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#51 2019-02-20 10:22:52

tahanson43206
Member
Registered: 2018-04-27
Posts: 3,082

Re: Space Towers and Skyhooks

For SpaceNut ...

Perhaps this paper will be of interest to someone on the forum?
https://elib.dlr.de/112822/1/QSOs_aroun … ePhine.pdf

This paper was developed in support of a proposal to send a probe to study Deimos and Phobos.  The possible time frame is 2030 or so.

The element of the presentation I found most interesting is that the mass of both moons is too small (in the presence of Mars) to permit a "normal" satellite orbit, as we humans are able to do around our Moon.  The focus of the paper appears to be finding plausible orbits of Mars which are influenced by either moon so as to keep the sensor package near the moon of interest for a period of time.  This type of orbit is (apparently) called a quasi-satellite orbit.

Regarding the concern you raised about what would happen to the hardware at the end of the tether after release of the payload.  My impression is that the behavior of the delivery system would be similar to that of a bomber releasing a particularly heavy bomb.  While I can only judge by movie footage of planes dropping bombs, I get the impression the pilot is able to compensate quickly for changes in loading, so there is not appreciable change in flight posture that I can see.

In the case of the Phobos Tether Transport system, I am expecting the bulk of the lift in support of the payload at release point to be borne by the wings, and NOT by the tether.  The role of the tether (as I am thinking of it now) is to overcome drag on the delivery vehicle, drag of the payload attached to the delivery vehicle, and drag of the tether itself.  In other words, there should be NO snapback at all, if the pilot (human or AI) compensates correctly for the change in force caused by release of the payload.

Thanks too, for your observation that the wings of the payload delivery vehicle must be four times larger in area than the corresponding wings on Earth.

I'm intrigued by your idea that there would be a motor of some kind on the payload delivery vehicle.  That would seem to be a sensible precaution in case of failure of the cable, although I would also think that the payload delivery vehicle pilot could simply release the broken tow cable just as a glider pilot does on Earth, release the payload as a loss if it is still attached, and simply glide to the ground.

(th)

SpaceNut wrote:

The elevator topics have tons of calculations with in them...

I looked a bit with regards to helicopters and it does not seem to be feasible due to how it must be connected to the end of the tether where the blades are.

A glider like unit requires wings that are about 4 times the earth area of surface but it seems possible as all we are doing is making a boom  with the struture to support the cable to phobos and the down connection for grappling the returning ship. The wings are motorized for lift and for turning just like a normal plane with a tail rudder that does breaking by spliting just the same as the shuttle.

We can also do a heated balloon between the cabling with it wrapping around the balloon only using it for lift. Provide heat you get extra lift, cool it down and it sags.

One concern is once the payload is released is the cable snap back which will happen from any of the devices that we would place at its end to negate the drag mass products...

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#52 2019-02-20 18:05:37

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 19,222

Re: Space Towers and Skyhooks

Equal and opposite reaction....with planes both split the momentom change when the depart. The tether is fixed and does not move at the moons end of which the disconnecting end will move plus oscillate up to the moon along its length. That is one of the reason for putting the plane at the end of the cables release point so as to change the momentom point. With the plane activing as a means to dampen at the end with the underside of the plane having the drop cable length for releasal for the payload.

I see only the time limits for a pilot for the plane portion for the tether as the only issue which is supplies of air, water, power & food with the pilot returning back to Phobos one the payload is delivered to the surface.

So what speed is the plane flying at is the period of orbital time versus the distance at altitude, where we are at the releasal point. One might use prop generation power (think windmill) rather than running all the time on batteries or from a cable connection back to the moon. To supply the motors for moving the winglets surfaces of the plane.

The payload would have fuel for retropropulsion for being able to land.

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#53 2019-02-20 19:00:53

tahanson43206
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Registered: 2018-04-27
Posts: 3,082

Re: Space Towers and Skyhooks

SpaceNut .... thanks for continuing to think about, and to provide interesting feedback on the tether payload delivery concept!

Regarding bounce upon payload release .... The pilot (whether human or AI) should be able to insure that at the moment of payload release, the pull on the tether is held constant.  I am making this prediction because the airfoils will be carrying the bulk of the gravitational pull of Mars on both the vehicle and the payload.

Just as with a bomber releasing a heavy bomb, the payload delivery vehicle should be able to adjust the airfoils rapidly enough to insure that the drag experienced by the tether does not change.  In an earlier post, you had mentioned air foils that would deploy similarly to the Space Shuttle, and at the time, I did not recognize the value of that suggestion.  Now, I can see that deployment of spoilers at the moment of payload release would allow the pilot to deliver a constant (or nearly constant) load to the tether. 

Once the payload is on its way, the pilot should be able to gradually remove drag caused by the spoilers, and transition to a rapid acceleration of the vehicle to return to orbit.  The energy needed to return to orbit is going to be stolen (as Void might put it) from the momentum of the moon.  The acceleration needed to return to orbit would (presumably) come from the interaction of the airfoils with the atmosphere, while the vehicle is still inside the atmosphere.  Once the vehicle has risen above the atmosphere, it must have enough momentum to be able to make the long climb back to the orbit of Phobos.

