Author Topic: First manned mission to Phobos  (Read 30995 times)

Offline MickQ

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Re: First manned mission to Phobos
« Reply #40 on: 09/22/2010 06:48 am »
I have been thinking for some time that a major impact event in Mars younger days may have been responsible for a lot of things.  Imagine an asteroid striking the planet at what is now the Hellas Basin.  This pushed the core of the planet so hard that it bulged out the other side creating Tharsis and the big volcanoes.  Phobos and Diemos couold be ejecta fron this event.  This could also account for Mars elongated orbit.

Anyone ???

Mick.

Online Lampyridae

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Re: First manned mission to Phobos
« Reply #41 on: 09/22/2010 09:32 am »
A further factor is how much gravity difference can the human body take between the toes and the head?

We were designed to operate under a nearly fixed amount of gravity with some intermittent turning torque.
Human beings are about 2 metres high (6'6").

There seem to be somewhat adverse effects with a 2m radius centrifuge. The various organs are subjected to a range of different pressures, so you get the heart operating at 0.3g (in a 1g centrifuge), the head at near zero and the feet getting 1g. Plus your body exerts about 1/3 of its weight on the feet and anti-gravity muscles! The exercise effect seems all right, although you need hypergravity (1.5g+) for any real benefit.

Studies with longer arm centrifuges (~4m) exist, but aren't so common. DiZio's work was in a 5m diameter room, but that showed adaptation was possible. There is the added problem of vectoring your body to stand with these ground based tests. With a 4m radius, you get the head at 40-50% ambient. The big problems come when you start to move around in short radii systems. At 6RPM, you get one G but tangential velocity is 2.5 m/s. Very easy to step onto, but you start lifting off the floor when you walk anti-spinward and your RPM effectively drops to zero. Then when you walk spinward (at 2.5 metres per second), your RPM increases to 12. Coriolis force also causes problems. At 10RPM however, the tangential rises to 5m/s and Coriolis is more manageable.

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Online Lampyridae

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Re: First manned mission to Phobos
« Reply #42 on: 09/22/2010 01:02 pm »
I agree that astronauts can probably adapt to ~5-10rpm, which should be good enough for Mars-level gravity in something like a Bigelow Sundancer module. Heck, you could just build it after you orbited the module, inside the module. You could have an artificial-gravity section of the module where sleeping, exercising, and perhaps other activities that could benefit from artificial gravity (like fixing or making something... most rapid manufacturing techniques rely on gravity). Also, if even idle activity in artificial gravity is found to be helpful, computers and desks could be placed in the artificial gravity section.

The ring wouldn't need to be sealed at all (in fact, it would best not be sealed), and should be able to be spun-down at any time. Any structural considerations should be handled by the structure of the ring.

Just an idea.

EDIT: Part of the benefit of this idea is that the whole artficial gravity mechanical system would be inside a pressurized environment, and thus could be fixed mid-flight using conventional hand tools without a difficult and risky EVA.

Current BA 330 design is too small to accommodate an internal centrifuge. It *could* be done, with 6RPM you are looking at 0.12g, with 8, 0.2g. I would suggest a 10m diameter hab as a minimum (2001 Discovery centrifuge size). At these sizes, too *low* an RPM causes problems with Coriolis forces and walking speeds. But perhaps these aren't as big problems as we think they are.

A couple of rings of fluid around the rotation axis should keep instabilities down.

Gasbarri P., Teofilatto P. (2009) Fluid ring dampers for artificial gravity spacecraft. Acta Astronautica (64), 1286-1292
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Offline tankmodeler

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Re: First manned mission to Phobos
« Reply #43 on: 09/23/2010 02:52 pm »
One wonders how a Bigelow-type module could be designed so that it was of larger diameter and shorter length. If you could get it to fit within EELV launch shrouds you could have a 15m+ diameter centrifuge but the entire thing is only 2-3m wide. It is then docked to a more standard BA330 where zero-G storage and specialised tasks are performed. A centrifuge that narrow might seem kinda confining, but at 2 m wide would provide 94+ sq m (>2500 sq ft) of floor space which would support an awful lot of activities for a nominal crew of, say, 6 or 8 on a long term voyage. You could also have a second floor at a lower gravity level to allow the crew to prep for Mars and then on the way back they would move the first floor to prep for Earth gravity. A lot of mass turning, to be sure, but the coriolis effects may be more manageable. Certainly the negative effects of vertical movement would be diminished.

