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Artemis II safely splashes down

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Re: Artemis II safely splashes down

#81

Post by numpad0 »

philistine wrote: post #18
loloquwowndueo wrote: post #14

Earlier quoted context omitted.

Everything. No radio signals make it in or out of the capsule due to ionization from the heat and plasma of reentry.

I’ll note, since it is supremely interesting to me, that Starship is able to communicate with the ground during its whole reentry due to its sheer size and ability to connect with Starlink satellites. I assumed loss of signal due to reentry was a given for any spaceship!

Shuttle in its last days had antennas that protruded outside the plasma just enough for telemetry. Apollo and Artemis reentry are also direct entry from Lunar-Earth transfer orbit using ablative heat shields, so the plasma would be hotter and thicker than suborbital Starship shots with Shuttle style ceramic tiles.

Re: Artemis II safely splashes down

#82

Post by brianjlogan »

As an American I feel like I've been going through a bit of an identity crisis from what I remember growing up.

Probably the rose tinted glasses of being a child but being from Florida I always had a sense of amazement and wonder as I heard the sonic boom of the shuttle returning to earth.

Really felt like I was coexisting in this incredible scientific powerhouse of a country full of bright and enabled peoples that knew how to prioritize curiosity and innovation.

Feeling like a bit of a "vibe" post which is everything wrong lately but I can't help but feel some satisfaction that we're still able to accomplish something like this in our space endeavors.

Re: Artemis II safely splashes down

#83

Post by misterprime »

philistine wrote: post #18
loloquwowndueo wrote: post #14

Earlier quoted context omitted.

Everything. No radio signals make it in or out of the capsule due to ionization from the heat and plasma of reentry.

I’ll note, since it is supremely interesting to me, that Starship is able to communicate with the ground during its whole reentry due to its sheer size and ability to connect with Starlink satellites. I assumed loss of signal due to reentry was a given for any spaceship!

Yes, I remember when they used the signal out the back through the plasma during reentry. It was astoundingly good!

Re: Artemis II safely splashes down

#84

Post by albumen »

llbbdd wrote: post #52
philistine wrote: post #18

Earlier quoted context omitted.

I’ll note, since it is supremely interesting to me, that Starship is able to communicate with the ground during its whole reentry due to its sheer size and ability to connect with Starlink satellites. I assumed loss of signal due to reentry was a given for any spaceship!

Would this capsule had been been able to communicate if it was integrated with starlink or is the size more important? I'd imagine if they could have achieved communication via Starlink they would have done it, but just curious.

No, the plasma forms a teardrop shape around small craft like Orion, completely cutting off radio comms. Larger craft like starship or the shuttle which have a roughly cylindrical shape (vs Orion’s circular cross section) aren’t fully enclosed by the plasma. The shuttle had a transmitter attached to its tail for later flights, which could send back telemetry during re-entry.

Re: Artemis II safely splashes down

#85

Post by llbbdd »

brianjlogan wrote: post #82

As an American I feel like I've been going through a bit of an identity crisis from what I remember growing up. Probably the rose tinted glasses of being a child but being from Florida I always had a sense of amazement and wonder as I heard the sonic boom of the shuttle returning to earth. Really felt like I was coexisting in this incredible scientific powerhouse of a country full of bright and enabled peoples that k…

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.

Re: Artemis II safely splashes down

#86

Post by gerdesj »

Waterluvian wrote: post #43
philistine wrote: post #23

Earlier quoted context omitted.

I’d bet a million dollars that Orion will win every safety metric compared to the shuttle once it is retired. NASA deluded itself in thinking the Shuttle was safe. The reality is that the Shuttle was the most dangerous spaceship anyone ever built.

Space flight safety is a function of culture and I don’t have any confidence that the culture has improved.

I think we are a long way along from digging out Dr Feynman to look into why a shuttle exploded.

Unless you happen to have some deep links into NASA, in which case please elucidate us all, then why not celebrate a happy and safe return from a sodding dangerous mission that involved things like >25,000 mph relative velocity and some remarkable navigation.

When you depart earth (close quarters gravity, air resistance, things in the way), everything moves really fast, really fast and any acceleration becomes an issue really ... fast!

The moon moves, the earth moves: both famously in some sort of weird dance around each other and both orbit around the sun. Obviously the moon affects the earth way less than vice versa but it still complicates things.

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.

Re: Artemis II safely splashes down

#87

Post by marssaxman »

philistine wrote: post #23
areoform wrote: post #11

Glad 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…

I’d bet a million dollars that Orion will win every safety metric compared to the shuttle once it is retired. NASA deluded itself in thinking the Shuttle was safe. The reality is that the Shuttle was the most dangerous spaceship anyone ever built.

How could a comparison between such dissimilar programs ever be meaningful? NASA flew 135 Shuttle missions over the course of 30 years; Orion will be doing well to approach a tenth of that number.

Re: Artemis II safely splashes down

#88

Post by 420official »

ggm wrote: post #57
gct wrote: post #53

Earlier quoted context omitted.

Orbits do not work that way

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 gotten the return wrong but with a perigee of 119 miles they arent even in a stable orbit and likely could deorbit themselves using only rcs thrusters at apogee, or by just waiting a few orbits.

Re: Artemis II safely splashes down

#89

Post by rmunn »

Best comment exchange from a thread on a different site:

OP: "I'm happy they didn't die."

Response: "You're going to be less happy when they turn into the Fantastic Four and Dr. Doom shows up."

Re: Artemis II safely splashes down

#90

Post by Rebelgecko »

llbbdd wrote: post #8
Levitating wrote: post #5

Earlier quoted context omitted.

The LOS was also more than 6 minutes as predicted (I measured a bit over 7 minutes). What a tension.

I wasn't clear, was the LOS just comms or a full loss of telemetry from the craft? Either way, terrifying.

It seems like they had limited telemetry for a short period before they did any audio
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