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#126 2022-06-22 14:05:06

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 1,895

Re: Physics Topics

I was thinking more along the lines that free atomic oxygen would attack metallic components.  Then again I don't have a clear idea of how this propulsion system will be arranged.  It might turn out not to be an issue.  Ammonia would have better ISP because of the lower average molecular weight of the dissociation products.  But other propellants are possible.  We could use aluminium from the moon or even pure O2 that is bled through a porous aluminium oxide target.  Magnesium vapour has a slightly lower atomic weight than aluminium and is abundant on the moon.

Last edited by Calliban (2022-06-22 14:11:58)


"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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#127 2022-06-22 14:30:52

tahanson43206
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Registered: 2018-04-27
Posts: 10,397

Re: Physics Topics

For Calliban re #126

Thank you for picking up the thread here!  Void often tosses out ideas that are inspired, and leaves it to others to try to develop them.

He makes an agreeable argument, that transporting water in a space vessel is a LOT less challenging than transporting separated chemicals.

However, the energy to provide propulsion has to come from somewhere, and the best candidates I know of right now are solar flux (photons primarily) and nuclear fission.  Fusion will change the nature of the game, of course, but we don't have it.

What I'm hoping you might consider is a nuclear powered propulsion that uses water as the mass to throw, but (here I'm picking up on your objection) separates the molecules of water before throwing the mass overboard.

And! I'm wondering if the dissassociated plasma might be accelerated by electric means (I'm assuming magnetic?) to achieve high ISP ** and ** high thrust levels.

The direction I'm trying to head with this is to avoid using elements for propulsion that might be a problem downwind ...

Aluminum would make a coating on any space craft unlucky enough to fly through the plume, for example.

Plain hydrogen and oxygen ** should ** be less concerning, although I recognize your point that oxygen would do a job on materials it encounters.

(th)

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#128 2022-06-22 19:16:49

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 25,674

Re: Physics Topics

Kbd512 is using a modified solar sail approach by using lasers and a pusher plate for the target of the beams.

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#129 2022-06-23 07:59:00

tahanson43206
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Registered: 2018-04-27
Posts: 10,397

Re: Physics Topics

For SpaceNut re #128

Thanks for adding the novel propulsion ideas of kdb512 to the Physics topic!

While absolutely nothing like what kbd512 proposed has been tried (with one exception I will add) it certainly ** has ** been a focus of science fiction writers for many years.

It would be terrific if the Physics topic of the NewMars forum were to receive a contribution by a ** real ** scientist or ** experienced ** engineer on the subject you have raised in Post #128.

The exception is the pioneering research with photon pulse propulsion by a physicist at a University with a name like:
? Rennseler ?

I'll look up the reference and post it here.

Google came up with some encouraging snippets:

Dedicated Laboratory Setup for CO{sub 2} TEA Laser Propulsion ...https://www.osti.gov › biblio › 21439583-dedicated-lab...
In this paper we introduce a cutting-edge Laser Propulsion Laboratory created at Rensselaer Polytechnic Institute, one of the very few in the world to be ...

Rensselaer Scientists Unlock Some Key Secrets of ...https://science.rpi.edu › chemistry › news › rensselaer-s...
New research led by chemists in the Baruch '60 Center for Biochemical Solar Energy Research at Rensselaer Polytechnic Institute is seeking to detail the ...

Aerospace Science and Engineeringhttps://mane.rpi.edu › research › aerospace-science-and...
Combustion/Propulsion. Research Areas: Fuel chemistry; ... School of Engineering, Rensselaer Polytechnic Institute Jonsson Engineering Center, Troy, ...

Dedicated Laboratory Setup for TEA Laser Propulsion Experiments ...https://aip.scitation.org › doi › pdf
Rensselaer Polytechnic Institute, Troy, NY, 12180. Abstract. Laser propulsion research progress has traditionally been hindered by the scarcity of photon ...

Gallery #3 (RPI - Laser Propulsion Laboratory) - iisalvadorhttps://sites.google.com › site › israelsalvador › home › ga...
This Gallery section illustrates some of my previous work, which included setting up the laboratories required to do the research and the research itself.

Leik N. Myrabo's research works | Rensselaer Polytechnic ...https://www.researchgate.net › Leik-N-Myrabo-5890769
Dedicated Laboratory Setup for CO2 TEA Laser Propulsion Experiments at Rensselaer Polytechnic Institute. Article. Oct 2010.

I. I. Salvador's research works | Rensselaer Polytechnic Institute, NY ...https://www.researchgate.net › 2005422665_I_I_Salvador
Laser propulsion is an innovative concept of accessing the space easier and cheaper where the propulsive energy is beamed to the aerospace vehicle in flight ...

Laser_propulsion - chemeurope.comhttps://www.chemeurope.com › encyclopedia › Laser_p...
Laser propulsion systems may transfer momentum to a spacecraft in two ... developed by Leik Myrabo of RPI (Rensselaer Polytechnic Institute) and Frank Mead, ...

How Light Propulsion Will Work - Science | HowStuffWorkshttps://science.howstuffworks.com › ... › Future Space
Photo courtesy Rensselaer Polytechnic Institute. More than 20 years ago, the United States began to develop a missile defense system that was given the ...

