Rocket boosters

[Jared_80]

If I cannot hide them oh well they won't know about it untill after they loose. Yea I know that it is dangerous, but that is life. Besides if you are scared to die than you never truly live.

[Jared_80]

Originally Posted by SaabJohan

Thrust can't really be converted into hp in a "good way", it can be done but I don't see any reason to do it since it will be more of a number on a paper. You can however calculate how the thrust will affect you cars acceleration and top speed by calculating the drag and rolling resistance. By using F=ma, where F is thrust minus drag and rolling resistance and m is the mass of the car we can calculate the acceleration a. When calculating top speed the thrust will work against the drag and therefore reduce the engine power needed for any speed.

I would recommend that you use a liquid fuel rocket if you really want to do this since it can be shut of if anything happens.

There is also no way that you can hide the use of the rockets, the flames, smoke and noise will give you away.

Begin with reading this; "HOW to DESIGN, BUILD and TEST SMALL LIQUID-FUEL ROCKET ENGINES "
http://www.gramlich.net/projects/rocket/

Rocket engines have been used in dragracing, I think the fastest did the quarter mile in 3 seconds or so, this when the engine was shut down after half the length.

I know that it is a very long and technical process, but could you give me a rough estamate on how much thrust it would take to push a 2500lbs car down a standing 1/4 mile, in 10 seconds. Assuming a .30CD and 5% powerloss from rolling resistance.

[SaabJohan]

If we simplify and say that we have no drag or other losses a thust of 2500 lbs (11 kN) will accelerate your car by 9.81 m/s^2, that's 0-100 km/h in 2.9 seconds or a top speed of 310 km/h with a cda of 0.54.

If we want to build a 2500 lbs rocket engine using gasoline and gaseous oxygen as fuel with a combustion pressure of 20.4 bar the fuel flow rate will be 56 kg/s and oxygen flow rate of 16 kg/s. This means that the engine can use all the fuel in a typical car tank in one second! This would require way too much fuel so we must reach higher pressures = difficult. If we could reach the same values as the small liquid oxygen and hydrogen rocket does the fuel flow (H2) will only be only 5.6 kg/s and 1.25 kg of O2 per second.

[burly]

One (of many) problems you are going to run into here is a reliable and absolutely static mounting point for these rocket packs, especially in a FWD car, since the back axles and suspension tend to be much lighter. You are either going to have to weld the packs to the frame somehow, weld a pack "bracket" to the frame and then find an extremely secure way of mounting the packs in there. Due to the fact that the rockets come on to full power almost instaneously, it will put pretty severse stress on whatever you have it mounted to. Also, if there is any budge at all, the thrust vectoring will be totally off and you could end up lifting your back end up off the ground. If the pack slips out of its bracket, it will be launched under your car with very unpredictable consequences.

On to a matter of practicality. Sunken cost of developing and implementing the idea aside (which are not negligible) the simple cost of fuel, solid OR liquid, is too high. Solid fuels cannot be shutoff, and cannot be refilled easily. Many liquid fuels require preheating to start the ignition process. In the end, after a few quick runs, you would end up spending more on fuel alone, if you could even get the license to acquire it, then you would if yanked the engine and did a complete buildup. If not for safety's sake, then for monetary sanity, please do not attempt to build this machine, much less put it on the road.

[Cavallino]

Originally Posted by SaabJohan

This story isn't actually true, but it maybe can become true....

Are you sure? Im fairly certain Ive read that somewhere. I may have been wrong about him winning the prestigious award, he may have just been a runner-up, but Im pretty sure it happened. When they were investigating the wreckage at first they thought it was a small airplane that crashed into the side of the cliff.

[BLU CIVIC]

it wasn't true...it was featured on the darwin awards but wasn't true

[Cavallino]

You could jimmy rig somthing like this......

[BLU CIVIC]

btw....here's the story for those that don't know it:

http://www.darwinawards.com/darwin/darwin1995-04.html

Jet Assisted Take-Off
1995 Darwin Awards Winner
Confirmed Bogus by Darwin

The Arizona Highway Patrol were mystified when they came upon a pile of smoldering wreckage embedded in the side of a cliff rising above the road at the apex of a curve. The metal debris resembled the site of an airplane crash, but it turned out to be the vaporized remains of an automobile. The make of the vehicle was unidentifiable at the scene.

