Jumper cables for Apollo - Page 1
Forum section: electronics / general

author: Homer J Simpson
author_rank: Super Contributor
timestamp: October 03, 2018, 03:28:51 pm
content: Interesting read on the last ditch method to start the ascent engine on the LEM.http://finleyquality.net/dont-get-me-started/

author: German_EE
author_rank: Super Contributor
timestamp: October 04, 2018, 04:51:44 pm
content: Which only goes to show how brave those men were who went to the moon.

author: apis
author_rank: Super Contributor
timestamp: October 04, 2018, 05:19:56 pm
content: Brave, sure, but at the same time I, and many with me, wouldn't have hesitated to take those odds given the opportunity. While I wouldn't want to diminish the individual astronauts contribution, I think we tend to forget how much of a group effort it was. We often underestimate the contribution from the engineers (and other workers) who put their sweat blood and tears into that project.

author: amyk
author_rank: Super Contributor
timestamp: October 05, 2018, 12:32:02 am
content: All based on 1960s technology... I wonder if "modern" spacecraft would have the same sort of backup plans in place.

author: Stray Electron
author_rank: Super Contributor
timestamp: October 05, 2018, 01:46:26 am
content: A "modern" spacecraft would have so many backup and safety systems that they'd never finished designing it and even if they did, it would be too heavy to get off of the ground.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: October 05, 2018, 05:04:20 am
content: Quote from: apis on October 04, 2018, 05:19:56 pmA similar point of view is in this "The Moth" story by an astronaut who worked on the Hubble Space Telescope:https://player.themoth.org/#/storyId=928

author: Berni
author_rank: Super Contributor
timestamp: October 05, 2018, 05:45:52 am
content: Now this sure does sound like something in Kerbal Space Program (Space sim game where players often use crazy ideas).But i would assume this is really a backup of a backup of a backup of a backup idea. Things would have to go really wrong before they would need it, but they had it ready just in case.

author: rstofer
author_rank: Super Contributor
timestamp: October 05, 2018, 03:37:38 pm
content: And, in the end, it can come down to something as ancient as celestial navigation (Apollo 13):https://www.quora.com/How-did-the-Apollo-13-crew-manage-to-navigate-using-the-Earth%E2%80%99s-terminator-line

author: German_EE
author_rank: Super Contributor
timestamp: October 05, 2018, 07:53:25 pm
content: Eight years ago I navigated a yacht all the way from Sweden to Dubai using celestial navigation, a compass and charts. The owner of the yacht didn't think that it could be done but I needed to demonstrate that a vessel could still run if the electronics were dead.That was a FUN vacation and my only regret is that since then the yacht hasn't moved from its mooring in the marina.

author: raptor1956
author_rank: Frequent Contributor
timestamp: October 08, 2018, 03:28:52 am
content: Quote from: German_EE on October 05, 2018, 07:53:25 pmI've not had the chance to try my hand at celestial navigation for real but recently purchased a decent sextant -- the Astra III Professional. Perhaps not in the same league as a Cassens & Plath or a Tamaya, but it is one of those tools that is just cool to have. I do need to learn more about calculating a fix but I do have the basic idea. Amazing that a purely mechanical contraption with zero electronics can, in capable hands, determine your position within 0.5km or there abouts. I'd guess the more typical fix at sea would be a few km's but that's adequate at sea.Brian

author: rstofer
author_rank: Super Contributor
timestamp: October 09, 2018, 01:58:32 pm
content: For a number of years, the US Naval Academy dropped celestial navigation. It's back in the curriculum.Something about attacks against GPS.https://www.npr.org/2016/02/22/467210492/u-s-navy-brings-back-navigation-by-the-stars-for-officersThere are ways to work around it but you do need an accurate time mark. So what does NIST do? They decide to cancel WWV broadcasts. Really and truly stupid! What? You're thinking of getting your time hack from the GPS?http://insidegnss.com/the-death-of-old-time-nist-cutting-wwv/Three electronic watches with know drift rates are probably a work-around.I bought a hundred year old version of Bowditch just to find out how to get time from Lunar Distance.https://en.wikipedia.org/wiki/Lunar_distance_(navigation)

author: gildasd
author_rank: Frequent Contributor
timestamp: October 09, 2018, 10:52:14 pm
content: Sextants are ok for navigation, but for precise offshore work, GPS is a must...If a ship in theatre looses the lock, it automatically goes into safe mode and all the other ships in the zone must also stop...

author: raptor1956
author_rank: Frequent Contributor
timestamp: October 09, 2018, 11:11:57 pm
content: Quote from: gildasd on October 09, 2018, 10:52:14 pmYou could be more specific about what you mean when you say precise offshore work. GPS has only been available to non-military users since the late 80's and I do believe offshore work was done prior to then.Brian

author: chris_leyson
author_rank: Super Contributor
timestamp: October 10, 2018, 12:16:06 am
content: QuoteFor precise offshore work eLoran is good enough. Because of the low signal strength GNSS is really easy to jam, South Korea and Japan are upgrading their eLoran systems for precisely that reason. The UK are looking at using eLoran after successful sea trials and being excluded from Galileo might have had something to do with that.Interesting that celestial navigation is back on the US Naval Academy curriculum, just in case you don't have a clear radio sky. However, if you don't have a clear optical sky to get a star fix then you can use the sun, the Vikings navigated that way. Celestial navigation relies on an astronomical almanac in some form or another and good time keeping whereas time of flight navigation just needs reference co-ordinates. I know I've over simplified things but I would go for land based ground wave propagation time of flight navigation. Accurate enough and not so easy to jam. The good news in Europe is that I don't see MSF and DCF77 disappearing any time soon.

