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  #51  
Old 07-22-2019, 08:50 AM
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I wish Stranger on a Train would come back.
  #52  
Old 07-22-2019, 08:53 AM
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After watching First Man I learned Armstrong nearly died in Gemini 8 , they went into a spin they almost could not get out of. The mission was supposed to be 3 days but it was cut to 10 hours. They were testing docking with the Agena module.
Then there was the time he ejected from the Lunar Landing Training Vehicle, went back to his desk and didn't think to mention it to anybody. Alan Bean tells that story in the excellent documentary "In the Shadow of the Moon".
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Old 07-22-2019, 09:08 AM
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Right, his demonstrated coolness in an emergency, as well as his private nature, were why he was chosen to be the next Lindbergh.
  #54  
Old 07-22-2019, 10:22 AM
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Here's an article listing quite a few of his near-death incidents. If you're flying things like X-1B's and X-15's those are going to happen.

It also mentions the incident at Edwards with Chuck Yeager where they were disputing whether the lake bed had dried out enough. Armstrong decided it was, landed, and ... oops.

Going back to the Moon? Find yourself a bunch of people like this.
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Old 07-22-2019, 02:00 PM
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Personally, I'd guess that rather than do it all in one huge lift with a Saturn V class rocket, they'd do it in a series of launches- crew capsule, lander, fuel, and then rendezvous in orbit, and then do their TLI burn from there. That way, they could do it more economically; for example, the Falcon 9 is roughly equivalent to the Saturn 1B, so it could put a capsule in orbit without much trouble, and for considerably less cost.

I think the biggest change would be that I suspect that they'd want to spend significant time on the lunar surface relative to Apollo. Even Apollo 17 only managed 3 7-ish hour EVAs and brought back less than 250 lbs of samples. I have a feeling NASA would want much more than that when/if they go back.
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Old 07-22-2019, 03:31 PM
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Then there was the time [Armstrong] ejected from the Lunar Landing Training Vehicle, went back to his desk and didn't think to mention it to anybody.
I used to think that was a bit weird too, but then my understanding of the way the LLTV was used was flawed. I used to think the astronauts just went out to the field and hopped in to do some training like they might train in the T-38, but then I saw this video about how astronauts didn't do it alone. They had an entire mini-mission control working with them and each training flight was almost as rigorously scheduled and monitored as the real lunar landing mission. He probably felt it was Somebody Else's job to spread the word about the mishap.

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I thought Buzz Aldrin had that figured out.
Figured what out, exactly?

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Space isn't a place; it's a whole lot of places
And not just a whole lot of places, but a whole lot of energies/orbits. That's a Greater Infinity (channeling Michael McCollum there ).

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they'd do it in a series of launches- crew capsule, lander, fuel, and then rendezvous in orbit, and then do their TLI burn from there.
And probably without a space station.

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I think the biggest change would be that I suspect that they'd want to spend significant time on the lunar surface relative to Apollo..
Definitely. This will require either a much more capable lift vehicle than the Saturn V, or a bunch of smaller launches.
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  #57  
Old 07-22-2019, 03:39 PM
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Right. Nevertheless, the aerospace industry is skeptical. As the saying goes: "No bucks, no Buck Rogers".
I don't think his "order" was serious. But now he can say he is making America Great Again. When it doesn't work out, because not even his administration is asking for anywhere enough money, he will blame the democrats in congress for letting the country down. Win Win. NASA as always is the loser in this political charade.
The Democrats will be forced to argue with budgets and facts-always a losing argument with the public.
  #58  
Old 07-22-2019, 04:17 PM
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Figured what out, exactly?
Orbital rendezvous.
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Old 07-23-2019, 11:32 AM
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Something we could do without, for our next lunar mission: Quindar Tones (those annoying beeps): https://www.youtube.com/watch?v=wrB6uCV2F0k

Fortunately, NASA has already stopped doing this, so it's unlikely they'd start using them again.
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Old 07-23-2019, 02:33 PM
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I don't think his "order" was serious.
What do you mean by that? NASA is part of the executive branch of the US government. Realistic or not, NASA is committed to try to land a human on the Moon by 2024.
  #61  
Old 09-03-2019, 09:12 PM
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Apollo never stopped using pure oxygen though. Even the Apollo capsule for the Apollo-Soyuz Test Project used a pure oxygen atmosphere, and they had to connect to the Soyuz (which uses nitrogen/oxygen) through an airlock. The lessons learned from Apollo-1 was mainly about materials that are flammable in pure oxygen atmosphere.
Actually, the problem with Apollo 1 was that they used pure oxygen pressurized to 1 atm, which makes lots of things flammable. The actual missions used pure oxygen at 4.7 psi. At that pressure, the pure oxygen environment is fine.

