773meter/second (1700MPH) supersonic ping pong ball launch using vacuum and 81PSI helium 

Metric is much easier, especially for physics. My college classes were all metric (1974 to 1978) for my physics degree. My poor engineering friends had to deal with English units - especially bad for thermodynamics.

PSI?

@@davekni I would suggest increasing the velocity through decreasing the caliber!You can reach velocities of around 5 and more kilometers per second with similar setup!

When you have to do math in base 10 using distance, metric is easier. Physical reality is complicated enough without squabbling about how to measure things.. Too bad time is also divided by 12. A tenth of an hour converts to 6 minutes. I have not seen a pressure gauge in hectopascals either.

Personally, I like the sandals and velcro white trainers

Thank you for the compliment! Hope you've seen some of our short videos of even faster speeds last September (2016) at the OMSI Maker Faire.

Yes, we used a ping pong racket as target a number of times, in public demonstrations and for local media coverage. Scraps of plywood are much less expensive, and much harder to penetrate (thicker than the plywood of a racket). The thicker target makes for a better verification of our speed. BTW: We hit 806 meters/second a couple weeks ago and submitted that to Guinness. Haven't gotten around to posting video of that yet, although I gather that some students and teachers at Wilsonville High School (where we made the record runs) may have already.

The piston is another way to generate pressure. Would still need to be filled with helium first. (Air is too heavy, so not as fast.) Since helium is coming from a pressurized tank, there is no need for a piston mechanism to generate pressure. It is relatively easy to get more pressure. Issue is that more pressure crushes ping pong balls. Broken balls do not accelerate well. I have a video of a failed launch (broken ball). The trick to higher speed is slower initial pressure release behind the ball. The latest ping pong ball speed record holder used a smaller diameter diaphragm with a more stretchy material that ruptured more gradually (relatively-speaking). That allowed higher helium pressure without rupturing the balls.

Thank you for the compliment! Yes, I made and tested a couple C D nozzles too, which made performance worse. I think they might help at higher pressure, about the 90PSI or so that a ping pong ball can handle directly, since the nozzles reduce pressure. If you view our most recent videos, we beat this speed by 100m/s, reaching 873m/s at this year's Maker Faire.

Or, the extra 100mm:)

+George Wills Don't feel "dumb"! It took a lot of work and some luck to figure out that a vacuum reservoir at the end would make a big improvement. Yes, it does seem obvious after-the-fact. Most inventions are that way - obvious afterwards. To the best of my knowledge, we are the first ones to try that improvement. Also, I wouldn't really call it "diverging", as it isn't a flare shape. It's just a place for the excess air to go. If you are interested in more of the details, see my longer video "Supersonic ping pong ball luncher: high-speed flash images and description". Keep up the experimenting, with that or other physics. It's all fun and educational.

+Aj Rogers Glad you enjoyed it! Have fun with all your 2017 adventures!

That would probably work great for creating a shotgun blast of burning plastic fragments:) To launch a ball still intact requires controlled pressure. We've gone up to 93PSI, at which point the balls break up about half the time. What would help is something to maintain the pressure better through the launch. We need something that will slow the initial gas release while providing an increasing flow as the ball accelerates. I have some ideas I might try some day. They all require higher initial pressure, so a metal pressure chamber. Modifying a metal gas cylinder is beyond my skills, so I'd need to contract out that part.

Thank you for the compliment! The vacuum reservoir is made of two 8" to 2" PVC couplers glued together. There's a short section of 2" schedule-80 PVC pipe glued into the back coupler, and a short section of 2" schedule-40 pipe glued into the front coupler. The exit vacuum membrane (space blanket) is clamped around the front 2" exit pipe. The 1.5" schedule-40 launch tube is inserted through the 2" schedule-80 pipe and extends through to almost the start of the 2" schedule 40 exit pipe section. A rubber coupling and clamps seal the launch tube to the 2" schedule-80 pipe at the back side. The ping pong ball leaves the launch tube near the end of the vacuum reservoir and coasts through the short exit pipe and breaks the membrane. The gap allows space for helium to escape the launch tube and disperse into the vacuum reservoir.