Your observations about the need for provision for the needs of the pilot, both during descent and later during ascent, are helpful.  I would add another concern to those.  The pilot (and passengers if any) will start at a base on Phobos, and make a long slow slide out to the end of the tether, along the tether.  They will need provisions for that phase of the journey.  On the return, the pilot, and incoming passengers (if any) will need provisions for the slide along the tether to the base on Phobos.

Regarding speed at payload deployment ... Given the approximate speed of the Moon with respect to the surface of Mars as 4,000 miles per hour, I had originally imagined that the pilot would guide the vehicle is such a way as to accelerate ahead of the track of the Moon on the surface, in order to be able to slow dramatically as the payload drop off point approaches.  This is a variation of the well-explored concept of a looping tether, which is designed to place the tip of the tether near the destination at a speed of approximately zero relative velocity, for a brief moment during which a payload can be dropped off or a new one retrieved.

I agree with your prediction that the payload would be equipped with retropropulsion capability.  Even if this capability is not needed in a perfectly executed dropoff, it seems to me vital to include this capability for emergency landing, especially if people are in the pod.

(th)

SpaceNut wrote:

Equal and opposite reaction....with planes both split the momentom change when the depart. The tether is fixed and does not move at the moons end of which the disconnecting end will move plus oscillate up to the moon along its length. That is one of the reason for putting the plane at the end of the cables release point so as to change the momentom point. With the plane activing as a means to dampen at the end with the underside of the plane having the drop cable length for releasal for the payload.

I see only the time limits for a pilot for the plane portion for the tether as the only issue which is supplies of air, water, power & food with the pilot returning back to Phobos one the payload is delivered to the surface.

So what speed is the plane flying at is the period of orbital time versus the distance at altitude, where we are at the releasal point. One might use prop generation power (think windmill) rather than running all the time on batteries or from a cable connection back to the moon. To supply the motors for moving the winglets surfaces of the plane.

The payload would have fuel for retropropulsion for being able to land.

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#54 2019-02-20 20:19:12

SpaceNut
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Registered: 2004-07-22
Posts: 19,222

Re: Space Towers and Skyhooks

I have located this one spoiler to think about and its Phobos rotate ever so slowly....
Equatorial rotation velocity    11.0 km/h (6.8 mph) (at longest axis)

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#55 2019-02-20 21:52:37

tahanson43206
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Registered: 2018-04-27
Posts: 3,082

Re: Space Towers and Skyhooks

For SpaceNut ....

Great find! Thanks!

Can you provide a link?  I'm assuming this is different from the rotation due to tidal lock .... The body must rotate once per revolution, in order to remain tidally locked.   This rotation sounds like something different.

The orbital period of Phobos is given as 7 hours and 39 minutes, so it would complete a 360 degree rotation in that time.

https://en.wikipedia.org/wiki/Phobos_(moon)

The equatorial circumference of Phobos is 69.7 kilometers, according to this site:

https://www.universeguide.com/planetmoon/phobos

The orbital period is 7.65 hours, so I'll try dividing that into 69.7 ... The answer the online calculator provides is 9.11.

So (using these figures) Phobos rotates about it's center of gravity at a rate of 9.11 kilometers at the equator.

That result differs from the rotation you found, so I'll be interested to learn more about it.

At this site:
https://nssdc.gsfc.nasa.gov/planetary/f … sfact.html

I found three rows of axis data:

Subplanetary axis radius (km)    13.0   
Along-orbit axis radius (km)    11.4   
Polar axis radius (km)            9.1

I had been assuming ( I know, I know << sigh >> ) that a tidally locked body would be stable the way our Moon is stable.

However, Phobos is so much smaller, as reported in an earlier post, it cannot support a local satellite, so it may have other behaviors that differ from our Moon.

(th)

Edit 2019/02/21 … After poking around a bit, I think I may have found where those different numbers come from.

The moon is NOT spherical … in the long axis (the one that points through Mars) the radius is 13 kilometers.

When that radius is used to approximate the circumference of the moon, the result is greater than 67, which appears to be the radius if the "along orbit" figure is used.

I'm going to tentatively conclude that the moon is rotating about only one axis, which is the one at right angles to both the Along-orbit axis, and the one that runs through the center of Mars.  I've been unable to find a clarification of the term "subplanet axis", but I think that might be the one that runs through Mars. 

For the purpose of designing a Tether Payload Delivery system, it would be helpful to know for CERTAIN that the moon is stable in its rotation about Mars, and specifically, that it is NOT rotating on more than one axis.  It is not uncommon (I gather) for free flying objects in Saturn's rings, or in the asteroid belt, to be rotating around multiple axes.

(th)

SpaceNut wrote:

I have located this one spoiler to think about and its Phobos rotate ever so slowly....
Equatorial rotation velocity    11.0 km/h (6.8 mph) (at longest axis)

Last edited by tahanson43206 (2019-02-20 23:45:24)

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#56 2019-02-21 11:06:48

tahanson43206
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Registered: 2018-04-27
Posts: 3,082

Re: Space Towers and Skyhooks

For SpaceNut, and anyone else who may contribute to this topic:

I was curious to know what the orbital track of Phobos on the surface of Mars might look like, as it would determine where payloads could be delivered or retrieved using the Photos Tether Transport System under consideration in recent days.

It turns out (according to this article in Space.Com), that Phobos follows a track which is close to the equator of Mars.

https://www.space.com/28403-astronauts- … eimos.html

Phobos could never been seen from any location beyond 70 degrees north or south of the Martian equator.

