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#26 2016-02-16 22:47:47

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
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Re: Forget NTR, SEP is the Future

Aerojet Rocketdyne is one of 12 industry teams that were named by NASA to help build space and human exploration capabilities for deep space destinations as part of the Next Space Technologies for Exploration Partnerships (NextSTEP) initiative.

http://www.nasa.gov/nextstep/

Aerojet Rocketdyne Awarded Contract to Mature Development of a High-Powered Nested Hall Thruster System

valued at more than $2.5 million from NASA's Advanced Exploration Systems Division to develop and demonstrate a high-power electric propulsion system. Once fully developed, the technology will help reduce trip times and the cost of human spaceflight to cislunar space and beyond to Mars.

Under the contract, the Aerojet Rocketdyne team will complete the development of a 100-kilowatt Hall Thruster System, including a 250-kilowatt thruster that uses Aerojet Rocketdyne's patented multi-channel Nested Hall Thruster technology; critical elements of a 100-kilowatt modular Power Processing Unit (PPU); and elements of the modular xenon feed system. PPUs convert the electrical power generated by a spacecraft's solar arrays into the power needed for the Hall Thruster. The contract includes system integration testing, and will culminate with a 100-hour test of the 100-kilowatt system at NASA Glenn Research Center in Cleveland, Ohio.

Current electric propulsion systems operate at 5 kilowatts or below, and there are plans for near-term spacecraft using between 20 to 50 kilowatts, such as NASA's Asteroid Re-direct Mission. Much higher powers, such as the scalable 100-kilowatt systems being developed on this program, are required for transportation of the large payloads envisioned for sustained human missions to Mars.

Space Systems Loral (SSL), ADVANCES SOLAR ELECTRIC PROPULSION CAPABILITIES IN COLLABORATION WITH BUSEK TO TARGET U.S. GOVERNMENT NEEDS

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#27 2016-02-16 23:37:50

kbd512
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Re: Forget NTR, SEP is the Future

All I can say is that it's about time we funded the most technically feasible solution to the cargo transfer problem.

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#28 2016-02-17 20:04:47

SpaceNut
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From: New Hampshire
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Re: Forget NTR, SEP is the Future

Ok so we now have thruster R&D but without the power source developement ( which includes Solar panels and batteries or nuclear) its small money.
As with the conversation that we have had in the Rv'ing Mars to do a nuclear source will mean that we are at a mass of 20-25 mt and possibly more even if we get by the no nukes nonsense.....
I think that I worked out the amount of panels but had not worked out the masses for them or the batteries but I know that it comes with penalties as well....

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#29 2016-02-28 22:14:58

SpaceNut
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Re: Forget NTR, SEP is the Future

739997main_SEP_15_full_full.jpg

Solar Electric Propulsion: NASA’s engine to Mars and Beyond

grc-2015-c-01182.jpg


NASA Solar Technology Application Readiness (NSTAR) ion propulsion system Dawn spacecraft used three state of the art for electric propulsion systems are systems that operate at single digits of kilowatts, from 1 kW to 5 kW.
Ultimately we would like to have systems that are on the order of hundreds of kW. That would allow us to generate thrusts that are multiple pounds that can move things in months, with relatively large payloads. However, the jump from 5 kW to hundreds of kW requires advancing the technology to an interim stage to advance the technology to the 50 kW level. NASA Glenn is in the process of developing a 15 kW class SEP system. The 15 kW units would be combined into multiple strings to get the system to the 50 kW power level. The largest solar arrays currently flying today on high power robotic spacecraft produce 20–25 kW, with a voltage that might be from 600–800 volts to produce the thrust that we need. But for the future we will need an array that is capable of twice that.

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#30 2016-02-29 14:12:40

GW Johnson
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From: McGregor, Texas USA
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Re: Forget NTR, SEP is the Future

There's a scale effect here,  especially with nuclear-electric power sources.  Those tend to be big,  almost as if there is a min practical size,  for any of a variety of reasons.  If your mission thrown mass is big anyway,  then a 100 KWe to 1 MWe nuke power supply and electric thrusters make very good sense.  Although flight times will always be long because of the spiral-in/spiral-out stuff. 

Unless,  you mix electric and impulsive propulsion,  which makes thrown mass even bigger while drastically cutting transit times.  Some people object to bigger thrown masses,  but as the assembly of ISS showed,  it simply does not have to ride one big expensive rocket.  Commercial launchers are now cheap enough that a typical "exploration effort" could buy quite a lot of such rides.  And they promise to get cheaper yet. 

