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Liquid Hydrogen Powers a UAV For a Cool 48 Hours

Unknown Lamer posted about a year and a half ago | from the spy-longer dept.

The Military 72

An anonymous reader writes "While liquid hydrogen may not be a mainstream fuel for drones, the aerospace industry has said it holds the promise of flight endurance on the order of days, seemingly just another far-fetched aerospace industry pitch ... until now. The Naval Research Laboratory just announced that the Ion Tiger, a diminutive 37-pound airplane with a 17 foot wingspan, flew for 48 hours and 1 minute on liquid hydrogen and a fuel cell (anyone else notice the oddly specific duration? Guess it's better than 47 hours 59 minutes). This is a dramatically different scale than the liquid hydrogen powered 150 foot wingspan Boeing Phantom Eye and 175 foot wingspan AeroVironment Global Observer, which have yet to live up to their multi-day endurance projections. Interestingly enough, the well-known Global Hawk only has an endurance of 33.1 hours, which barely cracks Wikipedia's list of notable UAV endurance flights. Of course, solar-electric airplanes have flown for two weeks continuously, but that sure seems like refueling!"

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There's nothing odd with 48 hours 1 minute (0)

Anonymous Coward | about a year and a half ago | (#43682577)

Why would you think so?

Does the idea of planning a '48 hour flight', and then spending a minute extra on landing after achieving the mission goal, seem strange to you?

Re:There's nothing odd with 48 hours 1 minute (1, Interesting)

VortexCortex (1117377) | about a year and a half ago | (#43682681)

Why would you think so?

Does the idea of planning a '48 hour flight', and then spending a minute extra on landing after achieving the mission goal, seem strange to you?

All those extra minutes add up over time. IMO, all drones should have "instant landing" maneuvers. Simply start by pitching the nose to a moderately steep angle of 90 degrees down to cut out a lot of that landing time. Bonus: no need to calculate fuel usage time for any future flights...

Alternatively, as soon as the drone gets to its destination air-space, it could simply detonate any remaining fuel. ::KaBang:: - The sound of a drone reaching a state of perfection in usefulness to mankind.

Protip: Removing the human element from surveillance and war devalues it dangerously. Grow up children. Your toys can not do your jobs for you.

There's something odd about the discrepancy (1)

bothemeson (1416261) | about a year and a half ago | (#43682785)

Great comments :-) - notice how the navy's own page says "The craft shattered all previous endurance records [having previously noted the navy's 40-minute flight in 1924] performed by similar, propeller driven, fossil fuel and battery-powered UAVs by completing an uninterrupted 26-hour flight carrying a five-pound payload."?

More like marketing: "Over 48 hours!" (1)

fantomas (94850) | about a year and a half ago | (#43683757)

The odd minutes may add up but I suspect it sounds better in marketing-speak: "Over 48 hours!" sounds more impressive than "48 hours 1 minute" or "2 days" perhaps?

Plus as somebody else had noted maybe there's a government contract which specifies money will be given if a prototype can be shown to run for at least 48 hours. Over 48 hours? 48 hours 1 minute, send us the money!.

These guys aren't into marketing... (5, Informative)

PseudoCoder (1642383) | about a year and a half ago | (#43684015)

I worked with this group and I can tell you they're not into marketing, but the press people that prepared the release probably are.

The bulk of what this NRL section does is technology demonstrators. They were also the first to air drop a drone from another drone. The odd number is probably an exact accounting of the time spent on powered flight; climb, cruise and loiter segments are the most significant for accounting for energy use during flight. Gliding and coast segments are not so interesting.

Props to my old crew at NRL, and to the memory of Jim Kellog who developed the first prototype of what became the Ion Tiger.

Re:These guys aren't into marketing... (2)

wagnerrp (1305589) | about a year and a half ago | (#43686687)

Gliding and coast segments are not so interesting.