Because both Phobos and Deimos move almost exactly parallel to the Martian equator, the best views of both moons would come at the planet's equatorial region.

That is a situation that limits the option of reaching points on Mars away from the equator (with an exception to be offered below).

On the other hand, it would seem to help to simplify mission planning, both for the customer and for the transport staff.   Pick up and drop off sites could be located along the equator, and local transport systems could handle movement of goods or people North or South of the equator.

The exception is that if it is cost effective to do so, the air foil equipped payload delivery package could simply release from the tow cable and glide to a destination.  Since the air foil equipped vehicle would be valuable in its own right, the vehicle could be returned to the equator using surface transportation, for pickup at a convenient time.  This delivery option might be particularly attractive for human passengers, who might appreciate (and be willing to pay for) direct delivery to a destination away from the equator.

As a nod to SpaceNut's observation about the undesirability of an uncontrolled tether tip, I would expect the tether tip flight vehicle would remain attached to the tether tip after release of the airfoil equipped payload package, to insure a smooth return to orbit.

(th)

Last edited by tahanson43206 (2019-02-21 11:30:56)

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#57 2019-02-21 12:29:19

Void
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Posts: 3,475

Re: Space Towers and Skyhooks

I guess I might be considered "Anybody".  I will try to play.  Hopefully my post will be useful more than an interference.

I would like to mention Skyhooks for both Earth and Mars, as I feel more confident of what I think is most plausible for Earth, but would like to try to bridge it to Mars.

Carl Edward Sagan in his book umm.... Contact, if I recall correctly mentioned baby steps.  I guess I would say lets reduce our ambitions down to something more plausible for us to handle.  It might be worth the bother, if we can achieve an output which suits our desires/needs.

I have previously been interested in associating the "New Shepard" capsule with a rotating skyhook.  I guess the hope is to avoid the use of a strong type of heat shield.

But now that I understand that Starship will use stainless steel with and without active cooling, I think I would like a weak heat shield.  This would allow a sub-orbital altitude of a higher height.  I do not want to include active cooling however.  As for the New Shepard 1st stage, I propose that it be a stronger booster, and I don't know if it is possible, as the stresses may be excessive, but I would like it to try to use a spinning re-entry.  As it would be re-entering sub-orbital, I expect the heat load to be reduced.  I would hope to use a combination of propulsive re-entry for it along with spinning the booster to distribute heat across the cylinder surface.  Stainless Steel again I suppose.

I am guessing that with a higher ballistic apex, the stresses imposed on the skyhook can be reduced.  As I have said, I think we would want to start small, baby steps towards adulthood.

However unlike the existing purpose of the New Shepard, I would be extremely shy about exposing crew to this system, until it were absolutely proven as worthy and of a very high probability of success.

So, then what might the purposed of the capsule be, if not for humans?  Well, I guess cargo going up from Earth is a thing to consider, and if possible cargo going down to Earth.  If you are going to use this system efficiently you probably want to load it's volume as maximally as you can afford to.  Constraints on that are system failure potential.

So then, if you can actually spinning method skyhook a capsule to orbit, what about dropping a load into the atmosphere.  Well the skyhooks purpose in this case since we would be doing baby steps, is to release the capsule at such a altitude and speed, that a simple stainless steel heat shield would do.  If the cable breaks then the capsule may very well suffer catastrophic failure due to re-entry failure.

What about the rest of the descent?

You have mentioned "airfoil equipped payload package".  Well with the capsule we do already have the payload, so lets add an airfoil/parachute.

But to be efficient we wanted to possibly load this capsule with lots of stuff.  Lets hope it is Rare Earths from Phobos, Demos, or and asteroid.  Maybe some platinum group metals / gold???

So, I am not sure that it will be proficient to do this and have a atmospheric deceleration device of that type, where the capsule will land with reasonably survivable speed.  So, I would like to add something more.

You have an airfoil, but its effectiveness is limited to the terminal velocity which is achievable with the Earth's atmosphere.  But we overloaded the capsule because we are greedy/have business sense.  Your airfoil should have ability to modify the navigation down so that the payload can hit a receiver station, which would assist in buffering the stresses of impact/landing.

And so I suggest "Ground Engines" and Elon Musks bouncy house, and also throw in a pond of water if you can or the equivalent (If Mars).

On Earth, "Ground Engines" would be powered by Natural Gas perhaps.  Maybe Jet engines that breath air.  Maybe rocket nozzles.  On Mars, I am thinking Carbon Monoxide + Oxygen or Methane + Oxygen.  Since it is likely to be near the equator, most likely Carbon Monoxide + Oxygen.  Rocket engines on Mars I would have to suppose.

The purpose of ground engines would be to help with the final landing, augmenting the capabilities of your airfoil.  They would be pointed upward, while being mounted on the ground, and so would provide a timed upwelling pressurized gas bubble for your load to fall into, and so brake terminal velocity more.

On Earth you may have a giant bouncy house on a pond of water to do the final deceleration, without including destructive disassembly we hope.  It would be a air cushion device on top of a pond.  That should help.  If need add whoopy cushion option where the air cushion emits air. smile

The pond dissipating remaining terminal velocity I hope, as water waves, as the cushion pushes into it.