Interesting thought, but sulfur hexafluoride would perform much worse. It's one advantage is higher heat capacity, so it would cool more slowly as it expands down the launch tube. However, its much higher density would be far more detrimental than any heat capacity advantage. There is one gas that would be better than helium (both lighter and higher heat capacity), but too dangerous for us to play with.

+davekni Oh I know it would be worse. I purposely mentioned Sulfur Hexafluoride as supposed to Helium because I thought it would be interesting to see how much worse it would do. The comparison would be a *great* way for people to see for themselves the macroscopic effects of slow vs fast moving gases. Wouldn't you agree?

Yes, it would be interesting, at least to a few of us physicists. It would be difficult to interest most of the public in something that performs worse, just to explain why it's worse. Helium generates more interest, since it enables speeds faster than Mythbusters or any other group has demonstrated. And we do have helium vs. air demonstrations.

davekni True. And on the heat capacity note, another advantage of hydrogen would be its diatomic nature, yes? If you could heat up the hydrogen gas to a high temperature, the rotational and vibrational states could store more energy so that it doesn't cool as much during the expansion (as you mentioned earlier with the SF6), and the super fast moving hydrogen molecules would *really* accelerate that ping pong ball I imagine! I'm not saying you should do it though. You don't want to end up like the Hindenburg lol

Yes, exactly! Diatomic is what gives the higher heat capacity. It is two ways of stating the same advantage. BTW, only the rotational states help significantly. Even the lowest vibrational state of hydrogen isn't populated until significantly above room temperature - its quantum energy is too high.

Yes, we get occasional self-launches. The membrane is as thin as can usually hold the pressure, so as to break away quickly. Occasionally it doesn't hold up to the pressure.

Yes, exactly. The Purdue University launcher worked only that way - raise the pressure until the membrane breaks. We added controlled membrane breaking (most of the time) so that we could get the pressure to the maximum possible without (most of the time) breaking the ping pong ball at the start of the launch.

ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-msgfm4DHiyc.html

Thanks! For more fun, see our newer videos such as: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-5xuwu4gjNbQ.html In 2016 we reached 873 m/s (1950 mph), enough to break through 3/4 inch plywood.

A longer launch (vacuum) tube does help, as in our faster 9/2016 runs at OMSI Maker Faire: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-5xuwu4gjNbQ.html Adding additional membranes in the ball's path wouldn't help, as that doesn't provide a source of additional pressure (helium) behind the ball. (Unless I'm not understanding your suggestion correctly.) If we were to pursue even higher speeds, higher initial pressure, combined with something to slow the initial pressure rise (to avoid breaking the ball) would be the next logical step. Something like the converging/diverging nozzle in other's launchers. Such nozzles don't't help below 90 psi, but likely would at higher pressures. Pursuing that would require more mechanical construction skills than I posses, and a bunch of money too.

Small objects would generally be easier. A bb could be launched like a standard bullet using gun powder, and easily beat our 1950 mph record. The ping pong ball is tricky because it is light and large and delicate (relatively). Above 90 psi, the ball often breaks due to the pressure. A bb can handle much higher pressure, and higher temperature, so gas combustion products (gun powder ...) can be used. I'm not familiar with blowgun darts, but they are likely also more robust than ping pong balls.

Ball mass matters quite significantly. We see a bit of that even with mass variation from one ping pong ball to the next. A golf ball would launch much more slowly at the same pressure. A golf ball could handle much higher pressure without breaking, however. At sufficiently high pressure, the golf ball could theoretically get to the same velocity. For example, high-speed rifles can be a little faster than our ping pong ball.

+Md Nazial Kadir Yes, around mach 2.2. I didn't list a mach number, since that is based on sound speed, which varies with temperature, so isn't as precise as distance per time (meters per second or miles per hour).

Sounds like a fascinating experiment! Please post a comment with link if you get videos of such. Air is fine for supersonic speeds. See ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-biMj5Dom_-g.html for our air launch video. For construction details, see this video: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-zIdxIQ4hVbk.html Both links are in the "show more" tab below this video. If those two don't answer your questions, please ask again. Oh, concerning launch tube length, the optimum appears to be between 5 and 6 meters (17 to 20 feet). We did experiments on that last year, getting to 565 meters/second with air and to 873 meters/second with helium. There are some videos from that on my channel too, including the first link in this video's description.