Whether there's a scale effect for solar electric,  I'm not at all sure.  That stuff does seem to work in small sizes and low-thrust applications,  such as satellite station-keeping and a couple of unmanned deep space probes now.  What happens when you try to scale it up very much larger,  well,  who knows?  We have not tried,  yet.  It's certainly past time we tried,  though.

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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#31 2016-03-01 11:25:18

kbd512
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Re: Forget NTR, SEP is the Future

GW Johnson wrote:

There's a scale effect here,  especially with nuclear-electric power sources.  Those tend to be big,  almost as if there is a min practical size,  for any of a variety of reasons.  If your mission thrown mass is big anyway,  then a 100 KWe to 1 MWe nuke power supply and electric thrusters make very good sense.  Although flight times will always be long because of the spiral-in/spiral-out stuff.

NASA has already determined that nuclear power options have a lower limit on payload size.  Their lower limit seems to be around 1MWe with total masses in the 100t+ range.  With any lesser total mass or power requirement below 1MWe, it seems that solar panels are more mass/volume efficient.

GW Johnson wrote:

Unless,  you mix electric and impulsive propulsion,  which makes thrown mass even bigger while drastically cutting transit times.  Some people object to bigger thrown masses,  but as the assembly of ISS showed,  it simply does not have to ride one big expensive rocket.  Commercial launchers are now cheap enough that a typical "exploration effort" could buy quite a lot of such rides.  And they promise to get cheaper yet.

The solar / chemical mix only seems to make sense when you start in higher orbits with heavier payloads.  Using commercial vehicles, NASA can afford to buy more than enough launches for exploration missions to the moon or Mars.  There's little to no incentive to retain insanely expensive super heavy lift vehicles that only have one potential use.

GW Johnson wrote:

Whether there's a scale effect for solar electric,  I'm not at all sure.  That stuff does seem to work in small sizes and low-thrust applications,  such as satellite station-keeping and a couple of unmanned deep space probes now.  What happens when you try to scale it up very much larger,  well,  who knows?  We have not tried,  yet.  It's certainly past time we tried,  though.

GW

Yep.  NASA has already executed a contract to scale up SEP to the level required for cargo delivery.  The only real requirement for SEP that I can see is delivery of ascent vehicles.  Those things simply weigh too much to cost-effectively deliver using chemical propulsion.

Last edited by kbd512 (2016-03-01 11:27:28)

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#32 2016-04-20 19:43:55

SpaceNut
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From: New Hampshire
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Re: Forget NTR, SEP is the Future

NASA Orders a New Solar-Powered Ion Engine to Explore Deep Space and Go to Mars

Today, NASA awarded a contract to Aerojet Rocketdyne, Inc. to design a new Advanced Electric Propulsion System, mainly for use on robotic deep space ships like those used in its Asteroid Redirect Mission.

The AEPS contract lasts for 36 months, and is valued at around $67 million, in which Aerojet will design, construct, and test the engine.

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#33 2017-05-16 16:59:50

SpaceNut
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From: New Hampshire
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Re: Forget NTR, SEP is the Future

This sort fits here as well:

louis wrote:

http://www.nextbigfuture.com/2015/09/na … power.html

I think this sort of system could be used for automatic deployment in a pre-landing scenario where we need PV power to produce water, methane, CO, oxygen and other gases from the atmosphere.

This would be a high efficiency system. Probably 500 Kgs of solar array would be enough to do the job.

NASA developing megawatt solar power arrays and will be used with solar electric propulsion

NASA Glenn Research Center, GRC, currently has several programs to advance near-term photovoltaic array development. One project is to design, build, and test two 20 kW-sized deployable solar arrays, bringing them to technology readiness level (TRL) 5, and through analysis show that they should be extensible to 300 kW-class systems (150 kw per wing). These solar arrays are approximately 1500 square meters in total area which is about an order-of-magnitude larger than the 160 square meters solar array blankets on the International Space Station (ISS).

The ISS has the four (pair) sets of solar arrays that can generate 84 to 120 kilowatts of electricity. Each of the eight solar arrays is 112 feet long by 39 feet wide and weights 2400 pounds.

These are being designed in the same manner as the ATK units.....and its huge.....

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#34 2018-08-31 16:47:22

SpaceNut
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Re: Forget NTR, SEP is the Future

The common theme of this topic starts with electrical proplusion AKA Ion Thrust to which Aerojet Rocketdyne demonstrates advanced electric propulsion capabilities

Under the AEPS contract, Aerojet Rocketdyne will develop and qualify a 13-kilowatt Hall thruster string for NASA, bolstering future exploration missions, as well as commercial space endeavors.

This most recent test focused on the power elements of the AEPS Hall thruster string: the discharge supply unit (DSU) and the power processing unit (PPU). The test proved the system's ability to successfully convert power at a high efficiency level, producing minimal waste heat.