author: chris_leyson
author_rank: Super Contributor
timestamp: October 10, 2018, 12:46:55 am
content: @raptor1956. Could have been Decca Navigation or Hi-Fix or Loran-C if you go back far enough. Good enough to place a drilling platform to a few metres. Back in the day I could pick up Decca channels with just a few feet of wire and a Loran transmitter up the coast made topband more or less unusable.

author: raptor1956
author_rank: Frequent Contributor
timestamp: October 10, 2018, 02:38:07 am
content: How far out to sea will Loran be viable for, say, 10m accuracy? I had Loran on a small boat I had back around 1989 but that never left the Hudson River so I never had to test it's ocean going capabilities.The value of celestial navigation, even today, is not so much near shore but further out in the ocean when the only electronic aid with decent accuracy is GPS and if you have a GPS failure or an electrical failure then you'd better have a sextant and know how to use it. Even the Apollo astronauts had to maintain celestial navigation skills with all the tech they had at there disposal.For me, however, the real reason is more of a nerdly interest in the technology that permitted ocean navigation in the days before ANY electronics.Brian

author: gildasd
author_rank: Frequent Contributor
timestamp: October 11, 2018, 01:51:54 pm
content: Quote from: raptor1956 on October 09, 2018, 11:11:57 pmBefore that, position keeping was done on the basis of anchors and buoys.For example finding and extracting the lost atoms bombs in 1966 needed a whole fleet and the most advanced military and civilian equipment available, Billions in today’s Dollars.Now, any decentish ROV equipped survey vessel could do the search and retrieval.Our boat could, and it is not special.Even 10 years ago, a heavy lift in the North Sea (setting a platform on its jacket), despite using GPS, needed a least 4 precisely set anchors (often 6) and that was fun to do with all the junk in the bottom (cables, pipelines, wrecks and lots of unexploded ordenance) now the crane ship can rock up in DP2, do a final survey pass, go to the start point, move to the lift, do the lift and the post lift survey while moving back.And what they called precise in the 80’s, is often found to be up to be hundreds of meters from where they thought it was in the original “as done” survey (especially out of sight of land with no other point to triangulate from). That position has been updated multiple times since, especially with platforms, but we still find things like cables not where they are reported to be.

author: rstofer
author_rank: Super Contributor
timestamp: October 11, 2018, 02:39:56 pm
content: I would think on a small boat, at sea, position finding within a mile or two would be more that adequate. It's not like you are going to miss Hawaii. It's all over the place! One anchorage might be just as good as another. Stop in and ask directions! Ever watch "Captain Ron"?By any definition of 'precise', this isn't it. If you need 10 meters, GPS is a better solution. As long as you realize that the system can be degraded on command by an airman in Colorado. Bump one little switch (metaphorically) and the whole system goes down.Don't have the time? Well, 'easting' still works. Get your latitude from meridian transit and sail the boat along the parallel of latitude of the destination. It was done that way for a very long time. The sailors knew the latitude of the destination so getting there was easy. Longer, perhaps, but easy. Unfortunately, the pirates also knew exactly where the boats would be coming from. OTOH, the boat didn't need to stay strictly on the parallel, it only had to be there before they went past the destination. They could still approximate a great circle route.We have a lot of nice technology. It is still fun to think in terms of 'old school'.

author: raptor1956
author_rank: Frequent Contributor
timestamp: October 11, 2018, 08:22:31 pm
content: Interesting comments on the pre-GPS methods for precise positioning and the fact that even into the mid 80's precise might still be on the order of 100m or more. GPS for long term accuracy and INS for short term, particularly under water.At sea the accuracy a captain needs is probably more like 10 miles unless you're trying to find a tiny atoll or similar. A decent sextant should comfortably achieve 10 miles and can, in skilled hands with favorable seas permit sub mile accuracy which is good enough to make a direct approach to a preferred harbor/anchorage.The economic impact of the large US investment into GPS is many times the total cost and one of the best investments of the last 50 years.Brian

author: gildasd
author_rank: Frequent Contributor
timestamp: October 11, 2018, 11:18:20 pm
content: If you set our ship 10cm from the quayside in DP2, then try to pull it closer with ropes, it will resist with all five thruster (10mW +) and not budge. Until the ropes, the bollard or the winches fail.We have gps but also the Russian and European equivalent. And if all that fails, we have put precise radio beacons on the sea floor to let us retrieve the trencher or the ROV or slack the cable to get out of the 500m zone safely.

author: a59d1
author_rank: Regular Contributor
timestamp: October 14, 2018, 04:29:54 am
content: I'm going to be seeing the author of the excerpt, Harrison Schmitt, in a couple weeks' time; if any of you have questions you'd like me to ask him, fire away!