My
Theory On A "Space Steamer",
Using Steam Straight Up
(pun intended)
Instead Of Burning The Separate Elements First
By Tom Chatterton
Mini Menu:
Using Microwaves for Heat Middle Bottom
My theory is based on the idea that today's container technology can withstand 2,000 psi, with off the shelf products, and could go higher by improving the technology, because steam has unlimited energy depending on temperature and pressure. I believe there is MORE potential energy in high pressure steam than in fuels such as hydrazine. Steam can easily climb to 10,000 psi, or 1.4 million pounds of thrust over a one foot diameter orifice. (144 approx. sq. in. x 10,000 lbs. = Wow!) And, it is easily produced/stored and renewable. Water has these special properties. CO2 is an alternate source...and explosive thawing of dry-ice is another scenario...for locations (planets) where H2O may not be available. That can be discussed at another time.
I have an educated hunch the thrust potential of super heated steam is identical to the rapidly expanding H2O vapor/gas of the exothermic reaction, and the end results are the SAME (LH2/LOX thrust from hyper exploding steam), without all the encumbrances of cryogenic fuel tanks. (If you read to the bottom, I just about prove my theory, in a loose fashioned type of way through estimates.) Bare with me, I run the figures in different scenarios several times. It is because I came in here and re edited the text over several days, that it got so long. <g>
What I've been thinking...
Why not just start with the water from the very beginning...and use its MASS instead??? Either way can work (steam or hot water), depending on pressure tolerances...which is the only limit here. If the container can withstand 10,000 psi, a miniature rocket can possess awesome thrust on just steam. But I have my doubts such a container exists, yet. Steam has an almost infinite scale of gaseous pressure that can be produced, depending on how much energy can be stored before the container fails. Your only limit? Container technology. There are concerns for water weight, but how much can be pushed out is dependent on the psi.
Yeah...I know there's another limit, G forces on humans. That's not the technology reaching its limits, however. Most folks can withstand 5 G's if in reasonable health...so that may be our practical limit for a few minutes without a gravity drive. <g> Fighter pilots routinely experience 9 G's. Unique case: A rocket scientist experimented on a rocket sled to test negative 40 G's on himself in the 50's, as it hit a water brake. (It's a History Channel clip I've seen many times before when America was getting ready for the Space Race.) He survived, but his eyes' capillaries burst, temporarily blinding him. (Red Out) 9 G's is considered the safest survivable limit. Well, anyway, the neat thing about steam thrusters are they can be throttled down...but at full unrestricted thrust...we can easily see accelerations in the teens. (10x plus G's) This is perfect for cargo lifting if nothing else.
Just THINK...three exit nozzles, each 1" in diameter, push 30,000 lbs. of initial thrust (10,000 psi x 3) on what is considered a tiny rocket! And, today's composite material is lighter than aluminum but stronger than steel...so in reality...it can withstand MORE psi than a steel tank, right?
We KNOW the thrust is at least 30,000 pounds. 500 gallons of water weighs 4,170 pounds...so let us figure 4,500 pounds for a small composite designed rocket. I'll adjust figures in my Acceleration Calculator until I have 4,500 for the craft and 30,000 thrust.
A fat "phone booth" rocket with 500 gallons of steamy water will go 6,300 feet under power, and an airspeed of 143 mph, with 30,000 lbs. thrust, in 15 seconds. Ending altitude will be closer to 8,000 before it slows under gravity and falls back, then opens its parachute. 32 ft/sec/sec (minus one G) will put at least a negative 320 ft/sec on the rocket within 10 seconds, to end its vertical climb. By then, it will have gone another 1,500 feet. But, this isn't too bad for a "small" test. You know something...I didn't add in any kinetics...humm. This exploding "phone booth" steamer would make a great booster for local travel, or for a glider. When the rocket is empty, it will probably weigh less than 1,500 lbs, including the pilot. How can I guess THAT? Look SpaceShipOne weighs 6,000 pounds full...so we are in the ballpark here. At 8,000 feet a skilled glider pilot can keep his craft airborn for hours in uplift drafts, or at least 30 minutes if heading for a destination.
