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#1 2017-07-12 08:14:02

Oldfart1939
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Registered: 2016-11-26
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Advanced Electric Propulsion System successfullu ttested.

Here's an update on Rocketdyne's latest Advanced Solar Electric Propulsion system.

http://www.spaceflightinsider.com/space … ch-center/

I really consider these tests to be "baby steps" forward, and Electric Propulsion is undoubtedly limited by size of the necessary Solar Arrays. These systems are influenced by distance from Sol as well as the deployed areas. My view is these are not the ultimate solution to deep space missions--not until we have an alternative source of energy driving them. They are counting on long application of a nominal thrust vector to provide the necessary impulse resulting in the delta V.

I wish these articles would include actual numbers for the resultant thrust developed.

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#3 2017-07-12 19:47:14

Oldfart1939
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Re: Advanced Electric Propulsion System successfullu ttested.

I just can't get that excited over this system...we're going to be using chemical propulsion for a long time to come. If solar arrays are needed in building up the velocity of an ever widening orbit until an escape trajectory is attained, there will of necessity be an elaborate tracking system involved for the PV panels.

Last edited by Oldfart1939 (2017-07-12 19:48:23)

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#4 2017-07-12 20:28:48

GW Johnson
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Re: Advanced Electric Propulsion System successfullu ttested.

These ion propulsion things can be quite useful if you use them for what they are best suited.  They are not suited for manned vehicles,  because the accelerations are too low and the trip times too long.  But for cargo and equipment sent ahead,  or for unmanned probes,  or for satellite repositioning or station-keeping,  they seem to work just fine. 

That choice really won't change with really effective nuclear power supplies,  because the hardware far outweighs the thrust,  not to mention the rest of the vehicle.  But higher power and the accordingly higher thrust is a bit more attractive.  And with nuke power,  they work in the outer solar system as well. 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#5 2017-07-12 21:23:27

Oldfart1939
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Re: Advanced Electric Propulsion System successfullu ttested.

GW-

Yes, I understand the applications being better suited for unmanned vehicles. I support continued research on these projects. But I would also support a Nuclear Thermal Rocket, which would have better applications, short term. Need a deep space booster stage that could become a shuttle between Earth orbit and Mars orbit? There's an application for the NERVA type space vehicle! With a reported Isp of 900, that does a lot when plugged into the Rocket Equation.

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#6 2017-07-13 09:12:27

GW Johnson
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Re: Advanced Electric Propulsion System successfullu ttested.

I remember NERVA,  Project Rover actually.  There were several reactors with names like Kiwi,  Phoebus,  and some others.  By about 1971 or so,  they had a core design that had several hours' life and would survive 5-10 restart cycles.  The startup and shutdown transients are long compared to what we are used to,  with chemical engines.  But they had pretty well demonstrated a practical feasibilty for Isp ~ 900 sec at engine T/W about 4.  It made a much better deep space engine or an upper stage engine at that T/W. 

The problem is that all the guys who knew the science and the art of doing these things are gone now,  dead or retired.  And the corporate experience bases in which they operated,  those of experience with nuclear rockets,  have evaporated over time from disuse.  We would be starting over from scratch with only what was written down 4-5 decades ago.  That's deceptively inadequate. 

Remember how true my trite little saying is:  "Rocket science (or any other branch of engineering) ain't science,  it's only about 40% science,  and it's about 50% art,  and 10% blind dumb luck.  And that's in production work.  In development work,  the art and luck factors are even higher." 

The science part is what got written down.  The art part was never written down,  because no one wanted to pay for that.  Instead it was passed-on from the older experienced hands to the newbies one-on-one on the job.  Until the managers started firing all the older ones so they could pay less with newbies-only on their staffs. 

As starkly ugly and pessimistic as that assessment is,  it is quite accurate.  The art is no longer passed-on on-the-job,  and the corporate experience base evaporates very quickly now,  precisely because of egregiously-bad management of talent and labor.  Because of this,  things done more than only a decade or so ago are entirely lost to us. 

