90 votes
Accepted

Why was it necessary to program InSight with an ability to land in dust storms?

Because it's at the end of a 6 month cruise and there's no turning back. InSight will not enter closed orbit around Mars - its trajectory is hyperbolic so either it misses Mars entirely or it enters ...
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  • 9,834
55 votes
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What is a "suicide burn"?

For a powered descent to the surface of a massive body like the Moon, it turns out to be most fuel efficient to do all your deceleration at the very end of the trajectory, right before impact. (This ...
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32 votes

Why was it necessary to program InSight with an ability to land in dust storms?

InSight doesn't enter Martian orbit before EDL; it plows straight into Mars' atmosphere from interplanetary space. Thus, the time of landing is pretty much un-alterable after its final midcourse ...
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27 votes
Accepted

Why is InSight's nylon parachute a "soft good"?

I'm pretty sure that by "soft good" he means it's an element of the system that can't be completely constrained from a simulation or engineering standpoint, in this case fabric. If you're working with ...
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  • 14.6k
22 votes

Why won't NASA show any computer screens?

A long, long time ago, I managed to arrange to get two passes to see the first light from one of the Voyager flybys of Jupiter. I collected on lots of debts and pulled lots of strings to get those ...
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  • 62.9k
21 votes

Is there a risk that re-entering capsules or other components will hit ships or islands?

Partial Answer: From Apollo by the Numbers we can see that even in the 1960s and 1970s the splashdown point was quite predictable. Page 305 shows the maximum miss distance to the target point was 3 ...
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17 votes
Accepted

When things land on Mars what fraction of their velocity do they remove propulsively?

Taking Mars Pathfinder and Viking 1 as examples: Mars Pathfinder was a direct entry at 7600 m/s and removed about 0.7-0.8% of that propulsively. Parachute deployment was at 360-450 m/s, and landing ...
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16 votes

How does a Mars lander reach a chosen landing site?

There are typically five planned trajectory correction maneuvers on the way to Mars, referred to as TCM-1 to TCM-5. (Also there is a slot for an emergency TCM-6 a few hours before entry, but it is not ...
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  • 57.5k
15 votes

Curiosity and Perseverance landing - with so much dust blown everywhere, what's the point of the skycrane?

because it would prevent the rockets from contaminating the landing site. No they weren't There was some possible advantage from that, to be sure. But missions to Mars undergo serious levels of ...
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  • 1,728
13 votes
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What happens to Insight's parachute on Mars?

I'm pretty sure it will be like the Phoenix lander. Collectively that part of the lander is referred to as the "Backshell". This is the image of Phoenix of the hardware on the surface. This is ...
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  • 118k
12 votes
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How does a gamma ray altimeter work? What kind of sensor is used?

It's called the "Kaktus-2". The sensor is referred to as a "NaI(TI) crystal detector" which appears to be a scintillation counter. The device has a 2 of 3 voting scheme to avoid false positives. "....
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12 votes

Is there a risk that re-entering capsules or other components will hit ships or islands?

Partial answer: According to russianspaceweb.com, there are a set of large, pre-selected landing sites for the Soyuz capsules. Soyuz can land with an accuracy of only 28 kilometers, (with a ...
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11 votes
Accepted

Why does in-flight mission abort often ends in ballistic high-g reentry?

When you're in orbit you have velocity roughly parallel to the atmosphere, a flat-ish shape angled properly can "fly" across it in a lifting entry where you can dissipate energy in the thinner upper ...
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  • 18.7k
11 votes

What happens to Insight's parachute on Mars?

During the parachute descent, InSight's trajectory is at an angle to the vertical. After the backshell and parachute separate, the engines fire, leveling the craft. This allows some horizontal ...
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  • 46.3k
10 votes

Can a blimp dead drop on Mars or Earth this way?

NASA is working on an inflatable heat shield. Not quite a blimp, but a heat shield that's inflatable to a size much larger than the probe it's attached to. The extra area helps decelerate the ...
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  • 121k
9 votes
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Blimp on Earth, but a glider on Mars?

Unfortunately my answer won't contain the crucial "yes" or "no" - for the simple reason that one hinges upon fine parameters and would likely require a good NASA study for actual answer. But the ...
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9 votes
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Archimedean braking for low density Venus lander + subsidiary question

Surprisingly the answer is yes there was studies done on that subject. A simple google search could yield this result: BUOYANT PLANETARY ENTRY https://apps.dtic.mil/dtic/tr/fulltext/u2/642361.pdf ...
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  • 12.2k
9 votes
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How long does the descent of the Falcon 9 first stage take?

It will vary somewhat mission-to-mission, but it's generally about 6 minutes from separation to first-stage touchdown. It's not very different between LEO and GEO missions, as the first stage only ...
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9 votes

Is there a risk that re-entering capsules or other components will hit ships or islands?

The first of your several questions is about controlled reentry of devices designed for reentry. You then ask about devices not designed for reentry, which I address (partially). Undesigned reentry ...
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9 votes

Why won't NASA show any computer screens?

In trying to explain my feelings on this question in comments on the other answer, I came around to a possible explanation -- There could be a real PR cost to publishing raw data streams in real time. ...
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  • 6,377
8 votes

How different was the Apollo LM descent trajectory from the most fuel-efficient?

The limiting case assumes a perfectly spherical moon and a lander that can do instantaneous burns of any magnitude. In this case, starting from a 110km circular orbit, the lander does a brief burn ...
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8 votes
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Meteor color hints at chemistry

Absolutely, it's the same as heating up metals with a blowtorch. The colour of the flame tells you what is present. Wikipedia actually has a handy list giving an indication of the significant elements ...
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  • 13.4k
8 votes
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Can we significantly reduce entry velocity with this method by airbraking alone for interplanetary travel?

You can use skip reentry to gradually reduce your speed when arriving from an interplanetary journey. NASA also studies skip reentry for the Shuttle, as a way to reduce the heat load during reentry. ...
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  • 121k
8 votes

Why was it necessary to program InSight with an ability to land in dust storms?

To deal with dust storms, two of the changes between Phoenix and InSight are mechanical in nature: InSight uses a thicker heat shield, partly to handle the possibility of being sandblasted by a ...
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  • 46.3k
8 votes
Accepted

Why Crew Dragon needs 18 hours between ISS separation and descent?

There are a few necessary activities and schedule considerations that contributed to needing 18 hours between undock and entry. Sleep Loading the Crew Dragon with returning (“down-mass”) gear, ...
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8 votes

Curiosity and Perseverance landing - with so much dust blown everywhere, what's the point of the skycrane?

The two media articles I have been able to find on this, at Spaceflight Now and Space.com, didn't really talk about the problem of material being blown around by the rockets. According to both ...
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  • 6,903
7 votes

Can a reusable electric powered blimp stage for launch possible?

Context Mars density is less than 1% of earth's. This is what earth looks like from 30 000 meters high (where air is about as dense as Mars) It's going to be too heavy Using this book as a reference, ...
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  • 12.2k
7 votes
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What is crossrange and downrange for an entry vehicle?

Downrange is the distance traveled in the direction of flight. Imagine the orbit of a spacecraft as a circle around the Earth, 'downrange' is the distance traveled along this path. When you do a ...
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  • 121k
7 votes
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How could the landing date of Perseverance Rover be fixed irrespective of 26 days launch window?

It is deliberate choice. See this tweet from Tory Bruno, CEO of ULA who is launching the mission. This of course doesn't tell us the exact reasoning behind the date, however. Why this is is actually ...
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