Comment by somenameforme | Hacker News Reader

Comment by somenameforme | Hacker News Reader

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Obviously we'd been wanting to go to the Moon before that speech, but there was no secret technology that we were just being coy about. We still knew nothing, had nothing and were in the process of figuring out what John Glenn's fireflies were during a flight where, if he wasn't such an uncannily good pilot, he probably would have died.

Saying we'd be on the Moon in 7 years was not something that looked achievable except to the most fanatical of enthusiasts. To the average layman it would have sounded no less impossible than me saying we'll have a man on Mars in 7 years from today. And landing on Mars in many ways will be much easier than the Moon. Not only is the terrain broadly more hospitable, but you have an atmosphere to enable aerobraking which simplifies both landing and braking and enables various options (like some sort of parachute staging or backup). The biggest and really only complexity with Mars is its distance. Outside of that it's easy mode.

> To the average layman

That’s a meaningless yardstick here. People at NASA definitely thought hitting that target was achievable before the speech.

> Landing on Mars

Landing isn’t the issue. Get people there alive and having enough deltaV to get back is.

No, NASA also didn't think it was possible at the time. There's an informative little paper here. [1] It only gets more informative from the first sentence, "Mathematical risk analysis was used in Apollo, but it gave unacceptably pessimistic results and was discontinued." By the time of the launch to the Moon NASA's internal estimates were looking at around a 50% chance of success based on Gene Krantz's (mission controller) "Failure is Not an Option" book.

It was a mission they dedicated themselves to, and humans have this way of making things happen when we actually set our minds to tasks. A reality that's often been lost in modern times as we have mostly moved away from pursuing, let alone achieving, great things in the real world. One of the many reasons to get humans on Mars.

[1] - https://ntrs.nasa.gov/api/citations/20190002249/downloads/20...

You’re confusing specific low odds of success for “didn't think it was possible.”

The Apollo missions got unbelievably lucky in that none catastrophically failed despite multiple close calls. However, if you’re willing to try multiple times the odds any mission being successful is much better than every mission being successful.

IE: Six missions landed on the moon. If they each had independent 50% odds then six heads is a long way from impossible ~1.6%, but at least 1 head is quite likely ~98.4%. I doubt we would have tried for a 6th mission after 5 failures in a row, but the point is definitions of success matter a great deal here.

Similarly failures improve odds of success in the future because you learn from mistakes and success means the system is functional eliminating some risks.

What I'm demonstrating is that we indeed knew basically nothing. There was no secret tech or expectation of success. Mathematical models doomed the entire idea to failure, and all the way up to the day of the launch people who spent years in a bubble of optimism still didn't really expect more than a 50% chance of success.

> a 50% chance of success.

On that specific launch, which is another way of saying they believed the project had a very good chance of having someone walking on the moon. Failure there wouldn’t even mean people died, just that they didn’t walk on the moon and then safely get back on that mission.

That 50% was after years of bubble optimism and actively blinding themselves to data strongly suggestive otherwise.

Had the Apollo missions failed you would obviously be arguing, using the exact same data, that they 'knew they never had a chance.'

> Had the Apollo missions failed you would obviously be arguing, using the exact same data, that they 'knew they never had a chance.'

No, an earlier post argued that 6 successes doesn’t mean the odds of success on every mission was high. “Got unbelievably lucky” https://news.ycombinator.com/item?id=43130343

The exact opposite position after 6 failures would be that the odds were good that at least 1 mission would have succeeded.

Obviously, things aren’t actually completely independent, but 6 lunar landings could have successfully been completed with a huge range of different odds. 50% odds of success on the first launch isn’t inconsistent with 6 successful launches or 6 failures, it’s just not enough data to really narrow things down.

On the contrary, we can easily get people there alive. What exactly do you think is beyond our capacity to send crew to Mars while still being alive? Crew regularly do year long expeditions on ISS (edited for clarity), with total radiation dose similar to Mars transit (and show no measurable effects of that radiation).

Again, I’m addressing the point “getting them there alive”. Unquestionably, we know how to get crew to Mars alive, and even for the full mission duration, radiation isn’t even in the top 10 of the hazards that could actually kill them during the mission. (It’s a long term hazard, comparable to lung cancer if you’re a cigarette smoker.)

