Author Topic: Space Elevator for Mars  (Read 17290 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
"One bit of advice: it is important to view knowledge as sort of a semantic tree -- make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to." - Elon Musk
"There are lies, damned lies, and launch schedules." - Larry J

Offline LMT

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Re: Space Elevator for Mars
« Reply #69 on: 11/11/2017 09:21 PM »
Integrating new SpaceX spacecraft into the Omaha Trail:  quantifying efficiencies and radiation protection, in conference at the British Interplanetary Society.

Press release Nov. 7.

Dr. Lades presented new Mars Lift feasibility details, plus our estimates of Omaha Trail efficiency and radiation shielding for new (2017) SpaceX designs. 

Highlights:

- Number of Earth launches for cargo cut 71%.

- Number of Earth launches for crew cut 83%.

- Solar flare proton flux cut 90%+, eliminating dedicated solar flare shelter.



Omaha Trail, crew flight staging. Deimos propellant and water shielding.


Offline meberbs

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Re: Space Elevator for Mars
« Reply #70 on: 11/12/2017 06:03 PM »
Integrating new SpaceX spacecraft into the Omaha Trail:  quantifying efficiencies and radiation protection, in conference at the British Interplanetary Society.

Press release Nov. 7.

Dr. Lades presented new Mars Lift feasibility details, plus our estimates of Omaha Trail efficiency and radiation shielding for new (2017) SpaceX designs. 

Highlights:

- Number of Earth launches for cargo cut 71%.

- Number of Earth launches for crew cut 83%.

- Solar flare proton flux cut 90%+, eliminating dedicated solar flare shelter.
...

Omaha Trail, crew flight staging. Deimos propellant and water shielding.
So many problems with your claims. First of all, the benefits aren't even real benefits. There is no "dedicated solar flare shelter" because SpaceX is just using the supplies that would be onboard anyway as shielding. You aren't particularly clear on how you cut proton flux by 90%, but that would basically involve heavy shielding everywhere, wasting much of the carrying capacity.

Your reduction in Earth launches is pointless, because the Earth launches are relatively cheap, you are ignoring the costs of getting those extra ships you are using as tankers there to start with, and the much more limited lifetime of ships used for interplanetary transfer due to heat shield ablation. Plus there are other problems, since it does not seem like your propellant amounts would work out. You have 3 ships leave Deimos, spend fuel on a trans-Earth injection, more fuel to capture at Earth (even with aerocapture) transfer fuel from one of them to the crew ship, by magic then have all 3 of these ships full again so they can do a full trans-Mars Injection and then capture/landing. This is even worse given that the only way SpaceX is keeping their landing propellant cool is by having the outer tanks empty during interplanetary cruise.

Offline LMT

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Re: Space Elevator for Mars
« Reply #71 on: 11/13/2017 12:48 AM »
First of all, the benefits aren't even real benefits. There is no "dedicated solar flare shelter" because SpaceX is just using the supplies that would be onboard anyway as shielding.

?  No, absent additional shielding a dedicated shelter space is needed.  Hence the R&D of SR2S, etc.  Likewise Omaha Trail shielding. 

That's why SpaceX included a dedicated shelter space in the new spacecraft design

Why did you think otherwise?

You aren't particularly clear on how you cut proton flux by 90%, but that would basically involve heavy shielding everywhere, wasting much of the carrying capacity.

It's a 130-ton water shield from Deimos.  What's unclear? 

As for "carrying capacity", ascent cargo payload limit applies during ascent.  It has no bearing in transit.

Your reduction in Earth launches is pointless, because the Earth launches are relatively cheap, you are ignoring the costs of getting those extra ships you are using as tankers there to start with

Extra ships?  No, fewer because less propellant is used. 

Also it's far cheaper to build and operate a fleet of, say, 25 giant boosters than a fleet of 100.  That itself is justification, though of course the Omaha Trail would offer other benefits.

it does not seem like your propellant amounts would work out

Did you calculate something?  With Omaha Trail facilities, the numbers add up.