Hey...WAIT! The rocket LOSES weight during flight! Hummm. If we assume 1/2 the weight is gone in 15 seconds ---
I just did another estimate if we add on extra acceleration for a rocket that weighs 2,250 lbs. at 1/2 flight. Now, you have a craft that has gone over 12,000 feet up in 30 seconds, and is going almost 300 mph...so this little phone booth is definitely zooming away. If my calculus wasn't so rusty...I'd have a better handle...but it is lookin' good. I estimate it will top out above 15,000 feet. That's not too bad for an extra large hot water heater...and is definitely a useable altitude for local travel if you mini shuttle glides back to Earth.
If your parafoil opens at 15,000 feet, there is no telling what kind of range it could have with a light wind. And the fuel is renewable stuff.
Yeah, I know the math below is probably flawed. Bare with me and try and see the potential. <g> The math is FUZZY math, and the figures fast and loose...but I am just trying to get an idea here. Somebody with the actual formulas can give a more exact estimate of how much thrust or range for given fuel. I am just using what I call educated guesses, but if I use my Acceleration Calculator I programmed, available as a download in another link on these pages, the results are even more profound when you plug in some of the numbers. I think high pressure steam propelled water/mass will give surprising results.
Wanna TEST the power of compressed air pushing out lots of water? Get a balloon...fill it with water plus blow in some air until you have 1/2 water and half air. (Imagine the water is boiling hot...and the air is getting compressed even further with gaseous steam.) Attach the sealed balloon to a small pole or makeshift rocket. I guarantee if you get into pressures over 35 psi in a more advanced setting...it will move pretty fast! YES...I fully understand the initial psi is going to drop dramatically as the volume of water squirts out the orifice...but the pressure to EXPEL the water will still be there if you start with high psi's for a small container (over 1,000 psi)...and especially if you are still ADDING heat to the boiler while the water is still there. New steam might just replace the old. <g>. Read on.
Recommended psi??? For serious testing only. Anything over 1,000 psi, and probably better than 2,000 psi for maximum thrust of water/mass. If we can reach 3,000 to 5,000 psi then you really have an amazing performer for its size. Imagine...a 1" orifice on a very small rocket producing at LEAST 3,000 pounds of thrust at launch! We have the container tech...and this pressure can be produced TODAY with off the shelf technology, probably beyond 2,000 psi. Humm. You could slice through a truck with this thing at those pressures. It's enough for a strong tipped rocket to penetrate 1/8" sheet metal from a 6 feet launch. In addition, standing behind it, the blast is strong enough to rip skin. (No way your skin stays on the bone with 2 1/2 TONS ripping at it!) You want to be behind a protective barrier (at least 1'" steel plate) not only at launch, but as soon as the water reaches 212 degrees or risk being fragged if the container fails.
BONUS: I just don't think you can get these kinds of pressures with a small fuel pump, nor can you get much performance per weight if you are too tied up mixing the LH2//LOX formula...which only MATCHES the exit performance after all that hardware, of my theoretical steam rocket. Only steam can produce the high pressures needed to push out liquid mass at such a high flow-rate, that it produces high kinetic thrust for its size and weight. The biggest problem may be running out of water before altitude...but if the lift to weight ratio is high enough...the craft should have good altitude and downrange for its size. Look at it this way...you are ALREADY carrying the LH2 plus the weight of the LOX, plus the weight of any insulation and machinery. Why not ditch the extra weight???
I feel the reason this has never really been tried much before, or overlooked...is because container technology and heating technology have dramatically changed in the last 30 years, and has essentially been ignored...so now the unbelievably high pressures steam can produce when trapped can be harnessed directly.
(Microwave emitters and composite tanks were invented AFTER the original rocket designs of the 1930's, with more advanced composites being less than 10 years old. So, the technology has changed, but the methods have stayed unchanged.) My theory is that the trust in original design rockets originates from the exploding water vapor into high temperature steam. I believe the exothermic reaction can now be skipped, due to advances in container and heating technology, and we can deal with the end product - high temperature water flashing into steam - directly...at least for sub-orbitals. I'll sort of prove my point below. Read on.
For the next 50 years at least, SUB-ORBITALS are where the money is!
