Heat Shield for NASA's Next Mars Mission Breaks During Testing

The heat shield for NASA's next Mars spacecraft just cracked open. Luckily, engineers found this out during testing here on Earth, long before the Mars 2020 rover mission leaves for the Red Planet in search of habitable environments there.

In preparation for landing, both the rover and the craft's landing gear will be encapsulated in a protective material — a heat shield — to keep them safe during the scalding trip through the Martian atmosphere

Source: Heat Shield for NASA's Next Mars Mission Breaks During Testing

This is why they test, test, test, test here before launching. Is this a problem for the mission, seems it will not be one......

Engineers discovered the fracture on April 12, after a week of structural testing at Lockheed Martin. The crack was unexpected, but NASA's Jet Propulsion Laboratory – which manages the mission development – said the mission should still lift off in 2020, as anticipated.

No cause is yet known for the Mars 2020 heat-shield crack. JPL struck a note of reassurance in its statement: "While the fracture was unexpected, it represents why spaceflight hardware is tested in advance so that design changes or fixes can be implemented prior to launch."

After all, this IS rocket science stuff.

a reply to: Krakatoa

But on a side note, NASA's Parker solar probe, had its final test today of its faraday cup - the apparatus that will scoop solar wind, and it passed.
That was the final test before launch.

The heat shield for the Mars lander will have all the kinks worked out long before the final launch window in 2020.

a reply to: Krakatoa

a heat shield — to keep them safe during the scalding trip through the Martian atmosphere

How hot can it get? The Martian atmosphere is 100 times less dense than Earths and there is a lot less of it in terms of altitude.

P

originally posted by: pheonix358
a reply to: Krakatoa

a heat shield — to keep them safe during the scalding trip through the Martian atmosphere

How hot can it get? The Martian atmosphere is 100 times less dense than Earths and there is a lot less of it in terms of altitude.

P

Those were my first thoughts too. Something about Mars is being withheld from the people who pay for these missions...which is all of us.

a reply to: pheonix358

there is a lot less of it in terms of altitude.

Actually, not terribly different. Since the surface gravity of Mars is so much less than that of Earth, its atmosphere extends just about as high even though it is not nearly as dense at low altitudes.

The upper reaches of both have about the same density. Fast things start to vaporize at close to the same altitude on both planets.
agupubs.onlinelibrary.wiley.com...

a reply to: Phage

From the source you quoted.

The temperature at the top of the density profile (around 140 km) is not known. In this study we assumed that it ranged between 100 and 250 K.

So ... they don't know but they do have models they work with.

Similar models on Earth have never got it right.

Mars has only 1 % of Earth's atmosphere and only 40% of our gravity.

Sorry, not yet convinced. Thank you for the reference Phage, it was interesting.

P

a reply to: Krakatoa
Even with testing things still can go sideways.

The cracked heat shield was first tested a decade ago, back in 2008. It was originally constructed as a backup shield for the successful Mars Curiosity rover.

originally posted by: pheonix358
How hot can it get?

Close to 1000º Celsius.

Until 2012 they had to base their calculations on theoretical models, as it's not possible to replicate the conditions on Mars here on Earth.

Because of that, the usual approach is, like in all technical problems, to over-engineer things, but that results in making heat shields that are probably too heavy for their work, on missions in which weight is one of the most important parameters.

With the Mars Science Laboratory mission the engineers finally had the opportunity (no pun intended ) to add several pressure and heat sensors to the heat shield, so they could get real data they could use to base their models on for future missions.

From what I could find on the Internet, this PDF file appears to explain it better (although too technical for my knowledge), and on page 8 we have this:



You can see the different data for the different sensors, with the highest temperatures reaching values close to 1000º C 0.254 cm (1/10 of an inch) below the surface on the area that was facing the descent.

originally posted by: pheonix358
a reply to: Krakatoa

a heat shield — to keep them safe during the scalding trip through the Martian atmosphere

How hot can it get? The Martian atmosphere is 100 times less dense than Earths and there is a lot less of it in terms of altitude.

Earth's atmosphere is just as thin as Mars' atmosphere at the point when a heat shield is required for atmospheric entry.

The altitude at which atmospheric entry on Earth occurs (and when the atmosphere begins to heat up objects coming in at extreme velocities) is about 60 miles up. At that altitude, Earth's atmosphere is extremely thin -- about the same density as Mars' atmosphere.

The altitude of atmospheric entry for Mars is about 50 miles. As phage mentioned above, due to Mars' lower gravity the atmospheric density does not vary as greatly from the surface to the altitude of atmospheric entry as it does for Earth.

Thank you all for the lesson.

With 40% Gravity, wouldn't your entry speed be a lot less?

Interesting subject.

P

a reply to: pheonix358

Reentry velocity is not the result of Mars' gravity field. It's more the result of the Sun, since the spacecraft is "falling" in orbit around the Sun on its way to Mars. It gets going really fast, something over 50,000 mph. That's relative to the Sun, it gets tricky trying to compare it to Earth (or Mars).

Maneuvering during what is called the Approach Phase (which begins 5 or 6 weeks before entry) sets up an atmospheric entry speed of about 13,000 mph.