Rocket-Powered Dragsters: Faster than Wheel-Driven?

In summary, the conversation discusses the role of weight in determining the speed of a rocket-powered dragster and whether lighter objects can accelerate faster with the same power. Participants discuss different examples of fast-moving objects, such as protons in the LHC and cosmic rays, and the concept of power vs. energy. The conversation also touches on the potential for a heavier object to break the record for the fastest quarter mile time with the same power. Ultimately, the conversation concludes that weight does indeed play a role in determining acceleration and top speed, and that the relationship between mass, velocity, and energy is important to consider.
  • #1
Mohd Abdullah
99
3
Hey guys,

We all know that weight plays an important role in determining the speed of a vehicle, such as dragster like Top Fuel. But how about a rocket-powered dragster that uses hydrogen peroxide? Rocket-powered vehicles indeed accelerate faster than any wheel driven vehicle, but do weight still played an important role in determining its speed? The record for the fastest elapsed time for the quarter mile straight race/drag race is held by a rocket-powered hydrogen peroxide dragster at mere 3.22 seconds.
 
Physics news on Phys.org
  • #2
What do you think and why?
And why does weight matter for the top speed, as opposed to the acceleration?
 
  • #3
Nugatory said:
What do you think and why?
And why does weight matter for the top speed, as opposed to the acceleration?

I don't know. I don't really have much knowledge about it. Don't misunderstand me, I'm not asking answers for a homework.

But in my own opinion, I think weight don't play a role in determining the acceleration speed of a rocket-powered vehicle. Am I correct?
 
  • #4
Have a look at Newtons Laws.
 
  • #5
Is there anything with very light weight moves very fast besides light? For example at 50 miles in one second with energy equals 80000000 joules per second?
 
  • #6
Mohd Abdullah said:
Is there anything with very light weight moves very fast besides light? For example at 50 miles in one second with energy equals 80000000 joules per second?
80000000 joules per second (80 megawatts) is not a measure of energy. It is a measure of power. What is it that you are trying to accomplish with this fast light weight? A kinetic energy weapon?
 
  • #7
Mohd Abdullah said:
Is there anything with very light weight moves very fast besides light?

Protons in the LHC (very close to the speed of light).
Cosmic rays (Protons very close to speed of light)
Alpha particles (about 5% of speed of light).
Beta particles (about 60% to 90% of speed of light)
Plasma ejected by black holes (99.9% of speed of light from http://www.space.com/694-blazing-speed-fastest-stuff-universe.html)
 
Last edited:
  • #8
jbriggs444 said:
80000000 joules per second (80 megawatts) is not a measure of energy. It is a measure of power. What is it that you are trying to accomplish with this fast light weight? A kinetic energy weapon?

No, I'm not talking about weapons afterall. Actually what I want to say is, say, if a bullet weigh at mere 4 grams moves at 80 megawatts, or equal to 107282 horsepower, how much distance that it can cover in less than a second?

Are there anything, such as something that is lightweight other than particles, that can accelerate over 5 miles in a second in the real world with power equivalent to millions of horsepower?
 
  • #9
Mohd Abdullah said:
No, I'm not talking about weapons afterall. Actually what I want to say is, say, if a bullet weigh at mere 4 grams moves at 80 megawatts, or equal to 107282 horsepower, how much distance that it can cover in less than a second?
In addition to not being an energy, 80 megawatts is not a speed. What are you really trying to ask?
 
  • #10
CWatters said:
Protons in the LHC (very close to the speed of light).
Cosmic rays (Protons very close to speed of light)
Alpha particles (about 5% of speed of light).
Beta particles (about 60% to 90% of speed of light)
Plasma ejected by black holes (99.9% of speed of light from http://www.space.com/694-blazing-speed-fastest-stuff-universe.html)

You're familiar with the sequentially timed all-optical mapping photography” (STAMP) that was created by a team of Japanese scientists with 4.4 trillion frames per second, right? Do you think this type of camera can record or capture a still image of those things that you had mentioned?
 
  • #11
jbriggs444 said:
In addition to not being an energy, 80 megawatts is not a speed. What are you really trying to ask?

Okay, if you are familiar with Top Fuel dragsters, those dragsters can cover a quarter mile in just around 4 seconds with 10,000 horsepower. Top Fuel dragsters weigh at 2300 pounds. Are there anything with much lighter weight that can also accelerate fast with power equivalent to 10,000 horsepower or more in the real world?
 