With high efficiency 22% efficient solar cells on the wings of a shuttle (at least 20 sq. yards on each wing), and knowing 220 watts (with today's tech) can be converted per sq. yard (out of a possible 1,000 watts of sunlight available per sq. yard), 8,800 watts of heating power is readily available today in bright sunlight above the clouds, besides stored power before takeoff. With further advances in solar tech, you can get even MORE power per sq. yard; up to 40,000 watts within 40 sq. feet on the wings...if efficiency should ever approach 100%. The solar cells used can be identical to the ones used to launch the solar electric airplane that went to 93,000 feet a few years ago. They were 22% efficient by 2005.
Where did I get the 40 sq. yards, you ask? Well...a square yard is 3x3 feet, right? If you put 10 panels (cells) of them end to end...that is 30 feet long. If you assume the wings are at least 30 feet long and 6 feet wide...you get 20 sq. yards per wing, give or take. (20x2 = 40) If the shuttle is bigger, you'll have more area to generate power, including on the roof...for an extra 20 yards (60 feet), for possibly another 4,400 watts, for a grand total of 13,200 watts - if your shuttle is about 70 feet nose to tail. That's MORE than enough raw microwave power to help heat a composite boiler that holds 2,000 to 5,000 gallons of water to explosive steam within a few hours. (The shuttle only needs to run once or twice a day.) On the ground, it will be plugged in for additional power before takeoff, to heat the water sooner.
For reference, you can boil a gallon of water in a 1,000 watt microwave in about 15 minutes. Two separate cups of water (at 8 Oz.) takes about 2-3 minutes, but I believe there is residual power in the oven for more water/mass to heat simultaneously than we can see in simple observation. I think you can bring to boil about 2,000 gallons with 1,000 watts in about 8 hours. If you have 13.2 times the power (13,200 watts), it can be done in about 40 minutes. (.6 hours) Double that, and you can bring to beyond boiling 4,000 gallons in about 90 minutes. If the boiler can withstand the pressure, the steam power can be ramped up to 5,000 psi within 2 hours before launch. (My educated guess without working out the calculus.) If you only want 2,000 psi...you will be ready a lot sooner...if your boiler doesn't explode before you can get it launched! <g>
The trick is to not let the steam kick out the hot water before you've had an opportunity to boil it off, unless that is your alternate plan. Humm. (see below) A water tank that rapidly drops water into a "combustion" chamber might be a good idea. (Two stage heating.)
*** However, for quick shuttle jumps under 1,000 to 2,000 miles, (with NO layovers), kicking out the WATER TOO for a more mass moving thrust is probably a fantastic idea. I don't know if the passengers can withstand G's over 10 for more than a few seconds, however. <g> Read on.
More Steam propulsion theory? Use the power to keep the boiler very HOT, until the shuttle reaches sub-orbital altitudes, then it glides to its destination. It's like a high tech exploding boiler, but the rapidly escaping steam and vapors produce lots of thrust. (Super heated steam can reach pressures beyond 10,000 psi, and rip almost any container apart at those levels, if not throttled down. Most LH2/LOX rocket engines run on only 500 to 1,000 psi at the MAX, until the exothermic reaction, I found out. So, as I see it, dealing directly with the steam itself is more practical; to red lining beyond 2,000 to 5,000 psi directly, if the technology is now available.) Oh well...that's a subject of debate...but at least I brought it up...and maybe it could be used for shorter shuttle flights that only go up 10-30 miles altitude. (150,000 feet) <g> Because the tank's parts are probably not corrodible, ordinary tap water could be used...but there's probably a whole distilling industry (and its employment) here for airports equipped to launch one of these "Space Steamer" shuttles.
2nd look, while I am on this subject: If the rocket orifice is a cheese wiz of little 1 inch holes to help maintain back pressure...you'll have at least a square foot area of little holes pushing out 5,000 psi of high velocity steam and/or water, if the exit orifice is at least a foot in diameter. Rough calculation = somewhere around 144 sq. inches (sq. foot roughly rounded) times 5,000 psi or around 720,000 POUNDS of thrust per engine, in the initial pulse. Not bad at all!
Not enough yet? Just turn up the psi. if your boiler can stand it. Or, kick out the hot water too as the exploding steam pushes it out from the top bubble in the tank...for rapid water vapor thrust that is also pushing mass, for readings that are off the scale. <g> Hehehe. Yeah, I know the orifice might melt from intense friction, but maybe some Teflon coating might help!