In this case, they are. The aircraft was powered by cryogenic liquid hydrogen. Even when they were coasting, they were still generating fuel (hydrogen gas), and that fuel could only be stored for a short period before rising tank pressures would have necessitated venting. Their fuel had a limited lifetime regardless of whether they were actually using it.

Re:There's nothing odd with 48 hours 1 minute (0)

Anonymous Coward | about a year and a half ago | (#43696465)

>Protip: Removing the human element from surveillance and war devalues it dangerously. Grow up children. Your toys can not do your jobs for you.

Thank you for your brainless, poorly thought out tip.

Drones mean that, instead of firing and forgetting a cruise missile 20 minutes before impact, you can wait until the last moment to abort. Drones mean that dozens of people, in the sober thinking position of a far away base, from the pilot, to legal and political observers are making the fast decisions-- rather than someone in immediate fear for their life. Drones mean the ability to wait until confirmation of identity or location is recieved, and execute immediately, maximizing the chance for successfully hitting the target, and minimizing collateral damage.

But yeah, some meaningless abstraction and 'the human element', and idiotic rhetoric about 'toys' is much more important than reducing civilan casualties and mistakes in war.

Re:There's nothing odd with 48 hours 1 minute (4, Insightful)

wonkey_monkey (2592601) | about a year and a half ago | (#43682903)

It's so no pedantic arseholes sneer about them probably rounding up.

Re:There's nothing odd with 48 hours 1 minute (1)

Sulphur (1548251) | about a year and a half ago | (#43684145)

It's so no pedantic arseholes sneer about them probably rounding up.

This has everything sneering pedantic arseholes, refueling solar planes, and rounding.

Re:There's nothing odd with 48 hours 1 minute (4, Interesting)

redback (15527) | about a year and a half ago | (#43683941)

also if you say '48 hours' it sounds like you are approximating. but 48:01 is precise enough for people to know that you are serious.

The first man to calculate the height of mt everest calculated it to be 29,000 feet exactly. To make it sound as precise as it was, he said it was 29,002 feet.

Re:There's nothing odd with 48 hours 1 minute (1)

X0563511 (793323) | about a year and a half ago | (#43684629)

Another way to do it without lying is to slap a .0 at the end.

I think liquid hydrogen is dangerous as hell (0)

Anonymous Coward | about a year and a half ago | (#43682599)

I think I heard it's more dangerous than handling pure hydrogen peroxide. One miss-step and boom!

Re:I think liquid hydrogen is dangerous as hell (0)

Anonymous Coward | about a year and a half ago | (#43682619)

You mean, nitrogen tetroxide oxidizer, or more technically, dinitrogen tetroxide.

Hyrdogen is bad and can go boom it forms a concentrated cloud. But no wear near as dangerous as longer burning fuels.

Re:I think liquid hydrogen is dangerous as hell (2)

maxwell demon (590494) | about a year and a half ago | (#43682671)

Actually hydrogen mixed with oxygen in the relation 2:1 is much worse than hydrogen as a concentrated cloud.

Re:I think liquid hydrogen is dangerous as hell (1)

Anonymous Coward | about a year and a half ago | (#43682697)

That is.... Water!

Re:I think liquid hydrogen is dangerous as hell (4, Funny)

maxwell demon (590494) | about a year and a half ago | (#43682717)

That is.... Water!

After the explosion, yes.

Re:I think liquid hydrogen is dangerous as hell (1)

flayzernax (1060680) | about a year and a half ago | (#43682729)

Obligatory http://www.dhmo.org/ [dhmo.org]

Re:I think liquid hydrogen is dangerous as hell (0)

Anonymous Coward | about a year and a half ago | (#43682719)

Yes, imagine http://www.youtube.com/watch?v=MMB2VR0087w but much bigger ;p

But that's what I meant. I should have specified "a specific concentration" Thanks for the clarification though.

At least it doesn't generally leave a mass of still burning flames behind. Jet fuel is a bitch. If the thing malfunctioned it would likely burn out quickly. Spilling is less of a problem.

