Hot answers tagged

70

Maybe some visual intuition for what actually happens in the Hohmann transfer helps? It's already very close to what you are describing. In the top arc, the spacecraft (yellow), is going a bit slower than Mars (red), so it's indeed "waiting" for the planet to catch up to it. It only touches the orbit of Mars in a point, but that's all we need if we time ...


38

It depends whether or not you want to orbit or land softly upon Mars, or just hit it. For the former, you have to match orbits with it, that probably means burning more fuel. For the latter, you can skip the Mars orbit injection and just crash. This is quite fuel efficient, especially as the reduced delta-V requirements mean that you need less fuel for the ...


17

could we launch a vehicle in space for Earth, stop right on Mars trajectory... Yes, you could have a trajectory that came to a stop (briefly) in the path of Mars like how a ball thrown upwards stops (instantaneously) before falling down, except in this case you'd have to be moving directly away from the Sun on a straight-line trajectory with eccentricity = ...


8

Partial answer because I learned a new word. The lines / treads on the wheels are called "grousers" and they are indeed wavy. Why: Extensive testing in JPL's Mars Yard has shown these treads better1 withstand the pressure from sharp rocks but work just as well on sand. (from the 1st link) 1In comparison to Mars Science Laboratory's wheel design


7

There is no "stopping" in space - no matter how far you are from other celestial bodies, the force of gravity will always be tugging on you, pulling you in some direction. Within the Solar System, that tug is typically pulling you toward the Sun, unless you happen to be quite close to another planet or moon. If you were to try to get to the same path as Mars ...


4

Earth has a much larger and fluffier atmosphere than Mars. Mars’ atmosphere provides little deceleration until about 50km or below (depends on location and angle), but then the deceleration turns on quite solidly. The result is a very narrow window to do any maneuvering in the brief interval that the speed is dropping. Source, originally from ...


4

There is a popular idea that has been put forward that one can return to Earth via Venus, and to achieve that one has to launch within a few weeks of landing on Mars. I suspect that the author is confusing that. You can take a look at http://clowder.net/hop/railroad/sched.html for when the times are, and see that the times pretty closely overlap. ...


4

Phobos, on its surface, has some protection against radiation beyond being just in deep space. But the real advantage comes where Phobos is easy to dig in to, and thus you could have a habitat under the surface of the planet. But if you compared the surface of Mars and the surface Phobos facing Mars, you would probably get roughly equal exposure. The ...


4

You cannot "stop on Mars' trajectory" - that is not how physics works. If you want to go out as far as Mars' orbit, then expend energy to stop orbiting the sun, you will leave that orbit. This will take a lot of energy, and you will not end up in the correct orbit. Lowest dV is worked out through running multiple simulations - Hohmann Transfer seems to ...


3

The usual answer would be that the Hohmann transfer orbit is already essentially there. But those are meant for lowest dV direct transfer - e.g. a straight shot from the Earth to Mars. They are extremely fuel efficient - the trip from Earth to Mars can take around 3.9 km/s dV - compare that to Mars' orbital velocity of about 24 km/s or the Earth's of 30 km/s....


3

As noted in the answer by Michael, a precise chemical composition is not known at this time. We can, however, consider the overall mineral composition on the surface of the Gale Crater. This diagram provided by Curiosity's CheMin analyzer (source) shows that the composition varies with depth inside the crater: The lower part of the crater contains large ...


3

Mudstone, although the precise chemical composition is unknown at this time (at least to the extent I was able to find it out). From the Planetary Society, it is identified as being mudstone. Unfortunately, from wikipedia, it is clear that mudstone is a very general type of mineral and can be composed of many different things, as long as it was once ...


3

Yes indeed, SpaceX has announced publicly about uncrewed landings on the Moon before 2022 ! From the article Spacex wants to land Starship on the Moon before 2022, then do cargo runs for 2024 human landing: "Aspirationally, we want to get Starship to orbit within a year", Shotwell said. "We definitely want to land it on the Moon before 2022. We want ...


3

Sunset on sol 956, april 14, 2015 Almost twilight !


2

As a Mars dust devil guy, I can say that the ubiquitous dust is NOT generally considered sharp-edged. Almost all of it is one of several clay minerals. Due to the absence of open water and given that the dust has been recycled continuously over many millennia (eroded, transported, deposited, re-eroded, etc), that dust is uniformly fine (2-4$\mu$m), "soft" (= ...


2

Acceleration and Deceleration costs $\Delta v$ (Delta is scientific notation for "change of something" and V stands for Velocity) of which a spacecraft has a set budget (how long the engines can burn). Here's an analogy: imagine that the spacecraft is attached by a thin string to your hand (representing Earth). You start spinning it around faster and faster,...


1

It's theoretically possible to use a lens, but in reality it is extremely unlikely. In order stay in one place relative to Mars and the sun it will have to be at the L1 point, which is relatively close to the planet, and as the sun is relatively weak out there the lens would have to be far, far bigger around than the planet itself. This would require ...


1

Altho I'm a Mars Dust Devil researcher, my work is mostly conducted on terrestrial desert analogs (so I'd want to check my details if this were crucial... ). My understanding is that 1) the dust is re-cycled so much it's now very fine clay (2-4um), dry and often recently draped over surface roughness elements. Meanwhile, 2) weathered quartz leads to fine ...


Only top voted, non community-wiki answers of a minimum length are eligible