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34 votes
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Could a Mars rover go to Phobos or Deimos instead?

No, for a lot of reasons. The Mars rovers slow down based on aerodynamics, heat shields, and parachutes. None of that is available on one of the Moons, meaning that the fuel requirements are much ...
PearsonArtPhoto's user avatar
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14 votes

What are and could be all the advantages and disadvantages to have a crewed station on Phobos before landing crewed missions on Mars?

Establishing a human presence on Phobos would require development of a vehicle specifically for that purpose. Such a vehicle would have a far larger fraction of its arrival mass devoted to propellant ...
Christopher James Huff's user avatar
12 votes
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Venus-Mars-Venus cycler?

Is it possible to create a cycler that can travel from Venus to Mars, then back to Venus? Yes. When only two planets are involved, there are several infinite families of cycler orbits. Given the 434 ...
SE - stop firing the good guys's user avatar
12 votes
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What modifications would be necessary to make to a Mars rover to let it land on Phobos or Deimos?

The very low gravity would require a total redesign. Phobos is the larger body and has a surface gravity of around 0.6 milli-g, or around 1500 times less than here on Earth. The newest rover, ...
John McCarthy's user avatar
11 votes
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Could Phobos be easily saved from falling apart?

Something is very badly wrong with your calculations. Even putting aside that if you want to raise the orbit of something, you need to thrust in the direction of travel. But to actually calculate the ...
Blake Walsh's user avatar
  • 4,221
11 votes

Is there a synchronous orbital height for Phobos?

No, or at least there isn't a useful synchronous orbital height. As you pointed out in your question, the mean radius of Phobos is 11.26 km, but if you look closer the sphere of influence of Phobos ...
1337joe's user avatar
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10 votes
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What are and could be all the advantages and disadvantages to have a crewed station on Phobos before landing crewed missions on Mars?

This NASA paper explores some of the rationales and implications of using Phobos as a staging point for human Mars surface missions. The conclusion is stated in the abstract: Results from this ...
Armadillo's user avatar
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9 votes
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Is the cause of the Phobos-2 probe failure definitively known?

There is a pretty good description in the book "Soviet Robots in the Solar System: Mission Technologies and Discoveries" Summarizing: Received radio signals indicated spacecraft had lost attitude ...
kert's user avatar
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9 votes
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What would be the trajectory and initial speed of a chunk launched from Phobos to get as close as possible to any pole of Mars?

The direct trajectory is an ellipse intersecting the pole: We do not have the semi-major axis of this trajectory, however, so we must obtain that first. For that, we can use one of my favourites, the ...
SE - stop firing the good guys's user avatar
8 votes

What modifications would be necessary to make to a Mars rover to let it land on Phobos or Deimos?

A partial list of subsystems that would need to be redesigned: Since the gravity is low, there's a high chance that you will flip over at some point. You will need to ensure that you can flip back, ...
Florent's user avatar
  • 81
7 votes

How much energy is needed to bring Phobos closer to Mars?

First of all, the best place to place any such rockets would be at the point where the rocket is facing the direction that Phobos is rotating around Mars. That would give you about 4 x more bang for ...
PearsonArtPhoto's user avatar
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6 votes

Is there a synchronous orbital height for Phobos?

By definition, the only stationary points in a two-body system are the Langrangian points This applies as Phobos is tidally locked to Mars, and thus the two periods are equivalent. Even L3, L4 and L5 ...
SE - stop firing the good guys's user avatar
6 votes
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How thick is the dust layer on Phobos?

Nobody knows! We've never done radar sounding of Phobos, and we have no idea what lies beneath its layer of dust. We can surmise minimum depth by looking at craters - the estimate range is 5 - 100 ...
user19742's user avatar
  • 957
6 votes

What's the escape velocity at the near/far end of Phobos considering tidal forces?

I created a crude surface gravity map of Phobos using a Digital Elevation model (DEM) available on Astropedia$^1$. I assumed a uniform 1000 meter 3D grid of equal mass blocks to find the gravity field ...
BrendanLuke15's user avatar
5 votes
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How Safe Is Phobos in Terms of Radiation Exposure?