Thanks for your reply Dave. Sorry, I did find those other videos later. I'm not sure whether I'll use ping pong balls or something smaller yet...smaller would fit better within the 10" mirror I have.

Phil, If something heavier and smaller would work, you could use a bullet. Launching with gun powder and no vacuum is much easier. It just doesn't work for a ping pong ball - breaks the ball.

Behind the target is a piece of 6" pipe stuffed with rags and packing foam, backed by a piece of 6mm polycarbonate. The fragments of ball and target that don't scatter end up buried in the packing material within that pipe. We've broken through 2.3mm polycarbonate, but I think 6mm is safe. The ball fragments never make it all the way to the back anyway, as the rags/foam are good at absorbing energy as they tear apart. Polycarbonate is a tough plastic, the primary material used in bullet-proof windows (although even thicker).

Sure, I'd be happy to help. Have you viewed my slide-show presentation of the launcher and how it works (13 minutes)? The link is in the description (click "show more") for this video. BTW, we just made 6 runs at Wilsonville High School, hitting 806 m/s (1803 MPH) for the final launch. We're sending that in to Guinness for hopefully an official world record.

I'm using 5mm green LEDs for light and 5mm yellow LEDs for photo-diodes, with local amplification of the photo-diode current. The amplified signals are digitized by a Tektronix TDS754 oscilloscope. LEDs can make good photo-diodes with a couple cautions: The receiving LED should be of a longer wavelength (lower photon energy) than the light source, although matched wavelengths does work some. Photo-diode current is relatively low, so needs local amplification to avoid being slowed down by cabling and/or digitizer input capacitance. Also, LEDs vary dramatically in capacitance. I had some yellow parts that happened to have low capacitance, so worked well here. The advantage of LED photo-diodes is that the LED can be driven initially to aid in optical alignment. Using a photo-diode also avoids the delay common with photo-transistors.

davekni got a circuit diagram? I only have an MCC USB-204, that's all I can afford.

Haven't found it yet - will look a bit more tomorrow. It's not likely something to copy anyway - made it of discrete FETs, VP1306 and VN1306, because that is what I had around. An opamp circuit would be more stable and simpler. If you can place the digitizer close enough, you might even get away without amplification. I'd be happy to sketch an opamp circuit, but I'd recommend first measuring photo-diode (LED used as receiver) capacitance, and current when illuminated by your driving LED. That's where I started before making a circuit. My yellow photo-diode LEDs were DigiKey's part number 365-1190-ND, with 20pF capacitance and about 10uA current with the green LED shining on it and aligned. (The green LEDs were generic from EBay.) Do you have opamps and/or other parts around? Many would do, something like MCP6002 would work well on the 5V supply from you MCC USB-204. Yes, the MCC USB-204 should work well enough when configured for two channels - 250K samples per second, or 4us per sample. The photo-diode signal should be slow enough to catch two points for interpolation at that rate. If you want to continue conversation by email, I'm davekni@yahoo.com. BTW, the circuit will need some level of shielding - grounded aluminum foil is cheap - as fast ping pong balls will generate static electricity. Not likely to damage the circuit, just inject false signals.

OK.... I've changed sensors, added grounding and shielding and now taking data with a digital oscilloscope and still getting crap. Would like to send pix of setup... can you PM me your EMail address???

I'm davekni@yahoo.com. Not sure what "PM" means in this context, but please feel free to email me.

+Troy Lee A really good canister vacuum cleaner might remove 20% of the air, probably not enough to launch a ping pong ball through the vacuum membrane at the end. If you have an air compressor, you can launch a ping pong ball with pressure only. Then you need only one membrane, between the end of your pressure chamber and the beginning of the launch tube. Pressure only will not go as fast as pressure combined with vacuum. My guess is that pressure only, with say the 90PSI typical of standard air compressors, would get barely above the speed of sound, perhaps 350 meters/second. That's higher than we achieved with vacuum only (304 meters/second). Might be enough to break through a paddle. Of course, be very careful with whatever you use as a pressure chamber. Keep the actual pressure way below the rated pressure, especially if using water pipe (which isn't rated for use with air or other gasses). Compressed water doesn't explode on pipe failure, but compressed air does.

