Author Topic: Space Elevator for Mars  (Read 13175 times)

Offline Paul451

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Re: Space Elevator for Mars
« Reply #60 on: 08/15/2017 04:15 PM »
Ancient workers used clay bricks to make grain silos more than 10 meters high.  With gravity 1/2000 a structure made with equivalent material can be built to the Lagrange points.

{laughs} That's a hilarious image.

An unfired, hand pressed clay brick has a crush strength of around 15kg/mē and a course height of around 100mm. At Phobos surface gravity (but completely ignoring the reduction of gravity with height) that lets you build a structure 170km tall. Which is way beyond the Phobos/Mars L1 point.

On Phobos, you can build a brick staircase to orbit.

Offline LMT

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Re: Space Elevator for Mars - Dr. Lades' Mars Lift
« Reply #61 on: 09/24/2017 01:36 PM »
Dr. Martin Lades has now solved the longstanding MSE problem of Phobos/tether collision.  His numerical analysis of an off-equator tether has determined that a reasonable tether design can passively avoid Phobos. 

In one example, an MSE base station just 13 degrees off the equator has a tether curve that clears Phobos.  No active tether management is required.

Our Omaha Trail press release here.

« Last Edit: 09/24/2017 01:37 PM by LMT »

Offline Asteroza

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Re: Space Elevator for Mars - Dr. Lades' Mars Lift
« Reply #62 on: 09/25/2017 11:13 PM »
Dr. Martin Lades has now solved the longstanding MSE problem of Phobos/tether collision.  His numerical analysis of an off-equator tether has determined that a reasonable tether design can passively avoid Phobos. 

In one example, an MSE base station just 13 degrees off the equator has a tether curve that clears Phobos.  No active tether management is required.

Our Omaha Trail press release here.




Off-axis elevators are certainly an interesting solution and provide continuous ops, rather than a two step Deimos/Phobos tether pair with central coast phase.

The coilgun launcher above Deimos near Deimos L2 is not very clear in this design, nor are the advantages relative to just jumping off the counterweight at the appropriate time. Guess we have to wait for the full paper/presentation?

Offline LMT

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Re: Space Elevator for Mars - Dr. Lades' Mars Lift
« Reply #63 on: 09/25/2017 11:52 PM »
Dr. Martin Lades has now solved the longstanding MSE problem of Phobos/tether collision.  His numerical analysis of an off-equator tether has determined that a reasonable tether design can passively avoid Phobos. 

In one example, an MSE base station just 13 degrees off the equator has a tether curve that clears Phobos.  No active tether management is required.

Our Omaha Trail press release here.




Off-axis elevators are certainly an interesting solution and provide continuous ops, rather than a two step Deimos/Phobos tether pair with central coast phase.

The coilgun launcher above Deimos near Deimos L2 is not very clear in this design, nor are the advantages relative to just jumping off the counterweight at the appropriate time. Guess we have to wait for the full paper/presentation?

Yes, his off-equator solution allows for continuous operation.  Moreover, having a base station at 13 degrees latitude allows the tether to retain nearly all of its strength for vehicle support.

As for Deimos, there is of course the option for spacecraft to depart the L1 "Deimos Dock" via rocket propulsion, but one would like to avoid that expenditure if possible.  A tethered superconducting helical coil electromagnetic launcher could fit the bill, if extended through L2 with sufficient length and power to get craft to Mars, or to cloud-skimming periapsis for Earth-return.  Luckily 1 km/s is the requirement in either case; a speed that's relatively modest, compared to the orbital-launch speeds floated elsewhere. 

And yes, one might extend the Deimos Rail Launch tethers further for drop-launch outward, but that loses the gravity-assist of Mars periapsis, and increases tension.

One might extend the simpler Mars Lift tether to drop-launch from that tether instead, but that requires more tension and also more infrastructure to manage the dynamics; especially collision-avoidance tech, to dodge Deimos.  As they are, Omaha Trail tethers passively avoid both moons, and each other, continuously.

A possible DRL extension:  one might combine methods in a second deployment by attaching a long, simple tether to the counterweight of the shorter, more complex DRL tethers.  Craft bound for Mars launch via DRL.  Other craft drop-launch from the attached tether.  However DRL tethers would require reinforcement or replacement to manage the greater tension.

