Author Topic: Station On Phobos  (Read 17561 times)

Online Bynaus

  • Full Member
  • ***
  • Posts: 385
  • Planetary Scientist
  • Switzerland
  • Liked: 266
  • Likes Given: 161
Re: Station On Phobos
« Reply #40 on: 05/23/2016 07:05 PM »
@Jim: you are right that propellant might indeed be a problem. So yes, rather a long-term thing, if anything. Perhaps the propellant could eventually be baked out of the Phobos regolith, solar wind implanted H, Ar (for ion propulsion) and O from silicates or oxides should be available. Alternatively, a solar/laser sail? I am not saying this is something that can/will be done from day one when the station is built. Its just a possible further application down the road (granted, if a source of propellant can be found). But perhaps I am indeed underestimating the fuel needs.

I also wasn't suggesting to move the entire station to the target orbit. Servicing would need a small "sortie" vehicle with a reasonable delta-V budget. This.could be smaller than in Earth orbit due to the slower orbital velocities.

Offline the_other_Doug

  • Senior Member
  • *****
  • Posts: 2450
  • Minneapolis, MN
  • Liked: 1492
  • Likes Given: 2609
Re: Station On Phobos
« Reply #41 on: 05/23/2016 07:28 PM »
@Jim: you are right that propellant might indeed be a problem. So yes, rather a long-term thing, if anything. Perhaps the propellant could eventually be baked out of the Phobos regolith, solar wind implanted H, Ar (for ion propulsion) and O from silicates or oxides should be available. Alternatively, a solar/laser sail? I am not saying this is something that can/will be done from day one when the station is built. Its just a possible further application down the road (granted, if a source of propellant can be found). But perhaps I am indeed underestimating the fuel needs.

I also wasn't suggesting to move the entire station to the target orbit. Servicing would need a small "sortie" vehicle with a reasonable delta-V budget. This.could be smaller than in Earth orbit due to the slower orbital velocities.

Yeah, but -- are you aware of the amount of energy you need to change orbital inclination?  Just as an example, after the Columbia tragedy, a lot of less-well-informed people demanded to know why, if there was even a hint that Columbia's tiles were damaged, they didn't just fly her to the ISS and let the crew shelter there until another orbiter could come and pick them up.  The reason was that the Shuttle orbital inclination was something like 32 degrees from equatorial, and the ISS inclination is something like 53 degrees.  (These numbers are from the top of my head and aren't exact, for the nitpickers out there.  They are very much in the right ballpark.)

They would have needed another fully fueled external tank and a full 12 minute burn of the SSMEs to change the orbital inclination that much.  It would have taken as much energy to change the orbital inclination that much as it took to get into orbit in the first place.

Changing inclination is an extremely delta-V costly thing to do.  I don't care that Mars is only 38% as massive as the Earth -- you would still need more propulsion to go from Phobos' roughly equatorial inclination to a polar orbit than it would take to launch the same repair mission from the surface of Mars.  Really.  So, from any point of view, it would actually be more useful to maintain a quick SSTO repair ship on the surface of Mars for this kind of satellite repair than to try and base such a repair service out of Phobos.

So, please -- Jim is right.  It's not that it wouldn't be nice to have such a repair facility on Phobos, it's just that physics lays certain limits, and this is one of those that you just can't sidestep.  Unless you have a multiple-orders-of-magnitude breakthrough in propulsion technology, the idea is dead, just from the rules of orbital mechanics.

Sorry...
-Doug  (With my shield, not yet upon it)

Offline Impaler

  • Full Member
  • ****
  • Posts: 1283
  • South Hill, Virgina
  • Liked: 362
  • Likes Given: 0
Re: Station On Phobos
« Reply #42 on: 05/23/2016 09:33 PM »
People seem to be thinking in terms of ISS-on-Phobos, the thread title certainly suggests that.

But their are only two reason to go to Phobos, either as stop-over radiation sheltering point for a manned in-space transit vehicle during a dry-run mission prior to landing on Mars (any science is just to kill time).