On Mars a whoopy cushion may have to do the job without a pond.

So, what is achieved?  Well you don't have to push a load from the surface of a planet to orbit entirely with chemical burning.  And you don't have to use thrusters to get back into the atmosphere. And you don' have to use a full on heat shield.

Is that enough to justify the method?  Perhaps as a research process.  And then maybe you want to see if you can extend the capabilities of the skyhook to take more load off of the other sub-parts of the system.  Reducing heat shielding requirements, and perhaps reducing the altitude of the sub-orbital pseudo-New-Shepard.

Eventually if it makes economic and technological sense, you might be able to get to a skyhook that can reach the ground, or not.  Don't know.  Additional test information required to make a reasonably accurate estimate.  Can't get to that in a rational way without baby steps.

……

To Phobos/Mars next then.  See what might drift through the clouds in my/our head(s).

Done.

Last edited by Void (2019-02-21 13:17:03)


I like people who criticize angels dancing on a pinhead.  I also like it when angels dance on my pinhead.

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#58 2019-02-21 13:14:48

tahanson43206
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Registered: 2018-04-27
Posts: 3,082

Re: Space Towers and Skyhooks

For Void #57 above ...

I hope what I will offer here is new to you.  It is possible you know all this already.

https://space.nss.org/l5-news-the-rocke … mbination/

During the years when the L5 Society was a dynamic, growing concern, it published a newsletter/magazine called the L5 News.

In those pages appeared a number of (at the time) very advanced concepts, such as skyhooks.

If you have time to look at the link above, someone has preserved the article for your amusement.

In particular, I would like to point out the discussion of rotating skyhooks.

However, while you appear to be interested in applying this idea to Earth, I am focusing upon Mars and particularly Phobos, which offers a momentum platform that is not available to Earth beings.

Thus, there is room in the Solar Systems for both sets of ideas, yes?

(th)

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#59 2019-02-21 13:34:36

Void
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Registered: 2011-12-29
Posts: 3,475

Re: Space Towers and Skyhooks

Yes, of course plenty of room.  I enjoyed the materials you provided.

My processes, typically are a bit shy.  I would rather gravitate to things more established, and then try to reach for more.  So, one reason I start with the Earth.

The other reason, is actually while it might be useful down the line to lift up materials from Mars to Mars orbit, our earlier most important objective is to move useful stuff from Earth to space, and then from Earth/Moon to Mars/Phobos/Demos.

I worked in Metrology for part of my working life.  I have enjoyment of fantasy, but prefer Sci Fi, if I am trying to get from point A to point B, to try to accomplish something.  So, working with Earth first has at least two reasons for Mars, but then potentially gives example to translating that to Mars.  One foot anchored at least in some semblance of reality and then reach into chaos, try to pluck something useful from it.  Where chaos exists order will emerge.   Chaos is actually a higher order, or rather a type of order requiring a greater ability???  We prefer order which grants efficiency, but reduces possibility.  Got to have a balance there.  Got to be able to eat, and not be eaten. That's the law of the jungle.  A law we really can't escape in the long run.  We can run but not hide forever.

……

I fear the length of a tether to use the momentum of Phobos to do a skyhook to Mars.  The longer the tether, the more probability of failure from collision.  I do have some favorite tricks to try to do with Phobos.  Lets see if between participators we can hope to get close to pulling something useful out of chaos.

Per Phobos, I am interesting in inserting a habitat into it's interior.  But you need energy for a habitat.  Weird notions say lets capture the differential voltage produced by the solar wind.  But wanting to have at least a toe of one foot on the ground, lets instead suppose we will do a surround of Phobos with a shell of photo panels.  This can also prohibit Phobos from projectile vomiting it's substances into space if we disturb it by burrowing into it.  Should this shell be preferred to be a constant of size or will we alter it's size/shape?  Well lets opt for constant.  Phobos apparently is porous.  If we burrow into it, then there is some room.  But if we burrow out materials and construct space machines from it's materials, then we can make room for a colony (I hate that word, because it allows nasty's to exploit us (Amused??(We are gonna get um. (Bastards!))) SETTLEMENT of the interior of that moon. 

I don't like the length of a cable to extend from Phobos to some useful contact with Mars.  Too long.  Rolling the dice, gonna get sliced by something, I fear.

But what about the space machines we extruded from Phobos?  Well with tethers, we might hope to harness energy from tethers.  Lowering the orbit of the machine to optimal.  Then perhaps a spinning tether method, but before that perhaps during the lowering using a non-spinning method to harvest Martian atmosphere up into the machine.

So, in the end you get a settlement of people in the interior of Phobos, and ultimately some machines of inertia associated with spinning skyhook methods, habitats also suitable to humans say 50-100 or more above the terminal orbit of Martian atmosphere.

Tired now, later OK?

Done.

Last edited by Void (2019-02-21 13:55:27)


I like people who criticize angels dancing on a pinhead.  I also like it when angels dance on my pinhead.

