Highlights from the 2014 LA Auto Show

Ion Tiger sets new UAV endurance record

By

May 13, 2013

The Ion Tiger UAV completes its record-breaking flight

The Ion Tiger UAV completes its record-breaking flight

Image Gallery (2 images)

Back in 2009, the US Naval Research Laboratory (NRL) set an endurance record for electric unmanned aerial vehicles (UAVs) when its fuel cell-powered Ion Tiger aircraft managed to stay aloft for 26 hours and 1 minute. Now, NRL has announced that the same aircraft has trounced that record, by remaining in flight for 48 hours and 1 minute.

In its previous record-breaking flight, the UAV’s Polymer Electrolyte Membrane (PEM) fuel cells were running on compressed gaseous hydrogen stored at 5,000 psi. On its latest flight, which took place from April 16th to 18th, cryogenic liquid hydrogen was used instead. Liquid hydrogen has three times the density of gaseous hydrogen, thus its ability to power a much longer flight.

The NRL crew with the Ion Tiger – from left to right: Dan Edwards, Mike Baur, Steve Carrut...

One challenge lay in developing a lightweight dewar (a double-walled insulating vessel) for carrying as much of the fuel as possible, while keeping it sufficiently cold. If the liquid hydrogen were to get too warm, it would boil off at a rate faster than the UAV could use it.

NRL is particularly interested in using fuel cells for such drone aircraft, as internal combustion engines are inefficient and loud (and thus not particularly stealthy), while battery electric UAVs have a very limited range. The researchers are hoping to develop a system in which an onboard electrolyzer and energy source (such as solar or wind) could be used to electrolyze, compress, and refrigerate liquid or gaseous hydrogen from water.

Source: Naval Research Laboratory

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away.   All articles by Ben Coxworth
7 Comments

The ICE engine is cheaper, can be muffled and and have the sound directed up, burn much cheaper, and storable fuel that is also more energy dense. The fuel can be stored in the wings or other oddly shaped spaces leaving the fuselage available for payload making the aircraft more aerodynamically efficient.

But hey fuel cells are cool.

Slowburn
13th May, 2013 @ 05:29 pm PDT

Actually, liquid H2 has about 3 times the energy density by weight as petrol and the fuel cell typically runs at about 50% efficiency vs. 25-30% efficiency of an internal combustion engine. I'm sure the engineers at the NRL have weighed the costs/benefits of internal combustion vs. fuel cell with respect to duration, weight, aerodynamics etc. Give them some credit. :-)

prokaryote
13th May, 2013 @ 06:27 pm PDT

From an earlier article on Gizmag:

"The Ion Tiger is a UAV research program that merges two separate efforts - UAV technology and fuel cell systems. The Ion Tiger weighs approximately 37 pounds and carries a 4- to 5-pound payload. The 550 Watt (0.75 horsepower) fuel cell onboard the UAV has about four times the efficiency of a comparable internal combustion engine."

So multiply the 3 time energy density by 4 times the engine efficiency and you have to carry 12 times the weight of petrol to equal the useful energy of the hydrogen/fuel cell combo. I'm guessing that at the slow speeds this flies at, the added drag is more than made up for by the reduction of lift needed, hence a reduction in the lift induced drag.

prokaryote
13th May, 2013 @ 06:36 pm PDT

Yes, but hydrogen detonates. Hard to see it being used in atomic form in other than military or aerospace applications.

As a hydrogen aside, in the mid '70s I lived in Palo Alto, CA and would often see huge liquid hydrogen tankers passing through on El Camino Real. This disturbed me so I wrote the fire and safety official in Palo Alto to express my concern. I was assured by letter that liquid hydrogen presented no danger to the large metropolitan area on either side of El Camino Real from San Francisco to San Jose (my house was one block off of it.) I actually considered hijacking one, taking it to some wide open space and setting it off to make an unequivocal point.

Sure wish I still had that letter. :-)

DonGateley
14th May, 2013 @ 11:35 am PDT

re; prokaryote

Even if your numbers are right it is still more cost effective to use ICE.

re; DonGateley

The hydrogen transport trucks are less dangerous than diesel transport trucks. Hydrogen being lighter than air dissipates much faster and does not contaminate anything. Cost is the issue not safety.

Slowburn
14th May, 2013 @ 03:46 pm PDT

What and petrol doesn't explode? Aparently a hydrogen tanker is much safer than petrol as the heat doesn't radiate out as much.

Marc 1
14th May, 2013 @ 09:07 pm PDT

re; prokaryote part 2

With hydrogen having to be stored in the fuselage means the wing structure has to carry the entire load to the center whereas with diesel (or Avgas) stored in the wing the load is distributed reducing the structural requirements. Also the smaller space requirement reduces airframe mass and aerodynamic drag.

Slowburn
15th May, 2013 @ 12:01 am PDT
Post a Comment

Login with your gizmag account:

Or Login with Facebook:


Related Articles
Looking for something? Search our 29,494 articles