I imagine some material review/replacement was also done, but the main issue was using pure oxygen at sea level pressure.
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Old 09-03-2019, 09:22 PM
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As for the moon mission in 2024, I would lay serious bets that they don't make that deadline either. But the point to the 2024 deadline is to break NASA out of its perpetual 10-20 year manned spaceflight project estimates, which generally translate into 'never'. When an organization says, 'we will get this done in 10 years or so', it's easy to get into analysis paralysis, it's easy for politicians to delay funding, etc. It creates a project management mess. However, saying you will do it in six years means you had better get your ass in gear and get your ducks in a row pronto, and any changes in funding are guaranteed to cause schedule slip, which the politician who championed it has to own. Also, really long engineering programs can lead to scope creep, the killer of projects. Especially so in a highly politicized environment.

So it's much better to demand that something be done in six years and have it get done in eight, rather than say you'll get something done in a decade, and have it mutate so much on the way that it never happens. This is especially important for NASA, because new presidents always want to put their stamp on things, and it's much easier to demand radical changes to a project in year two or three of a ten year plan than one that's more than halfway done on a six year plan.

So I don't expect a manned landing before 2026, and if NASA slips more than that, say to 2030, my money is on private space doing it first.
  #63  
Old 09-04-2019, 11:01 AM
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I wish Stranger on a Train would come back.
Ditto.
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Old 09-04-2019, 09:02 PM
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Actually, the problem with Apollo 1 was that they used pure oxygen pressurized to 1 atm, which makes lots of things flammable. The actual missions used pure oxygen at 4.7 psi. At that pressure, the pure oxygen environment is fine.

I imagine some material review/replacement was also done, but the main issue was using pure oxygen at sea level pressure.
I had wondered about that, thanks, Sam.
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Old 09-06-2019, 06:09 PM
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After watching First Man I learned Armstrong nearly died in Gemini 8 , they went into a spin they almost could not get out of. The mission was supposed to be 3 days but it was cut to 10 hours. They were testing docking with the Agena module.
Been meaning to ask - is there now technology to prevent spins like that, or is it still a realistic risk?
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Old 09-06-2019, 08:41 PM
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Been meaning to ask - is there now technology to prevent spins like that, or is it still a realistic risk?
I wasn't aware that they almost died. Armstrong was a damn good pilot. There is probably better technology now, I wonder if there was a gyroscope failure on that mission. Three rings spin in a gyroscope, and if two of them move to together, the gyroscope is locked and the spacecraft cannot manuver. There may be electronic versions now that do not lock.
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Old 09-06-2019, 10:02 PM
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I wasn't aware that they almost died. Armstrong was a damn good pilot. There is probably better technology now, I wonder if there was a gyroscope failure on that mission. Three rings spin in a gyroscope, and if two of them move to together, the gyroscope is locked and the spacecraft cannot manuver. There may be electronic versions now that do not lock.
It was a stuck thruster. Armstrong eventually used a separate ring of thrusters to bring the Gemini under control.
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Old 09-07-2019, 05:55 AM
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Been meaning to ask - is there now technology to prevent spins like that, or is it still a realistic risk?
The problem on Gemini 8 was caused by an electrical short that caused a roll thruster to stay on. It was difficult to diagnose because it happened when the spacecraft was not within range of a ground station, hence there was no telemetry. Had there been telemetry, mission control could have told them immediately that thruster #8 was stuck on.

Today there are TDRS relay satellites so all crewed spacecraft are never out of communications.

A secondary cause of the problem was the attitude thrusters (by design) still had electrical power even if the thruster electronics control system was turned off. Removing power from the thrusters themselves required turning off circuit breakers. After Gemini 8 this was changed to de-power the thrusters if the control system was turned off.

The Gemini 8 incident took place over roughly 18 min. The problem began slowly since the stuck thruster was on the spacecraft which was docked to the much larger Agena vehicle. The total mass damped the motion.

Due to a long history of previous problems with the Agena the astronauts were mentally conditioned to suspect that as the first cause. Thus when they managed to reduce the rates to about 5 deg. per sec they undocked. Unfortunately this made the problem much worse because the stuck thruster started rolling the smaller spacecraft faster, reaching about 300 deg. per sec. About 2 g of negative g (toward the head) was reached and this was sustained for several minutes. They were not at risk of blackout or "red out" but vertigo was an issue.