The AEPS thrusters could be used on the power and propulsion element of NASA's Gateway, the agency's lunar orbiting outpost for robotic and human exploration operations in deep space. Built with commercial partners, the power and propulsion element will demonstrate 50-kW class solar electric propulsion to support exploration on and near the Moon, and beyond, including Mars.

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#35 2019-07-14 15:33:17

SpaceNut
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From: New Hampshire
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Re: Forget NTR, SEP is the Future

On topic use of solar:

Here are a couple of documents that relate to the use of once upon a time ATK megaflex arrays which are now owned by Northrop grumman.

Solar Array Structures for 30-300 kW SEP
https://ntrs.nasa.gov/archive/nasa/casi … 000360.pdf

An Elegant and Innovative Design for In-Space Assembly: Optimizing Modularity through an Umbrella Mechanism
http://bigidea.nianet.org/wp-content/up … Austin.pdf

Solar Power and Energy Storage for Planetary Missions
https://www.lpi.usra.edu/opag/meetings/ … uchamp.pdf

https://www.northropgrumman.com/Capabil … _Array.pdf

https://www.northropgrumman.com/Capabil … tsheet.pdf

Of course if we had  a solar only topic we would be making this same content  in it so as to keep all knowledge for solar use within it....

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#36 2019-11-16 18:43:47

SpaceNut
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Re: Forget NTR, SEP is the Future

What if we could move faster with current payloads or move more mass at the current space speeds of an ION engine?
Thruster for next-generation spacecraft undergoes testing at Glenn

NASA's Evolutionary Xenon Thruster - Commercial (NEXT-C) fired for the first time recently inside a vacuum chamber at NASA's Glenn Research Center in Cleveland. NEXT-C is a powerful next-generation solar electric propulsion system that could propel future long-duration science missions. NEXT-C is scheduled for in-space testing on the Double Asteroid Redirection Test (DART) mission in 2021.

https://www1.grc.nasa.gov/space/sep/gri … rs-next-c/

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#37 2019-11-16 20:39:55

kbd512
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Re: Forget NTR, SEP is the Future

SpaceNut,

We would first need to accept that chemical propulsion is too inefficient to move the kind of tonnage we say we want to deliver.  Whether using LOX/LCH4 or LOX/LH2, all chemical propellants mandate the expenditure of many thousands of tons of additional propellants for refueling to deliver 100t of useful payload to Mars- after you expend thousands of tons just to get that 100t payload into orbit.  Chemical propulsion is only required for takeoff and landing.

More efficient in-space propulsion is at-hand and should be viewed as a hard requirement if sustainability is any consideration- and it most definitely is for colonization.  To that end, we should be conducting testing with Argon and Hydrogen rather than Xenon and Krypton, since those are the most readily available and inexpensive propellant options.  Argon would only be used for "low gear", switching over to Hydrogen propellant for "high gear" cruise propulsion.

Instead of "coasting" to a destination and landing out of necessity rather than intention, low-thrust propulsion systems permit orbital altitude and plane changes, along with excursions to other objects of interest in and around the primary target area.  It's a heck of a lot easier to get to and from the surface of Mars after establishing a circularized orbit.  When you have the Delta-V capability to do that, there's little reason not to.  Reentry from low orbit should significantly improve the precision of landing attempts.  Since there's far less speed to bleed off than there is from an interplanetary reentry, lighter or reusable heat shields also become practical.

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#38 2019-11-19 12:44:09

elderflower
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Registered: 2016-06-19
Posts: 1,260

Re: Forget NTR, SEP is the Future

But direct entry saves a big fuel burn on arrival to get your vehicle into orbit.
If you do put it into orbit you may find it convenient to leave some part of it there and deorbit less mass than you otherwise would.

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#39 2019-11-19 13:51:03

tahanson43206
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Registered: 2018-04-27
Posts: 3,496

Re: Forget NTR, SEP is the Future

For elderflower re #38

In another topic in this forum, the benefits of docking with Phobos are under consideration.

A major benefit which seems possible but which needs verification is that the exhaust from a vehicle approaching Phobos can be collected and processed for re-use.  If that idea proves feasible, then the mass expenditure will be minimized, and if solar energy is used to collect the exhaust (as frozen material) and process it for re-use, then another of Elon Musk's objectives would be realized.

In another topic in this forum, the potential of using a tether from Phobos to let aircraft gently down into the atmosphere of Mars, and to retrieve them as they rise from below is given some consideration.

The net effect of all these practices (if proven practical) would be to dramatically reduce what traditional approaches would yield as great costs.