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Leik N. Myrabo's <<== this is the gent whose research I am remembering

(th)

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#130 2022-06-23 08:04:34

tahanson43206
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Registered: 2018-04-27
Posts: 10,397

Re: Physics Topics

This topic is available for anyone who would care to make a contribution of actual research on the subject of laser propulsion.

Wild science fiction about laser propulsion belongs in the Chat topics of the NewMars forum.

For SpaceNut:

Salvador, Israel I, Kenoyer, David, Myrabo, Leik N, and Notaro, Samuel. Dedicated Laboratory Setup for CO{sub 2} TEA Laser Propulsion Experiments at Rensselaer Polytechnic Institute. United States: N. p., 2010. Web. doi:10.1063/1.3507165.

You could invite these gents to participate in the forum.  Without authoritative voices in the forum, we can only collect reports of work by others.

(th)

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#131 2022-06-29 09:23:09

tahanson43206
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Registered: 2018-04-27
Posts: 10,397

Re: Physics Topics

This article (with YouTube video) shows a design for a space craft with two counter rotating passenger habitat rings.

What is novel (to me for sure) is the arrangement of the counter rotating rings.  I have been visualizing the rings of recently proposed spacecraft as like two doughuts on a stick.  This article shows a completely different arrangement, which seems to me to have very attractive features.

https://physics.stackexchange.com/quest … properties

Would a double gyroscope still have gyroscopic properties?
Asked 6 years, 8 months ago
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Imagine you have a gyroscope that has two spinning parts, one on top of the other. When you pull the string, the two halves spin in opposite directions. Would this cancel out the gyroscopic properties, or double them?

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asked Oct 14, 2015 at 1:58
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Jason Chen
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Which properties are you talking about exactly? –
anon01
Oct 14, 2015 at 2:19
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Short answer: it cancels the gyroscopic effect (with caveats).

As long as the system holds together (see below), if the two halves spin with exactly the same magnitude but opposite sign angular momentum, from the point of view of an outside observer, the system behaves like one of zero angular momentum. In particular, it takes negligible torque on the part of an outside observer to rotate the system, and there is no phenomenon of precession or nutation. Indeed this kind of principle is sometimes used in robotics and mechanical engineering to allow high speed rotating components to be manipulated easily.

However: from the standpoint of each rotating component, each requires a torque to change its own angular momentum. Indeed, if you spin the system quickly, you're forcing the angular momentum of the two separate components to change extremely fast. The two spinning components must therefore exert huge torques on one another to achieve this. Rotation of the whole system, although easy for the outside observer, begets huge stresses on the shaft joining the two components. If you set a system like this up and rotate it, you can see the shaft between the components bending slightly at right angles to the plane of rotation, as the massive torque between the components sets up high bending moments in the shaft. This kind of experiment needs to be done with great care, with very lightweight components and with safety glasses on. Systems like this can explode if the joining shaft fails, and whenever the principle is exploited in robotics, the control system imposes very strict limits on the maximum rate of rotation of the system as a whole, if the rotation is in a different plane from that of the two components' angular momentums.

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answered Oct 14, 2015 at 2:18
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Selene Routley
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Can you give a concrete example of usage of this phenomenon in robotics? –
Ruslan
Oct 14, 2015 at 12:08
@Ruslan I've seen it used in CNC cutting and grinding machines. Optical element making robots are a big user of this kind of idea (such as those built by makers such as Statisloh) –
Selene Routley
Oct 14, 2015 at 12:17
There was a propellor-driven VTOL called Pogo -- en.wikipedia.org/wiki/Convair_XFY_Pogo with counter-rotating props. This both eliminates gyro and eliminates the tendancy for the body to counter-rotate. –
Carl Witthoft
Oct 14, 2015 at 15:56
It took me about this long before I could actually understand the specifics of what you were talking about. tongue
Jason Chen
Dec 12, 2016 at 3:49
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This would cancel out the gyroscopic properties. Here is a youtube video that demonstrates this effect: https://www.youtube.com/watch?v=bzbVwiIeM0M

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#132 2022-06-29 09:34:29

kbd512
Administrator
Registered: 2015-01-02
Posts: 5,693

Re: Physics Topics

tahanson43206,

I see you've discovered why I'm using counter-rotation in my ship design.  Otherwise we would need a very large, very heavy, and very energy-intensive moment control gyro to counteract gyroscopic precession- an effect very well known to those of us who fly or have flown aircraft with propellers.  We're operating at very low speeds, but the masses involved are quite large, and so are the forces acting on that center barrel section and slewing ring bearings, which is why it's made here on Earth where inspection is much easier.

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#133 2022-06-30 08:46:20

tahanson43206
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Registered: 2018-04-27
Posts: 10,397

Re: Physics Topics

For kbd512 re #132


Thanks for your contribution to the Physics topic.

Let's look at the video during next Sunday's Zoom.  The difference is "real Universe" actual working hardware vs theoretical hand waving.


SearchTerm:gyroscope Test Package for Spacecraft Habitat Configuration

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