They couldn't blindly shut down all reaction control circuit breakers because that would leave them with no control to reduce the spinning/rolling.

They finally activated two separate reaction control systems in the spacecraft nose and managed to bring it under control, then deactivated all the OAMS circuit breakers. When slowly activating those one by one they determined thruster #8 was stuck on.

The two RCS "rings" used to get control were designed only for reentry use and they exhausted 75% of that fuel. The remaining 25% was safe to control attitude during reentry but mission rules required an immediate deorbit.

Attitude control is absolutely critical in any spacecraft. Even back in Mercury and Gemini they knew this and there were multiple redundant control modes and backups.

Apollo was similar. On the Lunar Module the RCS system was divided into two separate groups, each of which had separate propellant tanks and plumbing. Besides this there was physically separate backup wiring to physically separate control solenoids on each thruster. This was only activated if the hand controller was pushed to the limit, the so-called "direct" mode. So if both primary and backup computers failed and if half the RCS system failed, they could still control the vehicle.

Unlike the Command/Service Module, the Lunar Module could cross feed propellant between the main engine tanks and the RCS system. If somehow both RCS systems became depleted of fuel, this could be supplied by the main tanks. Or if during ascent from the moon the main engine shut down early, they could run all four RCS thrusters using the main engine propellant. These produced about 11% of the main engine thrust but if run long enough they could compensate for a significant main engine under-performance.

So they spent lots of time thinking about contingencies and building in safeguards and redundancy. Presumably any future moon mission would do likewise.
  #69  
Old 09-07-2019, 06:20 AM
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Thank you, joema. We miss Stranger just a bit less now!
  #70  
Old 09-07-2019, 06:48 AM
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...

Today there are TDRS relay satellites so all crewed spacecraft are never out of communications.

...
May I shamelessly mention that shortly after college I worked on a team that wrote the software for one of the TDRS ground terminals?

With that bit of shameless self-promotion out of the way, along with aknowledging that it gives me zero credibility regarding space flight or lunar missions, what about the idea of a lunar cycler?
https://www.spaceflightinsider.com/m...o-no-man-gone/
Does the idea make sense, at least when talking about a permanent presence or at least regular visits?
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Old 09-08-2019, 06:30 AM
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That’s cool, davidm.

I’m bumping this because I’m curious about the cycler idea, too.
  #72  
Old 09-09-2019, 06:47 AM
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May I shamelessly mention that shortly after college I worked on a team that wrote the software for one of the TDRS ground terminals?

With that bit of shameless self-promotion out of the way, along with aknowledging that it gives me zero credibility regarding space flight or lunar missions, what about the idea of a lunar cycler?
https://www.spaceflightinsider.com/m...o-no-man-gone/
Does the idea make sense, at least when talking about a permanent presence or at least regular visits?
What I don't get with cyclers: to get on, don't the passergers and payload have to accelerate to injection speed anyway? And isn't it the same in reverse when reaching the destination? I understand that accelerating/decelerating a small capsule is easier than changing the speed of the cycler itself. This would justify a Mars cycler (see The Martian) that needs to be pretty large in order to provide lots of radiation shielding and medium-term life support and living space; but for relatively short trips to the Moon, what benefit does the cycler itself bring?
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Old 09-09-2019, 06:56 AM
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I agree with Little Nemo. By far, the biggest difference would be our computer technology. In the sixties, it was a joke compared to what it is now. Our advances in propulsion and ship design pale in comparison.
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Old 09-09-2019, 07:28 AM
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What I don't get with cyclers: to get on, don't the passergers and payload have to accelerate to injection speed anyway? And isn't it the same in reverse when reaching the destination? I understand that accelerating/decelerating a small capsule is easier than changing the speed of the cycler itself. This would justify a Mars cycler (see The Martian) that needs to be pretty large in order to provide lots of radiation shielding and medium-term life support and living space; but for relatively short trips to the Moon, what benefit does the cycler itself bring?
Those relatively short trips to the moon aren't actually all that short. Short compares to Mars, but accelerating a small pod that can sustain people for a few days to lunar rendezvous is much cheaper than accelerating the kind of ship that can sustain you for weeks and get you down to the lunar surface.