We give some of the reasoning, tech, numbers and references in the conference presentation attached to the press release.  Feel free to ask about things not shown in presentation.
« Last Edit: 09/26/2017 01:12 AM by LMT »

Offline Asteroza

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Re: Space Elevator for Mars
« Reply #64 on: 09/26/2017 08:21 AM »
Ah, firing the Deimos coilgun inward as a lead-in boost for a conventional oberth maneuver departure burn then, didn't catch that.

The structural arrangement baseline for the coilgun relative to the L2 tether would be interesting to see, along with the Deimos L1 dock arrangement considering the no capstan rule.

Offline LMT

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Re: Space Elevator for Mars
« Reply #65 on: 09/26/2017 11:31 AM »
Ah, firing the Deimos coilgun inward as a lead-in boost for a conventional oberth maneuver departure burn then, didn't catch that.

Right.

The structural arrangement baseline for the coilgun relative to the L2 tether would be interesting to see, along with the Deimos L1 dock arrangement considering the no capstan rule.

re: L1 Deimos Dock

Deimos Dock is needed only as a transfer station for propellant and water.   There's no need for cargo transfer.   The only "climber" envisioned would be a low-speed inspection/repair vehicle.  Capstaning is therefore allowable on the Deimos Dock tether.  However it doesn't seem necessary.  Pressure from paired wheels should be adequate, on a straight tether, as in Pearson 2005.

re: DRL through L2

Presentation slides 36-38 are just intended as conversation starters, with a suggested approach for adaptation of Engel's helical coil launcher.  (Engel 2004, Engel et al. 2015.)  A few notes:

Whereas Engel's high-acceleration projectile launcher requires a thick fixed-box construction, the low acceleration (0.5 m/s2) of the DRL should allow a light tethered construction.  The stator can be a skinny, flexible coiled tube of high-temperature superconductor.  HVDC power can be delivered by thin outrigger tethers.

In slide 37 the redundant stator pair is shown in red.  Each stator is flanked by a pair of HVDC tethers in white.  Two additional pairs of tethers in white are added at the periphery.  They serve, notionally, only to provide extra power line repulsion force, to balance repulsive forces on the load-bearing tethers and keep the wires roughly in parallel for easy passage of platform Lorentz tubes.

Engel has demonstrated record-setting launch efficiency by cooling the armature in liquid nitrogen, to cut electrical resistance.  At Deimos LOX would substitute.  Full efficiency would be obtained by cooling both armature and stator to high-temperature superconducting range with LOX.  A LOX dewar would travel with the armature.  The stator is however stationary by definition.  One would deploy the flexible stator hollow, filling it with LOX from Deimos base station prior to launch.
« Last Edit: 09/27/2017 01:04 AM by LMT »

Offline Phil Stooke

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Re: Space Elevator for Mars
« Reply #66 on: 09/26/2017 11:38 AM »
Very interesting - just one minor point.  The 'Taylor Oner' you credit with the Deimos image is really Tayfun Oner.

Offline LMT

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Re: Space Elevator for Mars
« Reply #67 on: 09/26/2017 01:47 PM »
Very interesting - just one minor point.  The 'Taylor Oner' you credit with the Deimos image is really Tayfun Oner.

Fixed, thanks.  Interesting for us as well.

It was especially interesting to see how far CNT materials have now advanced toward the required Mars Lift specific strength.  Dr. Lades analyzed Mars Lift tethers at 7-13 MYuri, and CNT film is reported from 2016 at 5.2 MYuri  (J. Knapman, from Xu et al. 2016:  9.6 GPa / 1.85 g/cc.) So specific strength is getting there, apparently.  It justifies consideration of a Mars Lift system proposal for 2036 timeframe, don't you think?

Offline whitelancer64

Re: Space Elevator for Mars
« Reply #68 on: 09/26/2017 02:06 PM »
Ancient workers used clay bricks to make grain silos more than 10 meters high.  With gravity 1/2000 a structure made with equivalent material can be built to the Lagrange points.

{laughs} That's a hilarious image.

An unfired, hand pressed clay brick has a crush strength of around 15kg/mē and a course height of around 100mm. At Phobos surface gravity (but completely ignoring the reduction of gravity with height) that lets you build a structure 170km tall. Which is way beyond the Phobos/Mars L1 point.

On Phobos, you can build a brick staircase to orbit.

This is the kind of trivia that I wish were common knowledge :p
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