No one has ever done a "years long" expedition to ISS, and the radiation flux in transit to Mars, in particular GCR dose, is much higher than experienced on the space station.

I’m well aware, just mistyped. The total equivalent radiation dose on a fast transit to Mars is less than some ISS expeditions.

Note that the magnetic field only deflects lower energy galactic cosmic rays which have a lower gyro radius than the real whoppers. The magnetic field is less important to overall radiation shielding than the earth’s atmosphere.

Total GCR dose is 3-5x in transit to Mars compared to what you get on ISS; on the Martian surface it's from 1.5-2x the ISS dose. (see https://www.swsc-journal.org/articles/swsc/pdf/2020/01/swsc2...).

On a long-stay Mars mission, that adds up to 12-18 times the accumulated GCR exposure compared to a six-month ISS increment.

Ah, you’re being tricky. You’re ignoring the substantial trapped radiation dose on ISS (it is, after all, the total dose that causes the defects). That, combined with GCR, gives an equivalent dose the same at Curiosity altitude as on ISS.

In fact, look at Table 2. It shows that at ISS, the dose from the SAA is about the same as the GCR dose, so by ignoring trapped radiation, you’re manipulating the result by a factor of 2.

The world record duration still sits at 438-days after 35 years. We limit people below that due to medical issues, suggesting no we don’t know how to safely do multi year space flight.

It’s possible people spending significant time on the surface of mars would recover, but that’s more speculation than proven.

The person who went 438 days was Valeri Polyakov, and he experienced exactly 0 ill effects from such, going so far as to intentionally briefly walk immediately after landing precisely in order to demonstrate that working on Mars after any transit would be possible.

Going beyond that is not really meaningful since that's far longer than any normal transit to or from Mars, which is the immediate target.

[1] - https://en.wikipedia.org/wiki/Valeri_Polyakov

A young formally fit person being capable of making a few steps doesn’t demonstrate “0 ill effects.” He was vastly weaker upon his return as shown by making a few steps being considered a significant achievement rather than an actual sign of fitness like lifting a heavy weight and moving it around.

Living on mars at 38% earths gravity is believed to make things worse over time, so no you can’t just consider transit times independently. On arrival they would likely be fine inside a habitat. But trying to walk around in an Apollo 11 era 180 lb pressure suit in 38% gravity would be nearly as strenuous as walking around on earth and we’d like them to be able to work not just take a few steps and sit down. It’s possible to reduce that weight, but needing to carry oxygen tanks means there’s quickly a tradeoff between lighter weight and less time outside.

Now, for an extremely brief touch Mars and come back while burning a huge amount of fuel to make a shorter trip sure they’ll survive. But start talking a 3 year mission and things don’t look good.

Polyakov was 52 years old when he did his 438 day stay, and astronauts always take a couple of days to readjust to gravity. The overall effects of well over a year in space seem pretty comparable to a few months in space. It's just not a big deal. Those Boeing astronauts (both around their 60s) have been stuck on the ISS for going on 9 months now, and NASA's basically like ¯\(ツ)/¯.

Back on Mars they'll be able to quickly regain their motor skills coordination, as well as strength/bone density. So it will be effectively equivalent to Earth in this regard - actually it will be even better than Earth because the reduced gravity will probably send the overall adjustment time down from a couple of days to a couple of hours, especially with a normal duration transit.

Yep 52, as I said still young. John Glenn flew a useful mission at 77 that’s old. Strength will often peak around 35 barring significant injury. Show me a 52 year old who’s happy to make a few steps and I’ll show you someone with significant impairment.

> stuck on the ISS for going on 9 months now

Stick right next to earth and all the medical care they would want on landing. That’s the difference they don’t need to be functional on earth.

> regain motor skills and coordinate

Meaning they’re nearly helpless for a significant period on landing. That’s a massive safety concern and limitation on mission profile.

> as well as strength/bone density

There’s serious concern around retaining let along regaining bone density on Mars. 38% g isn’t a well studied environment here but it’s a long way from earth and likely to result in significant bone loss up to a point. Meaning their trip back is now significantly more risky.

Never double down on stupid, just don't. At some point it might not just become a show.

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