Thank you for your reply, Then I will first try to reverse a high pressure bike pump that can pump up to 11 bar. I have seen that people reversed the piston and could vacuum a plastic cola bottle. Will let you know the outcome.

+davekni Hello davekni, We did it! We managed to penetrate a cola can with a ping pong ball. We had to use a PVC pipe with an inner diameter of 45 mm.In Holland we have different standard sizes. We were able to get all the air out with the reversed bicycle pump (it took quite some strokes) to prevent that the air would get back in we used a non return valve in between. Also mounted a gauge that showed when we reached 1013 mbar. As membrane we also used "space blanket". Overall it was a big succes, the kids loved it at school.

Congratulations! I'm impressed that you succeeded with 45mm inside-diameter pipe. We are fortunate to have a close fit as standard pipe here with "English" dimensions. I hope you have inspired some new young scientists!

No, no hole without ball. You can also see this when the ball breaks apart at start of launch due to applied pressure. Broken bits of ball are insufficient: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-lEt9rrkGYho.html For more detail: The helium by itself would transfer a similar amount of momentum, but spread out over a longer time, so lower peak force. The ball is more concentrated (more dense) than the helium, so transfers its momentum rapidly, creating much higher peak force.

The sensor is made of four LEDs, two emitting light (green), and two yellow LEDs used as photodiodes. They are narrow-beam 5mm LEDs recessed into 5mm holes on opposing sides of the ball path, 100mm apart center-to-center. The photodiode signals pass through linear amplifiers to two channels of a TDS754 oscilloscope, which measures the delay from one pulse to the other. Although the 5mm beams make for slower fall and rise times of the ball shadow signal, that also allows many sample points along the transitions for comparison and averaging. I also manually average the leading and trailing edge delays. (The scope is measuring two delays, lead-edge to lead-edge and trailing-edge to trailing-edge.) That way any slight deviation in the ball path from exactly parallel to the beam separation is compensated for. Using linear amplifiers on photodiode current avoids pulse distortion that would occur if normal phototransistors were used as saturated switches as is common in simple photogates. To verify the beam separation, I made a fixture of two 40mm (same as ball) diameter cylinders (spools) mounted on a small board, 100.0mm apart. This fixture was easier to measure directly with a micrometer. (I also measured the LED placement directly, but couldn't be certain that the LED beams were exactly centered in the physical LED housings.) Then I pulled the fixture through the photogate assembly, verifying that the two beams were broken at the same time. This procedure actually indicated that the beams were 100.5mm apart, but I calculate speeds based on 100.0mm. That gives us a margin of 0.5% to make sure we at least achieved what we claimed. The high-school science teachers who served as expert witnesses for our Guinness record also measured the LED spacing directly and came up with 100.5mm. BTW, our official record is on page 122 of the Guinness 2018 hardcover book, at 806m/s.

Hi @@davekni, Thanks for your prompt reply. I really appreciate how open you are in sharing these information. I'm also curious, did you include a gauge to check your vacuum pressure? If so, what are the specs of your vacuum pump and also how low your vacuum can reach?

Yes, we had a gauge, but only a simple mechanical one. The mechanical gauge read something around -14.7 PSI, which roughly matches our air pressure here at just above sea level. If I recall correctly, the pump was rated for 50microns (0.05mm Hg). The nameplate says "Rotary Vacuum Pump Model VP25, 2.5CFM", but I don't have the spec. sheet around. I doubt we got that low due to imperfect sealing of the membranes and out-gassing of the PVC piping. We were probably around 1 or 2mm Hg.

Hi @@davekni, I was wondering how did you manage to achieve so close to perfect vacuum? Are there specific type of fittings used to prevent very subtle leaks?

The joints are either glued (PVC glue) or clamped with rubber couplers. Both seal well. The hardest parts to seal completely are the two 12um mylar membranes at either end of the launch tube. There is a thin rubber layer (12mm wide rubber bands) over the ends of the PVC launch-tube pipe, slightly hanging over the ends of the tube by 2-3mm. The mylar is stretched over the end, followed by rubber coupler halves and clamps. The mylar membranes need to be replaced after each launch. The first is ripped open by the helium pressure and the second by the ping pong ball. When we do have problems getting vacuum, it is almost always because of a wrinkle in the rubber bands.