Just a thought.
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Offline Robotbeat

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Re: First manned mission to Phobos
« Reply #44 on: 09/23/2010 03:05 pm »
On a long trip, there may well be a need for repairing or even manufacturing parts. Rapid-prototyping machines almost all require gravity to work, especially powder-based ones.
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Offline tankmodeler

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Re: First manned mission to Phobos
« Reply #45 on: 09/24/2010 05:47 pm »
On a long trip, there may well be a need for repairing or even manufacturing parts. Rapid-prototyping machines almost all require gravity to work, especially powder-based ones.
For the foreseeable future this won't be an issue and certainly not with current rapid prototype materials. None of them have even a small fraction of the strength of standard aerospace materials so there are no parts that will be repaired by rapid prototypes using today's technologies. If we posit some magic that can rapid prototype out of flight-grade materials, then we may not have to worry about gravity. No sense even putting it on the radar as its a completely "magic" technology at this point

Paul
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Offline Robotbeat

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Re: First manned mission to Phobos
« Reply #46 on: 09/25/2010 06:40 am »
On a long trip, there may well be a need for repairing or even manufacturing parts. Rapid-prototyping machines almost all require gravity to work, especially powder-based ones.
For the foreseeable future this won't be an issue and certainly not with current rapid prototype materials. None of them have even a small fraction of the strength of standard aerospace materials so there are no parts that will be repaired by rapid prototypes using today's technologies. If we posit some magic that can rapid prototype out of flight-grade materials, then we may not have to worry about gravity. No sense even putting it on the radar as its a completely "magic" technology at this point

Paul
Perhaps "rapid prototyping" is the wrong word... There already exist "additive manufacturing" systems capable of making items out of flight-grade materials:
http://www.designnews.com/article/510610-3_D_Printers_versus_3_D_Production_Systems.php (shows a picture of landing gear for a Russian aircraft produced on a "3d production" system) There are many materials that are available now for additive manufacturing, including stainless steel. It's not magic. Do your research!

Get with the times. ;)

(However, a small lathe or multi-axis cnc machine may make more sense for some things... also could benefit from some gravity, although probably could be made to work without gravity)

But for the lower end machines, there are also aerospace-certified (using that term loosely) thermoplastics which can be used:
http://www.engineerlive.com/Design-Engineer/Materials_Processes/Fortus_900mc_3D_Production_System_gains_four_new_materials/22033/

EDIT:Here's a neat website where you can upload a 3d model and order the object fabricated on-demand in all sorts of materials, like plastic, glass, a temp-resistant ceramic, and (of course) stainless. Price is per-cubic-centimeter, and stainless is the most expensive at $10/cm^3 (others are more like $2/cm^3), and details to within about 0.2 mm (depending on material):
http://www.shapeways.com/materials/
(This is mostly an artistic shop, but other places are more aerospace-friendly... and probably with more of an aerospace price!)

Paul Breed of Unreasonable Rocket has started to use 3d printing for some of his rocket engines.
« Last Edit: 09/25/2010 07:01 am by Robotbeat »
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 SpacexULA

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Re: First manned mission to Phobos
« Reply #47 on: 09/25/2010 07:07 am »
On a long trip, there may well be a need for repairing or even manufacturing parts. Rapid-prototyping machines almost all require gravity to work, especially powder-based ones.

Actually the thermoplastic additive process does not require gravity to work properly.



I have actually replicated this test with my Makerbot, and it works just fine.

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Offline A_M_Swallow

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Re: First manned mission to Phobos
« Reply #48 on: 09/25/2010 07:35 pm »
Great video.

It is worth testing the equipment on its side just in case some pipes only work when vertical.

Offline orbitjunkie

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Re: First manned mission to Phobos
« Reply #49 on: 09/27/2010 02:22 am »
On a long trip, there may well be a need for repairing or even manufacturing parts. Rapid-prototyping machines almost all require gravity to work, especially powder-based ones.
For the foreseeable future this won't be an issue and certainly not with current rapid prototype materials. None of them have even a small fraction of the strength of standard aerospace materials so there are no parts that will be repaired by rapid prototypes using today's technologies. If we posit some magic that can rapid prototype out of flight-grade materials, then we may not have to worry about gravity. No sense even putting it on the radar as its a completely "magic" technology at this point

Paul

I must disagree. I recently mentioned the relatively new direct manufacturing technology Electron Beam Free Form Fabrication (EBF3). Works in vacuum and zero gee with aerospace materials such as Al and Ti. Not sure about Al-Li.
http://forum.nasaspaceflight.com/index.php?topic=22716.msg639117#msg639117

I spoke to an engineer at MSFC a few years ago who was working on more traditional rapid prototyping technology that worked with some powdered metals. I asked how the end product compared to something produced by traditional methods on the same material. The answer surprised me, in that they can be superior. That particular process, at least, produced more homogeneous material with more uniform structural and thermal properties. Combined with the ability to make unique shapes and finer scale structures (imagine a part made of tiny trusses through and through instead of solid metal) there could be big potential gains over traditional aerospace processes.