Mass storage of hydrogen is. It could be a real bad logistics problem. It might not be to bad to produce it on the spot though.

Re:I think liquid hydrogen is dangerous as hell (3, Insightful)

delt0r (999393) | about a year and a half ago | (#43683853)

I think you where misinformed. H2O2 is not really a good fuel on its own. Too heavy for starters for so little energy. But its less safe mostly because its also unstable.

Like all mono propellants, it can break down to a more stable less energetic configuration without the need of getting mixed with anything. So say the fuel tank wasn't cleaned properly? Well we get H202 decomposition which liberates O2 and heat. Now its hotter and it decomposes faster, which produces more heat and faster decomposition.... I have personally seen this with my own monopropellant rocket.

Can you handle H202 safely? Yes. But you can also do that just fine with LH2 with the added benefit its pretty safe till you mix it with oxygen, and its has much more energy per kg. An important feature for long endurance flights.

Re:I think liquid hydrogen is dangerous as hell (1)

wagnerrp (1305589) | about a year and a half ago | (#43686747)

On the other hand, you have to insulate the tank extensively, and you still have constant evaporation. A small aircraft like this can't afford a heavy refrigeration unit. There was a fair amount of design and planning that went into making sure the natural evaporation rate of the fuel roughly matched the consumption rate during cruise.

Two furlongs a fortnight... (5, Funny)

Anonymous Coward | about a year and a half ago | (#43682633)

How about you try to use units that make sense? Here's a diagram that illustrates the sillyness https://7chan.org/sci/src/132255181954.jpg [7chan.org]

Re:Two furlongs a fortnight... (4, Funny)

maxwell demon (590494) | about a year and a half ago | (#43682709)

Yes, they certainly should have used "172.86 kiloseconds" instead of "48 hours, 1 minute". Those odd factor-60 minutes and hours should die. It's not that hard to remember that a day is 86.4 kiloseconds and a year is about 31.5 megaseconds, after all.

Re:Two furlongs a fortnight... (1)

julesh (229690) | about a year and a half ago | (#43682737)

What are these archaic "day" and "year" units you're using? I haven't felt the need for units based on the orbital mechanics of one single planet for a significant fraction of a gigasecond. And besides, 10*PI megaseconds is a much more interesting period of time. :)

Re:Two furlongs a fortnight... (3, Interesting)

maxwell demon (590494) | about a year and a half ago | (#43682761)

Actually a good way to remember the length of a year is to remember that pi gigaseconds give (almost) a century.

decimal time (1)

manu0601 (2221348) | about a year and a half ago | (#43691961)

Those odd factor-60 minutes and hours should die

There has been an attempt at decimal time [wikipedia.org] during the french revolution, but it did not catch up

Re:Two furlongs a fortnight... (0)

Anonymous Coward | about a year and a half ago | (#43683019)

7chan, really?

Re:Two furlongs a fortnight... (1)

Anonymous Coward | about a year and a half ago | (#43683321)

Surely it was to meet a contract stipulation: "...shall fly for a period exceeding forty-eight (48) hours..."

Re:Two furlongs a fortnight... (0)

Anonymous Coward | about a year and a half ago | (#43683471)

yeah 10 hour days, 100min hours, 100sec minutes

Wait..what?! (0)

Anonymous Coward | about a year and a half ago | (#43682649)

So 48 hours is some kind of record for a UAV??! I thought they could stay in flight for weeks at a time...why don't these things have RTG's, like voyager?!

Re:Wait..what?! (1)

backslashdot (95548) | about a year and a half ago | (#43682689)

Why don't they have RTG's? When one crashes in your backyard you'll be glad.

Re:Wait..what?! (3, Insightful)

TapeCutter (624760) | about a year and a half ago | (#43682763)

An RTG is only a problem if it lands on your head, those things are designed to withstand an uncontrolled reentry from space.