With the short trip though, wouldn't it make more sense to have a space station in orbit of the moon instead? Astronauts would ride a rocket up to a space station around Earth (a reusable, small pod that can just get them to the station, along with tons and tons of cargo, then return to Earth) then a transfer vehicle to the moon (on a free return trajectory, with a small transfer craft that stays in space and so can be cheaper and smaller as well as fully reusable) where they'd dock with a lunar station for long term habitation equipped with landers.
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Old 09-09-2019, 07:33 AM
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The LM was supposed to keep two people alive for two days, not three people for four days. The command module had enough chemical "scrubber" canisters for removing CO2, but they were designed for the command module and didn't fit the system in the lunar module. In the end, they had to fabricate an adapter so they could fit the CM's square canisters to the LM's round sockets. They didn't transfer back to the CM until shortly before reentry.
I do hope nowadays there would be enough standardization of parts to make items such as scrubber canisters interchangeable throughout.
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Old 09-09-2019, 08:54 AM
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I do hope nowadays there would be enough standardization of parts to make items such as scrubber canisters interchangeable throughout.
They were incompatible because the LEM was made by Grumman, and the command module by North American Aviation. This situation will persist. The Orion capsule is made by Lockheed, and the habitation module of the Gateway station will be made by Northrup Grumman. I don't think the Artemis lander contract has been awarded yet, but there's a good chance it will be neither of the above. NASA could require each company to conform to standards, and I don't know if they are doing that for CO2 scrubbers, but every requirement NASA imposes on a contractor has a cost & schedule impact.
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Old 09-09-2019, 10:31 AM
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...every requirement NASA imposes on a contractor has a cost & schedule impact.
This is correct but it would have been virtually no cost to have compatible CO2 scrubbers on the CM and LM - had the contractors been given this as a design criteria.

The problem was the "lunar lifeboat" contingency was not envisioned until around Sept 1966 -- well after the LM was already designed. Initially the discussion centered around trajectory, propulsion and on-board computer issues for an unlikely scenario where the LM descent engine had to back up the service module SPS. At that point they didn't apparently get into mission planning specifics or environmental/consumable issues.

It was not until around January 1969 that significant trajectory, guidance and propulsion planning took place for a variety of LM-assisted lunar abort scenarios. These are documented in Howard Tindall's January 21, 1969 memo: http://www.collectspace.com/resource...allgrams02.pdf

It's likely that they were focused on the service module engine "just won't start", not systems implications of why it might not start. In the case of Apollo 13 it wouldn't start because there was no electric power due to an O2 tank explosion which also eliminated the breathing oxygen.

In hindsight it seems obvious you want maximum interchangeability but the square-vs-round thing might have happened even if North American had built the LM. The problem is the LM contract was not given until about 1 year after the CM contract, so Grumman was always in a position of having to play "catch up".

The original plan was the Command/Service Module would land on the moon with a lower stage, then the entire CM/SM would blast off for earth. That is why the SPS engine was so big. Later when the Lunar Orbit Rendezvous mission was accepted and the LM design began, they retained the "big" SPS engine.

The CM and LM used two different contractors for their Environmental Control System (ECS). Airesearch made the CM system and Hamilton Standard made the LM system. This may have contributed to the difference.
  #78  
Old 09-09-2019, 11:42 AM
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I agree with Little Nemo. By far, the biggest difference would be our computer technology. In the sixties, it was a joke compared to what it is now.
Right. It means we can use CGI instead of a sound stage in Arizona.





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Old 09-09-2019, 12:07 PM
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Those relatively short trips to the moon aren't actually all that short. Short compares to Mars, but accelerating a small pod that can sustain people for a few days to lunar rendezvous is much cheaper than accelerating the kind of ship that can sustain you for weeks and get you down to the lunar surface.

With the short trip though, wouldn't it make more sense to have a space station in orbit of the moon instead? Astronauts would ride a rocket up to a space station around Earth (a reusable, small pod that can just get them to the station, along with tons and tons of cargo, then return to Earth) then a transfer vehicle to the moon (on a free return trajectory, with a small transfer craft that stays in space and so can be cheaper and smaller as well as fully reusable) where they'd dock with a lunar station for long term habitation equipped with landers.
It's very hard to orbit the moon for a long time, because the moon has a very 'lumpy' gravity field. Most orbits wind up being unstable because of it. There are a few 'frozen' orbits that are stable, but getting into them means a plane change manoever at the moon, and those orbits may not be where you'd like them to be.

The 'cycler' idea is a little dated, in my opinion. Back in the stone age of say, ten years ago when we threw away every rocket and our rockets were much smaller than the generation to come, it was incredibly expensive to get mass into lunar orbit. And if we go back to the moon in a big way, we can't expect people to ride there cramped in a tiny pod. But we can't afford to continually send huge spaceships to the Moon. So the cycler was a way to inject an element of reusability into the system. Launch the big heavy thing once, then just launch people to it over and over again. It made a certain amount of sense.