Offline meberbs

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Re: Space Elevator for Mars
« Reply #72 on: 11/13/2017 03:02 AM »
First of all, the benefits aren't even real benefits. There is no "dedicated solar flare shelter" because SpaceX is just using the supplies that would be onboard anyway as shielding.

?  No, absent additional shielding a dedicated shelter space is needed.  Hence the R&D of SR2S, etc.  Likewise Omaha Trail shielding. 

That's why SpaceX included a dedicated shelter space in the new spacecraft design

Why did you think otherwise?
Solar storm shelter is not a dedicated area, and the shielding comes from supplies that are carried anyway. Try actually reading my post before you respond next time.

You aren't particularly clear on how you cut proton flux by 90%, but that would basically involve heavy shielding everywhere, wasting much of the carrying capacity.

It's a 130-ton water shield from Deimos.  What's unclear? 

As for "carrying capacity", ascent cargo payload limit applies during ascent.  It has no bearing in transit.
You should go research the rocket equation, weight matters a lot when leaving LEO, not just during ascent to LEO. You won't get to "in transit," because it takes delta V to leave Earth and go to Mars, and you will lose a lot a delta V due to the unnecessary extra weight.

Your reduction in Earth launches is pointless, because the Earth launches are relatively cheap, you are ignoring the costs of getting those extra ships you are using as tankers there to start with

Extra ships?  No, fewer because less propellant is used. 

Also it's far cheaper to build and operate a fleet of, say, 25 giant boosters than a fleet of 100.  That itself is justification, though of course the Omaha Trail would offer other benefits.
You clearly have not actually understood SpaceX's plans. Their fleet of boosters will probably be < 10 without your changes (unless they get that point-to-point use case going). Also, your plan involves ships leaving Deimos, but you have made no mention of how they got there to begin with. These ships can be used many fewer times due to the heat shield ablation from aerocapture, and you need multiple in parallel, compared to the single ship that can be reused many times refueling from Earth.

it does not seem like your propellant amounts would work out

Did you calculate something?  With Omaha Trail facilities, the numbers add up.
Yes I calculated something. Assuming you somehow have 3 ships leave Deimos starting with full fuel Lets call this amount of fuel 3. They will spend some amount of fuel that we can call X departing for Earth and then capturing at Earth. You then have a total of 3-X fuel. Unfortunately to send 3 ships back to Mars from LEO (without the excess weight from your unnecessary radiation shield), you need a total fuel of 3 full ships. Since 3-X < 3 you do not have enough fuel.

Offline LMT

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Re: Space Elevator for Mars
« Reply #73 on: 11/13/2017 05:03 AM »
Solar storm shelter is not a dedicated area, and the shielding comes from supplies that are carried anyway. Try actually reading my post before you respond next time.

It's dedicated.  Musk said as much.  It's "a small part of the ship," and noted in presentation. 

You clearly have not actually understood SpaceX's plans. Their fleet of boosters will probably be < 10

Booster ratio is invariant.  Musk's intention (2016) was "1,000 or more spaceships" per window.  With 2017 resizing that payload needs ~2,000 ships and ~12,000 booster launches.  A single-digit fleet couldn't do that.

Did Musk explicitly abandon the intention?  I hadn't heard.

You should go research the rocket equation

No, that's wrong and inappropriate.

I calculated something. Assuming you somehow have 3 ships leave Deimos starting with full fuel Lets call this amount of fuel 3. They will spend some amount of fuel that we can call X departing for Earth and then capturing at Earth. You then have a total of 3-X fuel. Unfortunately to send 3 ships back to Mars from LEO (without the excess weight from your unnecessary radiation shield), you need a total fuel of 3 full ships. Since 3-X < 3 you do not have enough fuel.

That's not the rocket equation.

Cutting [X], that's kinda what Omaha Trail facilities are intended for.  Maybe you can find improvements.