  • #12
Mohd Abdullah said:
You're familiar with the sequentially timed all-optical mapping photography” (STAMP) that was created by a team of Japanese scientists with 4.4 trillion frames per second, right? Do you think this type of camera can record or capture a still image of those things that you had mentioned?

No.
 
  • #13
A rifle achieves a muzzle energy of between 2000 and 6000 joules over an interval of a few milliseconds. That's one megawatt.
A kinetic energy penetrator (e.g. 125 mm APFSDS) might have a muzzle energy around 6 megajoules. That's into the terrawatt range.

[APFSDS = Armor Piercing, Fin Stabilized, Discarding Sabot]
 
  • Like
Likes Mohd Abdullah
  • #14
CWatters said:
No.

Thanks. Can you elaborate your answer?
 
  • #15
jbriggs444 said:
A rifle achieves a muzzle energy of between 2000 and 6000 joules over an interval of a few milliseconds. That's one megawatt.
A kinetic energy penetrator (e.g. 125 mm APFSDS) might have a muzzle energy around 6 megajoules. That's into the terrawatt range.

[APFSDS = Armor Piercing, Fin Stabilized, Discarding Sabot]

Is it possible for a much heavier object to move as fast as those things with the same power just like those things that you had mentioned? The record for the fastest elapsed time for the quarter mile straight race/drag race is held by a rocket-powered hydrogen peroxide dragster at mere 3.22 seconds. Can something heavier break this record with assumed same power at 5000 pound thrust?
 
  • #16
If you hold thrust constant and increase mass, what happens to acceleration? See post #4

If you increase mass and hold velocity constant, what happens to energy?
If you hold power constant and increase energy, what happens to time?
 
  • #17
Mohd Abdullah said:
Okay, if you are familiar with Top Fuel dragsters, those dragsters can cover a quarter mile in just around 4 seconds with 10,000 horsepower. Top Fuel dragsters weigh at 2300 pounds. Are there anything with much lighter weight that can also accelerate fast with power equivalent to 10,000 horsepower or more in the real world?

So you are interested in things that can accelerate fast?..

Let's do some back of the envelope calculations and work out how fast your dragster is accelerating. We will assume the acceleration is constant to make the figures easier...

Start with the SUVAT equation (Google or Wikipedia them)..

s = ut + 0.5at2

If starts from rest then u=0 and it simplifies to
s = 0.5at2
rearrange to give an equation for a..
a = 2s/t2

A quarter mile is 402 meters, t = 4 seconds so the acceleration is roughly..
a = 2*402/16 = 50 m/s2

If you prefer it in "g" then that's about 50/9.8 = 5g.

Now let's do the same for a bullet..

Google says 300m/s is a reasonable muzzle velocity for a rifle and the barrel is say 1m long so. We can use another SUVAT equation to work out the acceleration..

v2 = u2 + 2as

again u=0
so
a = v2/2s
= 3002/2
= 45,000m/s2

which is about 45,000/9.8 = 4600g

So compare..

Dragster = 5g
Bullet = 4,600g


No contest.
 
  • Like
Likes Mohd Abdullah and jbriggs444
  • #18
Mohd Abdullah said:
Thanks. Can you elaborate your answer?

Nuclear rays are too small for one thing.

The plasma ejected by a black hole has already been photographed moving at close to speed of light..
http://www.space.com/694-blazing-speed-fastest-stuff-universe.html

blazar.jpg
 
  • #19
In the USA, NHRA reduced drag distance from 1320 feet to 1000 feet for top fuel dragsters and top fuel funny cars, mostly due to not having enough run off distance at many tracks.

As for weight, it still makes a difference, which is why some high speed rocket sleds are multi-stage. This one achieved 157 g's of acceleration on it's final stage.

 
  • Like
Likes Mohd Abdullah
  • #20
CWatters said:
Nuclear rays are too small for one thing.

The plasma ejected by a black hole has already been photographed moving at close to speed of light..
http://www.space.com/694-blazing-speed-fastest-stuff-universe.html

View attachment 110119

I thought what you meant by your previous answer "No", was even fastest camera with 4.4 trillion fps can't capture a still image or record those things that you had mentioned earlier. I was wrong.

What things in the universe that no matter how fast or advanced our technology is, we will never be able to capture a single frame of it or record a video (be it slow-mo or otherwise) of it?
 
