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#301 2019-09-16 07:41:36

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,905
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Re: Apollo 11 REDUX

Mine was a K&E Deci-Lon.  Never wore it on my belt,  but I carried it with my notebook and texts everywhere as an engineering student.

I still have it.  It's the back-up when the electronics fail.  And they do.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#302 2019-09-16 12:14:20

tahanson43206
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Registered: 2018-04-27
Posts: 2,566

Re: Apollo 11 REDUX

For OldFart1939 and GW Johnson ....

If you are interested, it may be possible to incorporate Slide Rule lore in a web site that might be created to provide mission planning for Asteroid Mining.

There are (probably) a billion computer programmers on Earth today, or will be soon.  There are only a tiny number of human beings alive who encompass the knowledge and skills you've described in this forum.

GW Johnson, you have indicated on several occasions that computer skills are not something you've invested in, but my counter to that is that people who could translate your vision of a web site to provide click-click generation of mission profiles are available in great numbers.

What I'm thinking about here is that in addition to the simple calculator-like functions a web site could provide, there could exist a capability of showing images of slide rules positioned appropriately at each stage of a calculation.  Such a display would be a lasting educational opportunity for future generations who might want to learn about an analog computing method which can be relied upon when electronics fails,

I'm not talking about an "instant" development project.  The original concept I had in mind would take a year (with all volunteers), and this new feature would easily add a year.

But as said previously, I don't see a need for expenditure of funds by any of the (hoped for) participants, except as might be inspired by the project, for purchase of books or scientific calculators or (gasp) even slide rules.

This would need to be sponsored by SpaceNut, who would need to negotiate with the Mars Society for computer resources, and for guidelines on what such a web site might look like, to adhere to Mars Society expectations for look-and-feel, performance and perhaps other factors.

(th)

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#303 2019-09-16 16:23:40

Oldfart1939
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Registered: 2016-11-26
Posts: 1,835

Re: Apollo 11 REDUX

Actually, there is still one segment of the population still learning to use a slide rule, and that's anyone wishing to become a private pilot. Using the E6b circular slide rule-flight calculator. Granted, it doesn't have all the bells and whistles of the high-end slip sticks, such as log scales and fancy trig scales, but for doing point-to-point navigation, they are hard to beat.
BITD, a really GOOD slide rule could cost $60.00! I had a Post slide rule, because they were a stark white color, and were easier to read thand the K & E slip sticks. Mine was stolen a few years ago, but I guard my Texas Instruments Scientific Calculator with my life! (TA-30XA). This is now becoming something of an historical artifact, too.

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#304 2019-09-16 19:30:18

SpaceNut
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#305 2019-09-16 19:47:13

tahanson43206
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Registered: 2018-04-27
Posts: 2,566

Re: Apollo 11 REDUX

For SpaceNut re #304 ... the tinas link was quite interesting.  Go down far enough and you'll find a UK Monarchy family tree calculator << grin >.

I found one used logarithmic slide rule on offer on Amazon for $120.

However, ebay is where I found an (amazing to me) list of Soviet or 1960's era slide rules, and even a World War II German slide rule.

However, no one appears to be making new slide rules.

The Scientific Calculator is the ubiquitous replacement, no doubt.

(th)

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#306 2019-09-16 21:23:23

kbd512
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Registered: 2015-01-02
Posts: 3,452

Re: Apollo 11 REDUX

Oldfart1939,

The paper charts and E6B's are better than nothing if that's all you have, but we much prefer ForeFlight.  I know some of our old timers are interested in returning to the way things were in the good 'ole days, but there was nothing all that great about the navigation technology of the time.  I can guarantee that your TI-30XA has nothing on the graphing calculator apps for the iPhone and iPad.

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#307 2019-09-16 22:10:52

Oldfart1939
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Registered: 2016-11-26
Posts: 1,835

Re: Apollo 11 REDUX

kbd512-

I still have my E6b, but it's a replacement,  an electronic version. I normally navigate when flying using a Garmin 530W interfaced to a Century 21 Autopilot with STEC altitude control. Yeah, I can still use the paper charts, too. I can navigate from VOR to VOR, my preferred means of navigation, on the Victor Airways.

I'm not mired in the past.

P.S. I also have an iPad and an iPhone. Two laptops, each with a Terabyte of memory and 8 GB RAM.

Last edited by Oldfart1939 (2019-09-16 22:13:11)

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#308 2019-09-17 11:13:03

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,905
Website

Re: Apollo 11 REDUX

My old C-170 has a good radio and a VOR and a transponder.  An antique like that is actually more fun to fly the old way with a paper chart and a circular slide rule.  While it can be flown IFR,  that's not near as much fun as day VFR.  It's way faster than a Piper Cub,  but not so fast you really need the sophisticated electronics that can crap out on you.