Offline meberbs

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Re: Space Elevator for Mars
« Reply #74 on: 11/13/2017 10:02 AM »
Solar storm shelter is not a dedicated area, and the shielding comes from supplies that are carried anyway. Try actually reading my post before you respond next time.

It's dedicated.  Musk said as much.  It's "a small part of the ship," and noted in presentation.
Small does not mean dedicated. My post already explained why it can't be considered dedicated.

You clearly have not actually understood SpaceX's plans. Their fleet of boosters will probably be < 10

Booster ratio is invariant.  Musk's intention (2016) was "1,000 or more spaceships" per window.  With 2017 resizing that payload needs ~2,000 ships and ~12,000 booster launches.  A single-digit fleet couldn't do that.

Did Musk explicitly abandon the intention?  I hadn't heard.
That you for the continued evidence that you haven't read SpaceX's plans. In terms of passenger count, the number of ships hasn't changed, they still plan to fit around 100 passengers per ship, so there is no doubling of ships sent. Each booster is expected to be good for 1000 uses, which means a single digit number of boosters can launch 6000 times. Though they will probably

You should go research the rocket equation

No, that's wrong and inappropriate.
Wait, you are saying the rocket equation is wrong? No seriously, the rocket equation states that contrary to your previous post, the mass of what you are trying to move matters a lot for on orbit maneuvers. It is not a hard equation to understand if you bother to look it up.

I calculated something. Assuming you somehow have 3 ships leave Deimos starting with full fuel Lets call this amount of fuel 3. They will spend some amount of fuel that we can call X departing for Earth and then capturing at Earth. You then have a total of 3-X fuel. Unfortunately to send 3 ships back to Mars from LEO (without the excess weight from your unnecessary radiation shield), you need a total fuel of 3 full ships. Since 3-X < 3 you do not have enough fuel.

That's not the rocket equation.

Cutting [X], that's kinda what Omaha Trail facilities are intended for.  Maybe you can find improvements.
I never said that was the rocket equation, it makes it even easier by making use of the fact that SpaceX engineers already calculated that capabilities of their vehicle. Rather than redo the calculations with incomplete information, I can simply recognize that X is a positive number, and nothing you do can ever make it 0, which is what would be needed for your architecture to work.

Offline LMT

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Re: Space Elevator for Mars
« Reply #75 on: 11/13/2017 12:18 PM »
Wait, you are saying the rocket equation is wrong? No seriously, the rocket equation states that contrary to your previous post, the mass of what you are trying to move matters a lot for on orbit maneuvers. It is not a hard equation to understand if you bother to look it up.

No, telling people to "look it up" is wrong and inappropriate.  And you're not using it yourself.  You should use it.

--

No Tankers

Notably, one of the benefits of the Omaha Trail proposal is that cargo flights can be launched without dedicated tanker ships. 

No tankers at all.  Just returning cargo ships.

This could be especially beneficial to the construction phase of SpaceX's Mars City, which could take decades.  The work might go 10x faster at Omaha Crater, but still, it's a benefit.



Cargo flight staging. Deimos propellant. Mars Lift space elevator in gold.

Offline meberbs

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Re: Space Elevator for Mars
« Reply #76 on: 11/13/2017 02:46 PM »
Wait, you are saying the rocket equation is wrong? No seriously, the rocket equation states that contrary to your previous post, the mass of what you are trying to move matters a lot for on orbit maneuvers. It is not a hard equation to understand if you bother to look it up.

No, telling people to "look it up" is wrong and inappropriate.  And you're not using it yourself.  You should use it.
The only thing inappropriate is that you are trying to propose changes to an architecture created by experienced engineers when you apparently don't understand the most basic of equations governing rockets, and that you refuse to even do basic research on your own.
 
