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  #861  
Old 05-30-2012, 05:55 AM
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Currently designing: add-ons for ESA's Mars Express paper model
Hmmm. Sounds interesting. It's in my "soon" to do file. Will you also be doing Venus Express?

Les (Friendly Airplane Asylum & ex-NASA flack)
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  #862  
Old 05-31-2012, 12:34 AM
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Originally Posted by umtutsut View Post
Hmmm. Sounds interesting. It's in my "soon" to do file. Will you also be doing Venus Express?

Les (Friendly Airplane Asylum & ex-NASA flack)
I just designed a few enhancements for the Mars Express model. Basically, the ESA model was kinda 'flat' on the bottom, where as the real Mars Express has four small cubes on the corners of the bottom panel. Each cube holds a set of RCS thrusters. I designed those and I'm designing more accurate side-walls of Mars Express. Will also be doing more accurate omni-directional antennas. But it's a free-wheel personal project. I only do work when I have the time for it. Having a very busy professional life and personal life, not a whole lotta time is left. Not to mention all the time I recently put into editing and authoring a DVD about the IRAS satellite.

Will I be doing those additions for Venus Express? Maybe, if I find the time someday.
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  #863  
Old 07-10-2012, 08:01 AM
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Never mind... Got my answer

Last edited by MECO; 07-10-2012 at 08:32 AM.
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  #864  
Old 08-07-2012, 12:56 PM
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You may already know about this resource, but whilst looking for something else I saw this 27.64 MB 'International Space Station Overview' PDF on the NASA website, amongst Press Kits and similar stuff. A lot of detail that may be of interest to ISS model builders:

http://www.nasa.gov/pdf/508318main_I...de_nov2010.pdf
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  #865  
Old 08-08-2012, 01:44 AM
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Wow, it's been a LONG time since I've worked on my ISS. Thinking about getting back to it......
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  #866  
Old 08-08-2012, 05:44 AM
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that's a nice link there, thanks for the heads up!
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  #867  
Old 09-06-2012, 06:58 AM
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on the topic of the ISS (but off topic re paper models)....

I pose a question to you that are more knowledgeable than me:

Just heard about the plan to scuttle the ISS in a few years.
Apparently it will be crashed into the Pacific, since it cannot be left as
orbiting "debris".

This I understand.
But why scuttle it? Why crash it to earth?

Why not add a couple of cameras?
Throw in some outdated electronics and give it the ability
to send a photo or data back to earth every now and then.
Then give it a nudge out into Space and send it on its way.
Its already up there...why not use it for something else?

Or put it into orbit around the Moon?
Turn it into an orbiting Moon platform.

Crash it into the Sun...to see how close it gets.
Have it take photos and send back data right up to the point of incineration?
Imagine the closeup views of the Sun we could get!

I am fully aware of the reasons not to salvage it...salvage costs quite often outweigh the values.
I guess I am just having a big problem with the idea of just crashing it into the Ocean and throwing it away so easily.
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  #868  
Old 09-06-2012, 09:21 AM
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I guess the short answer is money.
The ISS is so heavy that you had to spend an incredible amount of fuel to kick it into anything else than an earth orbit. If you just want cameras flying somewhere, you don't need so many tons of unneccessary man-rated modules. That's why we build unmanned spacecraft, they are small and light to take the maximum velocity from the limited amount of fuel.
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  #869  
Old 09-06-2012, 09:26 AM
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Dave, all this has been discussed over at NASASpaceFlight.com check out the forum there.

I agree with you, tossing/crashing/burning up 100 Billion dollers of nice shiny equipment is crazy. Personally I think it will get another extension, living beyond 2030.
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  #870  
Old 09-06-2012, 10:56 PM
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Quote:
Originally Posted by airdave View Post
on the topic of the ISS (but off topic re paper models)....