Or as a logistical hub where in-space transit vehicle transfer cargo to landing craft that shuttle between Phobos and the surface, analogous to McMurdo station in Antarctica.

ISRU on Phobos (or any asteroid) is not something I think will ever happen, I don't even think Martian regolith will be collected for anything other then burying structures for radiation protection for a lot longer then any one imagines.  Rocks and rubble are a truly horrible horrible source material for any resource extraction, we only do it on Earth because it's the only way to get metal and metal is kinda important.

A dry-run is absolutely going to happen in any mission as complex as Mars landing, NASA is planning to send Orion on a dry-run mission around to moon first unmanned then manned before trying anything, and that is a just the moon a body 3 days away that's already been landed on.  It is not a matter of going to Phobos because we want to study it so specifically, we can get to NEA much more easily, it's just something to do when on a dry-run mission that would be happening if Mars had no moons at all.

Offline CuddlyRocket

Re: Station On Phobos
« Reply #43 on: 05/24/2016 12:18 AM »
A dry-run is absolutely going to happen in any mission as complex as Mars landing, NASA is planning to send Orion on a dry-run mission around to moon first unmanned then manned before trying anything, and that is a just the moon a body 3 days away that's already been landed on.  It is not a matter of going to Phobos because we want to study it so specifically, we can get to NEA much more easily, it's just something to do when on a dry-run mission that would be happening if Mars had no moons at all.

Orion is going to the Moon because why not? It's got to be tested in space anyway so it may as well be on the way to the Moon and back; it wouldn't cost much if anything more and is much better PR! Whereas a dry-run mission to Mars is a lot more expensive and doesn't test anything that can't be tested in cislunar space.

Offline A_M_Swallow

  • Elite Veteran
  • Senior Member
  • *****
  • Posts: 8148
  • South coast of England
  • Liked: 248
  • Likes Given: 103
Re: Station On Phobos
« Reply #44 on: 05/24/2016 12:53 AM »
With their large and easily damaged solar panels it is unlikely that SEP tugs and SEP transfer vehicles will land on Mars. They will stay in orbit. Will they be left by themselves? Or docked to an orbiting spacestation?

Any spacestation and associated propellant depot would need setting up.

Offline the_other_Doug

  • Senior Member
  • *****
  • Posts: 2450
  • Minneapolis, MN
  • Liked: 1492
  • Likes Given: 2609
Re: Station On Phobos
« Reply #45 on: 05/24/2016 01:06 AM »
With their large and easily damaged solar panels it is unlikely that SEP tugs and SEP transfer vehicles will land on Mars. They will stay in orbit. Will they be left by themselves? Or docked to an orbiting spacestation?

Any spacestation and associated propellant depot would need setting up.

And even microgravity helps keep things stay where they're put, especially relatively massive things.

I think a manned presence on Phobos will happen eventually, and IMHO it does make a good destination for a check-out flight of the Earth-Mars transit system, without needing to add the complexity of a landing mission into the mix.  But I'll agree, it doesn't add a lot to Mars surface operations, though it's quite interesting in its own right.

I still like my idea of using a Phobos station as part of a stand-in for the current Mission Control paradigm, using some of a Phobos station crew to serve something of the same function flight controllers serve in crewed LEO operations.  But since no one else seems to like it, I'll admit that, this aside, there's really no crying need to have a Phobos base in place before you start manned landings...
-Doug  (With my shield, not yet upon it)

Offline The Amazing Catstronaut

  • Full Member
  • ****
  • Posts: 1071
  • Arsia Mons, Mars, Sol IV, Inner Solar Solar System, Sol system.
  • Liked: 755
  • Likes Given: 628
Re: Station On Phobos
« Reply #46 on: 05/24/2016 01:13 AM »
I feel that the moons (and any station on them) should come after the parent planet. As noted upthread, they are of less direct scientific interest. Any preliminary robotic test runs for, say, Deimos/Phobos ISRU (I'm in the Deimos camp), could hypothetically be secondary payloads on a manned mars surface mission.
Resident feline spaceflight expert. Knows nothing of value about human spaceflight.

