By Chris Bowlby
Producer, Robo Wars, BBC Radio 4
A US Air Force pilot 'flies' a Reaper by operating a sensor control station
Mark Jenkins is an experienced RAF pilot, flying combat missions over Afghanistan.
But he works from an airbase in Nevada, 8,000 miles away.
"I've got a 45-minute drive home. And then by the time I'm home, I'm kind of straight into family life."
He is one of a new generation of pilots who fly drones - or unmanned aerial vehicles, UAVs, as the military prefer to call them.
Flt Lt Jenkins trained on conventional planes - but there are now pilots joining the RAF who may never leave the ground, according to Air Vice Marshal Tim Anderson, a top Ministry of Defence planner.
Drones look in many ways like conventional planes. But in place of a cockpit with a pilot they have noses full of hi-tech surveillance devices and are often armed with missiles and bombs.
They are launched near areas of combat but are then "flown" by remote control, via satellite links, operated by pilots who may be thousands of miles away.
The drone revolution addresses two urgent requirements for today's military:
- There is no risk of your pilots dying
- Pilotless planes promise to be cheaper to make and run than conventional fighter jets
The US military already has over 7,000 unmanned aerial systems, and the RAF is following in its wake.
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is on Radio 4 on Monday 1 February at 2000 GMT
The RAF's 39 Squadron flies Reaper drone missions over Afghanistan from the Nevada base. The US authorities refused a BBC request to visit, but we were able to speak to RAF personnel there by phone.
Andy Baverstock analyses the images beamed back from the Reapers' cameras. He describes his team's advanced situational awareness as they watch intently what's happening in Afghanistan.
"Because you're doing it for so long, you can tell whether a group of people are moving tactically or whether it's a group of guys going to irrigate a field."
How do they decide whether to use lethal force when they are so far from the battlefield? Wing Commander Jules Ball replies that they often respond to requests for support from soldiers on the ground.
Otherwise, "we would most definitely be having to go to higher headquarters in order to ensure that what we were doing was appropriate, necessary, proportional and legal. We wouldn't be doing it autonomously if you like from 8,000 miles away".
It is not just the military who fly drones.
The CIA uses them to attack al-Qaeda and Taliban targets, sometimes on the territory of Pakistan, a US ally.
Pakistan has been publicly critical of US drone attacks
The US government believes drones enable it to strike back at terrorist leaders where conventional forces have failed. Pakistani media have reported hundreds of civilian deaths in such attacks.
CIA operations like this require presidential authorisation. According to the New America Foundation, a think tank, President Obama has been authorising drone strikes at a higher rate than President Bush.
Such is the secrecy surrounding CIA operations that there are no clear rules of engagement. There is "no accountability after the fact" says Philip Alston, UN special rapporteur on extra-judicial executions.
Vicki Divoll, who worked for several years as a CIA lawyer, refuses to confirm that such attacks happen as reported. But based on "what we believe to be happening," she reveals deep divisions within the CIA about the use of drones.
Using drones to kill people has been "extremely controversial" at the agency, she says.
"When the controls are manned by someone in a suburb of Washington rather than by someone in the field you become so detached that there's no cost, there's no limitation on you."
The implications of the robotic revolution are profound.
The US is already recruiting drone pilots from among young men skilled at computer games. Instead of flying into danger they may never need to leave the security of a cabin full of computer screens on home soil.
Will this revolution change attitudes towards killing and make governments feel war is less costly or risky?
Air Vice Marshal Tim Anderson, trained in British military tradition, has his concerns.
But he hopes that responsibility for combat will still "imbue within operators an appropriate sense of culture and ethos, such that it never becomes a video game".
What does it mean for the British pilot Mark Jenkins, based in Nevada, when he kills people remotely?
"It's going to weigh on your mind. It does. I don't think you'd be human if it didn't. But I've got a family at home and I need to be there for my family, so I deal with it."
is on BBC Radio 4 on Monday 1 February at 2000 GMT. Part Two, about robots to fight in wars, is on Monday 8 February at 2000.