But with Starship hopefully flying eventually, there will be a fully reusable craft that can take dozens of people to the moon at once, or take 50 tons of stuff all the way to the lunar surface then fly home and land. Reusability and in-space refueling changes the entire equation. I'm not sure the cycler makes sense in a world with the SpaceX Starship or Blue Origin New Armstrong in the mix.
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Old 09-10-2019, 06:40 AM
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I agree with Little Nemo. By far, the biggest difference would be our computer technology. In the sixties, it was a joke compared to what it is now. Our advances in propulsion and ship design pale in comparison.
It is true computers are now much more powerful but I'm not sure that alone would make a major functional difference in a modern "Apollo" project.

The original Apollo project was not made possible by on-board computers. In fact the primary navigation mode was ground-based. The idea of using the on-board computer for fly-by-wire control was added late in the project. Before that it was simply a backup navigation method to the ground-based primary method. Originally the Apollo CSM and LM would use an analog control system. The CSM as flown did not have a backup computer like the LM but a non-computerized "Stability Control System".

Several unmanned Surveyor spacecraft soft-landed on the moon using only analog electronics, partially analog telemetry, and no on-board computer.

The Apollo LM had a practiced contingency procedure of liftoff and achieving lunar orbit without any computer whatsoever. If both LM primary and abort guidance systems failed, they could still control the vehicle. The procedure was use a stop watch and align successive window etchings with the lunar horizon every few seconds.

Without an on-board computer or guidance system they would have no means of determining cross-track error during the lunar ascent, which in turn determines orbital plane. However huge 210-foot radar dishes and mainframe computers on earth would analyze spacecraft doppler data in real time (even at lunar distance) and give verbal guidance commands of trajectory cross-track and altitude to the astronauts.

The Gemini program proved you can rendezvous and dock without any on-board computer. The spacecraft had a very primitive digital computer (even by Apollo's standards) but they were prepared to rendezvous without this and practiced it.

So it is likely that given the right mission mode and vehicle design, a manned lunar mission could have been done without any in-flight digital computers. It would have been more expensive and riskier, but possible.

A modern "2019 Apollo" mission would use much more powerful on-board computers and tasks that were formerly manual would likely be automated. However this by itself doesn't mean the overall mission would be cheaper, safer or faster to develop. Ultimately the forces, materials, risks and energies required to throw a 100,000 lb spacecraft assembly to the moon, land and safely return are roughly the same now as in 1969.
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Old 09-10-2019, 07:35 AM
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I wasn't aware that they almost died. Armstrong was a damn good pilot. There is probably better technology now, I wonder if there was a gyroscope failure on that mission. Three rings spin in a gyroscope, and if two of them move to together, the gyroscope is locked and the spacecraft cannot manuver. There may be electronic versions now that do not lock.
Gimbal lock is a real issue with mechanical gyros, but as joema has explained, that wasn't the problem on Gemini 8.

Ring laser gyros are indeed immune to the gimbal lock problem, since they don't actually have any gimbals.
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Old 09-10-2019, 09:03 AM
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The Gemini 8 case and the so-called "checklist errors" on Apollo 10 and 11 are examples of how modern computers could possibly improve safety. In Gemini and Apollo it was up to the astronauts to set many switches and enter sometimes hundreds of DSKY keyboard commands. There was very little error checking. A wrong switch position could have killed them and in Apollo 10 it nearly did.

With Gemini 8 a modern on-board computer would be constantly monitoring all switch positions and various "talk back" indicators. A stuck thruster would have instantly been identified. Just like some modern fighter planes take control from the pilot to keep from hitting the ground, a modern crewed spacecraft would likely try to auto-stabilize itself or automatically shut down a stuck thruster. In Apollo 10 a modern computer would have likely identified the PNGS/AGS switch position error, or maybe avoided the error through automation.
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Old 09-11-2019, 03:18 PM
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Some of the unused lunar modules were sold for scrap. I wonder what they went for.
Hope they removed the gold foil first!!


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Old 09-11-2019, 04:08 PM
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It is true computers are now much more powerful but I'm not sure that alone would make a major functional difference in a modern "Apollo" project.
Except for being able to say "Man on the Moon" we probably would not send astronauts to the moon for exploration in 3019, IMO.

The comms transit times are short enough to permit near-real time control of an unmanned lander and explorer (and we've learned enough from the Mars lander programs to automate landing and semi-autonomous nav).

Landing, looking around for a few hours, grabbing some samples and returning home? Exceot for bragging rights we'd send a robot or three instead of humans.
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