  • #21
rcgldr said:
In the USA, NHRA reduced drag distance from 1320 feet to 1000 feet for top fuel dragsters and top fuel funny cars, mostly due to not having enough run off distance at many tracks.

As for weight, it still makes a difference, which is why some high speed rocket sleds are multi-stage. This one achieved 157 g's of acceleration on it's final stage.



Ah, rocket sled. I think this thing hold the record for the fastest accelerating land vehicle if I'm not mistaken. No wheel-driven vehicle including Top Fuel dragsters can match the speed of rocket sleds. Top Fuel dragsters covered quarter mile in mid 4 seconds while rocket sleds can cover a quarter mile less than a second. That's mind-boggling.
 
  • #22
Thoughts?
 
  • #23
keep in mind, HP is the rate of change of KE.. that is acceleration, almost by definition. you can accelerate very slowly, and get to any top speed. the more mass, the longer the time to a top speed. (less acceleration) . If force is contstant, as it is in a rocket, then power goes down with velocity, but acceleration is constant, but will be determined by Newtons laws. same force, lighter weight , greater acceleration.. it's that simple.
 
  • #24
Your original question seems to imply that weight is not necessarily a factor. But the mass you are trying to displace (accelerate) is always affected by the mass vs accelerating force ratio. The thing that makes the rocket faster in your example has less to do with the type of powerplant and whether it is wheel driven vs rocket driven than the amount of sustained force producing the acceleration. In traditional internal combustion engines as RPM increases the torque decreases. Greatest acceleration occurs during initial launch of the vehicle and tapers off due to reduction in torque with speed, even when you are talking massive horsepower! The rocket engine on the other hand produces the same thrust acting on the vehicle throughout the run, essentially starting slower acceleration but continuing to build acceleration as thrust remains constant. THERE IN LIES THE DIFFERENCE :) As the engine driven dragster accelerates an initial 5000 lbs torque to the wheels diminishes to a much lower value with speed. However with say 5000 lbs thrust in the rocket engine will remain constant as the vehicle accelerates down the track regardless the speed. Both vehicle types have to deal with similar issues of drag which is a completely different subject... The drag will increase as the square of the velocity change.The rocket powered vehicle has a great advantage as the thrust remains constant, while the traditional dragster has less and less torque with speed to overcome drag increases.
 
Last edited:
  • #25
zanick said:
If force is contstant, as it is in a rocket, then power goes down with velocity, but acceleration is constant,
This is backward. If force is constant then power goes up in proportion to velocity. ##\frac{dE}{dt}=\vec{f} \cdot \vec{v}##
 
  • #26
Mohd Abdullah said:
What things in the universe that no matter how fast or advanced our technology is, we will never be able to capture a single frame of it or record a video (be it slow-mo or otherwise) of it?

The inside of a black hole.
 
  • #27
Capn'Tim said:
In traditional internal combustion engines as RPM increases the torque decreases. Greatest acceleration occurs during initial launch of the vehicle and tapers off due to reduction in torque with speed, even when you are talking massive horsepower!
In the case of top fuel dragsters or top fuel funny cars, there's excessive power, that is literally burnt off by the slipping clutch (these are single forward gear cars). Peak acceleration occurs well beyond the initial launch. At initial launch, the only downforce is due to the exhaust (it is a significant downforce). Peak acceleration occurs later when the wing also exerts downforce, allowing the tires to provide more acceleration. The clutches are mechanically programmed (the rules don't allow electrical based programming), including mechanical timers (air / oil mechanisms), to increase output torque to the tires during a run, based on estimates of available grip made by the team tuning a drag car for a run.

 
  • #28
All points well taken. My point was intended to be more simplistic so as not to get buried in all the physics at work in the whole process. Indeed there is massive amounts of energy being released in the top fuel engine, however only a very small portion of that can be transferred to the wheels as useful acceleration force, particularly during early acceleration. As the vehicle accelerates further down the track it also needs the benefits of significant down force to facilitate traction adequate to manage torque at the tire/track surface. The rocket dragster is much less affected, only requiring enough down force to ensure it doesn't become a lifting body! The science of drag car acceleration is a very sophisticated engineering challenge most do not appreciate. My point was that the rocket engine being used actually is translating less energy but more effectively using that energy in the form of sustained accelerating force. The true capabilities of the rocket engine are barely manifest in a 1000 or 1320 foot contest. Drag racing is my favorite sport since childhood. Nothing like top fuel, but I did a significant amount of amateur bracket racing as a hobby. My first exposure to Top Fuel was watching an exhibition by Don "The Snake" Prudhomme(sp) at the old Irwindale Raceway back in 1969! Though my home was 7 miles from the track, on Friday and Saturday nights when top fuel cars were competing you could hear them from my home even over the background noise of Southern California bustle!
 