Offline alexterrell

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Re: First manned mission to Phobos
« Reply #50 on: 09/27/2010 12:22 pm »
On a long trip, there may well be a need for repairing or even manufacturing parts. Rapid-prototyping machines almost all require gravity to work, especially powder-based ones.
For the foreseeable future this won't be an issue and certainly not with current rapid prototype materials. None of them have even a small fraction of the strength of standard aerospace materials so there are no parts that will be repaired by rapid prototypes using today's technologies. If we posit some magic that can rapid prototype out of flight-grade materials, then we may not have to worry about gravity. No sense even putting it on the radar as its a completely "magic" technology at this point

Paul
Even if you're correct that rapid prototyping materials are weak (and the SLAs and SLSs I've received are flakey), many of the parts won't need to be flight-grade materials. Toilet lids, air-conditioning blades, the silly widget that holds the cables in place, the feeding tube that our lab rat nibbled through, the actuator on the air-con unit, the ventilation grill you broke with you head - all these will go wrong. In a low-g environment, the majority of parts don't even need Earth-g grade materials, let alone flight grade.

Offline alexterrell

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Re: First manned mission to Phobos
« Reply #51 on: 09/27/2010 12:27 pm »
I have been thinking for some time that a major impact event in Mars younger days may have been responsible for a lot of things.  Imagine an asteroid striking the planet at what is now the Hellas Basin.  This pushed the core of the planet so hard that it bulged out the other side creating Tharsis and the big volcanoes.  Phobos and Diemos couold be ejecta fron this event.  This could also account for Mars elongated orbit.

Anyone ???

Mick.
Given the decay in their orbits, one would surmise that the impact was fairly recent (~100 million yrs?) and not early solar system. To create the Tharsis bulge would have been like making Earth's moon.

If Phobos is from Mars, it may have less water and hydrocarbons. However, it could be a composite body - it really does a need a manned visit.


Offline MickQ

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Re: First manned mission to Phobos
« Reply #52 on: 09/28/2010 01:06 am »
I have been thinking for some time that a major impact event in Mars younger days may have been responsible for a lot of things.  Imagine an asteroid striking the planet at what is now the Hellas Basin.  This pushed the core of the planet so hard that it bulged out the other side creating Tharsis and the big volcanoes.  Phobos and Diemos couold be ejecta fron this event.  This could also account for Mars elongated orbit.

Anyone ???

Mick.
Given the decay in their orbits, one would surmise that the impact was fairly recent (~100 million yrs?) and not early solar system. To create the Tharsis bulge would have been like making Earth's moon.

If Phobos is from Mars, it may have less water and hydrocarbons. However, it could be a composite body - it really does a need a manned visit.



Alex.  I agree.  Phobos should be a priority target.  I think it was Kkattula who recently posted that it is essentially a NEO with a great view.  A perfect place for an outpost to conduct teleoperated research of Mars as well.

Mick.

Offline Lars_J

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Re: First manned mission to Phobos
« Reply #53 on: 09/28/2010 01:11 am »
Is Phobos tidally locked with Mars, or does it spin?

Offline orbitjunkie

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Re: First manned mission to Phobos
« Reply #54 on: 09/28/2010 02:17 am »
Is Phobos tidally locked with Mars, or does it spin?

It is tidally locked, though it is not in a synchronous orbit so Mars spins beneath it.
« Last Edit: 09/28/2010 02:18 am by orbitjunkie »

Offline MickQ

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Re: First manned mission to Phobos
« Reply #55 on: 09/28/2010 05:16 am »
Is Phobos tidally locked with Mars, or does it spin?

It is tidally locked, though it is not in a synchronous orbit so Mars spins beneath it.

If I recall correctly, Phobos is above the Mars horizon for something like 4 hours at a time, twice a day, for any location on the surface in a broadly equatorial region.  From a base on the Mars facing end of Phobos multiple surface units could be teleoperated in succession during each orbit for hours at a time.

Mick

Offline John Santos

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Re: First manned mission to Phobos
« Reply #56 on: 09/28/2010 06:09 am »
Is Phobos tidally locked with Mars, or does it spin?

It is tidally locked, though it is not in a synchronous orbit so Mars spins beneath it.

If I recall correctly, Phobos is above the Mars horizon for something like 4 hours at a time, twice a day, for any location on the surface in a broadly equatorial region.  From a base on the Mars facing end of Phobos multiple surface units could be teleoperated in succession during each orbit for hours at a time.

