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#1 2018-01-21 14:56:25

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 21,706

ION Drive a fast transit to Mars

We have been discussing this being the enabler to make it to mars on less mass in terms of fuel.

Louis brought up this topic elsewhere and its really should be its own as it is a technology that is on the slow path currently.

Go to Mars and back on ONE tank of fuel: Student creates radical ion drive system that he says out performs Nasa's engines

Created by Paddy Neumann, a PhD student at the University of Sydney Works by hurling particles backwards so that probe can move forwards, Nasa's current HiPEP system allows 9,600 (+/- 200) seconds of impulse, This is a measure of thruster efficiency and dubbed 'bounce per ounce',  New drive developed by Neumann has achieved up to 14,690 (+/- 2,000)

https://newatlas.com/neumann-ion-drive- … ine/39490/

So where are we with the ION Drive of Nasa:

The current record holder for fuel efficiency of an ion drive is Nasa with its High Power Electric Propulsion (HiPEP) system, which allows 9,600 (+/- 200) seconds of impulse.

Nasa ION Propulsion

https://www.space.com/22735-new-nasa-io … video.html

Build an Ionic Thruster like NASA Uses for Space Propulsion

NASA’s NEXT ion drive breaks world record, will eventually power interplanetary missions

1000px-Electrostatic_ion_thruster-en.svg_-640x442.png

Antimatter to ion drives: NASA's plans for deep space propulsion

Nice images and info

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#2 2018-01-21 16:18:10

RobS
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From: South Bend, IN
Registered: 2002-01-15
Posts: 1,701
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Re: ION Drive a fast transit to Mars

Fantastic! Now we just need a 50,000 kilowatt power source that doesn't weigh a ridiculous amount to power the thing. That's the problem with ion propulsion, and if I understand things right, if you double the exhaust velocity, you have to quadruple the power demand. With a few hundred kilowatts of solar power, this thing would probably take over a year to get astronauts to Mars, but when they arrive they won't have used up much fuel!

If SpaceX really can get stuff into orbit for less than $100 per kilogram, or whatever the BFR promises, there's no reason to develop ion drive. The New Horizons probe that went to Pluto passed the orbit of Mars in about a month, and it was using chemical propulsion. Chemical do that if you can launch enough of the stuff into LEO cheaply.

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#3 2018-01-21 16:37:30

Terraformer
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From: Logres
Registered: 2007-08-27
Posts: 3,353
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Re: ION Drive a fast transit to Mars

For the same thrust, doubling the exhaust velocity only doubles the power demand, since thrust is proportional to exhaust velocity.

If we get microwave beaming working, electric propulsion would be really great.


"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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#4 2018-01-22 02:21:51

kbd512
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Registered: 2015-01-02
Posts: 4,175

Re: ION Drive a fast transit to Mars

Terraformer,

At first I thought this beamed power stuff wouldn't work very well.  Then I started reading about past experimentation and ongoing research.  The more I read, the more this looks like the most probable way to "get the most bang for our buck".  Since it divorces the power supply and its mass from the mass of the object being powered, within reason, the power supply can be considerable to say the least.

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#5 2018-01-22 05:27:19

elderflower
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Registered: 2016-06-19
Posts: 1,262

Re: ION Drive a fast transit to Mars

I think Rob is right, Terraformer. To double the thrust for the same propellant flow per unit time, you have to double its momentum which is proportional to its velocity. However the energy required to do this is proportional not to v but to v squared. Power is energy per unit time so you need to increase the power by the square of the increase of thrust.

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#6 2018-01-22 11:24:48

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 21,706

Re: ION Drive a fast transit to Mars

https://en.wikipedia.org/wiki/Wireless_power
https://en.wikipedia.org/wiki/Microwave … ansmission

What I understand is it atenuates with distance from source to reciever and does not do as good in wet conditions.
http://www.zdnet.com/article/capturing- … ectronics/

http://iosrjournals.org/iosr-jeee/Paper … 452428.pdf
https://www.ijser.org/researchpaper/WIR … ISSION.pdf
http://www.ursi.org/proceedings/procGA1 … BDJK-2.pdf


Then again you can also go with lasers:
http://www.esa.int/gsp/ACT/doc/POW/ACT- … er-WPT.pdf

Same as before is focus, tracking with distance must change to keep loss from being to great to transfer the energy.