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#60 2019-02-21 17:31:11

SpaceNut
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Registered: 2004-07-22
Posts: 19,222

Re: Space Towers and Skyhooks

I think I have a way to correct for the moons wobble and rotation if we rebalance the moons axis to allow for mass to reshape it. Then I would put what amounts to roller coaster tracks afix all the way around to center of the moons spin axis. With a trolley assembly for the crane drum to roll out the cable from. You could power the trolley from the rails. The payload would be attached to the plane link with a short section of cable with the center point opposite having the cable connecting back to the drum length. Fire thrusters to lift the payload and plane to roll ou the cable as it fires until gravity of mars catches it and starts to draw it towrds the planet.

The concept is to reduce fuel use to mars, heatshield mass to allow for a greater payload mass to the surface.

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#61 2019-02-21 19:05:36

tahanson43206
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Registered: 2018-04-27
Posts: 3,082

Re: Space Towers and Skyhooks

For Void #59 ...

Your concern about the cable caught my attention.

I'll put that on the back burner to try to find a strategy to ease the worry you might feel if you were the pilot, or a passenger.

Please note that in the case of an elevator in a tall building in a city, you and your fellow elevator passengers are depending upon reliable operation of VERY long cables, which have to work flawlessly for years.  You are enjoying the reliability and smoothness of operation of cable travel, as compared to riding a hot rocket exhaust up the side of the building, or down to the ground.  While I can only speak for myself at this point, I would MUCH prefer to ride a glider pulled by a cable from a moon, than ride a hot rocket vehicle behind an ablative shield or a weeping stainless steel vehicle wall.  From a business investment standpoint, I expect that the vast majority of human passengers are going to prefer the reliability of a cable pulled glider over any other option that current physics allows.

For SpaceNut ... thank you for your additions to the concept to compensate for any wobble that may exist.  At this point, I'd like to point out that (to my knowledge) we humans have NO data on any wobble that might exist.  Phobos may be as stable as an aircraft carrier on a glassy ocean steaming at four knots, for all I know.  However, you have provided for the possibility that some wobble may exist.

One adjustment to your concept I would like to make is the idea of a reel to pull the tether in between uses.  I think it would make sense to trail the tether permanently behind Phobos, and use small station keeping rockets to move the payload package in or out along the cable. 

If the cable is 6000 kilometers long (as I have imagined earlier) the size of the reel would be large (if not huge) and I see no need for moving the cable once it is deployed.

Your summation of the value of the concept really catches the spirit of the idea, and adds benefits I had not thought of.   

Void has expressed concern about risks to the cable at Mars, but I think they are much less than would be true at Earth, because only a few satellites orbit Mars at this point.  If the cable is planned for as Mars is developed, it might be possible to reduce risk to the cable, by (for example) keeping new permanent satellites at elevations greater than 6,000 kilometers.  I recognize that existing satellites (such as MRO) are operating well inside the orbit of Phobos.

In addition, since we are planning for the airfoils on the tether vehicle to allow for maneuvering with respect to the flight path and Phobos, it should be possible to plan for any orbiting equipment and time deployment to avoid the problem, or maneuver to avoid it.

Void has spoken (several times) about accommodations built into the body of Phobos, and I think such accommodations would be perfect for guests arriving after long voyages from Earth (or elsewhere in the Solar system), and Phobos would become a major intersection point, with attractions of its own.

In addition, Void has spoken of building "artificial gravity" facilities, and I think those would be much appreciated by travelers needing to acquire land legs after months of very low gravity.

Finally, much to the distress (I'm sure) of Louis, I recommend that the investors who will be building on Phobos should secure recognition of the moon as an International Waypoint.  Since existing treaties insure that the United States will be responsible for vehicles which lift off from the United States, it should be possible to establish the United States as the government responsible for US sourced facilities on the moon, and finally, if a non-profit entity is responsible for day-to-day operations, it would follow a well-established pattern in the United States.  Non-profit entities are responsible for some (if not all) United States government laboratories, so it seems (to me at least) perfectly feasible for the Mars Society (were it to so choose) to bid for a contract to operate facilities on Phobos. 

(th)

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#62 2019-02-21 19:45:08

SpaceNut
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Posts: 19,222

Re: Space Towers and Skyhooks

So connecting the payload would be much more difficult due to mars orbital entry speeds to sychronize with phobos place in speed and orbital time. As you would be trying to catch it to be able to hook up to the end. Manning the plane would be out due to steady state of being unfurled. To climb back out to orbit might be possible using just the plane and a small rocket engine but it would decay over time. Then there is the issue of refueling the plane combo to make it work. Will look at AG facility creation for those on Phobos.

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#63 2019-02-22 06:37:23

tahanson43206
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Registered: 2018-04-27
Posts: 3,082

Re: Space Towers and Skyhooks

SpaceNut ...

As the vision for what is possible develops over time, we may discover differences in individual views.

SpaceNut wrote:

So connecting the payload would be much more difficult due to mars orbital entry speeds to sychronize with phobos place in speed and orbital time. As you would be trying to catch it to be able to hook up to the end. Manning the plane would be out due to steady state of being unfurled. To climb back out to orbit might be possible using just the plane and a small rocket engine but it would decay over time. Then there is the issue of refueling the plane combo to make it work. Will look at AG facility creation for those on Phobos.

Today I'd like to offer the example of the Panama Canal.  I have been studying the operations of the Panama Canal in detail for several months, after discovering they provide a nice webcam view of their two major lock locations.  I supplement those views with the Marine Traffic service, which responds with ship location and characteristics when given "find vessel name-of-vessel".

