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https://en.m.wikipedia.org/wiki/Centrifugal_pump
Elsewhere in this topic, and elsewhere in the forum, there is discussion of how best to harness the thermal energy produced by nuclear fission devices, for propulsion of space craft, near Earth and elsewhere in the Solar System.
Nuclear propulsion has not been demonstrated in space, although it has been demonstrated on Earth (see NERVA and related discussions)
Electric propulsion powered by thermal energy from decaying radioactive material is well established as a propulsion method for deep space probes.
The purpose of this topic is to report on development of centrifugal pumps as an efficient way to employ thermal energy from a nuclear fission reactor.
It is generally reported that the best efficiency that can be expected from a nuclear fission reactor is about 33%. The remaining 67% of thermal energy produced by the reactor is low grade thermal energy that must be disposed of.
The purpose of this topic is to find and report on development of very high performance centrifugal pumps for space craft propulsion.
While no such pumps exist today, the potential for development of devices of this type is shown by development of centrifuges for medical, commercial and military use. It appears that the top of the line in centrifuge technology features equipment that rotates at 1,000,000 RPM. The middle-of-the-road equipment operates at 100,000 RPM.
A high performance centrifugal pump for space propulsion would accelerate one kilogram of water to 5000 miles per hour in a package of the lowest possible mass, and be able to operate for years on end in vacuum.
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To give this new topic a running start, here is a list of manufacturers of centrifugal water pumps collected by Google:
This is just the top of the list. This appears to be a mature industry, with many players.
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Industrial Water Pump - Powered by Cummins®
cummins.com
https://www.cummins.com › dewatering-pump
Our portable pumps are designed to solve every water challenge. Contact us to learn more. Cummins manufactured and warrantied portable pumps are in stock and ready to ship.
4000 Lyman Dr, Hilliard, OH - Open today · 7:00AM – 12:00AM
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Scot Motorpump - Scot Pumps-Best Prices Onlinefusionpump.com
https://www.fusionpump.com
Send Us Your Specs And We Will Ship Any Scot Pump Model (or Parts) To You Directly
Sponsored
Magnatex Centrifugal Pump - Huge Inventory Of PumpsMagnatex Pumps
https://www.magnatexpumps.com
Since 1985 Our Passion Has Been Your Process Reliability And Profitability!High Performance Centrifugal Pumps
Braber Equipment
https://www.brabereq.com › ... › Water Pumps
High Performance Centrifugal Pumps. Sort By. Sort by Name · Sort by Low Price · Sort by High ... 1.5" Water Pump on Skid; Wildland. Part Number: WS1525SKID. Call ...
high performance centrifugal pump for water from www.brabereq.comCentrifugal Pumps | Water Pumps
Pentair Aquatic Eco-Systems
https://pentairaes.com › ... › Water Pumps › Pumps
From high-efficiency to self-priming, Pentair AES carries a complete selection of centrifugal pumps. We have the pump you need at a great price.
high performance centrifugal pump for water from pentairaes.comHigh Flow Centrifugal Pumps
Pumpbiz
https://pumpbiz.com › applications › high-flow-centrif...
Water pump for irrigation, water transfer, industrial applications. Silicon Bronze impeller. Obsolete due to DOE new efficiency standards. 7.5 ...
30-day returns
high performance centrifugal pump for water from pumpbiz.comGol Pumps High Efficiency End Suction ...
pump supermarket
https://www.pumpsupermarket.com › product › gol-p...
EA series end suction centrifugal pumps are designed complying to BS EN733 /DIN24255 standard. This series of pumps have great advantages in interchangeable ...
$951.42 · 6–10 day delivery · 30-day returns · In stock
high performance centrifugal pump for water from www.pumpsupermarket.comHigh Flow Centrifugal Water Pumps
waterpumpsupplier.com
https://www.waterpumpsupplier.com › surface-pumps
High Flow Centrifugal Water Pumps. Model:HFm-3. INSTALLATIONS AND USE .For pumping clean liquids without abrasive particles, which are chemically non aggressive ...
high performance centrifugal pump for water from www.waterpumpsupplier.com
More questions
How high can a centrifugal pump push water?
