I got a ticket for going 51 mph from a stopped distance of 900 feet. Is that even possible with a 2012 Honda Odyssey Touring? Anyone?

WOW, you probably won't win this one.. the reason the police use them is to be very precise.. and calibrated .. --YES- sure , 900 feet is plenty of distance if you floored it, they have a big 3.5 V6 engine.

Pay the ticket, you are just wasting your time. I have personally operated radar guns and issued many tickets (long time ago). The radar units are checked before the officer's shift and usually several times during the shift and after every car stop. There was nothing wrong with the radar. A few seconds of inattention is all that is needed to get you into trouble. 900 feet is plenty of space to accelerate to that speed.

Radar can be wrong- but you will never convince anyone- let it go- the police are used for revenue raising- this is the problem- you have just been taxed- whether it was just or not, you were caught in the fishing net- this is the problem in America today, that no one is talking about- the number of people killed, minorities and police, is due to this revenue collectin' habit of unnecessary traffic stops- all you can do,(until people become aware of this and the practice is halted) is move to a small town, one where they don't have many police cruisers 'cuz they don't have much traffic-