Offline redliox

  • Full Member
  • ****
  • Posts: 1691
  • Arizona USA
  • Liked: 318
  • Likes Given: 54
Re: Station On Phobos
« Reply #47 on: 05/24/2016 10:29 AM »
I feel that the moons (and any station on them) should come after the parent planet. As noted upthread, they are of less direct scientific interest. Any preliminary robotic test runs for, say, Deimos/Phobos ISRU (I'm in the Deimos camp), could hypothetically be secondary payloads on a manned mars surface mission.

I could agree although it's obviously more in the hands of NASA bureaucracy.  A direct path to Mars would definitely get you to where things truly need to be.  If a mission to the Martian moons is advocated, it's ultimately more an excuse to test fly the orbital equipment and a cheaper way to impress while the Mars gear is under wraps/works.  Whether first or second, I think a visit to Phobos/Deimos should be on the itinerary, whereas a station/base on them not so much.
"Let the trails lead where they may, I will follow."
-Tigatron

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 26861
  • Minnesota
  • Liked: 6767
  • Likes Given: 4800
Re: Station On Phobos
« Reply #48 on: 05/27/2016 03:03 AM »
Phobos operations are the Apollos 8 and 10 to landing on Mars's Apollo 11.  A full dress rehearsal mission - with useful science content including Phobos and Deimos exploration (much simpler lander required) and operation of assets on Mars, especially sample collection.  Imagine for instance sample collection of polar volatiles, with maybe a 48 hour travel time to the Phobos and/or orbital base for quick analysis rather than trying to keep a cryogenic sample in good shape for an 8 month trip to Earth.  That would be a really good precursor to the first Mars landing.  Probably essential, I would suggest, just like Apollos 8 and 10.

Such missions are not needed and would be a waste of resources.  Actually, they would not be like Apollo 8 & 10 because MOR (the Martian equivalent of LOR) is not likely going to be the conop (example, Mars Direct doesn't use MOR) and hence the missions would be dead ends.
Jim is a semi-closeted SpaceX fan, as we can see.

The NASA PoR (or the closest we have to one) uses Mars-Orbit-Rendezvous. Of all the different NASA paths to Mars, basically all assume MOR. SpaceX intends to go the Mars Direct route by skipping a separate transit vehicle.

Long term MOR between transit vehicles and landers is the only way to get any kind of colonization going.  A direct flight is simply untenable due to vehicle amortization, for a first mission I could see it being done but it would only be a stepping stone.
I don't see how separating them improves vehicle amortization to any significant degree, and it may make things worse. You'll still need amortization of the in-space element in addition to the large lander.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline KelvinZero

  • Senior Member
  • *****
  • Posts: 3464
  • Liked: 453
  • Likes Given: 113
Re: Station On Phobos
« Reply #49 on: 05/27/2016 11:09 AM »
We really should send some probes to those moons, just as we should investigate the lunar poles.

Precursor missions (that answer basic questions that could allow us to make informed decisions about destinations before committing to absurdly expensive HSF architectures) just fall through the gap between planetary science and HSF. It is depressing.

Offline redliox

  • Full Member
  • ****
  • Posts: 1691
  • Arizona USA
  • Liked: 318
  • Likes Given: 54
Re: Station On Phobos
« Reply #50 on: 05/27/2016 08:11 PM »
We really should send some probes to those moons, just as we should investigate the lunar poles.

Precursor missions (that answer basic questions that could allow us to make informed decisions about destinations before committing to absurdly expensive HSF architectures) just fall through the gap between planetary science and HSF. It is depressing.

I couldn't agree more.  Problem is, as I'm sure you've noticed, is that Mars itself overshadows Phobos and Deimos.  The last Discovery mission announcement included at least 3 proposals but none were selected (Venus and the asteroids became the current candidates).  At this rate, I suspect human footprints will be on them before any landing pads. 

The best candidate for a decent visit between now and the 2030s, albeit in the form of a 'passing glance' of sorts, will be from NeMo, the next generation Mars orbiter.  As a benefit, its spiral entry via solar electric propulsion will allow multiple flybys of Deimos and Phobos as it descends through high to low Mars orbits.  It is supposed to include radar and infrared instruments so on the good news it will be the best flybys the moons will ever see.