Is a high performance water pump worth it?
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What are the disadvantages of centrifugal water pumps?
FeedbackWater Centrifugal Pumps
McMaster-Carr
https://www.mcmaster.com › products › water-centrifuga...
Choose from our selection of water centrifugal pumps, including over 325 products in a wide range of styles and sizes. In stock and ready to ship.Pentair Berkeley B-Series High Flow ...
Pentair
https://www.pentair.com › en-us › agricultural-irrigation
High Flow / High Efficiency Centrifugal Irrigation Pumps are designed for clean water applications such as flood irrigation, water features, ...
high performance centrifugal pump for water from www.pentair.comHigh Flow/Efficiency Centrifugal Pump
James Electric
https://jameselectric.ca › Home › Pumps
High Flow / High Efficiency Centrifugal Irrigation Pumps are designed for clean water applications such as flood irrigation, water features, and pivot ...
high performance centrifugal pump for water from jameselectric.caCentrifugal pumps - Alfa Laval
Alfa Laval US
https://www.alfalaval.us › products › fluid-handling
The cost-effective LKH pumps are used for evaporation, high-pressure, self-priming and high-purity applications. SolidC focuses on initial cost.
high performance centrifugal pump for water from www.alfalaval.usHigh Pressure Pumps
Gorman-Rupp Pumps
https://www.grpumps.com › High-Pressure-High-Head
O Series pumps are self-priming, high pressure pumps for clean liquids. Depending on the model, VG and VGH Series centrifugal pumps reach heads of over 200 PSI.
high performance centrifugal pump for water from www.grpumps.com
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TH, are you talking about pumping the water overboard to generate thrust? 5000mph is 2.2km/s. I think the forces acting on the pump impeller will be enormous. Also, to avoid cavitation (which destroys the impeller) very high pressure pumps tend to the multistage. The pump achieves a pressure ratio, i.e the ratio between outlet/inlet. From memory, that is typucally about 10. So to expel water at 5000mph, you will need a multi-stage pump. A positive displacement (piston) pump, could be single stage. But these pumps are heavier and have higher pumping losses. Most applications on Earth use centrifugal pumps.
Dynamic pressure is the pressure that a stationary object experiences when impacted by a water jet. It gives you a measure of the sort of pressures that your pump casing and impeller will experience. From the Bernoulli equation for incompressible flow: p = 0.5 x rho xV^2
Putting in the numbers for a water jet travelling at 5000mph, gives dynamic pressure of 2.5GPa. There are maraging steels with yield strength that high. But the mechanical forces acting on the pump casing and impellor are intimidating. I would be curious to know what the pump is intended to be used for.
Additional: I had previously calculated dynamic pressure as being 3E16 Pa, which is about the same pressure as you would find at the heart of a white dwarf star! But I realised that I had forgotten to convert m/h to m/s.
Last edited by Calliban (2023-10-04 08:09:25)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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For Calliban re #3
Thank you for your close look at the proposal, and for your listing of challenges to be overcome.
The model I have in mind is the nozzle of the Space Shuttle main engines, which were dealing with molecules moving at 5000 miles per hour at temperatures in the thousands of degrees. The water to be impelled in this scenario would NOT be greater in temperature than the boiling point of water, if that makes any difference.
The figures you provided for dynamic pressure are most interesting, because they must match the conditions in the nozzle of the Space Shuttle, and in the nozzle of the more modern high performance chemical engines.
Here is a draft document for a pitch to investors.
Your summation of the magnitude of the challenge ** must ** be included as an appendix to the letter.
https://docs.google.com/document/d/1M5J … sp=sharing
Again! Thank you for your most helpful post!
