Back to the Future III: An (semi)obvious solution...

Cafe Society
1

I love BTTF 3, but not as much as the original. Yet…

The BIG problem of getting Marty back to the future in the 1st movie was generating the 1.21 jiggawatts.

The BIG problem of getting Marty back to the future in the 3rd movie, after severing the fuel line, and loosing the gasoline, was getting the Delorean up to the requisite 88 mph of acceleration.

So, what does the brilliant Doc Brown come up with to accelerate the time vehicle? He hatches a cockamamy plan to hijack a steam-powered locomotive on horseback, then using chemically treated bundles to increase the temperature of the boiler thereby pushing the steam engine up to an as yet un-tested and dangerous 88 mph, toward the “Eastwood Ravine” where the train track hasn’t even been bridged across, yet. Of course, it all comes down to the white knuckled, nick-of-time jaunt as the Delorean dangerously travels through time, shooting duel flame trails in mid air, and luckily arriving back in good ol’ 1985 on the long completed tracks. Good fun!

However… if all that was needed was 88 mph of inertial acceleration… why not just use gravity? Horse-draw the thing up a long, steep hill, grease the tires, and let the damn thing roll with reckless abandon until it hits 88.

OR

If the friction is still prohibitive. If the Doc had time to create 3 chemically treated bundles of fuel, then certainly he could’ve rigged the driver’s gullwing door to fly open and devise an ejector seat + parachute for Marty, and just push it over the tracks right into the Eastwood Ravine. Still dangerous, but much simpler and less guess work / less things to go wrong. Besides, he has the hoverboard for a nice, soft landing.

Unless it has something to do with the drivetrain, but that’s never mentioned.

IF SO,

I’m sure the Doc would be able to assemble a simple rocket assembly using a crude black-powder booster – or shoot, maybe even an H2O2 engine – with his chemistry know-how – then just let it do its thing and re-enter 1985.

C’mon Doc, you could’ve done better!

2

The problem with those plans is that it risks further damage to the DeLorean; slamming into a tree or rock. If that happens, they’re both screwed - at least for a few years (since Doc eventually knocks together a flux capacitor in a train anyway). The advantage of their plan is that it allowed a good, long, unobstructed run up for the 88mph in the form of the railway.

3

Which he knows will be there in 1985. Not true of a hill or a flat area to propel the DeLorean with a rocket. A rocket on the track would be a good idea, though. Perhaps the time factor limited that. Doc or Marty will be shot by Mad Dog before they can build the rocket.

4

Could the rocketry of 1885 have propelled something the weight of the DeLorean, let alone to 88mph? Seems like exploding would be a concern…although that should have been a concern with the ‘superfuel’ in the boiler…as demonstrated when the train goes boom after it goes over the edge.

Just realised I’m an idiot; grease up the wheels down hill on a track. The problem there is getting a steep enough hill with a track, which in the age of steam would have been a problem…even then, I’m not sure gravity and momentum would get you up to 88mph.

5

Doc probably did the math and reached your conclusion. :slight_smile:

6

I think Doc mentions (and dismisses) this as a possibility when Marty yells at him, “Monday! You’re going to be shot on Monday!” So they had to improvise.

7

Two problems with your idea:
1 - Greasing the rails would mean the wheels are not rotating at a rate which would make the speedometer register 88 mph, so the computer that operates the flux-capacitor would not activate it.

and

2 - Terminal velocity of an automobile in free-fall is about 60 mph, far short of the required 88. If you cannot get up to 88 mph in free-fall, you’re certainly not going to get there rolling down an inclined plane.

A far more elegant and easy solution would have been to reprogram the computer to activate the flux-capacitor at a more obtainable 20 mph.

8

Was the 88 mph just an arbitrary trigger then? I formed the understanding that the speed was necessary to enable the time travel at all, though I do not know where I got this from.

9

Presumably it wasn’t just a matter of when the computer would activate the flux-capacitor. I always assumed that there was something about the physics involved that required that speed.

Of course, that doesn’t explain what happened at the end of the second movie, where the car was just hanging in the air and got hit by lightning.

10

It’s because when that baby hits 88mph, you’re gonna see some serious shit!

11

If the wheels have to register a speed of 88 mph, then free-fall wouldn’t work regardless of terminal velocity. On the other hand you could jack the Delorean up on blocks if you could figure out how to get the tires to spin fast enough.

But I think it’s less a function of the speedometer’s reading and more a case that the car has to reach an actual ground speed of 88 mph. So greased track might be okay if you could get enough speed - but you’d need a good rocket. A train locomotive won’t go far on greased tracks.

12

This is why I figured the 88mph was just an arbitrary trigger. There would have been no way the Delorian could have accelerated to 88mph from a standstill in mid-air.

I figured Doc had decided on 88mph so there would be less of a chance of accidentally setting it off on the highway, and “if you’re gonna build a time machine into a car, why not do it with some style?”

13

Occasionally I roll down hills in my car at around 60 mph in neutral, and these are not very inclined planes. I can go even faster (probably have maxed out at 70) but when I exceed 60 mph is when I put it in gear to reduce the acceleration.

14

Are you starting from a standstill?

15

One thing that always bothered me about the railroad track idea: wouldn’t the tracks have shifted over a hundred years. Even a coulple of inches you have a spectacular derailment when the Delorean hits 1985.

16

Doesn’t matter. As long as you can get to 60 mph from a standstill, and you can get over 60 mph if you are already at 60 mph, you can get to over 60 mph from a standstill, given a long enough hill. That’s pretty much basic logic.

Given the way that acceleration works (where resistance rises as the cube or at least the square of speed,) you can deduce that if you can accelerate when you’re at 60 mph, then you can get to 60 mph from a standstill (barring stationary friction, which becomes negligible once you actually start moving.) But if you’ve already been given the above two snippets of information (plus the assumption that external forces (such as gravity, wind, and road conditions) will not change), then you can show that 60 mph is not terminal velocity for the automotive vehicle in question without even having to know resistance equations and the like.

17

Since when?

-or-

Cite?

18

When lightnight struck the delorean it caused it to spin at 88 miles per hour. It leaves behind in the air flaming 99s as a result of the spinning.

I never thought about whether the speedometer needed to indicate 88 or if the car just needed to be going 88 in some capacity

19

Doc considers simply rolling it down a steep hill, but says that they would never find a smooth enough surface

eta: oops sorry about the double post. I meant to edit my original post, not quote it.

20

Fair enough. As I said, terminal velocity is about 60. Obviously, this would vary with the car model. A low profile sports car would obviously coast at a higher speed than a VW Bug. At any rate, I doubt you could coast a Delorean with a nuclear reactor attached to its back up to 88mph.