And the sad part is that corporations-as-contractors is where the "smarts" really existed.  The government labs didn't have it,  they just strutted around crowing like they did.  None of those government labs ever built anything successfully for themselves,  not without talented contractors to do it for them.  Not since the first Sidewinder was built in a home's garage in Ridgecrest,  California,  by China Lake employees after hours.  And that was with a contractor's rocket motor. 

GW

Last edited by GW Johnson (2017-07-13 09:15:25)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#7 2017-07-13 10:04:38

Oldfart1939
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Re: Advanced Electric Propulsion System successfullu ttested.

It's not just engineering that's 40% science; so is chemistry. We always said that 40% was getting the reaction to start, 40% of the time getting it back under control after it ran away, and 20% of the time cleaning up the mess it made. Little details such as extracting the product from the ceiling tiles was NEVER in the research notebooks!

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#8 2017-07-13 13:49:05

GW Johnson
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Re: Advanced Electric Propulsion System successfullu ttested.

The chemistry experience does sound somewhat familiar.  I was never personally close to any propellant mix explosions.  We always did that stuff remotely.  Saw lots of motor tests that went bad,  though.  Lots of chiggers poking around in the tall grass looking for the explosion debris.  Not such a problem if the explosion set a grassfire.  Just sooty-dirty. 

A memory of high school chemistry:  funny how a steam-water mix moving upward at high speed will turn white ceiling tiles yellow.  Amazing how little sodium in the beaker of water will create that effect.

Project Pluto was the nuclear ramjet cruise missile effort.  It and Project Rover took place in adjacent facilities at the same Jackass Flats site,  on the Nevada nuclear test reservation.  Most of that test and facility hardware got scrapped off long ago.  What didn't still glows blue out there at night. 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#9 2017-07-14 11:53:56

Terraformer
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Re: Advanced Electric Propulsion System successfullu ttested.

The art part was never written down,  because no one wanted to pay for that.

Maybe we could crowdfund it? Pre-sell books written by old engineers of the parts which weren't written down.


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#10 2017-07-15 08:07:26

Oldfart1939
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Re: Advanced Electric Propulsion System successfullu ttested.

Getting back to the original hypothesis of the Solar Electric concept, in spite of some of the apparent advantages of the system, I really think that NASA is barking up the wrong tree at this point in time. Solar Electric becomes less and less effective towards the outer Solar System due to decreased irradiance on the solar panels as distance from the sun increases ( the reciprocal, or  inverse square relationship). This seems to limit the utility to as far out as the asteroid belt, recently demonstrated by the visit to Ceres.
Some other approach needs to be investigated, and we're reaching the limits of chemical propulsion in our efforts getting to Mars. I for one, support nuclear-thermal as the next step.

Last edited by Oldfart1939 (2017-07-15 08:28:20)

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#11 2017-07-15 08:52:43

SpaceNut
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Re: Advanced Electric Propulsion System successfullu ttested.

Yes GW, the earlier link(nextbigfuture.com) I did not post the image from which you speak of that the distance and attenuation of solar is what will cause the switch point to nuclear sources of power for this engine type.

149e3e60b277d25fa204080a420b3f81.jpg

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#12 2017-07-15 09:07:00

GW Johnson
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Re: Advanced Electric Propulsion System successfullu ttested.

Terraformer:

I'm writing the one on plain ramjet propulsion with the art as well as the science.  Nearly done.  Working an application to publish through AIAA through their continuing education series.

Spacenut & Oldfart1939:

I think the range for switch-over from solar to nuclear is not fixed for all time.  It will vary as solar power technology improves,  and as the thrust/power ratio improves of whatever electric drive system we are considering.  Availability and power/weight ratio for the nuclear sources figure into that as well.  As near as I can tell,  it is between Mars and the asteroid belt for the kinds of sources and thrusters we currently have. 

Oldfart1939:

I'm with you,  I think we ought to have a vibrant nuclear propulsion program.  Not just solid core thermal,  but gas core approaches  and explosion pulse propulsion,  too.  There's ground testing,  and certain limited flight demo missions that have to be flown,  before any of these can be turned over to mission designers as "ready-to-use" items.  Solid core thermal is by far the closest,  wit pulse propulsion a close second. 