Re:Wait..what?! (1)

Sockatume (732728) | about a year and a half ago | (#43683727)

The ones sent into space are designed to withstand an uncontrolled reentry from space. The ones used to power lighthouses (for example) are significantly less durable, and I dare say that one built into an aircraft would want the minimum acceptable shielding.

Re:Wait..what?! (1)

Terwin (412356) | about a year and a half ago | (#43685069)

The ones sent into space are designed to withstand an uncontrolled reentry from space. The ones used to power lighthouses (for example) are significantly less durable, and I dare say that one built into an aircraft would want the minimum acceptable shielding.

Mass for a spacecraft is far more expensive then mass for an airplane.
Also, if the RTG falls out of a lighthouse it is not going to fall very far, so not nearly as much need for shock absorbing, while the uninformed people will go OMG NUCLUEAR! and aeronautic approved RTGs will need even more protections than those in spacecraft.

Re:Wait..what?! (1)

flayzernax (1060680) | about a year and a half ago | (#43687255)

It's my under standing that the few times those lighthouse RTG's or other non-space application RTGs have been opened and recovered by civilians the casualties were low. They didn't kill even 100's of peoples.

Total fatalities due to RTGs to date is probably less then 100. And this is a horrible estimate. Completely inaccurate and unscientific, but leaning on the safe side enough to make a point.

RTGs are not that bad when handled properly. Soviets screwed up by widely distributing them and not decommissioning them.

The U.S. to my knowledge has never had an accident with an RTG.

Re:Wait..what?! (2)

m.alessandrini (1587467) | about a year and a half ago | (#43683073)

RTGs, if I'm not wrong, give a small amount of energy, useful in space where you need little energy but for very long times. Not to mention their weight.

Re:Wait..what?! (1)

wagnerrp (1305589) | about a year and a half ago | (#43683639)

The average RTG weighs several hundred pounds, and runs upwards of a kilowatt output. I would be very much interested in any viable aircraft you could design under those constraints.

Re:Wait..what?! (1)

fnj (64210) | about a year and a half ago | (#43683725)

The HINDENBURG carried engines + fuel totaling about 150,000 lb. Cruise power was 3200 hp (2400 kW) at 68 knots, but she could go 40 knots on 500 kW. That's 300 lb/kW. Is that close enough?

An airship that could travel at 40 knots for YEARS without stopping sounds pretty viable to me.

Re:Wait..what?! (1)

wagnerrp (1305589) | about a year and a half ago | (#43684331)

I suppose I should have specified heavier-than-air-craft...

Re:Wait..what?! (1)

fnj (64210) | about a year and a half ago | (#43688237)

I understand, but what does it matter by what design you achieve viable controlled flight a specified ratio of engine+fuel mass to engine power?

I am also pretty sure you could match that 40 knot figure with some kind of radical super-super-light huge-and-slow airframe such as is used in solar aircraft. Not sure if I would rate that viable except for special missions.

That's not long try 14 days (1)

garymortimer (1882326) | about a year and a half ago | (#43682757)

The QinetiQ Zephyr laughs aloud at this with its two week high altitude endurance record. There are several two day platforms out there, look harder ;-) http://www.suasnews.com/2010/07/470/after-14-nights-in-the-air-qinetiq-prepares-to-land-its-zephyr-solar-powered-unmanned-aircraft/ [suasnews.com]

Re:That's not long try 14 days (1)

Sique (173459) | about a year and a half ago | (#43682953)

To quote the blurb you are replying to: "Of course, solar-electric airplanes have flown for two weeks continuously, but that sure seems like refueling!"

Re:That's not long try 14 days (0)

Anonymous Coward | about a year and a half ago | (#43683335)

So during those two weeks extra hydrogen was added to the sun?

Re:That's not long try 14 days (1)

Sique (173459) | about a year and a half ago | (#43683555)

No, extra energy was added via solar panels to refuel the batteries.

Hate drones (1)

Anonymous Coward | about a year and a half ago | (#43682773)

Someone please come up with a small Arduino solution to shoot them down.