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TH, rocket exhaust velocity is indeed measured in km/s. But the pressures involved are much lower than you would experience pumping water to the same velocity, because the density of hot exhaust gases is much lower. The chamber pressure of RS-25 space shuttle engines was a little over 3000psi (20MPa), and liquid oxygen was injected at 30MPa, to avoid instabilities. That high pressure is still about 100x lower than your proposed water pump. In my opinion, it is on the edge of feasibility. It approaches the yield strength of the strongest steels ever made.
https://en.m.wikipedia.org/wiki/Maraging_steel
Maraging steels have yield strength up to 2.4GPa with UTS up to 3.5GPa. But even working close to this UTS, the pump shell thickness would be a large fraction of its diameter, making it very heavy. Maybe we will develop stronger materials in the future.
Last edited by Calliban (2023-10-04 08:51:31)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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tahanson43206,
I'm not a mechanical engineer, but this might be a bit impractical. I think it's possible to achieve Mach 6.5 / 2.2km/s, but I don't know for how long. I think you need a 35hp electric pump to achieve Mach 3. I heard they got that up to Mach 6 or so during the XB-70 program to cut metals for the honeycomb cores, but it proved impractical. I can't speak to the 324 billion atmospheres figure quoted by Calliban. That seems extraordinarily high for creating a 2.2km/s jet of water. Anyway, Mach 6+ has already been achieved many decades ago, the pump bodies simply didn't last long enough to be useful as refractory metal cutters.
I found this tidbit from a site about water jet cutters:
Running at 60,000 PSI (4100 bar) is typically the top of the ceiling before the maintenance issues become too severe to be practical in nearly all applications because of metal fatigue.
Even so, there are machines running up to 100,000psi or more. How long they last is another issue.
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Kbd512, 2.5GPa is the dynamic pressure of a water jet travelling at 5000mph hitting a stationary object. The earlier figure I gave was a calculation mistake caused by using m/h in the bernoulli equation instead of m/s. But 2.5GPa is 25,000bar or 367,000psi. There aren't many materials in existance that can take that kind of stress. Aramid has enough UTS, but would creep under sustained load. A specialist maraging steel might be just about strong enough, but would be extremely heavy. Sticking with the solid impulsive propulsion idea, a mass driver could accelerate a solid mass to produce thrust. Specific impulse could be as high as 1000s, if exit velocity of 10km/s could be achieved. But this mass driver would be large and thrust would be low.
I think it would be technically easier and no less efficient, to boil the water into steam and expand it through a nozzle. Specific impulse could approach 400s and the pressures are more manageable. If you heat the water past its dissociation point using microwaves, then performance could exceed that of chemical propellants, though thrust would be much lower.
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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For Calliban re #7
Thank you (again) for your support of this new topic!
Regarding ISP of 400 .... If you are willing to defer to GW Johnson, you would find that this ISP is unacceptable for the Large Ship propulsion problem.
Dr. Johnson's work is available for review in this forum, and there is at least one YouTube video of his presentation to the NSS Houston chapter.
His course on Basic Orbital Mechanics is available for you to study, if that should ever interest you.
Please stay focused on the objective of this topic, and try to avoid being distracted by well-worn approaches that happen to be new to you.
I am looking for a solution to ** this ** problem because Dr. Johnson has ruled out all others.
***
The challenge you have identified is cavitation. I'd like to set that aside for a moment, and ask you to please confirm that there is nothing in your experience to preclude the proposed spiral water accelerator, other than cavitation.
In other words, can you perform calculations that would confirm that the goal of 1 kilogram per second at 5000 mph delivery velocity could be achieved with known principles of physics?
Earlier, you showed that a centrifuge that holds it's load until release could perform the requested task.
Dr. Johnson has recently softened his opposition to impulse propulsion, by adding a requirement for a spring or similar force evening system.
I decided to investigate the continuous feed possibility because of the objection to impulse propulsion.
This topic is NOT about impulse propulsion, but it appears we need a topic to concentrate on that, because at this point the continuous feed idea may be blocked by cavitation.
Related ... traditionally, rocket engines are discarded after use. If cavitation ** is ** a problem that cannot be solved by human beings in the 21st Century, then perhaps the rate of cavitation can be managed, so that rotary acceleration equipment will last as long as it is needed.