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 ...
PearsonArtPhoto's user avatar
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5 votes
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If we were to land on Phobos, what could we gain?

The Japanese Space Agency JAXA is preparing such a mission, called Martian Moons eXploration (MMX). This mission is approved and in the works, the launch is foreseen for 2024 and the return to Earth ...
AtmosphericPrisonEscape's user avatar
5 votes
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Is it possible to get a boulder from Phobos to one of the poles of Mars?

The inclination change here is large, close to 90 degrees. For major changes like that, pretty much the only alternative is a Bi-elliptic transfer. That means the optimal manoeuvre here is to ...
SE - stop firing the good guys's user avatar
5 votes
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Could Mars be made much more habitable by boulders from Phobos?

$$\text{Some initial thoughts:}$$ Is Phobos even big enough to make a difference? Slowing Phobos down to hit the Martian atmosphere costs about 540m/s. Reaching escape velocity and then hitting the ...
SE - stop firing the good guys's user avatar
4 votes
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How much energy is needed to bring Phobos closer to Mars?

It is possible, but too costly! And the orbital energy reduction is done best by retro-thrust, and that means, the exhaust of the propulsion device must be on the face in the direction of orbital ...
AliRD's user avatar
  • 168
4 votes

If we were to land on Phobos, what could we gain?

There's no point in going to Phobos with the intention of looking at Mars. If you want to observe Mars from orbit, go to Mars orbit - there are already plenty of Mars orbiters, and they can do their ...
djr's user avatar
  • 1,705
4 votes

How do you find ZRVTOs between tethers from coplanar, tidelocked bodies?

Yes. Given the radii of the upper and lower moons and knowing their angular velocities, there are simple expressions that give the periapsis and apoapsis radius of the Zero Relative Velocity Transfer ...
HopDavid's user avatar
  • 15.7k
4 votes
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How much goes Phobos in the direction of Mars with a constant force in that direction?

I think this can be explained much more simply. Suppose we add a force $F$ pointing towards Mars at all times to Phobos. This will not change the angular momentum $h$ of Phobos. So if it is distance $...
Steve Linton's user avatar
  • 19.6k
4 votes

How much goes Phobos in the direction of Mars with a constant force in that direction?

In the (non-inertial) rotating frame of reference bound to Phobos, with nadir/prograde directions setting the axis, the constant force towards Mars is the weight of Phobos. Phobos semi-major axis (...
SF.'s user avatar
  • 55k
4 votes
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What is the timespan for a block of Phobos to reach a low orbit around Mars with a solar sail?

Let's make a quick simplified estimate. According to Wikipedia, the solar sail will exert a force of $8.17 \mu N / m^2$, when the Sun rays are perpendicular to the sail. So for a 100x100m sail this ...
BlueCoder's user avatar
  • 2,113
4 votes

How big is Mars as seen from Phobos?

We can start by noticing that Mars, Phobos, and the horizon forms a right-angled triangle. By trigonometry, the angular radius ($\alpha$) is then given by: $$\alpha = \sin^{-1}\left(\frac{r_{parent}}{...
SE - stop firing the good guys's user avatar
4 votes
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Can we land on either of Mars' moons?

You can land on any celestial body in the solar system provided that its surface is solid. Yes, one can land on either of the moons of Mars, Phobos and Deimos. However, it would be really hard. Both ...
Deko Revinio's user avatar
  • 1,474
3 votes

The Earth's Moon versus Phobos and gravity

Using Newton's Law of universal gravitation, we can calculate the gravitational force between those bodies. The equation is (Note: I use "," to seperate digits into threes and use ".&...
Star Man's user avatar
  • 5,918
3 votes

Calculating low-thrust capture delta-V with high $V_{inf}$

It sounds like the Red Dragon is relying on aerobraking to exit the Hohmann transfer ellipse and soft land on Mars. I don't think the cube sat would want to use aerobraking to shed velocity. For one ...
HopDavid's user avatar
  • 15.7k
3 votes

How much energy is needed to bring Phobos closer to Mars?

First, one assumptions: The acceleration is so low that instantaneous impulse solutions are out of the question, and the trajectory can be modelled as a very gentle spiral. This is quite reasonable, ...
SE - stop firing the good guys's user avatar

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