I went to the drag races over the weekend – something I’d never done before. Had a great time, and saw a top fuel funny car go over 330 mph which was fun.
Being somewhat geeky, I found myself wondering how fast the cars could go if they were computer-driven and could cut all the driver-safety stuff out of the design. I think the NHRA should think about adding a driver-free class to some of their sanctioned races.
Suppose a car must meet minimal requirements:
Pose no dangers to spectators beyond what currently exist.
Must run on existing tracks – no special track surfaces.
Must have 4 wheels and begin the race with all four touching the track.
I’m not sure if there should be any other restrictions. If so, please add them to the list.
Anything else – car design, fuel, etc. – anything goes. Feel free to postulate fuels that can exist but currently don’t. Same with materials used in the engine and frame.
How fast could such a car go in a standard drag race? (I’m certainly no expert, but my BIL sort of is. According to him, speed in a drag race is measured by the time elapsed to go the last 60 feet of the 1000 foot track. So please use the NHRA measure for the fastest possible speed.)
Other NHRA drag race rules would also apply. Cars can’t start more than a certain distance behind the starting line (sorry, don’t know how far this is, but based on where the cars were staged it isn’t far – just a few feet) and can’t cross the starting line early. Cars do start moving a split second before the green light. As I understand it, a rolling start gives a significant advantage over starting the race from a stop.
One driver I saw (last name Enders, I think – don’t remember her first name) won 4 times recently based solely on her “hole shot” – that is, she didn’t reach as high a speed or as short an elapsed time as the other driver, but crossed the finish line first. Assume that the computer-driven cars will maximize the advantage of exactly where to start and when to cross the starting line – presumably well within 1/100th of a second of the time the light turns green.
What’s the theoretical limit? Just how fast can a drag racer go?
your question is so open-ended that I don’t think a factual answer can be determined. ultimately, speed and acceleration are a matter of power and traction. A piston engine transmitting power to the ground is probably still the fastest way to do it short of a huge rocket motor. The nitromethane that Top-Fuelers burn is probably one of the best possible fuels for it; its energy content per unit volume is fairly low, but it’s just this side of being an explosive substance I can’t think of another suitable fuel that is safe to handle. plus, it brings enough oxygen with it that you can cram a ton of it into the engine. it’s very prone to detonation, though, so they run them so rich they’re getting close to a 1:1 air:fuel ratio.
traction is the second key part. on a street car, where the coefficient of friction between the tires and road is pretty close to 1.0, the maximum rate of acceleration is more or less capped at a 0-60 time of 2.8 seconds. Drag racers get around that by using tires which provide an “effective” coefficient of friction greater than 1.0. they use a very soft compound which melts when heated during the initial burnout, so the sticky surface of the tires uses adhesion along with friction to increase grip. Don’t see much room for improvement here apart from trying to go 4 wheel drive. And I see that as little more than an opportunity for more stuff to break.
the one thing computers would improve is reaction time. Humans can win or lose drag races simply by their reaction time to the tree. a computer would be quicker and more consistent.
The dragsters you saw run on nitromethane, have no cooling systems, and have an engine life (before rebuild) of MINUTES. :eek: (SECONDS :eek: :eek: at full throttle)
At Bonneville, wheel driven car records with similar but detuned engines that do have a significant life expectancy are 400+ MPH.
Do the cars have to be driven by the wheels or can you use jet/rocket power? If so, traction isn’t really an issue anymore and they run jet dragsters at existing tracks. The problem is spooling them up - wheel driven cars are much quicker at initial acceleration. If you added rockets (which I don’t think any dragsters currently use) I’m guessing you’d beat the wheel driven times.
How about an electric motor? You get very high torque from a standing start. Dunno if someone will work out a way to get as much overall power as an IC engine for the same weight (that is, batteries+motors vs fuel+engine).
NHRA tracks used to be 1320 feet (1/4 mile) and have been restricted to 1000 feet for some level of safety and an adequate shutdown space.
The drag race engines generate power levels adequate to get into the 400-500 MPH arena but the mechanical durability, aerodynamics, and tire stability of a dragster cannot support these speeds or even SURVIVE long enough to achieve this. Hence land speed racing designs that can.
Their current performance is likely about maxed out based on engine life, traction, and planning on stopping. Now if a computer driven car felt suicidal….
Many forms of auto racing, such as F1, NASCAR, and IndyCar, have placed artificial limitations on the cars and tracks in order to keep speeds down in the name of driver safety. AFAIK, NHRA top fuel dragsters have no such limitations, other than the aforementioned shift from 1320 feet to 1000 feet. Drivers can be subjected to up to 5Gs for a few seconds, which is well below fighter pilot levels. A driver’s reaction time is obviously hugely important for winning, but it doesn’t affect the top speed. Drivers can certainly screw up a race, but once the lights are green and they pull the lever, all they really do is make a token effort to keep the wheels straight and get ready to pull the chute.
In short, I don’t think you gain much by removing the driver other than the small amount of safety equipment – maybe a couple hundred lbs, tops, plus the driver weight. But dragsters are so far beyond caring about power to weight ratios that I don’t think it’d matter.
The dragster driver’s g-loading is also oriented fore-and-aft, making it easier to tolerate than the vertical g-loading that a fighter pilot experiences in a tight turn.
If you don’t need humans, the upper limit is rather faster. Just put wheels on a missile and let it go. Take the Sprint missile as an example; it accelerated at 100 gees. It would do the quarter mile in 0.9 seconds. Maybe remove the nuclear warhead for safety reasons.
electric motors make peak torque at stall (0 rpm, max current) but they do not make infinite torque at stall. the best battery tech can’t match the energy density of nitromethane, even as poor as it is compared to petroleum.
besides, traction is still a huge problem with dragsters; adding even more torque at low RPM is just going to make traction a bigger problem.
I hadn’t heard of the track length change for the big boys. I’d think for the purposes of this discussion we could stay with the traditional quarter mile.
Do we need batteries? Just run an overhead power source like you do with trains.
If you read a bit further, you’ll see that Tyson made a number of assumptions that don’t hold true in the real world, and for once work in the opposite direction. We know that acceleration is not capped at 2.8 seconds for a 0-60 run in the real world, because the Veyron SS can do it in 2.3 seconds. Most of that difference is down to weight transfer, but some is from downforce.
On a non-street-legal vehicle like a dragster you can generate even more downforce than a Veyron and the weight transfer would (I think) be even more pronounced because of the flex in the frame.