A 3rd look: If your mass of hot streaming water is empting the boiler at a modest 1000 gallons per minute...that is 8400 lbs of water per minute (water weighs 8.34 pounds per gallon), plus the velocity as it leaves the little 1 inch orifices to give some kinetic energy. Whatever the exit velocity is, it is probably over 200 mph (escape velocity for the propellant adds to the kinetics). I'm going to do some more guessing here. Let's suppose the hot water is blowing out at 200 mph. (It's just an estimate but with 3,000 psi behind it, it's gotta be moving FAST. This is still a hot momma if it is only blowing out at 100 mph.) How many feet per second if we consider the thrust can easily move the craft? It looks to be 293.3 fps or 17,580 feet per minute, without considering acceleration. That is about 70,320 feet straight up still under power for 2-4 minutes, if nothing else is considered. But, we'll arch a bit to get some ground distance going. The tank will be empty of its 4,000 gallons in less than 2-4 minutes (the faster it empties the faster it goes!)...just long enough to reach almost 150,000 feet after drift, if we get all 4 minutes. (Topping out at 25-30 miles) My hunch is the kinetic energy of the thrust will carry the shuttle much higher because of extra velocity beyond the exit velocity of the water itself. Think about it. Your comments are welcomed. My doubts...the mass thrusting G's are probably too much for humans to take if in a lightweight composite shuttle, when everything is calculated out. We'll have to scale (throttle) the "Space Steamer" down a bit for passengers...but it looks like the technology is ridiculously simple.
OK. OK. Let me try and do some more rough calculations to satisfy your curiosity: My first impression is the imaginary fact we have 8400 lbs of mass going out per minute. (Water weighs 8.4 lbs per gallon.) That's not too hard to imagine, if we have 5,000 psi or maybe even less, pushing at the back of the hot water. I do know for a fact we already have composite tanks than can withstand 2,000 psi. They are used in steam cleaning power washers. Somebody just needs to build a bigger one. We are now in a position of just USING the water itself for propellant, pushed out by high pressure steam on top of it, only. If the hot water is blowing out at 200 mph through narrow orifices...that is 293 fps or 17,580 feet per minute that the craft is at least moving in a few seconds, in an upwards direction until the "fuel" runs out. (Acceleration not included.)
17580 feet/min. * 8400 lbs/min. = 147,672,000 foot-lbs. or 2,461,200 foot-lbs of thrust. The minutes can be cancelled out.
2.46 million pounds of THRUST...you say - for FOUR long minutes???
Humm...wait a minute! That's NASA class thrust, isn't it??? <g>
I hope I calculated that right...hummm.
My handy Acceleration Calculator toy on this site says you'll be about 175 miles distant at the end of 4 minutes going about 2,500 mph...if you are getting a little over 720,000 pounds of thrust on a craft that weighs around 50,000 pounds full...<???> About 33,600 of that is the weight of the water at liftoff. (Are we in orbit? No, we aren't going fast enough yet...but we surely could be 1/2 way across the United States before we land.)
As far as I know...the ARES 1-X has loads of hardware to achieve a similar thrust value, plus booster rockets...but of course...it is an orbital craft...so the similarities end there. But I wasn't considering this for orbits...there are probably factors overlooked that effect deeper space operations, such as freezing temperatures. But, if microwaves can melt ice into steam, it might not make much difference after that is taken into consideration.
If I had the funds...I'd build a 10 ft prototype...and launch it in the Mojave Dessert, I suppose. Maybe it would go several miles downrange without much modification. Hummm...I can try and estimate its range, I suppose. 10 ft will hold about 100 gallons, if it is made stout. In comparison, a 6 ft hot water tank holds about 40 gallons. I'll get a headache trying to figure out the diameter.
Hummm, maybe I'll try. 1.78 liters equals a gallon, I think. That is a 178 liter tank. Each cubic centimeter of water equals a gram, more or less. There are 1000 cubic centimeters in a liter I think. So, we have 178,000 cubic centimeters. If our water tank were a perfect square, we'd have 59.3 centimeters to a side. If 2.54 centimeters equals an inch, we'd have a square tank that is about 24x24x24 inches. Hard to believe until you imagine 20 five gallon gasoline containers stacked up inside. If our rocket is only 18" in diameter, it might reach 10 feet high as the volume gets taller, but I'm not going to drag it out any further. My guess was initially based on the size of hot water heaters we see today, and this would be about the same if you include the rocket's avionics, parachute, and support structure. The best way to get your rocket going is to build the tank 10 feet high and slim but round as practical, then see how much water you can fill it up with. Let's just go with the weight and kinetics and some educated guessing to get us through.