For example, Dr. Johnson's Space Tug could push the Large Ship to near escape velocity in some knowable period of time. If the spinners can last that long, then perhaps reworking them back at Earth would be a reasonable price to pay for superior performance.
However, the idea of reloading propellant at a comet presumes the spinners will last longer than a few minutes.
***
Cavitation has been identified by Calliban as a challenge for a space rated rotary mass accelerator.
This topic is open for an in depth study of cavitation in this context.
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GW Johnson sent me a number of documents recently, relating to this topic, and to the impulse delivery parallel topic.
The overall impression that comes across to me is how difficult it is going to be to find a way to propel a spacecraft with a centrifugal technology.
This makes perfect sense to me. If something were easy, it would be done already.
This topic is set up to explore the fringes of what is known, in order to find any opportunities there may be to improve upon existing techniques.
I invite serious discussion and collection of facts that bear upon the problem.
This topic is dedicated to the continuous feed track.
The opening salvo of documents from Dr. Johnson about existing technology is concentrated in the continuous flow topic.
The problem to be solved is propulsion of a 5000 metric ton space vessel using water as the throw mass, and a nuclear reactor as the power source.
Dr. Johnson has thoroughly and exhaustively evaluated existing chemical methods, and existing nuclear propulsion methods.
Ion drives are not under consideration, because at this point, the thrust needed is not available, but if there is someone ambitious enough to develop that line of inquiry it might turn out that ions can produce tons of thrust. In any case, ** that ** is NOT what this topic is about.
Centrifugal pumps have been developed for use on Earth, and Wikipedia has a long and detailed article about them.
Centrifugal pumps to drive a 5000 ton space craft are going to be quite impressive, I have no doubt.
One hint of a possibility showed up in the Wikipedia article. Apparently there is a subset of centrifugal pumps that integrate the electric motor into the pump, so there are no bearings to deal with. The water (or corrosive liquid in the real life example) enters the pump at the center and exits via a port on the outer perimeter. A design for the space propulsion application would need to start with that feature.
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The transcript with ChatGPT4 at the link below takes up the question of designing a rotary pump able to deliver a kilogram of water per second at a velocity of 5 miles per second or 8046 meters per second. Setting aside the issue of material able to survive the stress of this exercise, ChatGPT4 computed a thermal output of the reactor needed as 122 MW. Of that, I'm assuming 33% goes to the drive, and 67% has to be disposed of.
https://docs.google.com/document/d/1ThW … sp=sharing
In comparison, it is my understanding (always subject to correction) that a nuclear thermal rocket is self-cooling. In other words, if I understand the concept correctly, the nuclear thermal rocket does not require additional cooling, because it delivers all it's thermal energy into the propellant.
The advantage of the centrifuge design is that it can work with water from any source, such as a comet, with minor filtering. A nuclear thermal rocket could also harvest hydrogen from a comet, with a bit more work.
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The transcript with ChatGPT4 at the link below covers setup with Blender to make a working model of a stretched centrifugal pump.
https://docs.google.com/document/d/1hIs … sp=sharing
The discussion includes design of a model using Blender, testing the model using a lathe, and the possible use of OpenFOAM to evaluate the model using computational fluid dynamics software.
The objective of the exercise is to evaluate the hypothesis that a mechanical solution exists for spacecraft propulsion, and that it is potentially superior to chemical propulsion or even nuclear thermal propulsion. That's a big ASK, and chances of success are slim,for the simple reason that if the idea has merit, someone would have developed it already.
Never-the-less, since the hypothesis is not precluded by physics, it would be limitations of materials that would deny successful implementation.
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The transcript at the link below covers discussion of erosion inside the walls of pipes inside a centrifugal pump.
https://docs.google.com/document/d/1G7g … sp=sharing
The loss of energy due to interactions between water molecules travelling this pathway had not occurred to me, but it makes perfect sense so that loss would detract from the kinetic energy to be delivered by the system, just as occurs in the Space Shuttle main engine, or any comparable chemical rocket engine.