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#7 2018-01-22 11:53:53

Terraformer
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From: Logres
Registered: 2007-08-27
Posts: 3,353
Website

Re: ION Drive a fast transit to Mars

elderflower,

My point is that doubling the velocity allows you to halve the mass flow rate for the same thrust. So you're only doubling the power requirement, rather than quadrupling it.

SpaceNut,

Fortunately, we don't have to worry much about wet conditions in space. Or atmospheric interference. Or being restricted to small areas for the receiver - we could conceivably have rectenna sizes measured in hectares. Like solar electric, only with far more power available due to the higher conversion efficiency and possibility of higher intensity beams.


"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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#8 2018-01-22 12:20:14

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 6,453
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Re: ION Drive a fast transit to Mars

Exhaust velocity is directly proportionate to specific impulse (Isp). So doubling exhaust velocity will double change in spacecraft velocity. That's for the same mass propellant. If you double exhaust velocity but halve total propellant mass, you end up slightly better than you started, about 10% higher velocity, but no mare. That's because you reduce the mass fraction that is propellant. To halve transit time to Mars you must double velocity, and if all you change is exhaust velocity, that means you have to double that too. That's without taking into account increase in mass of power supply.

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#9 2018-01-22 13:44:20

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 21,706

Re: ION Drive a fast transit to Mars

The waves are spreading after transmission in space just the same as solar does and the power levels drop as a function of distance from the source and you can not lug the generator with you......Same a nuclear for the size of the antenna growing in size to gather more energy as that cuts into payload.....

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#10 2018-01-22 17:04:03

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,335
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Re: ION Drive a fast transit to Mars

My thought was to take what we already have (electric thrusters with solar or potentially nuclear power),  scale it up to higher power and thrust,  and use it to send-ahead unmanned stuff to Mars orbit.  The manned mission meets up with it there,  later.  The thrown mass savings makes direct landing concepts far,  far less important. 

Very simple spiral-out / spiral-in orbital mechanics,  nothing new,  nothing we haven't got at least some experience with.  Just a high-Isp slowboat trip at 0.0001 to 0.001 vehicle gee with the unmanned stuff that doesn't care and needs no life support.  The robot tug that does this can use propellant residuals to come home for reuse. 

The fundamental idea is to go fly with stuff already in-hand,  because if you don't,  the experience base says you'll never fly at all.  Scaling something up is a lot less of a technological development than coming up with a truly new way to thrust.  If something new becomes "in-hand" later,  then switch to it,  by all means.  But it is very unwise to bet the mission on new stuff.

We need the scale-up so that what pushed 10's-100-kgs of satellite or probe around can push tons and tons of propellant and supplies,  at about the same low gee level we have been using. 

There is chemical rocketry.  There is assembly-by-docking.  There is storable propellant transfer.  There are electric thrusters on satellites and some probes.  There are capsule shapes and heat shields.  Very recently,  supersonic retropropulsion and landing has become quite real.  We know enough to do rigid-body spin gravity pretty easily and reliably,  cable-connected spin gravity is not ready yet.  We know what-all might be a good solar flare shield,  and that GCR is not a mission-killing threat.  You really can do a mission with that and no more,  and absolutely not break the bank.

If we can get water recycling and life support running better than it works on ISS,  well,  then,  we get to go with less thrown weight.  Otherwise,  bite the damned bullet,  throw the larger supplies weight,  and just go.  Life support "efficiency",  however that is defined,  is not the mission killer some talk it up to be.

GW

Last edited by GW Johnson (2018-01-22 17:07:59)


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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#11 2018-01-23 08:31:18

elderflower
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Registered: 2016-06-19
Posts: 1,262

Re: ION Drive a fast transit to Mars

It seems clear to me that we either have or have already under development, the means to put a small pioneering expedition on the Martian surface- except for the gravity thing, no effort seems to be put into that. Falcon heavy could deliver a manned module to Mars and other launches could deliver fuel and hardware. Rotating a Falcon heavy upper stage, with its payload, about a transverse axis would probably help with the gravity issue, but this needs study.
I don't understand why a pioneering mission isn't happening- perhaps it is and Musk isn't saying so.

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#12 2018-01-23 09:12:20

Oldfart1939
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Registered: 2016-11-26
Posts: 2,030

Re: ION Drive a fast transit to Mars

I fully align myself with GW's position as stated in his post #10 of this thread. Go now with what we've got, and the improvements can come later!

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