We'll make the orifice much smaller this time. I see a nozzle about 4" across. Bare with me...these are just my preliminary estimates. It gets better as you read down! The holes are still 1" in diameter, but there are only three. Three 1 " orifices pushing at least 1,000 psi (easy to achieve) should empty 834 pounds (100 gallons) in about a 20 seconds or so. One hundred gallons per minute is actually sort of slow for any kind of commercial water pump, although sump pumps can barely pump out 5 gpm, depending on size. So I upgraded my time estimate. Now it is 300 gpm, and the show is over in 20 seconds. Humm.
It just might empty a lot faster, which means the thrust will be much higher than what is written here (kinetics)...but it will only be for a few seconds...so the range is probably about the same if there is drift. Let's assume the steam can rush the water out at 50 mph effective velocity. (This is actually sort of weak - and I'm being super conservative to prove a point.) Assuming the rocket is light...it can easily match 50 mph within a few seconds, and then surpass it. We know for certain (through common sense) the rocket fully loaded weighs LESS than 3,000 pounds (about 1,000 lbs.), which is the weight of the water and the tank with fins, nozzle and electronics. It might weigh a little more, but an extra 100 lbs weight can be compensated by adding psi.
My initial estimates:
That's our initial lift, I believe (3,000 lbs. thrust) we can assume when the nozzles are opened (each of three 1" orifices is pushing 1,000 lbs.)...but the water rushing out the nozzle adds kinetic value. We have to remember to subtract the weight of the craft. So, we get 2,000 lbs. effective thrust at launch, until the water starts moving.
On extended thought...I've decided this thing will empty its 100 gallons at about 400 gallons per minute or in about 15 seconds. I could be wrong, it might empty at 1,000 gpm, which means it will empty in a big flash of steam in 5 seconds. That's a whole 'nother set of kinetics...but you are getting the idea, right? You might need to add a wetting agent to the water to make it slipperier on exit, and this may raise its boiling point a little. A better solution is probably widening the orifice...but I am thinking the initiated pressure may drop below useable levels if the opening is too big. EX: If the opening is 2 feet, and your rocket is 2 feet in diameter, your effective psi is only equal to the weight of the water for one second, or the time the load takes to hit the pad. Kaboom! You tip over, etc...if the steam blows it out as an explosion, and you'll lose all control.
Something is missing in my estimates...but I am getting close. <g> I do know a sump pump can pump 500 gpm with a 2" pipe, at manageable psi. It has to be low psi (under 150 psi), or at the higher values of 3,000 psi it would ripe the housing apart. Not being calculated are the water's viscosity, drag, and no exact figure on how FAST the water will flash out the back of the orifice. Side theory: the friction may be high enough the water comes out a heavy vapor instead of a liquid and might flash into steam from friction alone. But, since the psi in the tank is evenly distributed, we can always assume our rocket nozzles will indeed have 1,000 psi per nozzle, and 3 effective inches will add to make at least 3,000 pounds kicking towards the rocket launcher platform. Within a second, our exit mass adds kinetics. You'll notice on a rocket launch pad, it is not released until the exit velocity is up to speed (2-3 seconds). This is to include the kinetics upon liftoff. My opinion.
About hardware: You'll need a quick gate valve that can be opened (jerked out of the way) suddenly, probably by a strong cable. It will be made out of 1/2' to 1" sheet metal perhaps, and sealed at the bottom with a cable pull tab, that can be opened by exploding bolts or jerked cable. It has to open fast. By the time a needle valve is opened, the show is over! Humm...exploding bolts or an exploding valve might work better, so it can be sealed tight until launch.
In 15 seconds, the rocket will have gone 1,100 feet...or about 1/4 mile downrange and about 500 feet altitude under power, and about another mile to fall to Earth, based on speed, without much time to accelerate to really big numbers. The air also adds drag to slow it down. We haven't considered acceleration yet. What's the thrust, if our rocket/tank weighs around 1,500 lbs full? (834 lbs of water plus weight of the rocket dry.)