However this is supposed to be about putting stations on Phobos, so talking about probes is slightly distracting from topic.  My opinion on actual Mars moon stations is that they're unnecessary as opposed to either probes or an orbital vehicle visiting them and putting permanent equipment on Mars itself.
"Let the trails lead where they may, I will follow."
-Tigatron

Offline Impaler

  • Full Member
  • ****
  • Posts: 1283
  • South Hill, Virgina
  • Liked: 362
  • Likes Given: 0
Re: Station On Phobos
« Reply #51 on: 05/28/2016 02:15 AM »
I don't see how separating them improves vehicle amortization to any significant degree, and it may make things worse. You'll still need amortization of the in-space element in addition to the large lander.

It's rather obvious, you use the lander multiple times per synod taking cargo down to Mars surface, the exact same way the BFR booster is used multiple times per Synod to launch and fuel a fleet of vehicles before they depart en-mass during the window.  This is just applying the same logic at the Mars end of the transit that we employ at the Earth end.

Offline Blackstar

  • Veteran
  • Senior Member
  • *****
  • Posts: 10824
  • Liked: 2335
  • Likes Given: 1
Re: Station On Phobos
« Reply #52 on: 05/28/2016 01:31 PM »
We really should send some probes to those moons, just as we should investigate the lunar poles.

Precursor missions (that answer basic questions that could allow us to make informed decisions about destinations before committing to absurdly expensive HSF architectures) just fall through the gap between planetary science and HSF. It is depressing.

I couldn't agree more.  Problem is, as I'm sure you've noticed, is that Mars itself overshadows Phobos and Deimos.  The last Discovery mission announcement included at least 3 proposals but none were selected (Venus and the asteroids became the current candidates).  At this rate, I suspect human footprints will be on them before any landing pads. 

The best candidate for a decent visit between now and the 2030s, albeit in the form of a 'passing glance' of sorts, will be from NeMo, the next generation Mars orbiter.  As a benefit, its spiral entry via solar electric propulsion will allow multiple flybys of Deimos and Phobos as it descends through high to low Mars orbits.  It is supposed to include radar and infrared instruments so on the good news it will be the best flybys the moons will ever see.

However this is supposed to be about putting stations on Phobos, so talking about probes is slightly distracting from topic.  My opinion on actual Mars moon stations is that they're unnecessary as opposed to either probes or an orbital vehicle visiting them and putting permanent equipment on Mars itself.

Japan is going to do a Phobos sample return mission and NASA will hop on board that. So you'll get data that way.

Offline redliox

  • Full Member
  • ****
  • Posts: 1691
  • Arizona USA
  • Liked: 318
  • Likes Given: 54
Re: Station On Phobos
« Reply #53 on: 05/28/2016 07:03 PM »
Japan is going to do a Phobos sample return mission and NASA will hop on board that. So you'll get data that way.

That's promising.  Any news on that or NeMo?
"Let the trails lead where they may, I will follow."
-Tigatron

Offline oldAtlas_Eguy

  • Senior Member
  • *****
  • Posts: 3021
  • Florida
  • Liked: 1416
  • Likes Given: 95
Re: Station On Phobos
« Reply #54 on: 05/29/2016 04:11 AM »
From the standpoint of using Phobos as an Interplanetary transshipment transfer point, it is to deep into the Mars gravity well. The heavier elements being the interplanetary craft vs the SSTO craft would more logically place such a station at Deimos not Phobos. A lot like EML2 would be a similar transfer point. Characteristics: high orbit less delta V required of interplanetary craft. Phobos would only be useful in the scenario of a Mars SSTO that is DV challenged. The SpaceX BFS(MCT) would easily reach Deimos without having to refuel since it is supposedly being designed to reach Mars escape from Mars surface. Plus the sophistication of large cycler interplanetary craft, transshipment points, etc is fairly later in the Mars colonization/exploration timelines like 20 years after first man landing.

