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Perseverance Rover lands on Mars [video]

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Re: Perseverance Rover lands on Mars [video]

#161

Post by m4rtink »

erulabs wrote: post #120
thelean12 wrote: post #98

Earlier quoted context omitted.

> Also, remind me, did NASA develop reusable rockets? I can't tell if this is sarcasm or not but... yes, of course NASA developed reusable rockets. The space shuttle missions reused the shuttles and the boosters.

They did, you're not wrong at all, but just to add a little bit of clarity the space shuttle was never as reusable as was hoped - it wound up costing a huge amount of time and money to retrofit the shuttle again before each launch. Reusable and Re-usability are different things :P As far as I know no solid state boosters were ever re-used (how would that work?) - but then again SpaceX doesn't re-use solid state boost…

The SRB segments vere regularly reused, not sure about the parachutes and the nozzle stearing gear. Still reportedly it was more expensive to reuse the segments (basically big metal tubes) than to build new set if SRBs for each flight, possibly using better techniques (monolithic carbon fibre overwrapped solid motors, like on Ariane 5/6).

Re: Perseverance Rover lands on Mars [video]

#163

Post by FrojoS »

raphaelj wrote: post #47

NASA's ability of succeeding at landing things successfully on the first try on foreign bodies since 1969 is mind-blowing. Meanwhile, SpaceX takes half a dozen tries before managing to do the same on a fully known environment on Earth.

Rediciolous comparison.

The size of the objects that SpaceX is landing is much larger. The approach that was used here for Perseverance (Skycrane) would not work for larger ships, like those required for a human mission. Just like the previous approaches, e.g. Lithobraking with Spirit and Opportunity, would not have worked for Perseverance.

Larger objects are much more difficult to land. Simply put, while mass will increase by the power of three, surface area, which is used for aerobraking only scales by the power of two, relative to size.

In order to land something large enough to carry and support humans (10-100t), you need hypersonic retropropulsion. Guess who was the first to achieve this? SpaceX. And they remain the only ones. When they light the three engines for the entry burn the earth atmosphere is very similar to the relevant section of the future Mars decent. By developing the first stage landing of Flacon 9, they solved one of the biggest development challenges for humans landing on Mars and it was not by accident. NASA was very happy to get that data and helped them collect it with their chase planes.

Re: Perseverance Rover lands on Mars [video]

#164

Post by jussij »

garden_hermit wrote: post #44

Watching these is always a stressful experience, I can't imagine what it would be like sitting in that room, praying that the object you spend years of work on is able to land by itself 7 light-minutes away. I'm looking forward to what Perseverance will teach us.

This morning on the radio and Australian scientist told the listeners he had spent 10 years working on his small part of the Perseverance mission.

That would help to make the landing quite a nerve racking event.

Re: Perseverance Rover lands on Mars [video]

#165

Post by koheripbal »

tectonic wrote: post #14

You can also watch an EDL visualization in your browser: https://eyes.nasa.gov/apps/mars2020/#/home And read about how it will use Terrain Relative Navigation to find a safe landing spot: https://www.jpl.nasa.gov/news/a-neil-armstrong-for-mars-land... Perseverance is phenomenally complex, its Sample Caching System alone contains 3,000+ parts and two robotic arms. So exited for all the sciencing this nuclear-powered,…

Any idea when they will start experimentation? I want to find microbial life!

Re: Perseverance Rover lands on Mars [video]

#166

Post by avereveard »

alach11 wrote: post #20

Watching the stream, it's striking the difference in employee age between NASA and SpaceX. I won't speculate on the reasons, but I wish the best to the Perseverance team!

I don't think the video show a representative sample of the employee at either company; I suspect picks where selected for stage presence with a touch of preference for diversity.

Re: Perseverance Rover lands on Mars [video]

#167

Post by unanswered »

Something I don't understand: when they say "X is 1 minute from happening", does that mean it's really 1 minute from happening or does that mean "in 1 minute we'll receive the signal that X has happened"?

Maybe my question makes more sense in the case of "X is happening right now", because then I should either understand "we infer that X should have happened right about now" or "we have confirmed via signal that X has happened", and that's a big big difference.

I know in some cases they explicitly say the latter, so I guess my real real question is, do they just keep the communication delay implied in all countdowns & references in discussion, to avoid confusion?

(ETA: No need to let me know about simultaneity problems in relativity — earth and mars are, relative to c and to macroscopic time scales, essentially not moving relative to each other AFAIK, so that simultaneity is essentially well-defined. My question was about a much more boring classical-universe problem.)

Re: Perseverance Rover lands on Mars [video]

#168

Post by retzkek »

erulabs wrote: post #120
thelean12 wrote: post #98

Earlier quoted context omitted.

> Also, remind me, did NASA develop reusable rockets? I can't tell if this is sarcasm or not but... yes, of course NASA developed reusable rockets. The space shuttle missions reused the shuttles and the boosters.

They did, you're not wrong at all, but just to add a little bit of clarity the space shuttle was never as reusable as was hoped - it wound up costing a huge amount of time and money to retrofit the shuttle again before each launch. Reusable and Re-usability are different things :P As far as I know no solid state boosters were ever re-used (how would that work?) - but then again SpaceX doesn't re-use solid state boost…

> s far as I know no solid state boosters were ever re-used (how would that work?)

Nitpicking of "reuse" vs "refurbish" aside the SRBs were significantly reused:

> The RSRM was designed to make the most use of recoverable hardware. The majority of metal hardware was recycled through ATK’s Clearfield refurbishment plant in Utah and returned to a flight-qualified conditioned.

https://ntrs.nasa.gov/citations/20120001536

The boosters used for the final mission, STS-135, even included parts from STS-1! https://spaceflightnow.com/shuttle/sts135/fdf/135srbs.pdf

Re: Perseverance Rover lands on Mars [video]

#169

Post by shadowgovt »

raylus wrote: post #147
shadowgovt wrote: post #8

Earlier quoted context omitted.

Yeah, it was accessible until they mentioned it in the livestream. To their credit, I've watched NASA spend decades getting better at Internet services and generally being an online presence. Improvements year-over-year have been noteworthy. But I still have to chuckle a little bit that they triggered a DDOS protect by name-dropping themselves. Ad Internet Per Aspera, you crazy spacers ;)

Thanks!! Also wanted to mention, NASA is separate from JPL for the most part as far as web services go.

Great work today.

Re: Perseverance Rover lands on Mars [video]

#170

Post by PeterisP »

Daho0n wrote: post #136
emilecantin wrote: post #75

Earlier quoted context omitted.

Perseverance is one of the largest objects that NASA landed (along with the Apollo lander), and it's about the size of an SUV. SpaceX is trying to land things the size of buildings. Let's just say it's a very different problem.

.

Neither Perseverence or SpaceX landings involve latency for control commands, they are automated/preprogrammed in the vehicle and do not rely on real-time commands from the ground.
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