100 mph jet velocity of our water = 146.7 fps or 8,802 fpm (assumed)
834 lbs /15 secs. = 55.6 lbs/sec
146.7 fps * 55.5 pounds/sec. = 8,156.52 ft.-lbs./sec. (8K thrust on initiation) - not too shabby if this small tank really can be blown dry in under 30 secs., when kinetics are added. We can assume our tank weighs less than 1,500 lbs., so we have at least 6,500 lbs. pushing up, and then it will quickly increase as the weight drops, up to 8K thrust.
The only way to spot it will be its parachute, which could carry it a couple miles if it opens too early in a strong wind. <g>
With these kinds of numbers for a simple steamer for near Earth shuttles, who needs cryogenics?
BONUS: For a demo...I've decided the ONLY tank that needs to be plastic, composite, or light weight ceramic, is the HEATING chamber, if using microwaves...but ANY heating method will do for the test, so metal tanks are OK...up to a point. If fact, on a test rocket...the water can be brought to boiling and higher pressure at the PAD, and a high pressure hose is used to fill an aluminum or light weight metal reinforced tank inside the rocket, with the nozzle at the rocket's nose. The boiler can blow the extremely hot boiling water into the tank just before takeoff. As the water steams in an enclosed tank, the pressure will build internally very quickly. To launch after internal pressure is high enough, the gate valve at the bottom orifice is blasted open...and it's LIFTOFF! If you can't get the water boiled...a smaller test can be done with plain pressurized air pushing the water out. Just be sure and get up to as high as you can (500-2,000 psi).
This steam rocket will not really show its potential power for sub-orbitals until you can push hot steamy water at 2,000 plus psi.
I've flown water pressure rockets before as a kid. You pumped air into the water chamber with a hand pump. There was a plastic one for sale in our toy store. It climbs to 250 ft. in about 5 seconds, but that's a handheld that goes in a small launcher. It only held 3-4 ozs of water. It was probably about 80 psi...I just couldn't pump any more air in with my smaller hands, which is identical to the pressure of a well streaming garden hose. Even still, the performance was awesome. The nozzle was about 1/8th an inch.
If you can't LAUNCH it upwards, a wheeled steamer on land can be tested...but it will need some serious BRAKES! You also might not completely understand the practical rocket use if you just watch it roll...so it might be a waste...unless it is just done once to investigate the thrust. (If more than 100 gallons is to be rocketed at 2,000 psi, I recommend the Utah Salt Flats!) You'll lose all interest, however, if you only run this thing on anything below 500 psi. Seeing fast water squirt out a fancy sprinkler at 100 psi is not the idea. The pressure has to really be up there to get it going. The main reason folks have a hard time imagining a steamer rocket is they've never known the true power of steam and fast moving water. This baby can KICK!!!
Unfortunately, the mass of a car is 2x to 3x heavier than a rocket of the same size, slowing the acceleration...so you might initially be disappointed. Someone who tries that has to take the car's weight into consideration, plus the water. EX: At 8,000 lbs thrust, you'll only be going 30 mph, I just figured, after 15 seconds, based on a car that weighs 3,500 lbs, with our water, not considering friction. But, you will be going 45 mph after 30 seconds, and a half mile away. (Over 2,000 feet) You'll need more water. That is a slow gas guzzler kind of car...but at least you are moving! Have heart, after one minute, your compact 3,500 pound pickup will be breezing along at 91 mph! (And those brakes better work!)
I figure we'll need all 400 gallons for a one minute boost. That is 3,336 extra lbs, plus the container...hummm. Our "rocket" can only weigh 200 lbs empty. OK...let me try again. 6,836 pounds. Well...at least we'll be going 45 mph after one minute...not too bad. To really perform, the psi's have to be increased.
NOTE: you CAN put the steamer tank on top of a car, and the nozzle pointed backwards...but only serious high pressure will give you a good test. It will roll, however, if in neutral and the psi is at least 250 psi. I'm afraid if you exceed 2,000 pounds thrust, you might not be able to stop the car, or if you do, the tank will rip off the roof and keep going, if still under power! So, use a pickup truck to be safer, I guess...and have nothing in your way for 5 miles if blowing 100 gallons out the back at 100 mph exit velocity in a light weight. <g> Be sure and have a valve that can depressurize the rocket in an emergency. And, remember what I said about the Salt Flats?
