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Liquid Hydrogen Powers a UAV For a Cool 48 Hours
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!"
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
Actually hydrogen mixed with oxygen in the relation 2:1 is much worse than hydrogen as a concentrated cloud.
The Tao of math: The numbers you can count are not the real numbers.
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.
Why don't they have RTG's? When one crashes in your backyard you'll be glad.
That is.... Water!
That is.... Water!
After the explosion, yes.
The Tao of math: The numbers you can count are not the real numbers.
Obligatory http://www.dhmo.org/
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/
An RTG is only a problem if it lands on your head, those things are designed to withstand an uncontrolled reentry from space.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
Someone please come up with a small Arduino solution to shoot them down.
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."?
It's so no pedantic arseholes sneer about them probably rounding up.
systemd is Roko's Basilisk.
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.
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...
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?
Tic-Tac-Toe, Global Thermonuclear War, and relationships all have the same winning move.
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.
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.
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.
No kidding!!! What do you say at this point?
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.
I am very small, utmostly microscopic.
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!.
If the clock read 48:01:00 then that is what the clock read.
I am very small, utmostly microscopic.
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.
If information wants to be free, why does my internet connection cost so much?
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.
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.
"Now, I doubt any of you would prefer a rolled up newspaper as a weapon against a dictator or a criminal intruder."
It's so no pedantic arseholes sneer about them probably rounding up.
This has everything sneering pedantic arseholes, refueling solar planes, and rounding.
Yeah, I've spent some quality time navel gazing myself.
I suppose I should have specified heavier-than-air-craft...
Another way to do it without lying is to slap a .0 at the end.
For large sets, this will be our guide even unto death, for the LORD will work for each type of data it is applied to...
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.
[x] cheap
[x] useless
[x] have pointy edges
I say man the catapults!
CLI paste? paste.pr0.tips!
The liquid hydrogen can be used to cool the infrared sensors as well.
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.
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?
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.
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.
Those odd factor-60 minutes and hours should die
There has been an attempt at decimal time during the french revolution, but it did not catch up