Re:Hate drones (0)

Anonymous Coward | about a year and a half ago | (#43683103)

You have a lot of drones in your neighborhood? You may have bigger problems....

Re:Hate drones (2, Funny)

Anonymous Coward | about a year and a half ago | (#43683161)

I'd suggest some sort of catapult. Although I'm not sure Arduinos are the best type of ammunition.

Well they are (1)

fisted (2295862) | about a year and a half ago | (#43685375)

[x] cheap
[x] useless
[x] have pointy edges

I say man the catapults!

Re:Hate drones (1)

T-Bone-T (1048702) | about a year and a half ago | (#43683325)

So it is OK to shoot down a plane just because it doesn't have a person in it?

Re:Hate drones (1)

newcastlejon (1483695) | about a year and a half ago | (#43683451)

So it is OK to shoot down a plane just because it doesn't have a person in it?

That depends, are there a lot of people under it as well?

What's bad with solar? (1)

m.alessandrini (1587467) | about a year and a half ago | (#43683117)

Of course, solar-electric airplanes have flown for two weeks continuously, but that sure seems like refueling!"

Come on, that's terribly unfair! Refueling as you fly is not the same as having to return to base...

Re:What's bad with solar? (1)

drinkypoo (153816) | about a year and a half ago | (#43683945)

Come on, that's terribly unfair! Refueling as you fly is not the same as having to return to base...

It's not refueling at all. Refueling would be swapping batteries. This is recharging. It's foolish to try to describe recharging as refueling when there's already a separate name for each. Or, in this case, it was prevarication on the part of the commenter.

Nice comparison (2)

oodaloop (1229816) | about a year and a half ago | (#43683149)

The Global Hawk is the size of a 747. The Ion Tiger is a small lightweight drone with a 17" wingspan. And the Phantom Eye is large at 150" wingspan, but also described as lightweight. Comparing flight duration seems a bit unfair. Anyone have a better idea how to properly compare efficiency of engines?

Re:Nice comparison (1)

Anonymous Coward | about a year and a half ago | (#43683197)

For 'regular' turbine engines this is typically done with the 'specific thrust' and 'specific fuel consumption'. With these this allows you to make more reasonable comparison between engines of whatever size. Of course performance characteristics such as velocity of the plane etc should be the same.

Re:Nice comparison (2)

Sique (173459) | about a year and a half ago | (#43683267)

While the Global Hawk surely is large, it's a far cry from a 747. It has a wingspan of about 130 ft and a length of 48 ft. Compare that to the 211 ft wingspan and 230 ft length of a 747-400!

Re:Nice comparison (2)

gatkinso (15975) | about a year and a half ago | (#43683765)

I am sure the OP meant 737.

Re:Nice comparison (1)

T-Bone-T (1048702) | about a year and a half ago | (#43683317)

The Global Hawk isn't anywhere close to the size of a 747. A 747-8I is about 4x taller, 4x longer, 4x wider wingspan. It is a big drone but not especially large compared to other aircraft.

Re:Nice comparison (1)

T-Bone-T (1048702) | about a year and a half ago | (#43683333)

I got the wingspan wrong but it still isn't anywhere close to a 747.

Re:Nice comparison (0)

Anonymous Coward | about a year and a half ago | (#43683479)

size of a 747? doubt it http://en.wikipedia.org/wiki/File:RQ-4_Global_Hawk.jpg

Re:Nice comparison (1)

wagnerrp (1305589) | about a year and a half ago | (#43683705)

Global Hawk is a turbofan. Phantom Eye is a turbocharged piston. This one is electric. As a general rule, turbines are more efficient than pistons, and fuelcells/electrics are more efficient than turbines. The more important trait here is cruise velocity. The electrically powered Ion Tiger is going to be much slower than either of the other two, and thus will inherently consume considerably less fuel.