A 1/2 gallon steamer is a good place to start...but still try and exceed 250 psi. and an orifice that is about 2-5% or so of the tank's diameter or length. A 1/2 gallon may work best with an exit of about 1/4 of an inch. At 1,000 psi, your one gallon rocket will produce an initial thrust of 250 pounds, for instance, but only for 5 seconds or less. It will produce 500 lbs thrust for about 2-5 seconds if you make your rocket 1/2" copper. This is a dangerous speared projectile...so be careful! Even the little ones pack awesome power! I doubt domestic copper will stay together for 1,000 psi...it is too soft, so try something more durable.
Its length may increase for 1/2 gallon of liquid to 4 feet, but the copper is still light...under 7 pounds, including the water (4.17 pounds). After 2.5 seconds it could be going 109 mph (or about 160 fps)...and will embed deep into or penetrate your bedroom wall (or your chest if foolish enough)! Of course, if inside a lab...it will appear to move instantly...so the limited space might limit its velocity...but standing in its path could be fatal. A partially finned 1/2 gallon copper pipe rocket should shoot to around 500 feet at 250 psi. or bounce and slide 500 feet over several seconds if shot horizontally over concrete 2 feet above the surface. (It will be traveling 200 fps, minus friction with the ground after the 1st second.)
NOTE: I doubt all copper pipe can withstand 1,000 psi...but experimenting with 250 psi should be safe, as household pressures can approach 180 psi if below an elevated tank (unregulated), and copper pipe is rated to hold up under it. This will be enough to give you your 1st Ahaa! reaction. <g> Also note...when you get past 1,000 psi, common bonding materials may start to fail...so I suggest welding important parts in place, even if they look solid.
If you need seals, use metals, not rubber. The best are lead washers or brass against steel. You can tell a lead washer is sealed properly when it bulges slightly around the orifice as you tighten down on the bolts. For the psi's that really get you going, you'll probably have to use brass. Lead is soft, and brass is for very high psi's, or higher torque on bolts to seal it. But for medium high psi's, lead is better and easier to set. For psi's up to 1,000 to 2,000 psi, lead might do OK. Whatever material you use...the rocket CANNOT sit on the pad for long, as seals will start to spray high pressure steam, as the high pressure steam opens up paths to escape, and once up to operation pressures, you'll need to launch without delay or risk explosive failure. Even at psi's over 2,000 psi...if the tank has a pressure outlet (your rocket exit orifice), most of the energy will move towards the outgoing water, and help prevent containment failure. BTW - copper is too soft for really high psi's as a container, unless it can be reinforced...but makes a good washer like lead if torqued down hard against another flat metal surface. Lead is a better choice, however...as it fills micro crevices better as it gets smashed down. You can BUY lead washers commercially...especially for those 2,000 psi steam power washer/cleaners I was mentioning in here somewhere.
Another note: Flights over 150 feet within an urban area might require you to file with the FAA, if not in a designated test area such as the Mojave Dessert aerospace testing labs. I'd at least try this out in a rural area, away from people, or nosey neighbors.
A 120 inch tall tank can have an exit nozzle about 3 inches total diameter (3 one inch orifices), provided the tank is about 1 1/2 feet in diameter. Remember, if your rocket gets too big an impulse at the beginning, it will shorten its range. A smaller orifice of steady thrust may give a better performance. I think a 6" orifice (6 one inch holes) is about the max for a medium sized experimental rocket...and will probably hold over 1,000 gallons instead. At 2,000 psi, your 6 orifice rocket nozzle will produce at least 12,000 pounds of thrust, then subtract rocket weight when full for effective lift. Just remember it is easy to get up to 1,000 gpm with a 3" exit nozzle and 2,000 psi.
YES...I understand jetskies can throw water at 1,000 gpm. They go pretty fast, but not THAT fast. Their exit jets are about 4" and the bigger the escape orifice per gpm, the lower the thrust. Exit velocity is about 60 mph. Oh well...that is lower than expected. If it were only 2" at 1,000 gpm, it would about double the thrust, but at considerable HP that a jetski might not have.