Mick


Relaying through a few low-orbit comsats, it could be close to 24x7.  I think the rovers already use Mars Odyssey and MRO to relay to Earth and Phoenix used Mars Express.  It might be harder to track a spacecraft at Phobos because it's moving faster than Earth (angular speed, not absolute velocity!), but it should be doable.

Offline kkattula

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Re: First manned mission to Phobos
« Reply #57 on: 09/28/2010 08:09 am »
Relaying through a few low-orbit comsats, it could be close to 24x7.  I think the rovers already use Mars Odyssey and MRO to relay to Earth and Phoenix used Mars Express.  It might be harder to track a spacecraft at Phobos because it's moving faster than Earth (angular speed, not absolute velocity!), but it should be doable.

IMO, a priority and prerequisite for Mars exploration should be the establishment of a constellation of small Com Relay/GPS sats.

They don't need to be anything like the capacity or accuracy of the Earth's. They just need to provide basic support for the first couple of decades of exploration.

Maybe six in areostationary orbit (17,000 km) at 60 deg intervals.  Might need a few more for accurate GPS.

Offline Hop_David

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Re: First manned mission to Phobos
« Reply #58 on: 09/28/2010 08:25 am »
I have been thinking for some time that a major impact event in Mars younger days may have been responsible for a lot of things.  Imagine an asteroid striking the planet at what is now the Hellas Basin.  This pushed the core of the planet so hard that it bulged out the other side creating Tharsis and the big volcanoes.  Phobos and Diemos couold be ejecta fron this event.  This could also account for Mars elongated orbit.

Anyone ???

Mick.
Given the decay in their orbits, one would surmise that the impact was fairly recent (~100 million yrs?) and not early solar system. To create the Tharsis bulge would have been like making Earth's moon.

If Phobos is from Mars, it may have less water and hydrocarbons. However, it could be a composite body - it really does a need a manned visit.



Around 6 or 7 months ago, Mars Express did some close fly bys of Phobos. Evidently some of the data from those encounters is now being released. For example This BBC article on Phobos

A few paragraphs from that article:
Quote
Recent observations as thermal infrared wavelengths using the Planetary Fourier Spectrometer (PFS) instrument on Mars Express show a poor match between the rocks on Phobos and any class of chondritic meteorite known from Earth.

These would seem to support the "re-accretion" models for the formation of Phobos, in which rocks from the surface of the Red Planet are blasted into Martian orbit to later clump and form Phobos.

"We detected for the first time a type of mineral called phyllosilicates on the surface of Phobos, particularly in the areas northeast of Stickney, its largest impact crater," said co-author Dr Marco Giuranna, from the Italian National Institute for Astrophysics in Rome.

These phyllosilicate rocks are thought to form in the presence of water, and have been found previously on Mars.

"This is very intriguing as it implies the interaction of silicate materials with liquid water on the parent body prior to incorporation into Phobos," said Dr Giuranna.

"Alternatively, phyllosilicates may have formed in situ, but this would mean that Phobos required sufficient internal heating to enable liquid water to remain stable."

Offline alexterrell

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Re: First manned mission to Phobos
« Reply #59 on: 09/28/2010 08:32 am »
I have been thinking for some time that a major impact event in Mars younger days may have been responsible for a lot of things.  Imagine an asteroid striking the planet at what is now the Hellas Basin.  This pushed the core of the planet so hard that it bulged out the other side creating Tharsis and the big volcanoes.  Phobos and Diemos couold be ejecta fron this event.  This could also account for Mars elongated orbit.

Anyone ???

Mick.
Given the decay in their orbits, one would surmise that the impact was fairly recent (~100 million yrs?) and not early solar system. To create the Tharsis bulge would have been like making Earth's moon.

If Phobos is from Mars, it may have less water and hydrocarbons. However, it could be a composite body - it really does a need a manned visit.



Alex.  I agree.  Phobos should be a priority target.  I think it was Kkattula who recently posted that it is essentially a NEO with a great view.  A perfect place for an outpost to conduct teleoperated research of Mars as well.

Mick.
And:
- It can be reached every 2.2 years. NEOs with low delta V will have infrequent access opportunities.
- With Mars / Earth aero capture, delta V requirements are low - about 1.2km/s from Earth Moon L1
- A SDHLV (e.g. Jupiter 246) with SEP transfer stage can put 50 tons on Phobos.

A couple of months ago I became a fan of "Phobos Direct". Ignore Mars and set up a permanent, substantial base on Phobos. Four SEP cargo flights per year deliver 200 tons of supplies every year. Once the base is up, with ISRU and fuel production, exploring, and then settling Mars is "relatively" easy.

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