90

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 the atmosphere. There were six planned course corrections during the cruise phase, the final one of which - TCM 6 - occurred on the day of the landing. This ...


55

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 is because if you decelerate sooner than that, you will be in flight longer; the longer you're up, the more fuel you need to spend counteracting gravity ...


41

I think you may be confused about the nature of the problem the skycrane is trying to solve (however I also may be confused!). The rover, being a rover, does not need to stay at the landing site. If the landing site has a lot of dust blown off it, well, they can go somewhere else where the dust has not been blown off the surface. As the other answer says ...


32

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 correction maneuvers; it cannot wait for perfect weather conditions to land.


26

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 static systems or systems with a limited amount of degrees of freedom, it's possible to calculate and analyse every possible state the system can be in. For ...


22

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 passes. I brought a date. She. Was. Bored. (Needless to say, that was the end of that relationship.) And that was the first light from a vehicle that whose sole ...


21

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 nautical miles. The maximum distance to the recovery ship was 13 nautical miles. Note that the Apollo capsule was actively flown during entry by rolling the lift ...


15

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 rocket ignition at 52-64 m/s which slowed the vehicle to 0-25 m/s before cutting the bridle: https://mars.nasa.gov/MPF/mpf/edl/edl1.html Viking 1 landed from ...


14

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 decontamination to ensure contamination from Earth doesn't happen, so the risk was marginal at best. If you meant contamination from hydrazine, that's not a ...


13

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 expected to be used.) Also I sometimes refer to launch as TCM-0. That's the really, really big TCM. TCM-0 provides the energy to place the aphelion of the ...


13

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 mentioned in the official timeline. Powered Descent - Once the lander separates from its backshell and parachute, 12 descent engines on the lander begin firing and ...


12

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 probability of 0.9997), in the automated aerodynamic descent mode, AUS, relative to the center of the projected landing area. The main reason for such a low precision is ...


11

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 atmosphere before you hit thicker atmosphere. The first stage of a rocket uses most of its energy to gain altitude, getting above the thickest part of the ...


11

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 separation between the parachute and the craft: 11:52 a.m. PST (2:52 p.m. EST) — Activation of the radar that will sense the distance to the ground 11:53 a.m....


10

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. "...the source emits 13.7 Sv/hr point blank at 1 cm, and 1.3 mSv/hr at one meter. That's quite hot :)" Here's a picture of the device. And here's a block ...


10

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 spacecraft. So inflatable structures can be made to withstand the heat of reentry. Because Mars' atmospheric density is only 0.6% of Earth's, a blimp's lift will ...


9

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 answer I can give without that currently is "Quite likely so." 1) matter of sustaining the blimp in void. That one's easy "yes". If the blimp's envelope rated ...


9

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 In this study, it was assured that the large buoyant volune is deployed prior to atmospheric entry. The effect of buoyancy on the entry dynamics was ...


9

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 gets to around 1/4 of orbital speed. Here's the timeline for ANASIS-II, a GEO-bound launch. Stage separation is at T+2:36 and first-stage touchdown is at T+8:31. A ...


9

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 can be rather imprecise. Taco Bell made a sizeable bet on this imprecision. The Progress M1-5 deorbit of Mir had relatively large location uncertainty. (This ...


9

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. There's certainly a vocal subset of space geeks who want to see this. It would inevitably spawn hours of commentary in forums and on YouTube, folks with a wide ...


8

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 present: Orange-yellow (sodium) Yellow (iron) Blue-green (magnesium) Violet (calcium) And Red (atmospheric nitrogen and oxygen)


8

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. So you could use this technique to get below orbital speed before the final reentry starts. The lower your speed gets, the more difficult it will be to keep ...


8

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 dust storm. InSight’s parachute suspension lines use stronger material. https://mars.nasa.gov/insight/timeline/landing/entry-descent-landing/ The ...


7

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 to drop periapsis to 0 altitude, then burns to cancel its entire surface-relative velocity all at once when it gets there. The initial burn is about 25 m/s; ...


7

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, we can see that to lift 1T to 30 000m we need a 10T balloon (accounting for balloon and lifting gazes). Of course you'll need more since you'll want to produce ...


7

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 ballistic (uncontrolled) reentry, this is the path you travel. Crossrange comes into play when you make a turn, and you deviate from your orbit. It's the distance ...


7

Of your list only Soyuz, Dragon, Crew Dragon safely make it to the surface of the earth. ATV, HTV, Cygnus, Progress all burn up during rentry. For the first Crew Dragon mission, undocking from the station to landing is about 19 hours. The perhaps more interesting question is more from deorbit burn to landing. Which Wikipedia has as just under an hour. (52 ...


7

From the moment they undock from ISS to the moment they touch land (or splash into ocean water) In the case of the Crew Dragon Demo-2 flight it was a little over 19 hours, but for most of that time the Endeavour wasn't descending, but just orbiting. From the initiation of the descent burn to splashdown was about 52 minutes. Here's the planned return ...


7

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, readying the capsule for undocking and maneuvers, and prepping the astronauts themselves is a full day of work, even for the three U.S. astronauts that were on the ISS....


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