11-Pound Model Plane Vs. The Atlantic, Again

Luap Nanreffeh writes "Last year, (/. Story 1, /. story 2) Maynard Hill and some retired NASA buddies tried to set a record for flying a model aeroplane across the atlantic ocean (from Newfoundland to Ireland). Their plan, using GPS, onboard controllers, and a gallon of gas, would have been the first to cross the Atlantic under FAI rules. They didn't have much luck last year, but now they're at it again. The first launch should be tonight."

Comments

Wouldn't it be better...

[Sir Haxalot]

instead of giving an exact date, just waiting until weather conditions are perfect to fly it?

Re:Wouldn't it be better...

[Anonymous Coward]

There is NO "perfect solution when you are talking about the weather. Doubly true when you are talking about the weather on two continents and one ocean.

Re:Drug running

[Steffan]

What makes you think that they aren't already doing this. It's not like they'd post to Slashdot if they were successful.

Little planes too limiting.

[Anonymous Coward]

They much rather the use of big planes like L1011s and 747s. These much larger aircraft have proven to be far more reliable than tiny drones. Additionally, the larger craft are capable of carrying much larger loads which is a very important feature to the highly competitive drug trade. Basically, if the transport can't handle a ton or more of product, the more respected cartels won't touch it.

Possible Use

[thePancreas]

Drug Smuggling anyone? Or maybe strong encryption smuggling. Can't be radar visible if it's that small.

hm

[DNS-and-BIND]

Why don't they just build a dozen of these, and launch them an hour apart. The whole advantage of small inexpensive craft is the "swarm" approach.

Or...

[missing000]

A potential terrorist device?

I can see it now. Our next military campaign will be to eradicate model airplane building materials from the rest of the globe.

Re:This is as interesting as rocketry

[Doesn't_Comment_Code]

'd think more geeks would be into it, especially with all the equipment you get to work with.

But DANG would this be an expensive hobby! If you can get some financial backing or sponsorship it would be ok. But that's a lot of high quality, lightwight devices. And we all know that
high quality + heavy = expensive. And
high quality + small and light = super-expensive!

And the thing that really gets me, is that once you load up your huge investment into a tiny plane, you send it out to its almost certain destruction!

Now I'll spend money on something I'm going to improve on and keep for a long time. But dropping cash on a big project like this would be like shooting $100 bills into the ocean.

Without a better success rate, you'd have to be a drug smuggler just to afford the little marvels.

Re:By all other names

[oGMo]

So this is a automatous GPS-guided long-range flying vehicle? Isn't that a cruise missle?

So, a cat is a 4-legged mammal with hair? Isn't that a woolly mammoth?

Nope, invalid logic.

GNC

[deblau]

Let's start with navigation. They may be ex-NASA, but unless they applied for and received GPS PPS capability, they're navigating with SPS only, which is only +/- 100m with 95% confidence. Normal flight rules allow human pilots to use GPS for lat/lon determination only and not altitude, especially not for precision approaches. 50m +/- 100m isn't what you want to see on your altimeter. Normally, GPS should be backed up by something like LORAN, which has accuracy of 100ft, but even that isn't reliable over much of the North Atlantic due to poor coverage. The best system involves the use of GPS/LORAN-C in combination with some sort of inertial navigation system (INS). But you have to remember that gyroscopes precess, and that magnetic headings can be off by as much as 45 degrees in the North Atlantic due to magnetic deviation.

Realize that even as reliable as GPS is, satellites can give false information. There's a system to counteract this problem, called RAIM, but it requires 4 birds to be visible to detect a problem, and 5 to remove the faulty signal from nav calculations, assuming you have a redundant, GPS-compatible, digital barometric altimeter on board. Otherwise, you need 6 birds visible.

Guidance seems to be relatively straightforward: figure out where you are (with 95% confidence), and aim toward your next waypoint. Here's a quick overview of what that entails:

1. Determine lat/lon for you and the waypoint
2. Determine true (ground) course
3. Determine magnetic course after correcting for the aforementioned deviation
4. Determine magnetic heading after correcting for wind
5. Determine compass heading after correcting for onboard instrument magnetic interference
6. Issue commands to the flight control system to head that way

The wind correction is non-trivial. Last I checked, winds in the flight route were generally sustained at around 15 knots, and varied by a full 180 degrees relative to the course. This plane flies at about 40 knots. Grabbing a calculator and doing some trig, wind correction could be as much as arctan(15/40) = 20 degrees. Onboard interference is typically up to 10 degrees in GA aircraft. Here's a concrete example: if you want to fly due east (090) in the North Atlantic with a 45 degree deviation and winds from the south at 15 knots, with onboard interference of +10 degrees, you'd have to fly a compass heading of 165! That's almost due south.

That leaves flight controls. You need to maintain proper attitude, keeping in mind that there's gonna be turbulence. In order for any magnetic navigation system to properly realigned (remember gyroscopic precession?), you need to be flying straight and level, which requires extensive compensation for unsteady flight dynamics. It's not as simple as saying "pitch up" when your speed gets too high or your altitude is too low. What if you get inverted? It can happen. Even human pilots don't do so well flying instruments only -- see the NTSB findings in the JFK junior crash. Maintaining stability and control over dynamical systems is a hard problem, which is why many colleges offer entire majors in CDS.

Disclaimer: I am a Space Shuttle enthusiast and a student pilot (hopefully, that will change in two weeks). I know that NASA have the expertise to overcome these problems, and I'm willing to give these engineers the benefit of the doubt. I wish them good weather and no system malfunctions.