Dear NASA. Please dial back the poetics and rhetoric. Be more like ATC than Shakspear.
I read "Shakspear" as a combination of Shaquille O'Neal and William Shakespeare.
Artemis II safely splashes down
141–150 of 475 posts
Re: Artemis II safely splashes down
#142Earlier quoted context omitted.
> I think that NASA did a remarkable job of making Artemis II look almost routine and I don't think that was down to behaving as they did in the past. I have been excited for Artemis--yes it's big and expensive and late, but look how it has brought out the best of what humans can be--but, despite all that, the heat shield situation was textbook "normalization of deviance." Just as the O-rings were not designed to hav…
There will always be issues on something a mad as putting some people on a firework and shooting them at a moving target 100,000 miles away from a moving platform. The heat shield failure was a test and the result was a working heat shield, when it counted. That's the point of tests. NASA already had several working heat shields from the old missions but the new one needed testing - for the shape of the craft etc. Th…
The new one failed in ways it was not designed to fail. In C-compiler terms it was "undefined behavior." In Donald Rumsfeld terms it was an "unknown unknown."
The mere fact that the outcome was successful does not inherently indicate that the decision-making was safe: the O-rings "worked" for 24 missions and the foam/tiles "worked" for 111. Nevertheless there were ample warnings and close calls.
Reentry from the Moon is not routine. Re-entry speed was about 40% faster than from low earth orbit, and kinetic energy goes up by the square, so about double.
Re: Artemis II safely splashes down
#143Earlier quoted context omitted.
The analogies for these things like "hitting a golf ball into a hole in one 5,000 miles away" are always fun. I like starting from the fact that Ptolemy was able to get the accuracy of the "motions of the heavens" down so well that it took more than a thousand years to get observations that showed discrepancies. The math, it maths.
I feel like it’s “easier” with space math because there’s so little to interfere with the course. With a golf ball, the basic math is easy, but the slightest bit of wind throws it off way beyond the acceptable error, and you can’t model all the wind perfectly.
Agreed.
Fun info: The NASA orbital codes include things like photon pressure... from sunlight reflected off of other planets in the solar system. At some point, I think they are just showing off :)
Re: Artemis II safely splashes down
#144Earlier quoted context omitted.
Artemis rides on extended versions of the same SRBs that made the Shuttle ascent so dangerous.
Was any shuttle lost to the SRBs?
Yes, Challenger - although program management knew they were violating a launch constraint (temperature), and it was the low temperature that produced the conditions necessary for SRB failure.
As with any aerospace mishap, it's a chain of events, not just one cause.
Re: Artemis II safely splashes down
#145Earlier quoted context omitted.
Buoyancy is an easier equation to solve than lift.
>Buoyancy is an easier equation to solve than lift. That's a snappy one-liner but it doesn't address the real concerns. First of all, subsonic lift is well understood and has been for decades. The answer is much more mundane: The Artemis mission profile does not require payload doors that open, no Canadarm, no requirement to service, launch, and/or capture satellites in orbit, and so like good engineers they designed…
> subsonic lift is well understood and has been for decades
I said easy. Not well understood. I can fly planes. It’s hard, and has limited room for fucking up. (It’s also hyperbole to suggest we understand lift. We don’t.)
Piloting a boat is easier and more forgiving. Hence, splashdown. You don’t need direction. You don’t need lift. Parachute physics is a backbreaker, but it’s symmetrical. Same for splash.
Re: Artemis II safely splashes down
#146Earlier quoted context omitted.
The craft has aerodynamics and speed. It might be figuratively true "unrecoverable" but if it takes e.g. 2 weeks to complete a return, their oxygen and food and batteries ran out. Alternatively if it enters too fast they return ... in pieces. I think you're being a pedant, if your point is a grazing entry causing rebound skip ultimately returns to some orbital path downward.
You seem to intentionally be ignoring the original quote that any error may have caused them to be flung into space. This is patently false unless the one math error is pumping in hundreds of pounds more propellant and burning far longer than the scheduled burns. NASA would need to make a significant series of mistakes beyond orbital math for the "flung out into space" statement to be true. They certainly could've go…
This is underselling the risks. On top of the many trajectories which push them into unrecoverable situations, leaving them stranded in orbit, there can be trajectories where the moon gives a gravity assist strong enough to fling the spacecraft into escape velocity, fulfilling the OP.
In fact, the trajectory they chose for this mission exploited the opposite effect to yield a free return without propellant expense.
In the modern day, the chance of a math error being the root cause behind this failure mode are vanishingly small, but minor burn execution mistakes that do not require hundreds of extra pounds of propellant are definitely plausible. They were extremely common in the early days of spaceflight and plagued most of the very first moon exploration attempts. Again, with modern RCS this is unlikely. But reentry is still incredibly tight and dangerous. Apollo famously had a +-1° safe entry corridor, and Orion is way heavier and coming in even faster. If their perigee was off they could’ve easily burned up or doubled their mission time, which they may not have been able to survive.
Re: Artemis II safely splashes down
#147Earlier quoted context omitted.
I think especially online there's a lot of emphasis on "everything is wrong". A mission like this is hard to ignore and highlights the bias. On the whole, despite setbacks, we continue.
If you want to dispel a bit more of the ever-pervasive online pessimism bias, read up on global rates of hunger the last time we flew to the moon (1972) vs now. The reality is, for all the problems we face today, there's no sane answer other than today to the question "when would you prefer to be born as a random person on earth"
It is about trends and perceptions - 70s were very hopeful, now with global problems - wars, climate, AI, uncertainty, what is growing is desperation.
I definitely don’t envy kids that are born nowadays.
Re: Artemis II safely splashes down
#148Glad that they're safe and sound. It's worth pointing out that this is the first extremely public, widely acknowledged high risk mission NASA has done in over 50 years. The Shuttle was risky, but it wasn't thought of or acknowledged by NASA as being risky until very late in its lifecycle. According to NASA's OIG, Artemis acceptable crew mortality rate is 1 in 30. Roughly 3x riskier than the shuttle. There genuinely i…
> Artemis acceptable crew mortality rate is 1 in 30. This seems insane to me. That X decades later we accept, with all our advancements in tech, a weaker system than ever before. That if we send 30 people we _accept_ that one is possible to die. That's the starting point? That's what we document as acceptable?
Wai how is it weaker, like genuinely?
Re: Artemis II safely splashes down
#149Earlier quoted context omitted.
> Artemis acceptable crew mortality rate is 1 in 30. This seems insane to me. That X decades later we accept, with all our advancements in tech, a weaker system than ever before. That if we send 30 people we _accept_ that one is possible to die. That's the starting point? That's what we document as acceptable?
> That X decades later we accept, with all our advancements in tech, a weaker system than ever before how do you keep past performance while stop performing it for XY decades?
A lot of advancement is multipurpose. CNCs are more accurate than machinists, computers are faster. And we have a lot of the technical knowledge written down.
Re: Artemis II safely splashes down
#150Can somebody help me understand why this does a water landing, like the old Apollo missions, instead of like the space shuttle that lands like a plane?
A Space Planes is needed to land at a runway like a plane.
Space Planes are not only much more dangerous, but are not ideal for this type of mission. They carry a lot of extra weight (wings) that would affect how much fuel is needed to launch them to the Moon.
Capsules are safer and more lean in terms of weight.
The Shuttle was not ideal in many ways. It was used so long not because it was the best option, but because Congress wanted it to keep it going for jobs.