One detail that came out of the discussion at the link above is that angle-of-attack should be kept as low as possible, so the longer the pump barrel the better.
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The link below reports on a conversation with ChatGPT4 about the possible use of Nanotechnology to improve the performance of the surface inside a passage for water molecules in the Stretched Centrifugal Pump under discussion here.
https://newmars.com/forums/viewtopic.ph … 66#p214666
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You need a material with high specific strength to sustain the extremely high tip speed needed by the pump impellor. I would suggest...
https://en.m.wikipedia.org/wiki/Zylon
How about a rotating zylon disc, with holes around its rim, that expel water droplets at km/s speeds like a sprinkler? Water would enter along the central axis and would be accelerated through curved channels by centrifugal force. To achieve a 10km/s surface speed, a 1m diameter zylon disc would need a rotation rate of 191,000 revs. Force acting on the rim would be:
Acc = v^2/r = 10,000^2 / 0.5 = 200million m/s^2, or 20,387,000g.
Zylon has specific gravity of 1.54 and a tensile strength of 5800MPa. The stress acting on the outer rim would be:
Stress = rho x a = 1540 x 200 million = 308GPa. Which is over 50x zylon tensile strength. Tapering the disc would reduce cross sectional stress. But a tip speed of 10km/s does not seem realistic for a 1m diameter spindle. If diameter increases by factor of say 100, then stress at the rim reduces to 3080MPa for v = 10,000m/s. This allows a factor ~2 design factor between operating stress and UTS. But the spindle gets huge, some 100m in diameter. So the pump might work so long as it is extremely large.
Last edited by Calliban (2023-10-09 11:21:02)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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For Calliban re #14
Thank you very much for your contribution to this topic!
Apache didn't like something in the rest of the message so I'll save it and try later.
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This is more of the post attempted earlier
In the mean time, I'd like to point out that an RPM of 1,000,000 has been achieved for an Ultracentrifuge, as reported in the topic for impulse. This topic is about continuous flow, as requested by GW Johnson, and your post certainly seems to be advancing the topic toward that goal.
Apache didn't like something in the rest of the post, so I'll try it later
An objective of the design process is to insure the outflow from the centrifuge is travelling in the same direction as the ship, but opposite, so that momentum eventually makes it's way back to the ship itself.
I couldn't tell from your description in post #14 if the water would be traveling in parallel to the axis of rotation of the pump? A sprinkler (at least a lawn sprinkler) is designed to spread water out radially, at 90 degrees or so from the axis of rotation. Can the Zylon device you're considering be modified to eject water in parallel to the axis of rotation?
Thanks again for taking up this topic!
We have an aerospace engineer who can use the tool if we can create it.
We have an electrical engineer who can provide electrical power.
You are potentially an engineer who can assist with the reactor to power the rig.
The mechanical engineering of this piece of equipment is ALL yours if you want it.
I can make Blender models of a design, if I'm given specifications for what the model should look like.
I have a 3D printer, and can render the model in a 400 mm x 400 mm build volume. A model in plastic could show whether the flow is as intended, even at slow rates of rotation. A lathe can rotate a model at reasonable rates of rotation. The lathe needs to be set up outdoors, because water is going to be ejected from the downstream outlets.
The line that Apache objected to was about why I have to postpone reading your post until later.
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The post at the link below includes a link to a transcript about design of a 3D model of a "Stretched Centrifugal Pump"
http://newmars.com/forums/viewtopic.php … 05#p214705
The transcript includes a work plan for creating the 3D model using Blender.
The insight that ChatGPT(4) provided was the use of the Extrude feature to pull an existing model of a curved vane impeller a long the axis of rotation.
This is a sensible suggestion that I had not thought of, because I was thinking about using more primitive elements to try to create curved vanes.
If someone has already gone to the trouble of shaping the vanes in a mesh model, then extruding along the axis of rotation should be relatively easy.
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