I've seen ideas for fusion approaches,  too,  but these are going to need bench top fundamental-feasibility tests before anything can be ground-tested as a practical device.  That stuff is further-out in time.  But it needs investigation for sure. 

The safest place to do this work is on the moon:  close enough to be sort of convenient,  no neighbors to annoy,  and no air and water to pollute.  Problem is,  there is no one anywhere in government or industry looking at any of these tings in any serious way at all. 

GW

Last edited by GW Johnson (2017-07-15 09:10:37)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#13 2017-07-15 20:49:35

Oldfart1939
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Re: Advanced Electric Propulsion System successfullu ttested.

GW-

Having a Lunar based nuclear propulsion test facility is the best justification for returning to the moon. I think we should immediately resurrect the NERVA program with newer technologies, and I'll bet the Isp of the motors will increase somewhat. I especially like the fact it won't disturb the neighbors.

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#14 2017-07-15 21:06:45

SpaceNut
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Re: Advanced Electric Propulsion System successfullu ttested.

I agree that solar range can get a bit better with higher efficiency solar cells and larger arrays but at some point its about as good as a solar sail.

Now a nuclear engine research and developement test site on the moon would mean a hugh colony of builders and scientists for sure, so we will need cheap flights to aid in getting things going.

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#15 2017-07-15 22:13:43

RobertDyck
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Re: Advanced Electric Propulsion System successfullu ttested.

Oldfart1939 wrote:

I think we should immediately resurrect the NERVA program with newer technologies, and I'll bet the Isp of the motors will increase somewhat. I especially like the fact it won't disturb the neighbors.

That would be good. In 1991 NASA did a design study to update NERVA. The 1974 version had Isp (vacuum) 825s. The 1991 version 925s. So it was significantly improved. But I keep citing Timberwind, developed by the military in 1992. It had Isp = 1,000s, but it partially melted so it was not restartable. In both cases higher Isp was achieved simply by increasing temperature. Timberwind increased temperature too much, but its application was single use so that was considered acceptable. The great achievement of Timberwind was dramatic reduction of reactor mass. The NERVA 2 produced 34,000 kgf thrust in vacuum with 8,500 kg engine mass. Timberwind 45 produced 45,000 kgf with 1,500 kg engine mass.

If they could design an engine with the same Isp as NERVA 2, and the same thrust to engine mass ratio as Timberwind, and restartable like NERVA 2? I would be very happy.

One issue with NERVA 2 is they tried to design it to produce electrical power when not used for thrust. That dual use significantly increased complexity, and consequently mass. I would suggest forget that, just design for single use. Again, if you could achieve the same thrust and mass as Timberwind, but drop Isp to that of NERVA 2 in order to make it restarable? I would be very happy.

The other issue is you could develop a solid core NTR at the old test facility in Jackass Flats. You don't need to do it on the Moon. The Moon would be the best placed to develop an open cycle gas core NTR. That is expected to produce Isp 9,000 seconds, with as much thrust as a chemical rocket.

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#16 2017-07-16 07:26:26

Oldfart1939
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Re: Advanced Electric Propulsion System successfullu ttested.

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#17 2017-07-17 20:30:51

SpaceNut
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Re: Advanced Electric Propulsion System successfullu ttested.

Giving a push for in-space propulsion

3285a.jpg

SEP, the agency argued, could be used to propel cargo missions to Mars in advance of crewed missions much more efficiently than conventional chemical propulsion systems.

The Deep Space Gateway concept, though, remains just a concept, the first element of the Deep Space Gateway would be a power and propulsion module that incorporates SEP.

However, there’s no money for a 2022 Mars orbiter of any kind, let alone one with advanced SEP, in NASA’s proposed budget..NASA requested less than $3 million—that can keep alive a 2022 orbiter mission of some kind

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#18 2017-07-18 00:16:14

kbd512
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Re: Advanced Electric Propulsion System successfullu ttested.

SpaceNut,

All the individual pieces of the FDR pictured above have been tested and determined to function as intended.  Now it's just a matter of systems integration and demonstration.  A successful FDR demonstration would turn SpaceX's ITS spaceship into a 747 cargo freighter with SR-71 speed.  Imagine a 747 that could make the transit to Mars in about a month.  Imagine what that would do for consumables requirements when you can get people to and from Mars in less than 90 days.  FDR has the potential to drastically reduce mission mass, therefore cost, and risk.