We did, and finally have the record, at 806 m/s on 5/24/2016 at Wilsonville High School. Guinness is very slow, unless they are paid their "expediting fee", which we didn't do. Whole process took 18 months, and we beat our own record (873 m/s) before they awarded the earlier one. Our record still isn't posted on their public web pages, so you need to make a Guinness account (free) to find our record.

Our 806 m/s record did show up in the 2018 Guinness hard-copy book, a short paragraph on page 122.

Yes, I've wanted to do that. Got to do the next-best thing, though, shoot it the length of a high school gym: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-1vmzL4uYbV8.html It hit the far wall at about half the height and slow enough to not destroy the ball. Also see our even-faster shots from this year's (2016) Maker Faire: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-zexy27bpqLg.html ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-5xuwu4gjNbQ.html

At least for a given pressure chamber and valve (membrane), there is an optimum launch-tube length. This video was made when we had a length about 3.2 meters. We eventually achieved 806 m/s with this setup for our official Guinness record (page 122 of the 2018 book). The no-target video is from our record setup the prior evening:ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-1vmzL4uYbV8M.htmlythbusters had tried a 27 meter tube, which didn't work well. For our 9/2016 Maker Faire entry, we started with a 6.1 meter tube, then cut it down to 5.7 meters. The plan was to study performance vs. tube length. Murphy's Law prevented finishing the experiment, but the 6.1 and 5.7m lengths performed about the same. Our first run at 6.1m achieved 865 m/s:ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-zexy27bpqLgW.htmle got one run up to 873 m/s with the 5.7m length, but the averages were comparable. Here are target shots from some of the fastest runs:ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-5xuwu4gjNbQ.html

Thanks for the comprehensive explanation! How about the membrane, how did you safely secure it in place?

As for the pressure regulator, is it a single stage regulator?

Clamping of the pressure membrane is the weakest (most unsatisfactory) part of our design, so I wouldn't recommend copying it. (There's also a thinner 12um vacuum membrane at each end of the launch tube - a simple rubber pipe coupler and hose clamp work well for those.) For the pressure membrane, I glued an extra ring of CPVC pipe on the outside about 3cm back from the end. The pressure membrane is about 30cm square, placed over the end of the pipe (at the outlet end of the pressure chamber), folded back over the pipe and extra ring. We then wrapped MANY turns of small rubber tubing around the folded-back membrane behind and onto the extra ring. This had to be done and undone for every launch! At the end (for the 9/2016 Maker Faire), we switched to a rubber coupling with slits to allow it to stretch over the membrane and ring, with 5 hose clamps around it, each tightened to almost stripping. That was a little faster and better than the wraps of tubing. The membrane had a thin wire loop taped to it. Electricity heated the wire, melting a rip line (arc) to trigger the launch, although, in this video, the membrane ripped before pulsing the wire with current. We've had a few launch failures where the pressure membrane blows off the pipe at the end of the pressure chamber before the launch, with both versions of clamping. If we ever get back to this project, I need to come up with some form of bolted-together system. Any ideas would be welcome!

The pressure regulator is a simple single-stage, adjusted to a bit higher pressure than needed, around 100 PSI. The pressure chamber is filled with a manual valve, which we turn off when the gauge reads the target pressure, around 90 PSI. Our 806 m/s Guinness record was at 93 PSI, a pressure which sometimes breaks the ball. (Even 85 PSI breaks balls occasionally, depending on the brand and luck.) The ball broke on our first record attempt, which was also at 93 PSI.

I don't have any ballistic gelatin around, but we've now broken through 3/4 inch plywood: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-5xuwu4gjNbQ.html New top speed is 100 meters/second faster (873 m/s or 1950 mph) than this video, primarily due to a longer launch tube. We had previously been unsuccessful with 3/4 plywood.

