution, but in finding all the faults. We expects to find faults, and will be happy knowing that each fault we caught, is yet one more fault that will not happen in the games in July.

Here’s to a successful stress-test week.

Engine 58

Here’s our ship – ain’t it gorgeous?  You can tell this helicopter is well loved and content with its life.

A quick status report:

Yesterday we met with Sam, one of the two pilots that will fly the helicopter, and worked on the flight procedures – all to be tested out over the coming two weeks.

We then scooted down to Dryden for a full day of work - we had an airfield management briefing meeting, (the actual airfield is part of Edwards Air Force base, not Dryden), laser safety and operations meetings, watched a cable pull test to confirm that our cable meets its specifications (The cable is rated to hold 4200 lb, it started breaking at 5500 lb, so we’re good!), and worked on the parachute configuration.

Edwards is a very exciting place to drive in, since you get to see all sorts of airplanes you don’t usually come across at your community airport – F-22s and Global Hawks for example, just going about their business in the taxiways just across the fence. I really enjoy these visits.

The aforementioned parachute is a safety device we have at the top of the cable, which will slow it down in the case where the pilots for any reason have to jettison it. (There will be a handful of us within our 1-km safety radius, and we’ll appreciate this safety measure a lot if it is ever invoked)

The parachute is actually a drogue chute that is used to pull the main chute of a fighter pilot when he ejects. The reason we like using a drogue chute is that it is intended to be used at high air velocities.  Our cable, along with the mass of the hook assembly at the end will weigh over 400 lb, but as it nears the ground, the weight of the cable pretty much disappears and only the hook assembly remains, at well under 100 lb.  This means that when the cable starts collecting on the ground, the parachute will move at about twice the speed as when the hook reaches the ground. (We’re mainly concerned about the hook, since our cage has no problem handing the cable).

This is one more of these devices we truly don’t anticipate ever being used, but that makes us feel safe knowing that even if the unanticipated happens, there are still extra measures in place take care of us.

 The person helping us with the parachute, btw, is Sean Wilscam at the life support division at Dryden – they take care of such things as parachutes, oxygen masks, pilot protection… They also have the coolest insignia, I’ll post the image soon.  Sean clearly knows his way around parachutes – it’s good to know that we’re relying on a lot of proven expertise that’s just part of what Dryden is.

Tether Setup

Well so far we’ve covered the Helicopter and station keeping, as well as the winch on the ground, so the next thing to explain is the cable assembly that lies in between. As is the case with everything about these games, things are not as simple as they first seem.

Coming out of the winch, the 3/16″ steel cable first travels horizontally for 15 m (50′) or so, and hits a pulley that is attached to the ground.  (Well actually it is attached to a couple of highway crossing plates, so it really cannot move). Going through the pulley, the cable turns 90 degrees and heads up towards the helicopter.

An interesting item here is the grounding jack. It turns out that there’s a very high electric potential difference between air at 5000′ AGL (where the helicopter is) and the ground.  If the cable is not properly grounded, it will get charged up and since the cable-air system forms an effective capacitor, the shock can be quite serious.  We mitigate that by keeping both cable and winch grounded at all times.  The current flowing through the cable will be minuscule – the point is that the cable never has enough time to get charged.

100 m (300′) up the cable resides the “bumper” – a stand-off on which the climber rests before it takes off.  The bumper is provided by the team and is compatible with their climber. An an added benefit for the cable grounding is that we can easily discharge a returning climber by simply touching the bumper, so we’re not worried about getting shocked by it.

Going through the bumper, the cable proceeds upwards another 900 m until we hit the end-of-travel target that indicated a successful climb.

At this point, the cable is connected to a 1/4″ lift cable that continues another 300 m towards the helicopter.  This stretch is designed to leave clearance between the helicopter and the laser beam. It is thicker, since if there’s a cable break, we’d like it to occur below the helicopter, and it also increases cable sag in a way that’s adventagous to us. Right above the end-of-travel target is a wind-direction indicator flag.

At 1300 m AGL, the lift cable attaches to a “remote hook assembly”, which is a 30′ thick Vectran rope that has an electrically actuated release hook.  If the pilot needs to jettison the load, this will be his first choice. At this point we also attach a draug chute, to slow down the tip of the cable in case it gets jettisoned.