The folks in the lab finally figured out what it was, and pieced together the events that led up to its demise.

It seems that a former Air Force sergeant had somehow got hold of a JATO (Jet Assisted Take-Off) unit. JATO units are solid fuel rockets used to give heavy military transport airplanes an extra push for take-off from short airfields.

Dried desert lakebeds are the location of choice for breaking the world ground vehicle speed record. The sergeant took the JATO unit into the Arizona desert and found a long, straight stretch of road. He attached the JATO unit to his car, jumped in, accelerated to a high speed, and fired off the rocket.

The facts, as best as could be determined, are as follows:

The operator was driving a 1967 Chevy Impala. He ignited the JATO unit approximately 3.9 miles from the crash site. This was established by the location of a prominently scorched and melted strip of asphalt. The vehicle quickly reached a speed of between 250 and 300 mph and continued at that speed, under full power, for an additional 20-25 seconds. The soon-to-be pilot experienced G-forces usually reserved for dog-fighting F-14 jocks under full afterburners.

The Chevy remained on the straight highway for approximately 2.6 miles (15-20 seconds) before the driver applied the brakes, completely melting them, blowing the tires, and leaving thick rubber marks on the road surface. The vehicle then became airborne for an additional 1.3 miles, impacted the cliff face at a height of 125 feet, and left a blackened crater 3 feet deep in the rock.

Most of the driver's remains were not recovered; however, small fragments of bone, teeth, and hair were extracted from the crater, and fingernail and bone shards were removed from a piece of debris believed to be a portion of the steering wheel.

Ironically a still-legible bumper sticker was found, reading
"How do you like my driving? Dial 1-800-EAT-SHIT."

[Cavallino]

You're right. I was just about to edit my last post and put my foot in my mouth but seems you beat me to it.

[Jared_80]

Originally Posted by SaabJohan

If we simplify and say that we have no drag or other losses a thust of 2500 lbs (11 kN) will accelerate your car by 9.81 m/s^2, that's 0-100 km/h in 2.9 seconds or a top speed of 310 km/h with a cda of 0.54.

If we want to build a 2500 lbs rocket engine using gasoline and gaseous oxygen as fuel with a combustion pressure of 20.4 bar the fuel flow rate will be 56 kg/s and oxygen flow rate of 16 kg/s. This means that the engine can use all the fuel in a typical car tank in one second! This would require way too much fuel so we must reach higher pressures = difficult. If we could reach the same values as the small liquid oxygen and hydrogen rocket does the fuel flow (H2) will only be only 5.6 kg/s and 1.25 kg of O2 per second.

What would the volume of that 5.6 kg/s of hydrogen be in an avrage pressure cylinder? To put things simply would 1lbs of thrust accelarate 1lbs of weight at 1G (roughly 22mph/sec) assuming no other powerloss? Would I have to rig a cooling system if I was only going to run the rocket for say 5 seconds? (assuming that I only use common materials)
Could I fit all of these tanks and two combustion chambers into the trunk of an avrage car and keep it looking stock? Sorry I don't meen to drill you too much but it is rare to find someone here who knows about thrust propultion.

[Jared_80]

Oh and if yall see me on the Darwin awards you have my promission to laugh. (not as if I could stop you) Just remember that I died happy. And at those speeds I did not suffer.

[pod]

do you think it would be easyer to take an old crown vic and have it angled off the supports at an up angle of about 5 degrease

[SaabJohan]

Originally Posted by Jared_80

What would the volume of that 5.6 kg/s of hydrogen be in an avrage pressure cylinder? To put things simply would 1lbs of thrust accelarate 1lbs of weight at 1G (roughly 22mph/sec) assuming no other powerloss? Would I have to rig a cooling system if I was only going to run the rocket for say 5 seconds? (assuming that I only use common materials)
Could I fit all of these tanks and two combustion chambers into the trunk of an avrage car and keep it looking stock? Sorry I don't meen to drill you too much but it is rare to find someone here who knows about thrust propultion.