  • #29
All points well taken. My point was intended to be more simplistic so as not to get buried in all the physics at work in the whole process. Indeed there is massive amounts of energy being released in the top fuel engine, however only a very small portion of that can be transferred to the wheels as useful acceleration force, particularly during early acceleration. As the vehicle accelerates further down the track it also needs the benefits of significant down force to facilitate traction adequate to manage torque at the tire/track surface. The rocket dragster is much less affected, only requiring enough down force to ensure it doesn't become a lifting body! The science of drag car acceleration is a very sophisticated engineering challenge most do not appreciate. My point was that the rocket engine being used actually is translating less energy but more effectively using that energy in the form of sustained accelerating force. The true capabilities of the rocket engine are barely manifest in a 1000 or 1320 foot contest. Drag racing is my favorite sport since childhood. Nothing like top fuel, but I did a significant amount of amateur bracket racing as a hobby. My first exposure to Top Fuel was watching an exhibition by Don "The Snake" Prudhomme(sp) at the old Irwindale Raceway back in 1969! Though my home was 7 miles from the track, on Friday and Saturday nights when top fuel cars were competing you could hear them from my home even over the background noise of Southern California bustle!
 
  • #30
Mohd Abdullah said:
I don't know. I don't really have much knowledge about it. Don't misunderstand me, I'm not asking answers for a homework.

But in my own opinion, I think weight don't play a role in determining the acceleration speed of a rocket-powered vehicle. Am I correct?

well, think about it. is it easier to push a 5kg cinderblock on wheels up to a speed of x kph or a 50kg cinderblock on wheels up to the same x?
its the exact same with rocket engines, they just don't have as much of a problem with the mew (the coefficient of friction) because they are not powering wheels, instead they are using thrust.
so to answer your question, yes. weight does matter. if you look at the weight to power ratio, it may make more sense. more weight + less power= slow acceleration less weight + more power= faster acceleration. hope this helps.
 
  • #31
CWatters said:
The inside of a black hole.

So, we can record and take a picture of light in vacuum? I thought light don't actually accelerating because light is supposed to be already there even before we started to record or take a picture of it.
 

Related to Rocket-Powered Dragsters: Faster than Wheel-Driven?

1. How do rocket-powered dragsters achieve such high speeds?

Rocket-powered dragsters use a rocket engine, which produces thrust by burning a fuel and oxidizer mixture. This thrust propels the dragster forward at incredible speeds, allowing it to reach speeds over 300 mph in just a few seconds.

2. What type of fuel do rocket-powered dragsters use?

Rocket-powered dragsters typically use a combination of liquid fuel and oxidizer, such as nitromethane and liquid oxygen. These fuels are highly combustible and produce a large amount of energy, allowing the dragster to accelerate quickly.

3. How do rocket-powered dragsters differ from traditional wheel-driven dragsters?

Rocket-powered dragsters differ from traditional wheel-driven dragsters in several ways. The most significant difference is the source of power - rocket-powered dragsters use a rocket engine, while wheel-driven dragsters use a combustion engine. Additionally, rocket-powered dragsters have a much shorter acceleration time and can reach higher speeds than wheel-driven dragsters.

4. Are there any safety concerns with rocket-powered dragsters?

Yes, there are significant safety concerns with rocket-powered dragsters. The high speeds and powerful thrust produced by the rocket engine can be dangerous if not handled properly. As a result, strict safety protocols and regulations are in place to ensure the safety of both the driver and spectators.

5. Can rocket-powered dragsters be used for anything other than drag racing?

Yes, rocket-powered dragsters have been used for other purposes besides drag racing. They have been used for land speed record attempts and have also been used in rocket car shows and exhibitions. However, due to their high speeds and specialized design, they are not suitable for everyday use on roads or highways.

Similar threads

  • General Discussion
Replies
1
Views
637
Replies
12
Views
3K
Replies
12
Views
2K
  • General Engineering
Replies
2
Views
2K
  • Mechanics
Replies
16
Views
2K
Replies
271
Views
41K
Replies
10
Views
2K
  • Mechanical Engineering
Replies
4
Views
1K
Replies
17
Views
2K
Replies
73
Views
27K
Back
Top