We also place here a breakaway link, which is weaker than the cable. If the helicopter were to suddenly pull on the rope, and if the winch failed to yield (As it is designed to do) then cable disconnect will occur here.  It is important to connect the breakaway link above the parachute, not below it :).

Lastly, the remote hook assembly leads to the main disconnect hook at the helicopter, and a load cell, which tells the pilot how much tension he’s putting into the cable. 

I want to thanks Dave Lang of Lang & Associatesfor performing dynamic cable simulations for us, simulating oscillations and cable-break conditions.

Wagner Smith T1DPT

If this isn’t the world’s most forced pun, I don’t know what is.

A central part of setting up the games is to get the 1 km vertical cable raceway in place. The idea is to keep most of the cable on a spool, and have the helicopter pull it out, with the spool offering controlled resistance.  The process will be stopped by either increasing the resistance of the spool to above the helicopter’s pull force, or reducing the helicopter’s pull force to below the resistance of the winch.

The requirements on the winch are simple:  It has to work with at least 3000 feet of 3/16″ steel cable, it has to pull at anywhere between zero and several hundred pounds, and at speeds of zero to several meters per second (we want to cover 1000 m in about 5 minutes, so 3 m/s would be grand), and it has to work in both active (reel-in) and passive (pay-out) modes.

Turns out this is a pretty tall order.  Most winches do not go this fast, and if they do, they are weaklings.

Tow winches are too slow, and can’t take that amount of cable. Overhead lift winches – just the same. There are the winches used to launch gliders, but they are too fast and uncontrolled. Elevator motors are probably interesting, but I can just imagine the cost of building a portable elevator winch.

Luckily, we found an application with similar requirements – stringing power lines.  These are km-long operations, in which cable is pulled and tensioned as it is being fed into pulley on the power lines.  Perfect.  And the bonus is that often these operations are done with helicopters, so there’s precedent to using them in a fashion similar to what we’re doing.

The winch motor is hydraulic, which means there’s somewhat of a “soft touch” to it, and the breaking mechanism uses the engine as a hydraulic brake. Perfect.

The problem right now seems to be locating one. The king-of-the-hill is Wagner-Smith equipment, but these units are in strong demand and the nearest one I can find is located in Texas.  $2000 just to get it here, and probably another $4000 to rent.   Ouchie again. (and another reference to the “Help Us” box on the right!)

But the upside – we have the right winch. As a bonus, it a load cell measuring cable tension – very useful.  It also has a ground lug, which allows us to electrically ground the cable (more on that later)

Sikorsky S-58 - A Classic

We visited Aris Helicopters in LA today.  We’ve previously spoke with Kelly Liken (their general manager) and they seemed interested, but this is going to be the first meeting to discuss the details.

Aris is located in Riverside, at the municipal airport, so it was a relatively short drive from Dryden.  This is good, since the helicopter ferry charge won’t be too much.

We’ve met with Kelly, with Scott Donley Owner), Russ James (pilot).  A pretty sharp bunch, they’re obviously qualified to do the job. I do believe they think we’re nuts, but I also think from a helicopter’s point of view this is an interesting job. They previously flew a flight for the Mythbusters that involved a long-line heigh altitude hover, so have a feel for what we need.

The tether deploy/retrieve systems we’ve devised is acceptable to them, and they can perform what we ask for, except with two caveats:

We will have to use a larger helicopter than we originally expected to.  Once we moved to Mojave (from coastal Florida) we both increased our starting altitude from zero to 2200 feet, and we’ve moved to an area where we have hot dry air (as opposed to warm humid air) – which is less efficient at generating lift through the rotor system of the helicopter.

Our initial plans called for a light single-turbine helicopter, anywhere between a Hughes 500 (yeah, like what’s his name had on Magnum PI) to a Bell 202 Jet Ranger.  Instead, we’re having to move to a twin-turbine mid-size, and the one Aris has is a Sikorsky S-58 – a classic (meaning old) military machine with a very recognizableprofile – this is the type of helicopter that used to pull the old Gemini capsules out of the water.  (As it turned out, Keith Mackey, our helicopter guru, flew the History Channel re-enactments of Gus Grissum’s famous capsule incident - small world, ain’t it?)