Yes, I'm aware of the long-term issues with helium supply. Earthly helium is separated from natural gas. The vast majority of natural gas isn't processed to remove helium. Much more helium is "wasted" as natural gas is burned than is used for balloons and all other such activities. So, unfortunately, the helium gets lost whether we use it or not. The only real environmental cost of using helium is the energy used to separate it from natural gas. Long term, when we run out of natural gas, helium will become much more rare and expensive, unless we invent some new source. Storing helium is expensive, so not a great solution. The US got mostly out of that business a decade ago or so. Of course, helium3 is a different situation, as all of it comes from decay of tritium, which comes from nuclear reactors.

Its got some really important uses, too. Uses we will miss more than not being able to talk in funny hig voices...which you should have done for this video by the way...;)

i eat meat and i avoid bio and tofu crap. deal with it lol

For simple experiments, pressure is easier than vacuum. I've done a simple stomp-rocket style ping pong ball launcher using a gallon milk jug connected with old vacuum-cleaner hose to a ~3' piece of 1.5" PVC. Distance varies by how well kids jump on the jug. Use a balloon pump to reinflate the jug after each launch. For the next step up, I'd suggest using a bicycle tire pump with a smaller pressure chamber and no vacuum. Pressure chamber could be just another length of 1.5" PVC, or 2" with a reducer, cap on the back end and membrane (packing tape or ...) between the chamber and the launch tube with ball. I'm guessing you could get 50 to 100' up with that and still be reasonably safe. It would be somewhat like the pop-bottle water rockets. I keep those to 40PSI with younger kids around, sometimes up to 60PSI with older ones.

Helium is lighter (less dense). Even though we remove the air in front of the ball, the pressurized gas behind the ball needs to accelerate as fast as the ball to keep pushing it. The launch tube full of air weighs several times as much as the ball. Helium weighs much less, so wastes less energy accelerating itself down the launch tube, leaving more energy to accelerate the ball.

How about using scuba tank with 4000psi. The ping pong ball will probably get destroyed before leaving the cannon so maybe use a different projectile. I wanna see how fast it will get :D

Yes, the ping pong ball gets destroyed. At the 93 PSI of our record shot, sometimes the ball gets broken due to the pressure. A broken ball doesn't accelerate well (friction against launch tube and gas leaking by more), so speed goes down. That is what makes supersonic ping pong balls such a fun challenge. High-powered rifles go a bit faster, but that's already been done.

Our measurement was good to the three significant digits reported. Any fractions of an MPH are just guesses. We did get faster the next year, to 1950 MPH: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-5xuwu4gjNbQ.html

Yes, very useful stuff for the very-occasional repair work I do on my car.

Hadn't thought about that connection. I guess a plane is relatively light and hollow for its size, so somewhat like a ping pong ball - enough speed and it breaks through much more dense objects. even 3/4" plywood: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-5xuwu4gjNbQ.html

Check out my other videos - I have 10 on this ping pong ball launcher. One shows a failed launch where the ball broke in the launch tube and the remains buried themselves in the plywood rather than breaking through. Another shows triple-flash images of the ball in motion, and of it breaking through hardy-plank (and breaking apart in the process). One from last year shows our 5 shots through 3/4 inch plywood, using a 20' launch tube to get yet faster speed.

Heavier projectiles would penetrate thicker targets, but won't go as fast. Heavier targets can also be accelerated with a cannon. Ping pong balls are more of a challenge. Getting the best speed requires enough pressure to almost break the ball. At 85 PSI, a few balls break. By 95PSI more break. I'll eventually get to posting more videos. We just hit a new maximum speed of 873 meters/second at the Maker Faire 11 days ago, using 85PSI and a longer launch tube.

davekni Yeah I was wondering if a heavier object could be accelerated to the same speed if you used a longer barrel.

For any given set of conditions (barrel length, pressure, etc.), a lighter object (ping pong ball) will go faster. However, a heaver object will generally handle much higher pressure. With higher pressure, and a stronger launcher to handle the pressure, velocities would be similar.

"Fruity" might be an applicable description:) However, supersonic ping pong ball launching was first made popular by Purdue University, and then by Mythbusters TV show, so it wasn't our idea. We've beat their speeds by a wide margin now, so have the world's fastest ping pong ball. (We finally got the Guinness certificate, but they haven't put any of our record information on their web pages.)

Watch our newer video from 9/2016 - shows the target (3/4" plywood) as it is punctured: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-5xuwu4gjNbQ.html