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#19 2017-07-18 07:42:38

RobertDyck
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From: Winnipeg, Canada
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Re: Advanced Electric Propulsion System successfullu ttested.

kbd512, what is "FDR"? A NASA website with acronyms lists "Flight Data Recorder", "Final Design Review", and "Functional Design Review". None of those definitions appear to match what you're talking about.

And why would you fall for the claim that any form of electric propulsion would get you to Mars in a month or 90 days? Robert Zubrin has written about this many times. The mass of the nuclear reactor required to provide sufficient electric power undoes any advantage in Isp. And solar power just doesn't provide sufficient power to get to Mars in the same time as chemical, much less sooner.

After the Soviet Union broke up, the Russians sold everything that wasn't nailed down. In year 2000 I spoke with one engineer at the Glenn Research Center who had worked on the NSTAR ion engine for Deep Space One. He said NASA management had hired Russian engineers to teach them about their work on Hall thrusters. NASA thought Hall thrusters could only achieve Isp=1700s or maybe 1800s, but Russia got their Thruster Anode Layer (TAL) Hall thrusters to work as well as NASA's ion engines. And Russia developed their Hall thrusters in the 1960s and were using them on military spy satellites for station keeping. Russia bragged they had designed a high power Hall thruster that could achieve 8,400 seconds. The guys at Glenn took that as a challenge. They took the work done at Princeton on Magnetoplasma Dynamic thrusters (MPD) and improved it so that with LH2 it could also achieve 8,400 seconds. They actually built it and tested it in their lab. However, they used principles they learned from Russians to do that.

NASA's advanced propulsion group came up with a few designs. One was open cycle gas core nuclear thermal rocket. They didn't build any of the advanced designs, but they calculated this one could achieve 9,000 seconds.

This is why the VASIMR guys claim their engine can achieve 9,000 seconds. Their competition could, so they claimed they can too. Published data from laboratory tests only achieved 5,600 seconds using xenon, no work at all using LH2. Furthermore, VASIMR means "Variable Specific Impulse Magnetoplasma Rocket", but Robert Zubrin reports work on VASIMR has shown the "Variable Specific Impulse" feature hasn't worked well. It's supposed to drop Isp in order to increase thrust, but doing so dramatically reduces electrical efficiency, so with a fixed power supply you really don't get much thrust. It would be more efficient to just leave it at maximim Isp. And if you do that, you may as well use NASA Glenn's Magnetoplasma Dynamic (MPD) thruster, which uses less electricity for the same thrust.

Last edited by RobertDyck (2017-07-18 10:29:50)

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#20 2017-07-18 10:02:48

Oldfart1939
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Re: Advanced Electric Propulsion System successfullu ttested.

My point in starting this thread was simply to illustrate that we're YEARS away from any alternatives to chemical propulsion for manned spaceflight. We need to heed von Braun's approach: "we go with what we've got." The boys at NASA keep getting seduced by the fanciful claims of visionaries, and delayed as a result.

Note to kbd512: please use the full term of your acronyms once with the acronym parenthetically for the first reference; that would keep Robert and I a lot happier. Possibly everyone?

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#21 2017-07-18 10:28:58

kbd512
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Re: Advanced Electric Propulsion System successfullu ttested.

Rob,

It's a Fusion Driven Rocket (FDR).  That's what's pictured in the post SpaceNut linked to that I responded to.  MSNW LLC's flight model produces 36MW of jet power from 180kWe of input power.  It's an impulse thrust that occurs over a period of a few hours or days during each thrusting period.  MegaFlex or MegaROSA can provide that kind of input power.  ITS tankage containing cryogenic LH2 would provide superb neutron attenuation for the neutrons that aren't absorbed by the Lithium metal foil liner material vaporized in the D-T fusion process.  It's not speculative as to whether or not it works because that was proven between 2012 and 2013 in University of Washington State's plasma physics labs.