From these observations, I've gained a sense of the ebb and flow of traffic through the canal.

Please note that prices for passage range from $500 for a private sailing vessel, to $1,000,000 (or more) for an LPG tanker passing through the new Big Max locks.

In particular, I note that there are queues of ships above the Atlantic locks, below the Pacific locks, and distributed throughout the canal as the canal managers move ships as efficiently as possible.  I gather that one of the constraints upon transit activity is the availability of crew members to perform the multiple functions needed to perform a transit.

I foresee a close parallel in the Phobos Transit Station.  I am not persuaded that pilots cannot safely operate the tether guide vehicles, because AI can provide supplement as needed, but the job would be quite attractive to many folks, and (I expect) it would pay well.

However, pilots aside, there will be need for crew members to inspect incoming vessels, to collect fees for transit, and to attend to the myriad details of maintaining and supporting a full scale transit operation.

I see no reason (no physics reason, to clarify) why there cannot be more than one tether connected to Phobos, but I admit that management of multiple tethers would compound the challenge of maintaining safe operation.  My expectation is that only one tether would be in use at a time, while others are loading or unloading, refueling the tether vehicle, or otherwise keeping busy.

At the Panama Canal, there are (by now) large port cities on both the Atlantic and Pacific side, and I expect that over time the Phobos Station will grow to comparable size.  In addition, there are multiple smaller commercial activities scattered along the canal, where (I observe) private vessels often anchor to watch canal traffic.  The fully operational Phobos Transfer Station would (presumably) be supported by a sizable ground operation.

In your note above, regarding docking with Phobos vs trying to aerobrake in the atmosphere of Mars.  I get the impression that docking with Phobos is a MUCH easier navigation problem, and that fuel expenditure is significantly less than is required for a retrorocket landing on Mars itself.  The cost of fuel for docking with Phobos would be reduced by approaching the moon while it is receding from the vessel, in the moon's circuit of Mars.

In the case of the Panama Canal, I am under the impression that even the $1,000,000 fee paid by a Supermax tanker is a significant fraction of the cost of making the trip around South America, both in terms of fuel and salaries, but most importantly, in terms of travel time.  It is normal for ships to transit the canal in under 8 hours, and often the Supermax vessels are routed through in (about) four hours.  Those $1,000,000 appear to grease the wheels of commerce!

Likewise, the Phobos Transit Station should offer shippers significant savings of both time and money. 

However, there is another factor that may tip the balance in favor of the Transit Station on Phobos ... In the case of the Panama Canal, the passage offered is via secure inland water, protected from weather and other dangers of sea travel.  Transit around the southern tip of South America is not only time consuming, but it exposes the ship and crew to challenges of heavy weather and the need for accurate navigation.

In the case of the Phobos Transit Station, I am (admittedly optimistically) hoping that a well maintained tether system will prove safe and reliable, as well as efficient and accurate for shipment of both passengers and cargo.

(th)

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#64 2019-02-22 12:09:18

Void
Member
Registered: 2011-12-29
Posts: 3,475

Re: Space Towers and Skyhooks

tahanson43206,

I would like to start a new topic in the Terraform section, since it is the most permissive section.  But I have noticed that you operate in a polite manner (Up to now smile).

I will probably title it something like "Working with Rubble Pile Objects".  This then can include Phobos, and perhaps Demos, and quite a few small objects in the solar system, asteroids in orbit of the sun, moons in orbit of planets.  The terraform method is not able to improve the objects in such a way that they would have atmospheres of any significance, but it would potentially include:
-Tethers, various kinds.
-Synthetic shell habitats both inside the objects and perhaps on or near the objects.
-A possible shell around the objects of solar cells.

-In general I really want it to be an open architecture.  Sometimes it almost seems like this site wants to box creativity in with legalities.

I see your focus appears to be on a specific mega project.  I would start small and hope the project work its way up to more ambition, unless limited by real discovered bounds on the notions.

Is it OK for me to open such a topic.  You can weigh in also SpaceNut.

Perhaps I could commander "Antius's" topic: "Index
» Terraformation
» Asteroids & Shells".

I do not think we could get Antius back, but who knows.  If I did take over the thread, as I have indicated above I have the specific agenda of rubble pile worlds (Small), but an expandable agenda having to do with habitation of them and their use to assist human expansion in space, Mars included.


Thanks, Done.

Last edited by Void (2019-02-22 12:15:17)


I like people who criticize angels dancing on a pinhead.  I also like it when angels dance on my pinhead.

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#65 2019-02-22 13:09:22

tahanson43206
Member
Registered: 2018-04-27
Posts: 3,082

Re: Space Towers and Skyhooks

For Void ...

Thank you for proposing this interesting new direction for focus!

You are right that I am trying to bring the Phobos Tether Transport Service along as far as I can, and as the members of this forum will be inspired to carry it.

However, another objective always present in my thinking, is to try to inspire others to think in surprising new ways, and to develop their ideas as far as they can.

You have shown a noteworthy capability to think in surprising ways, so I look forward to watching as your new topic grows.

You are also right (if I interpret your post correctly) in thinking that study of burrowing into a rubble pile for fun and profit is potentially valuable to many constituents. 

(th)

Void wrote:

tahanson43206,

I would like to start a new topic in the Terraform section, since it is the most permissive section.  But I have noticed that you operate in a polite manner (Up to now smile).