A jet ski weighs around 750 lbs for a one person. (Educated guess based on Harley Davidson motorcycles.) They can go 55 mph in about 5-10 seconds, are about 30-50 HP, and produce about 16k thrust, if calculated. So, our rocket is still a rocket. The water the jetski runs through produces a little friction, btw, as does the wave action, to interfere in getting up to speed. As long as we can accelerate skyward, we have a rocket. <g> Hummm...now I understand the volume of water won't last long at 2,000 psi. I am a bit worried about sustained thrust. It will kick hard at over 1,000 to 2,000 gpm then be gone in a steamy flash. Instead of 4 minutes of thrust...it could be over in under two very hot and steamy minutes. Still...I do not want to give up.
My rocket orifice would be about 2" (two 1" exit holes) for the same flow. Just think, if the orifice was 12" it would barely move! If the water flowed out like a waterfall, it wouldn't move at all. The coefficient of friction for the water would almost hold it in place. It is the exit velocity of water/mass through a small orifice that gives it acceleration power. If you want 12" of available area, for a steam rocket, that requires you build a nozzle that has 12 one inch pipes at the exit. Each will express approx. (because they are round instead of square) the psi inside the tank at launch. But the impulse may go to waste if you run out of fuel too early. Because you dump 1,000 gallons of water in 15 seconds (4,000 gpm), you'll produce 32k thrust instead (double), be going 163 mph, but only have traveled seven 10th's of a mile before you run out of steam (literally). <g> There's still hope if somebody can build a high 3,000 psi steam rocket that carries 4,000 to 5,000 gallons of water/fuel, but the skin of the rocket needs to be kept light.
Another idea is for the composite tank construction. The walls of the composite tank need to be 2-3 inches thick for strength...but the wall can have a honeycomb design to save weight. They already build composites like this, for the skin of commercial aircraft, but for this test it will need to be double or triple the thickness, unless the technology advances. <g> Inside the tank will be struts crisscrossing the diameter to help hold the tank together, and the water flows around them. But for testing it can be an aluminum tank, or even a steel tank, but only if operating over 1,000 psi. so the exit pressure can still lift the rocket with 4 one inch nozzles. (4,000 lbs thrust) For comparisons, the rocket shouldn't exceed 2,000 lbs in weight during the initial phase, unless calculated thrust can lift it OK.
It doesn't have to be an ocean crossing shuttle...it works domestically TOO:
Hummm...here's another cheap way to fly...boost a small passenger glider to 68,000 something feet...and let it GLIDE down to your destination...no more flammables or hydrocarbons needed. On the (hopefully) gradual dive down to a useable altitude, it will pick up some kinetic speed besides, making the trip even faster than my estimates. These high variable G shuttle rides will only be for the adventurous, I'm sure.
At glider ratios of 32:1 for small gliders...range???
2,176,000 feet before runway touchdown...or 412 miles, from 68,000 feet. Here's another look. Only go up 40,000 feet, but be traveling at 500 mph horizontally before drag slows it down. The pilot(s) shut the engines down before it breaks the sound barrier. Hehehe. Range??? If we assume the glider can climb to 85% of it's initial height to stay aloft during our trip when needed...we can easily reach a destination 500 miles away in about an hour. <g> Not bad at all...for next to free fuel. A little enhancement, and a small 20 passenger glider with one of these blastoff boosters could glide from New York to Orlando, and maybe only charge $50 a seat one-way! (I'm always thinking about possible spin-offs.) If the glider has some residual water in the tanks (or held in a reserve tank), it can be used for retro rockets on the nose to slow it on touch down. You'll be able to recognize a steam glider/shuttle by the telltale clouds of steam rolling away from it just as it touches down. Other than that...it will almost look like a Boeing 737, only smaller. Youth will love the steam glider for its high G's...but the retired set might complain. <g> Airports will build a 20 degree slope takeoff ramp for the steamer, which climbs at a higher angle than other aircraft, and leaves the airport at nearly its service velocity.
The biggest bonus??? It still gets folks to their destination in a hurry WITHOUT using oil. <g>
I have a program I designed as an online toy. It's my ACCELERATOR page. You can download the Visual Basic program and run it on your computer or over the Internet. Look for the link on the main convention 2007 page. I'll also make some conversion calculation pages available if you'd like to play with numbers.
Thanks for reading,
- Tom Chatterton