On another point in a three body system like the two moon Mars system doing a 90 degree inclination change is rather easy by heading out from Phobos to Deimos using a gravity turn to change the inclination then circularizing at the desired orbit height or performing a direct return entry. The problem is that the maneuver still does not come cheap (DV wise) but significantly less than the alternative with also a bigger problem of a narrow window spaced at large intervals of time. Such a maneuver would not be a unplanned event but one planned literally months/years in advance suitable for planned deployments but not rescue or ad-hoc missions. A BTW you can use the Moon the same way but it sort of defeats the purpose since the DV needed to get to it and back may be larger than just landing back on earth and launching again into the inclination you want.

Orbital Mechanics: Gravity assist is your friend.

Offline redliox

  • Full Member
  • ****
  • Posts: 1691
  • Arizona USA
  • Liked: 318
  • Likes Given: 54
Re: Station On Phobos
« Reply #55 on: 05/29/2016 04:57 AM »
From the standpoint of using Phobos as an Interplanetary transshipment transfer point, it is to deep into the Mars gravity well. The heavier elements being the interplanetary craft vs the SSTO craft would more logically place such a station at Deimos not Phobos. A lot like EML2 would be a similar transfer point. Characteristics: high orbit less delta V required of interplanetary craft. Phobos would only be useful in the scenario of a Mars SSTO that is DV challenged. The SpaceX BFS(MCT) would easily reach Deimos without having to refuel since it is supposedly being designed to reach Mars escape from Mars surface. Plus the sophistication of large cycler interplanetary craft, transshipment points, etc is fairly later in the Mars colonization/exploration timelines like 20 years after first man landing.

This is why I favor Deimos more, coupled with its proximity to synchronous orbit.

Cycler craft, frankly, are stupid ideas.  You still have to waste launch fuel and rendezvous in open, interplanetary space which means, if you're misaligned in your little capsule, you're lost in space without a robot to yell "Danger Will Robinson, danger!"

On another point in a three body system like the two moon Mars system doing a 90 degree inclination change is rather easy by heading out from Phobos to Deimos using a gravity turn to change the inclination then circularizing at the desired orbit height or performing a direct return entry. The problem is that the maneuver still does not come cheap (DV wise) but significantly less than the alternative with also a bigger problem of a narrow window spaced at large intervals of time. Such a maneuver would not be a unplanned event but one planned literally months/years in advance suitable for planned deployments but not rescue or ad-hoc missions. A BTW you can use the Moon the same way but it sort of defeats the purpose since the DV needed to get to it and back may be larger than just landing back on earth and launching again into the inclination you want.

Orbital Mechanics: Gravity assist is your friend.

Earth's moon could provide gravity assist; Mars' moons...not in the least.  When I asked about the usefulness of gravity assists from a few members knowledgeable about it and electric propulsion, they pointed out how trajectory is a huge factor.  Basically, much as you have to hit a correct launch window, you have to hit a specific angle to get any use from a celestial body's gravity.

I'm not familiar with 'gravity turns,' but in general if you're trying to change orbits or escape Mars, simpler just to use fuel.
"Let the trails lead where they may, I will follow."
-Tigatron

Offline Impaler

  • Full Member
  • ****
  • Posts: 1283
  • South Hill, Virgina
  • Liked: 362
  • Likes Given: 0
Re: Station On Phobos
« Reply #56 on: 06/01/2016 04:58 AM »
Atlas & redliox:  You have it backwards you want to have your point for transfer between in-space vehicles and landers right at the atmospheric interface so each craft type spends essentially all of it's time and energy in the flight regime for which it is optimized, that will result in overall system optimization.  That would mean low orbit is ideal and Phobos is preferable to Demos. 

Phobos is only about 1400 m/s from LMO and has some features we already discussed which could compensate for this increased distance from the Martian surface.  A Mars shuttle lander would need 5.5 km/s to make the transit up and likely another 1 km/s to come down again.