1 lbs of thrust will accelerate a mass of 1 lbs with 1g, with the same mass and a thrust of 2 lbs the acceleration will be 2g and so on.

The example with fuel was liquid hydrogen, LH2, which has a density of 0,07 g/cc, so 5.6 kg will have a volume of 80 liters. It will also have a high cost, in 1980 NASA payed $3.60 per kg. LOX however is more dense and cheaper, 1.14 g/cc and cost NASA $0.08 per kg in 1980. So I think we would need to find a better option for fuel.

A rocket with hydrogen peroxide as a monopropellant should be the safest fuel, but the fuel requirement will be high. If we use kerosine together with hydrogen peroxide we can hower increase the thrust without increase the massflow of hydrogen peroxide. But I still think that the thust will be low based on what size of the tanks we can carry, at least if we want to use any longer burns.

The rocket powered funny car "Vanishing Point" did however used hydrogen peroxide as a fuel. In 1984 the car did 3.58 at Santa Pod Raceway.
http://www.draglist.com/Pictures/POD...POD-071302.htm
Miller died in 2002 but it hadn't anything to do with the rocket engines.

Then we have other fuels like hydrazine and so on but many of them are toxic and expensive.

The rocket engine must be cooled, it will be too dangerous to use a radiation cooled engine. If the chamber starts to melt it won't take long until the engines goes out with a bang. As a coolant water can be used, or as done on "real" rocket engines; the fuel serves as the coolant, this will however be more dangerous.

The combustion chamber of a model rocket engine is often made of copper, in real rocket engines it seems like stainless is often used (perhaps they have something better now?).

If liquid fuel/oxidizer are used we must also have a system that pressureized the fuel/oxidizer. This can either be a system with pressureizes the tanks with high pressure nitrogen or a system using turbine driven fuel pumps. The first way is the simplest but since the pressure must be higher than the pressure in the combustion chamber it will be difficult to use high chamber pressures.

If supercooled liquid oxygen is used we must also use a crygenic tank, this tank can for example be made of stainless steel and balsa wood (for isolation).

As for the motors they will be small and should be easy to hide, the problem is the fuel which will require some space. The nozzle outlet, the later part of the divergent nozzle, will also be large so it can be seen. It's also important that they will properly shield the heat from the car.

If a hydrogen peroxide-gasoline engine could be made, one that uses turbopumps and a high combustion pressure we can use gas direct from the cars tank and the hydrogen peroxide is quite safe, and it will only require one extra tank. The hydrogen peroxide is also quite dense, about 1.45 g/cc for 100% concentration. What the fuel consumption might be I don't know since I have no data of specific impulses for these fuels or higher combustion pressures.

[Sluttypatton]

While we're on the subject of the Darwin awards, anyone remember the old rocket car story? Here is the "true" story.

Warning: This story takes a LONG time to read, clear an hour from your schedual before attempting.

Here is the true story of the "Rocket car" myth...actually I have no idea if it's true, but if it isn't then the author is a great storyteller.
http://www.wagoneers.com/pages/RocketCar/rockit.html
Thoughts? Comments?

[bob_1029]

Ok you want rocket power... i will give you the closest feasible thing. Gas turbines. You have 2 options as far as gas turbines go, 1: Powered by the exhaust the engine generates (~1000lbs) or 2: Powered by turbine rotation (peak ~1400hp). If you are interested in getting an engine like this, http://www.everettaero.com/gnome.html offers a nice rolls royce apu. I would recommend a driveshaft-turbine setup, as propulsion by exhaust gases can be somewhat... dangerous. You will probably want some sort of reduction gearbox, as it spins at over 10000rpm at full throttle. These are also offered from the same dealer. Considering you actually manage to find someway to integrate this gas turbine into your drivetrain, provide it with necessary cooling, exhaust, fuel, etc... you are probably not going to have the stealth factor you want... b/c these engines are really loud. Allow me to illustrate:
http://www.gas-turbines.com/images/squirt_2/squirt2_(on_the_grand)lr.wmv That boat is running the same engine under discussion here. Best wishes on your endeavour...