I am using the rocket equation in the very post that you quoted. I draw a very basic conclusion from it that you previously denied:
As for "carrying capacity", ascent cargo payload limit applies during ascent.  It has no bearing in transit.
Which is wrong, because the cargo mass has a major impact on available delta V.
« Last Edit: 11/13/2017 03:00 PM by meberbs »

Offline LMT

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Re: Space Elevator for Mars
« Reply #77 on: 11/15/2017 06:14 AM »
Wait, you are saying the rocket equation is wrong? No seriously, the rocket equation states that contrary to your previous post, the mass of what you are trying to move matters a lot for on orbit maneuvers. It is not a hard equation to understand if you bother to look it up.

No, telling people to "look it up" is wrong and inappropriate.  And you're not using it yourself.  You should use it.
The only thing inappropriate is that you are trying to propose changes to an architecture created by experienced engineers when you apparently don't understand the most basic of equations governing rockets, and that you refuse to even do basic research on your own.
 
I am using the rocket equation in the very post that you quoted. I draw a very basic conclusion from it that you previously denied:
As for "carrying capacity", ascent cargo payload limit applies during ascent.  It has no bearing in transit.
Which is wrong, because the cargo mass has a major impact on available delta V.

That's a confused post.  Calculate some particular delta-v, flare shielding, or other quantity you imagine contentious, and try a comparison.

--

Potential Improvements

Results for the Mars Lift and the greater Omaha Trail are of course preliminary, and many improvements are conceivable, even now.  NSF posters might have useful suggestions.  Some areas to explore:

Tether specific strength:

In August ISEC noted the highest confirmed specific strength in a macroscopic carbon material:  a CNT film checking in at 5.2 MYuri.  But that result was published in 2016, and much research is presently targeting higher specific strengths.  Has a higher specific strength been reported recently?

Removing ice from the tether:

A Mars Lift tether can accumulate water ice and dry ice, which must be removed for safe rappeller passage.  One approach is Joule heating: a CNT tether circuit is established in the terminal 100 km, and its resistance melts or sublimates ice.  Electrical power on the order of 100 kW could warm the tether to clear 1 mm of water ice and an extra 1 cm of dry ice over 10 minutes.  What are some other plausible methods for ice removal?

Offline meberbs

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Re: Space Elevator for Mars
« Reply #78 on: 11/15/2017 07:19 AM »
Wait, you are saying the rocket equation is wrong? No seriously, the rocket equation states that contrary to your previous post, the mass of what you are trying to move matters a lot for on orbit maneuvers. It is not a hard equation to understand if you bother to look it up.

No, telling people to "look it up" is wrong and inappropriate.  And you're not using it yourself.  You should use it.
The only thing inappropriate is that you are trying to propose changes to an architecture created by experienced engineers when you apparently don't understand the most basic of equations governing rockets, and that you refuse to even do basic research on your own.
 
I am using the rocket equation in the very post that you quoted. I draw a very basic conclusion from it that you previously denied:
As for "carrying capacity", ascent cargo payload limit applies during ascent.  It has no bearing in transit.
Which is wrong, because the cargo mass has a major impact on available delta V.

That's a confused post.  Calculate some particular delta-v, flare shielding, or other quantity you imagine contentious, and try a comparison.
Exact calculations aren't necessary to know that 130 tons of extra cargo mass would greatly reduce the available delta V. You on the other hand made the nonsensical claim that this has no effect. After I have pointed out repeatedly how wrong this is, you simply refuse to accept this plain fact and offer nothing in the form of counterargument. You are the one who seems to be confused.

Offline LMT

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Re: Space Elevator for Mars
« Reply #79 on: 11/25/2017 02:44 AM »
You are the one who seems to be confused.

you apparently don't understand the most basic of equations governing rockets, and that you refuse to even do basic research on your own

Anyone calculating Omaha Trail efficiencies would use the rocket equation repeatedly, across many possible flight configurations, and with gravity losses where appropriate, as we did. 

You might have asked, nicely.

Dr. Lades appreciates that work, and all our work.  Hence his ongoing collaboration.  --  You're not going to accuse an ISEC Director of being confused etc... are you?  If not, you've reached the end of that mess.  You should just apologize for the misunderstanding.

« Last Edit: 11/25/2017 02:50 AM by LMT »

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