We go out to kick the tires (yes, this one has wheels, no skids) and it’s a BIG helicopter. Whereas the MD-500 is (as Dave Marcotte put it) a flying beer can, this helicopter is built like a Brinks truck.  You do NOT want to bang your head against it – it will not yield.  The inside is also very characteristic of military hardware.  Not a gram is wasted on frivolous things like sharp corner protectors.  Are you going to whine, SOLDIER?!!!

There’s only one down side to this Helicopter – it is about $3000 an hour to fly.  Practically a dollar per second. Ouchie.  (this is why we have the “Need you help” box on the right.

The other issue we have is station keeping, or the ability to maintain a hover over a specific point.

Helicopters are very touchy-feely devices. The pilot continuously corrects for the helicopter sporadic drift based on visual cues from the outside – the angle of the horizon, the view of the ground, etc.  When flying “long-line”, such as when placing air-conditioning units on the roof of a building, pilots learn to fly using “vertical reference”, which means they can do without the horizon.

However, all this works well when you’re flying at 100-300 feet above your target. We’re asking them to fly more than 5000 feet above the ground.  It is not clear at all that vertical reference is a good idea.

GPS would be good, except most GPS units do not have a compass built into them. Unless your moving, they do not know how they are oriented in space, since they rely on the assumption that you’re moving “face forward” as you would in a car.  If you were to ask a GPS to point you in the right direction using a screen arrow, it would do ok as long as you’re moving forward, but the minute you’ll start backing up, the arrow will flip to the opposite direction. 

Keith has come up with a very unique GPS-compass arrangement that will do the trick, and so the pilot will have a precise pointer to the target location, plus a distance indicator. What remains to be see is whether the pilot can do the station keeping based on this instrument. There will definitely be a learning curve involved.  Yes, at $3000 an hour…

We’re scheduling the first test flight to June 16th – We’ll find out soon enough.

The Lunar Lander Research Vehicle

This post is about a unique artifact on display at Dryden – The Lunar Lander Research Vehicle – one of the most impressive testaments to the spirit of the 60’s space program.  Not really a spiffy looking thing, the LLRV was not capable of amazing technological feats.  All it was designed to do was allow future lunar lander pilots to feel what a lunar landing would feel like.  Remember the computer-based flight simulators were not available back then.

So in true hard-core engineering fashion, a contraption was designed to simulate the lunar environment.

Step 1: Start with an aluminum-tube truss.

Step 2: Stick a large jet engine at its center, pointing downwards, so it tends to bouy the vehicle. If the jet engine is running at full power, the vehicle will rise to altitude. If the jet engine is then throttled back to provide a thrust equal to only 5/6 of the vehicle’s weight, then the vehicle will fall towards the ground at 1/6g – just like on the moon.

Step 3: Place the entire engine on a gimbal so it can tip and tilt so that it points exactly downwards even when the vehicle is not flying level (as the lunar gravity would act).  Also use the gimbal action to compensated for forces induced by air flow, such as wind and drag, to give the pilot a true moon-like flying environment.

Step 4: Add a set of rockets that replicates the real Lunar Lander rocket systems

Step 5: Add pilot and ejection seat.

Step 6: Voila! – Fly and enjoy.

The contraption looks like a tube warehouse and is 100% function – not a single component there gives it a better look, or a stylish appearance….  it is built to simply do.  I found it very refreshing.  What would cars look like if they were built to simply move people (safely, comfortably) from place to place?

Three of these flying bedsteads were lost, btw, but all pilots (including Neil Armstrong) ejected safely.

The craft was built in just a bit more than a year, btw, and were the only tool Neil Armstrong had to simulate the lunar landing.  This is really important to realize – when Neil Armstrong was descending onto the surface of the moon, with a fuel reserve of about a minute, he was playing real-life lunar-lander with his life, and the only previous experience he had was the flying bedstead.

Just another testament to the spirit of the Apollo program, here at Dryden.

(More on the LLRV here)