Re:Nice comparison (1)

marcosdumay (620877) | about a year and a half ago | (#43684563)

As a general rule, turbines are more efficient than pistons, and fuelcells/electrics are more efficient than turbines.

Fuel cells can be anywhere from 1% to 90% efficient. In this case it's probably nearer the 90% limit, but that's not the general case.

Re:Nice comparison (1)

wagnerrp (1305589) | about a year and a half ago | (#43684929)

90% seems awfully high. I was under the impression typical performance was around 40%-70%, depending on the chemistry and materials.

Re:Nice comparison (2)

tlhIngan (30335) | about a year and a half ago | (#43685439)

90% seems awfully high. I was under the impression typical performance was around 40%-70%, depending on the chemistry and materials.

In general, the limiting factor is the quality of the hydrogen - the oxygen can generally come straight from the atmosphere. In this case, it's pure hydrogen stored as a liquid, so fuel cells tend to be fairly efficient.

Take Apple's fuel cells powering their data center, and they're running off natural gas, which is 20% carbon for the most part (by stoichiometry) which is impure and has to be dealt with. And nevermind that natural gas, while being mostly methane, also contains longer gaseous hydrocarbons that provide more "poison" to the cell that has to be dealt with.

Of course, you could refine methane to hydrogen and carbon, but hydrogen itself is rather difficult to transport since it doesn't like to be contained easily.

Re: Nice comparison (0)

Anonymous Coward | about a year and a half ago | (#43683821)

sure. coompare the usefulness of thhe aircraft. Global Hawk routinely flies with NASA weather payloads. cameras and radars for surveillance, and a communicatiins payload. the rest are science fair projects that dont fly a real mission.

"oddly specific duration" (0)

Anonymous Coward | about a year and a half ago | (#43683615)

"anyone else notice the oddly specific duration? Guess it's better than 47 hours 59 minutes"

Well, yeah...
More than 2 days is and obviously sounds better than less than 2 days.

How is it an "oddly specific duration"?
You would've picked less than 2 days and used "47 hours 59 minutes"?

Re:"oddly specific duration" (1)

gatkinso (15975) | about a year and a half ago | (#43683803)

If the clock read 48:01:00 then that is what the clock read.

Re:"oddly specific duration" (0)

Anonymous Coward | about a year and a half ago | (#43684667)

"I endeavor to be accurate." - Mr. Spock

No comparison with Global Hawk (2)

gatkinso (15975) | about a year and a half ago | (#43683741)

It flies at 300 knots and weighs ~30,000 lbs (~14,000 kg).

I worked on the NASA Global hawks for a few years. They are incredible aircraft and certainly not in the class of the toys it is being compared with. Predator comes close (I was on an effort to put a sensor on the NASA Predator but funding got yanked) but Predator doesn't have nearly the capability of Global Hawk.

Naval Research Laboratory (1)

Anonymous Coward | about a year and a half ago | (#43684183)

Yeah, I've spent some quality time navel gazing myself.

48 hours and one minute ?? (0)

Anonymous Coward | about a year and a half ago | (#43685615)

Anyone want to cover a bet that in the contract, a large amount of monies were to be paid after a flight duration time greater than 48 hours? Just sayin' is all.

Other benefit (1)

wimpy (39015) | about a year and a half ago | (#43686275)

The liquid hydrogen can be used to cool the infrared sensors as well.

not impressed (1)

hurfy (735314) | about a year and a half ago | (#43686785)

Not sure that says much about the power system.
The plane appears to be very close to a sailplane. Drop the weight a bit and i think it would run on watch batteries and thermals.

17 feet is a lot of wing for 40ish pounds of airplane.

hmm, can we make a powered glider that can find a big thermal and reverse the circuit to recharge a battery in a dive?

Hybrid (0)

Anonymous Coward | about a year and a half ago | (#43687861)

Sounds like an easy hybrid: Add solar panels to a fuel cell to extend range (or fuel cells to a solar-power plane, depending on your design criteria)

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