The D-T fusion process produces no electrical power.  The super-heated plasma is intentionally allowed to escape from the magnetic bottle to produce thrust.  COTS super capacitors provide 1MA of current to implode the Lithium or Aluminum (tested) foil liner at supersonic velocities, which initiates D-T fusion using an exponentially increasing magnetic field collapsing at supersonic velocities, similar in basic concept to supersonic implosion initiation in certain types of nuclear weapons.  The RS-25's would provide impulsive burns for TMI and TEI.  The FDR would then add velocity to reduce transit duration.

If ITS allows for 90 to 110 day transits on its own, then cutting that figure in half with additional velocity provided by a FDR is not a particularly tall order for a low-mass (10t for the complete FDR itself and a variable quantity of Lithium metal propellant), high-thrust (tens of MW's), high-Isp (5100s) system.  It's just augmenting existing chemical rockets.

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#22 2017-07-18 11:01:52

RobertDyck
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From: Winnipeg, Canada
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Re: Advanced Electric Propulsion System successfullu ttested.

kbd512 wrote:

The RS-25's would provide impulsive burns for TMI and TEI.  The FDR would then add velocity to reduce transit duration.

Or other chemical rockets. The upper stage of Ares from 1990 was to use J-2S. Upper stage of SLS block 2 was to use J-2X.  Upper stage of SLS block 1B or 2B will use 4 engines: RL-10C.

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#23 2017-07-18 12:03:33

GW Johnson
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From: McGregor, Texas USA
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Re: Advanced Electric Propulsion System successfullu ttested.

Please forgive me if I am skeptical of a "fusion-driven rocket",  considering that controlled fusion has been 20 years away for over 60 years now.  Until I see in the refereed journals verified announcements of success,  I have to class that as science fiction. 

Not that it shouldn't be worked on,  mind you!  Just don't hold your breath waiting for it to happen. 

Von Braun was right,  you go with what you have in hand,  or else you will never go. 

The corollary is that there are a whole slew of things that might keep you from going,  but waiting on the emergence of a new technology that is critical to success vs failure is quite certain to keep you from going. 

GW

Last edited by GW Johnson (2017-07-18 12:04:07)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#24 2017-07-18 14:11:37

kbd512
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Re: Advanced Electric Propulsion System successfullu ttested.

GW,

Controlled fusion has been going on for decades.  Our scientists have never managed to get more power out than put into the reaction for purposes of generating electrical power, as a function of thermal losses and containment issues related to the low strength of the magnetic fields that earlier generations of superconductors were capable of producing for a given amount of electrical power consumption.  On that front, high-strength REBCO tape is a gamer changer.  There were plasma confinement issues in the past, but these have mostly been resolved with better containment methodologies and better superconducting electromagnets that generate higher field strengths that dramatically reduce field instabilities to hold onto the super heated plasma.  We've had the process going continuously for 102 seconds in China.

The FDR operates over fractional second time scales in pulses, which is something we've repeatedly demonstrated without issue.  That means we squeeze a foil liner out of an extruder, inject a D-T pellet into the chamber, as the D-T pellet passes into the throat of the electromagnetic nozzle, electromagnetic compression of the foil liner at supersonic speeds using a 1MA pulse of current through the electromagnetic coils creates an exponentially increasing B field around the D-T pellet which initiates fusion and turns the compressed foil liner into a plasma to absorb most of the neutrons generated in the process, and finally the exhaust products from the vaporized liner are ejected out the back of the electromagnetic nozzle at tremendous velocity, which is what creates the 5100s Isp.  This process repeats every 5 to 10 seconds as the solar arrays recharge the super capacitor banks.

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#25 2017-07-19 07:30:28

Oldfart1939
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Registered: 2016-11-26
Posts: 866

Re: Advanced Electric Propulsion System successfullu ttested.

We are no where close to having a workable fusion reaction system. The Livermore National Laboratory would be crowing from the rooftops were that accomplished. The drawback to the D-T fusion reaction is the liberated neutron in the reaction.

          D2 + T2 ------------> 2 He4 + 2 n  + delta H (enthalpy).

The resulting neutron flux requires massive shielding for the system.

Last edited by Oldfart1939 (2017-07-19 07:34:17)

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