I will probably title it something like "Working with Rubble Pile Objects".  This then can include Phobos, and perhaps Demos, and quite a few small objects in the solar system, asteroids in orbit of the sun, moons in orbit of planets.  The terraform method is not able to improve the objects in such a way that they would have atmospheres of any significance, but it would potentially include:
-Tethers, various kinds.
-Synthetic shell habitats both inside the objects and perhaps on or near the objects.
-A possible shell around the objects of solar cells.

-In general I really want it to be an open architecture.  Sometimes it almost seems like this site wants to box creativity in with legalities.

Thanks, Done.

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#66 2019-02-24 15:30:55

Void
Member
Registered: 2011-12-29
Posts: 3,475

Re: Space Towers and Skyhooks

I may be loosing it.  There already is a post from me about rubble piles, and it includes Phobos in materials.

http://newmars.com/forums/viewtopic.php?id=8924

Maybe I will be staying in a very special home in the south, if I am actually going South as it seems it may be.
I will use the existing topic, and may indeed include notions about tethers in it.

Done.


I like people who criticize angels dancing on a pinhead.  I also like it when angels dance on my pinhead.

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#67 2019-07-02 05:13:31

tahanson43206
Member
Registered: 2018-04-27
Posts: 3,082

Re: Space Towers and Skyhooks

Follow up to Post #30 in Space Towers and Skyhooks topic ...

While progress in design of a 3D printable Pneumatic Tower has been slow, some progress has occurred.

An experienced Blender programmer named (appropriately enough) Xen provided a model design, which is available for viewing on my Spaceways display.

If anyone is interested in seeing it I'll be happy to provide a URL.  Otherwise I will assume no interest and omit the URL from this or subsequent posts.

While I am unable to duplicate the sophisticated programming demonstrated by Xen, I am making progress in learning how to design a much simpler set of components to comprise a 3D printable Pneumatic Tower for deployment on Earth or anywhere else.

As a reminder, while JoshNH4H's vision was of a tower that would rise all the way to orbit, my more modest vision is of a pneumatic tower able to rise a distance of about 10 meters or so, suitable for loading and unloading a SpaceX ship which has landed in an unprepared location.

The components include:

1) Top segment with platform for carrying loads
2) Lift segments with flanges projecting inward at top and outward at bottom
3) Bottom segment with bottom platform to hold gas pressure
4) Adjustable feet to allow for setting the tower to vertical on uneven terrain
5) Gas pressure supply subsystem
6) Radio remote control for one person operation

An addition to the design concept is the use of O-Rings to assist with maintaining a gas tight seal.

O-Rings would also help to collect dust that can be expected to adhere to the walls of the lift segments.

A potential market for the Pneumatic Tower on Earth is lift situations where existing solutions include:

A) Construction of scaffolding to hold workers (eg, for installation of gutters, or replacement of light bulbs inside a building)
B) Use of ladders (very common solution)
C) Use of power lift equipment (eg, mobile crane)

A distinct advantage of the Pneumatic Tower for on-Earth lift situations is that the (proposed) system can be deployed while rotated to a wheel-like orientation, maneuvered through a narrow opening such as a doorway, and then rotated 90 degrees to deploy at the needed location.

(th)

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#68 2019-07-02 17:06:06

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 19,222

Re: Space Towers and Skyhooks

pnematic lifting tables are quite common in many industries and while they were not 3D printed for use the likely hood of use any where would be more than plausible. Having guide poles for ringlets to extend the height to greater than a few feet on a place that is a fixed location would mean we have transported a very light mass and doable product for early mars. Making the very high up on the body of a BFR more likely than a full crane device for lowering cargo to the ground.

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#69 2019-07-02 17:58:50

tahanson43206
Member
Registered: 2018-04-27
Posts: 3,082

Re: Space Towers and Skyhooks

For SpaceNut re #68 ... I'd be interested in links to the products you've described ... hydraulic lifters are in use widely, such as those for dump truck bodies.

Pneumatic pistons are much faster (I understand) and are likely to be found in robotic systems.

Thanks for noting my adaptation of JoshNH4H's vision ...

(th)

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#70 2019-07-02 20:12:44

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,222

Re: Space Towers and Skyhooks

There are many for of pnematic lift tables using pistons, scissor jack and bellow pillow forms.

Here is the pillow lift for bath
The-Mangar-Camel-inflatable-emergency-Lifting-Cushion-Chair-1.jpg

Using a variety of gasses in each of the chambers for lift and inflation would allow for the lift mass offset loading.

inflateable jack would be a more robust bag of lift distance of just 9 inches but capable of 22 Ton
Inflatable%20Jack%20-%2022%20tons.jpg

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#71 2019-07-02 23:10:50

tahanson43206
Member
Registered: 2018-04-27
Posts: 3,082

Re: Space Towers and Skyhooks

For SpaceNut #70 ...

Your powers of search continue to amaze me ... The industrial lift pad is particularly interesting to me, although the bath lift is interesting in its own right.

This text came from www.rigging.com ...