While your right that being high in the gravity well such as EML-1&2 is advantageous it would be the place to transfer cargo between cis-planetary in-space vehicles and helocentric transfer in-space vehicles.  I think we will have this distinction at the Earth end of the logistical chain because Earth Lagrange points are at roughly the halfway point of the entire DeltaV span between LEO and LMO. 

But the Martian gravity well is sufficiently small relative to the velocity needed to transfer to Mars that it makes little sense to make another transfer point their.  The two break points at or near atmospheric interfaces and one in gravitational 'divide' should suffice.


Offline redliox

  • Full Member
  • ****
  • Posts: 1691
  • Arizona USA
  • Liked: 318
  • Likes Given: 54
Re: Station On Phobos
« Reply #57 on: 06/01/2016 09:03 AM »
Atlas & redliox:  You have it backwards you want to have your point for transfer between in-space vehicles and landers right at the atmospheric interface so each craft type spends essentially all of it's time and energy in the flight regime for which it is optimized, that will result in overall system optimization.  That would mean low orbit is ideal and Phobos is preferable to Demos. 

By chance is this related to how perigee burns tend to work best when you're at closest approach to the target planet?  Whenever I see an elliptical orbit I can't help but think "sloppy" but, if you're trying to be fuel conservative, I can understand the merit is sticking to a simplified orbit without necessarily insisting on it being perfectly synchronized.

In the sense of orbital mechanics, I believe I understand the favoritism of Phobos now, although I still see equal if not better merit in Deimos' near-synchronous position higher up.

While your right that being high in the gravity well such as EML-1&2 is advantageous it would be the place to transfer cargo between cis-planetary in-space vehicles and helocentric transfer in-space vehicles.  I think we will have this distinction at the Earth end of the logistical chain because Earth Lagrange points are at roughly the halfway point of the entire DeltaV span between LEO and LMO. 

But the Martian gravity well is sufficiently small relative to the velocity needed to transfer to Mars that it makes little sense to make another transfer point their.  The two break points at or near atmospheric interfaces and one in gravitational 'divide' should suffice.

I believe you make a good point after all.  You're trying to explain how, in some ways, many of us are still thinking in an Earth-centric pov.  As far as breaking points, I doubt NASA would agree on a perigee near the atmospheric interface, but if you're employing a lander that would use aerobraking to slow down from high to low Mars orbit this would be advantageous...but again I'd expect the orbiter would keep its distance.  On the topic, where would the two 'break points' be located roughly from the Mars surface, which I presume you define as the Martian upper atmosphere at one end and the Hill sphere as the other?
"Let the trails lead where they may, I will follow."
-Tigatron

Offline redliox

  • Full Member
  • ****
  • Posts: 1691
  • Arizona USA
  • Liked: 318
  • Likes Given: 54
Re: Station On Phobos
« Reply #58 on: 06/01/2016 09:07 AM »
While on the topic of stations, Phobos, and Deimos, the International Conference on the Exploration of Phobos and Deimos is coming up fairly soon: http://phobos-deimos.arc.nasa.gov/
"Let the trails lead where they may, I will follow."
-Tigatron

Offline Impaler

  • Full Member
  • ****
  • Posts: 1283
  • South Hill, Virgina
  • Liked: 362
  • Likes Given: 0
Re: Station On Phobos
« Reply #59 on: 06/02/2016 01:31 AM »
If your using high thrust rocket propulsion the deeper gravity well plung is definitly preferable for Oberth effect, regardless of the final orbit you want to take at a planet if your coming in at above escape velocity you want a burn at just above the atmosphere to brake.

I had not really considered elliptical orbits at Mars, I had assumed that while initial orbital insertion (either propulsive or via airo-capture) would be elliptical and then airo-braking would bring it down to either LMO or to intersection with Phobos from which the landing on Phobos would be made.

Ultimatly a lot depends on what kind of propulsion the in-space vehicle has, I'm assuming SEP (without SEP their is not much point in stopping in Mars orbit anywhere) which is more likely to just spiral down from capture down to Phobos or LMO.  Then cargo/passengers can shuttle between the transit vehicle and the surface.

Tags: Mars Phobos Deimos cubesats