(th)

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#40 2019-11-19 17:57:17

SpaceNut
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Re: Forget NTR, SEP is the Future

From the gas of the exhaust if its H2 Lox then its going to fall as water on the surface if directed for a landing on its surface.
While chasing phobos the exhaust will form ice crystals in some areas and might remain in orbit of mars for a short period of time.
Methane Lox will make co2 and water to lead to mars moons or in its orbit around mars under the same conditions.
Once it freezes on the moons surface go scape it up and save it for later.

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#41 2019-11-20 11:32:28

elderflower
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Re: Forget NTR, SEP is the Future

I suppose that most of the inbound fuel burn will be used in attaining and circularising the orbit and exhaust condensate isn't likely to impinge on Phobos. The return launch burn might settle there to a greater degree but you then have no vehicle to refuel unless there are regular Phobos missions.
I think the initial four shipments will take hydrogen so that methane fuel and LOX can be made without mining, per Zubrin. For 1100 tonnes of propellant you don't need all that much Hydrogen, about 55te for stoichiometry.

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#42 2019-11-23 13:33:58

kbd512
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Re: Forget NTR, SEP is the Future

If we want to minimize propellant consumption, then why have we not spent more time on development of concepts related to magnetic / electric / plasma sails?  If we cut our propellant and power generation requirements to nearly zero, then nearly everything that gets delivered is useful payload.  Like it or not, at some point this will be all about money, so why not start with concepts that minimize mass and energy input?  In orbit around Earth, we can use electrodynamic tethers to raise orbits.  From there, all of these sail concepts can make use of the solar wind.  Rather than fighting with physics, we could try to use it to our advantage.

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#43 2019-11-24 15:42:04

GW Johnson
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From: McGregor, Texas USA
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Re: Forget NTR, SEP is the Future

Well,  things like ion (electric) propulsion and solar sails,  as we know them at this time in history,  are very low-acceleration items.  That's fine for cargo that does not care how long the transit time is,  or how much radiation exposure is.  Humans DO NOT fall in that category. 

The fallacy here is that what works for cargo immune to long travel times,  and immune to radiation exposure,  will also work for humans.  That is simply NOT true. 

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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#44 2019-11-24 16:05:27

SpaceNut
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Re: Forget NTR, SEP is the Future

Add multiple engines and you sum the thrust power will go up for making them work and so will the fuel consumption but that is just one way to make it arrive quicker.

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#45 2019-11-25 09:21:15

GW Johnson
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From: McGregor, Texas USA
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Posts: 4,077
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Re: Forget NTR, SEP is the Future

Well,  for any sort of electric propulsion,  there is the mass of the thruster machinery (quite large compared to the thrust force it produces),  and there is the mass of of the power supply (be it solar or nuclear),  which has to the supply the copious electricity used to get rather small thrust forces. 

If you delete the spacecraft and payload,  the thrust/mass of just the propulsion-power supply hardware is the upper bound on vehicle acceleration achievable.  Scaling this up does not change that picture.  Adding spacecraft and payload just decreases the acceleration below that upper bound. 

I'm less familiar with solar sailing,  but what I do know is the the thrust force generated is quite small compared to the required area of the sail.  With any imaginable material and construction method,  there will always be square-cube scaling law effects that effectively limit how large the sail could possibly be.  The upper bound limit is just a sail,  no spacecraft or payload.  This is basically the same as the electric propulsion problem.

I think electric propulsion and solar sailing are great ideas for any mission where the time spent traveling is not an issue:  i.e.,  slowboat cargo.  And,  that cargo needs to be fairly hard against radiation damage,  so it is unlikely to be foodstuffs. 

There's people,  and there's cargo subject to radiation damage.  Those are just going to have to fly a lot faster,  in the sense that higher vehicle accelerations are simply required.  Neither will ever spiral out through the van Allen belts on electrics or sails.  Ain't gonna happen.  The radiation exposure is just too high.  You'd have to add the weight of shielding,  and what if it failed?  Why risk that?

Now,  for smaller mission vehicles we have chemical rockets,  and we could have solid core nuclear thermal rockets,  which roughly double the Isp but are very heavy in terms of engine thrust/weight,  which makes stage inert fractions higher. Gas core nuclear thermal is the way around that problem,  but nobody has ever actually put one together and tested one,  so that technology is still decades away.

For really large mission vehicles,  of the type most suited to be colonization transports,  the best option has long been known:  some kind of nuclear pulse propulsion.   Lots of side effects,  you just have to deal with them if you want to use this technology.

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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#46 2019-11-25 13:17:27

Oldfart1939
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Re: Forget NTR, SEP is the Future

In concept, this is elegant; in practice, the thrust/mass ratio need to increase by ORDERS OF MAGNITUDE in order to become truly useful for human exploration of the Solar System.

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