I never had to reboot a book or a slide rule.  I have to reboot computers all the time.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#309 2019-09-17 17:00:40

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 18,560

Re: Apollo 11 REDUX

So where are we with a lunar lander....

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#310 2019-09-18 16:56:42

Oldfart1939
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Registered: 2016-11-26
Posts: 1,835

Re: Apollo 11 REDUX

My "take" on project Artemis is that it's not progressing on schedule. Inclusion of this LOP-G is a joke, creating as Bob Zubrin calls it, a "tollbooth." Pay the toll to Old Space and favored contractors. Blue Origin needs to begin stepping up with their lander and actually build one!

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#311 2019-09-18 19:33:57

SpaceNut
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#312 2019-10-27 10:28:18

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 18,560

Re: Apollo 11 REDUX

Number repost from the reuseable lander for moon operations

GW Johnson wrote:

How difficult this is depends upon what you are trying to accomplish,  and how complicated you intend the flights to be.  Here's a bounding analysis.

Lunar circular orbit speed is about 1.68 km/s at low orbit altitudes,  and surface lunar escape is about 2.38 km/s.  The worst-case delta-vee to and from an Earth-moon transfer trajectory is about 0.8 km/s.  There is no air drag loss,  and the lunar gravity loss is crudely 0.165*5% = 0.83%.  It takes worst case 3.29 km/s to depart LEO for the moon by that transfer trajectory. 

If you want a reusable (meaning single-stage) lander to-and-from low lunar orbit,  the two way delta-vee is 2(1.68 km/s)(1.0083) when factored for gravity losses.  That's 3.388 km/s min delta-vee capability for the vehicle.   At 330 sec Isp for vacuum engines operating on storable propellants,  Vex ~ 3.236 km/s.  Thus the required mass ratio is 2.849.  The mass fraction of propellant in such a vehicle (relative to initial ignition mass) is then 0.649. 

Now,  if you believe that the inert mass fraction of a vehicle that has propellant tankage (1 count) landing legs (1 count),  a small pressure cabin (half a count),  and sufficient structural robustness to survive a long life (1 count) is 3.5*(.05) = 0.175,  then its max payload fraction is 1 - .649 - .175 = .176.  While somewhat low,  it's not too bad,  really.  A 10 ton vehicle with 6.49 tons of propellant can fly 1.76 tons of payload two-ways to-and-from lunar orbit,  if its dry empty mass is 1.75 tons.

If you are using higher-performing propellant,  it gets even better. If there's water ice on the moon,  you could be using hydrogen and oxygen as your propellant,  with vacuum Isp nearer 460 sec. Vex ~ 4.511 km/s.  Required mass ratio 2.119.  Fuel fraction 0.528.  At inert fraction 0.175,  payload fraction is 0.297.  In a 10 ton vehicle,  that's 5.28 tons of propellant and 2.97 tons of payload,  with a 1.75 ton dry unloaded mass.

Now,  that orbit transport landing boat idea might serve rendezvousing with ships or a station around the moon.  But if your rendezvous point is out at one of the Lagrange points somewhere,  your delta vee is closer to lunar escape than orbit velocity.  2*2.38*(1.0083) = 4.513 km/s as factored for gravity loss.  To do that single stage with storable propellants,  required mass ratio is 4.032, much more challenging.  That's a propellant fraction of 0.752,  which with .175 inert fraction,  leaves only 0.073 as payload fraction.  Unattractive.  73 kg payload in a 10 ton vehicle. 

If hydrogen-oxygen,  this is mass ratio 2.719,  propellant fraction 0.632,  and for inert 0.175,  payload fraction 0.193. Still not very attractive,  which is why the Gateway station concept of NASA makes no sense at all for lunar exploration,  unless it really is in low orbit about the moon! They don't want it in lunar orbit,  because SLS block 1 and block 1B cannot effectively put it there. Block 2 could,  but the way things are going,  it will not ever be built.

I have not included any maneuver delta-vees for rendezvous in this,  but they would hopefully be modest.  YES,  a two-way reusable single-stage lunar orbit landing boat CAN be built!  For low lunar orbit. 

GW

Someday I will learn this...

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#313 2020-01-12 23:00:10

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 18,560

Re: Apollo 11 REDUX

http://systemarchitect.mit.edu/docs/hofstetter05b.pdf
Affordable Human Moon and Mars Exploration through Hardware Commonality

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