A radical new US military drone aircraft, intended to cruise high in the stratosphere on days-long missions in which it would take on many tasks currently requiring satellites, has made its first flight powered by hydrogen. The Global Observer on its first hydrogen-powered flight. credit: US Air Force Throw away that clunky …
Capable of storing advanced tracjectory and environmental sensors
and up to 100 nickels for strategic deniable clearance operations. CIA spokesman has expressed concern that this figure might drop substantially if they had to carry other local currencies.
Big Bad Bird!
I was wondering where they put all the hydrogen, then I realised this is no Reaper drone, it has a wingspan of 175 feet! All that for a tiny 400Lb payload (not even enough for a good-sized GPS-guided bomb). Surely a blimp would do better?
Look at the jetstream map
Afghanistan may not be straight on the main jetstream route over Asia, but it still has 50mph+ jetstream at <200 mb altitude for most of the year. As a result blimps have to stay at much lower altitude so that they are not blown out to China or Russia.
In fact, there are very few places around the world where a blimp is of any use at altitudes of 9000m or above.
Ref: Look at the jetstream map
This problem applies to all aircraft, it just that normal prop and jet aircraft have enough power to overcome the wind.
Not so sure how this one would do, given the apprent size.
Is there something special about hydrogen which makes it the only suitable fuel for such a mission?
I assume there is some good reason why they are using hydrogen?
I thought jet-fuel had a lot more energy per kilo than (liquid) hydrogen, although I'm also pretty convinced there must be a good reason for choosing it... there isn't a massive hydrogen industry affecting the choice of fuel after all.
Anyone know why the choice of hydrogen as fuel?
Volumetric Verses Gravimetric
Possibly because weight is the limiting factor here not Volume.
Liquid H2 is 10MJ/Litre And 120MJ/Kg
Gasoline is 35MJ/Litre but is only 45MJ/Kg
And if you can swap to a very high efficency Fuel Cell in a year or two then your on to a real winner.
In any hydrocarbon the energy needed to break each H - C bond is close to the energy given by the equivalent oxidising of the C . So the carbon is deadweight. All the energy comes from burning the hydrogen.
Hydrogen + Oxygen + Catalyst = Electricity + Water
At a guess... If you have a tank of hydrogen you can use some to topup some electric juice via a fuel cell as well as the rest for conventional propulsion. If its trying to be stealthy and emit a low ir signature you wouldn't want an apu kicking out lots of heat etc.
What conventional propulsion?
Its all electic drive. the H2 is used solely in an internal combustion Electric Generator.
Refer to the article.
"The craft's main special sauce is its hydrogen-powered generator, reportedly based on a fairly normal combustion engine, which supplies power for both propulsion and payload."
Main puzzle to me is how they store the hydrogen. If it's cryogenic, which I assume it has to be, does the boil-off rate match the consumption.
Rural broadband solution
"which offer broadband IP communications to and from from small, portable ground stations lying within the vast footprint covered by the high-flying drone."
Hey I just got a wi-fi signal!
it's being considered...
Re: Rural broadband solution
Yes, besides giving away the fact that one is operating in the area (hey chaps new targets), one can only hope that the US military has now worked out to switch on the encryption, so that the bad guys are not watching your own UAV footage. (which has previously happened)
"the beginning of high altitude, long endurance flight testing"
5000 feet for 4 hours?
The very beginning.
I thought that too
It is at least higher altitude than the Wright brothers' first flight :)
One & Half trick wonder
I think the best way of describing this UAV, is as a one and half trick wonder.
This is only a useful military tool, in very very limited circumstance
1. The bad guys have no ECM capability (jam the signals, your stuffed again for comms)
2. The bad guys have no high altitude air defence capability (remembering mountains put you closer to the aircraft)
3. The bad guys have no intel analisys capability (what can we learn by this being (a) here, (b) how it moves over time)
So, of possible use in Afganistan, briliant for humanitarian operations, useless in a real shooting war, even against 3rd world countries.
But none of them apply to this '1.5 trick wonder' that do not apply to satalites. So I don't understand what your post is eluding too. Jamming a sat is tricky because it is directional youd have to get between the bird and the ground station, this can be too! some bad guys can already shoot down Sats, the Russians, Americans and Chinese have already done so! what does knowing that its there tell you? especially when there is always one there... when these are working providing comms links they will always be operting above the forces! none of your points are valid.
This '1.5 trick wonder' can do everything a satalite can do and more. It has less Latency than a geo stat bird, whilst it is able to remain static above theatre, for the duration, which a lower latency LEO bird cannot do. IT can be moved into position within hours and if required can be refitted for various purposes within hours also, and it'll cost an absolute fraction of an on orbit sat.
The only real down side is that this craft is lower than a sat so slightly smaller missles 'could' get that far but what type would you suggest? the conventional (cheap and widely available) heat seaker will seriously struggle to home in without a jet exhaust. wire guided (the other cheap choice) stands no chance at that height, The only U2 shot down was done so by a command guided S75 which used a radar base station, which are among the first targets for an invasion force, and not your average terrorists toy thing.
Also remember these are a fraction of the size of a jumbo at twice its height, and no vapour trails as its only a small ic engine (Likely to be fitted with a condensor!)
Iraq started 2003 with a coordinated air defence system but this UAV could have been used after the second week of operations, by which time, the Iraqis had no useful aerial assets.
Hydrogen sucks as a fuel.
Loose the Hydrogen, install Solar Panels.
Aeroenvironment have *lots* of experience of this stuff
Mostly with earlier generations of drone partly derived from their Kremer prize winning man powered aircraft.
As for the first flight altitude these things are both big and *floppy* IIRC it took *days* to reach cruising height so you want to prove most features out at an altitude where (if you have to do something) the launch/test/land/fix/re-test cycle per item is not measured in weeks.
Long duration drones already exist. AFAIK they were developed in Australia or NZ for long term (but fairly cheap) weather observation but at relatively low altitude they'd be way too vulnerable to ground fire.
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