Item: Inflatable Jack - Individual - High Pressure - Industrial - Lift Height: 9.5 inches - Capacity: 22 tons

Application: Uses compressed air to inflate the bag, raising heavy loads sitting on top - For lifting of machines, cargo, heavy objects, rigging, lift truck service, relocating industrial machinery, and moving shipyard equipment

Description: Steel reinforced construction with higher strength and longer durability than Aramid only construction - Material will stand up to abrasion, puncture, tear and resist many gasses and chemicals, both petroleum and water based - Operating pressure 120 psi - Shop air operated - Large anti-slip surface - Use on hard or soft ground - For heavy duty / industrial applications

Industry Names: Also known as a 'mat jack', or 'lifting bag'

Includes: (1) one individual air bag jack and fittings (all components sold separately) - *NOTE: 'Regulator for Air Bottle' is sold separately as an optional accessory

WARNING: Never exceed rated capacity!

Optional Accessories:
Control Box: Controls the advance, hold, and retracting of the air bag - Controls are outfitted with pressure relief valves
Double Control Box: Allows for independent or simultaneous operation of one or more airbags
Air Supply Hose: Connects the control box to the air bag
Compressor Hose: Connects the compressor or air tank to the control box
Portable Air Tank or Air Bottle: May require a regulator at the tank to regulate the air coming out of the tank

What I appreciate about the product description above is the listing of related components required to use the lift pad.
All those items would be needed for the pneumatic tower.

I am not anticipating a lift capability greater than 150 Kg or so for a practical lift for Earth application, and am worried that the sliding sleeve nature of the design will be subject to gas escape at the seams.  In contrast, the lift pad is (apparently) a sealed unit which (I gather) assumes a spherical shape as gas is admitted to the interior of the pad.

(th)

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#72 2019-07-03 16:30:20

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 19,222

Re: Space Towers and Skyhooks

One could use a double stack system where the pressure put onto on that is connected to the next would with the help of a directional valve allow for even a partial inflation of the connected bag to cause lift to happen. The fluid in the bags can also be something other than air from mars as liquids would also work.

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#73 2019-07-18 09:16:00

tahanson43206
Member
Registered: 2018-04-27
Posts: 3,082

Re: Space Towers and Skyhooks

For JoshNH4H primarily, and for anyone else who might be interested

I quoted the post below because it includes a link to the sketch of the shape I had in mind for a Pneumatic Lift to offload SpaceX vertical landed ships.

tahanson43206 wrote:

For Josh: #1 ...
Your vision of an inflatable tower inspired me to look around a bit to see what might already exist.  I found a commercially available Ham Radio field antenna tower that inflates to a height of 30 feet.  It is held in place with a steady flow of air from a small gas engine powered air pump.
<snip>
https://www.dropbox.com/s/40ysvk22xr9tm … l.pdf?dl=0

As of last night I have updated my Shapeways shop with three objects related to this project:

www.shapeways.com/shops/tahanson43206

The purple model was created by a 20 veteran Blender designer named (really!) Xen.  He makes animation for display of commercial products for a living.
The purple model closely follows the vision of the original sketch, but it uses bevel which I have not yet mastered.

The black model is a crude (in comparison) but workable top for the tower.

The red model is the prototype for all the segments below the top.  It has an inward flange at the top, and an outward flange at the bottom.

I have yet to learn how to specify the dimensions of the segments to float smoothly against each other so as to minimize air loss.

This project is undertaken in an open source manner.  If anyone is interested in working with any of the models, I can turn on the download option at Shapeways.

My long term vision for this is for the segments to be manufactured by the aluminum 3D printer which SpaceNut showed us recently. 

As a reminder, SpaceX is building their Draco rockets using 3D printing and a material called Inconel (if my information and memory are correct).

Edit ... corrected spelling of inconel per SpaceNut (thanks!)

(th)

Last edited by tahanson43206 (2019-07-19 12:11:37)

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#74 2019-07-18 16:35:20

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,222

Re: Space Towers and Skyhooks

Thanks tahanson43206 for the 3D stuff its nice to see what can be done with the right tools.

The friction stirred methods that are being made use of for the SLS first stage tanks would also apply to a lift tower section as well.

Inconel is a family of austenitic nickel-chromium-based superalloys and there are a few recipes for the Iconel product of which one was used as the Apollo program heat shield. Apollo heat shields were nearly 7 centimeters (2.7 inches) thick and weighed 1,360 ... One promising material is a nickel-chromium alloy known as Inconel 617..
https://additivemanufacturingtoday.com/ … ne-chamber

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#75 2019-07-20 19:06:57

tahanson43206
Member
Registered: 2018-04-27
Posts: 3,082

Re: Space Towers and Skyhooks

As a follow up, I have uploaded a model to Shapeways comprising the odd numbered cylinders of the proposed Pneumatic Lift Tower. The model was evaluated as printable, but the only color available is white, and the cost is greater than my budget, by quite a bit. I'm planning to create and upload the even numbered cylinders over the weekend.  The total package will come in at around $600.

However, if anyone has a 3D printer and wants to take this on, for just the cost of filament, I would be happy to set the Download option ON.

If all goes well, the even and odd cylinders should slide together with a snug fit, so that the pneumatic feature can be tested.

As a side note in case anyone actually decides to try this, the cap on the top element was omitted from the model. It can be added easily enough by gluing a wooden cylinder in the opening.

https://www.shapeways.com/product/UXDZP … =113352360

(th)

Last edited by tahanson43206 (2019-07-20 19:07:59)

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