I pose a question to you that are more knowledgeable than me:

Just heard about the plan to scuttle the ISS in a few years.
Apparently it will be crashed into the Pacific, since it cannot be left as
orbiting "debris"..
Well, the plan WAS to sink her in 2016, under the old NASA Administrator Mike Griffin and the now-canceled Constellation plans... There simply isn't enough money in the NASA budget to allow for exploration missions and sustained ISS operations costs at the same time. Of course, after the oddyssey it took to build ISS, which actually started out in the mid-80's under Reagan as "Space Station Freedom", which then morphed into the ISS after the inclusion of the Russians in the early 90's after the collapse of the Soviet Union, and the fact that about $200 BILLION dollars has been spent on ISS, and the fact that the first piece of ISS didn't even enter orbit until 1998, about 12 years after Reagan first announced SSF, and the fact that it has taken another THIRTEEN YEARS to actually construct the thing after all that time, effort, and money, the idea of torpedoing it after only 5-6 years after its "completion" (which isn't actually complete per the original plans for it, just more like "construction halted" due to budget cuts and shuttle retirement) was never very palatable in Congress, which controls NASA's budget. Nor was it popular with the international partners, who after investing billions of their own (about 25% of the total from what I've read) not getting but about six years of actual use out of it before it ended up in a million pieces on the bottom of the Pacific. SO, needless to say, even before the cancellation of the Constellation project, that the ISS was granted a 'reprieve" and extended to 2020... it is fairly likely that ISS will be extended to 2028. At that point, the oldest components will have been in orbit for 30 years... at some point it's likely that ISS's expenses and upkeep will exceed its value and it will have to be retired... it's also likely that technology will surpass the capabilities of the ISS's equipment and it would just make more sense to do something more "up to date" than nurse along aging equipment and antiquated (by then) systems... much like shuttle before it.

Quote:
Originally Posted by airdave View Post
This I understand.
But why scuttle it? Why crash it to earth?.
ISS weighs several hundred tons... and it's the size of a football field. That means that it would be very difficult to do more than the periodic reboosts on it that continually raise its orbit from time to time to prevent it from reentering naturally over time. If ISS were merely "abandoned in place" and left in orbit, much like Skylab was, then its orbit would eventually decay due to its enormous size and the very slight but measurable drag it experiences from Earth's outer atmosphere... and it would re-enter in an uncontrolled fashion, just like Skylab. Skylab, due to its size, survived long enough during reentry to rain debris across a wide area, thankfully in a remote area of Australia and at sea. ISS, being larger, would be just as likely if not more so, were it to reenter in an uncontrolled fashion. Remember the brouhaha over the shootdown of the large spysat a couple years ago?? While it's likely the Air Force didn't want any "sensitive parts" coming down where they could potentially be salvaged and studied by unfriendly intelligence services around the world, the official reason was that the satellite was carrying a large quantity of hydrazine propellants, which are highly toxic, and could potentially contaminate a large area or even poison people on the ground were it to impact in a metropolitan area... and some of the components (like mirrors and such) were of such a mass and material it was likely they would survive reentry in such a fashion as to pose a hazard to people on the ground should they impact nearby. ISS poses a similar hazard. Therefore, when ISS IS "decommissioned", it will eventually be sent on a targeted reentry somewhere over the Pacific ocean, where any surviving pieces in its "debris footprint" will fall harmlessly (hopefully, but statistically so) into the ocean and sink.

Quote:
Originally Posted by airdave View Post
Why not add a couple of cameras?
Throw in some outdated electronics and give it the ability
to send a photo or data back to earth every now and then.
Then give it a nudge out into Space and send it on its way.
Its already up there...why not use it for something else?.
You don't just "nudge" anything weighing hundreds of tons out into deep space... just to escape Earth's gravity requires one to accelerate from 17,500 to 25,000 mph... such an increase isn't trivial, and amounts to an increase in speed of 43%... which would require a MASSIVE amount of propellant and rocket engines capable of converting it to acceleration. In addition, the loads imposed on the structure to accelerate it with such rockets would likely exceed its design limits. LONG duration, slow burns are very inefficient and would require even more propellant. The other option would be to use ion engines or electric thrusters capable of delivering low thrusts, but over MONTHS of burn duration, to slowly spiral the ISS out into deep space. This is possible, but it would NOT be cheap! The other issue is, what do you do with it once you get it into high Earth orbit, (HEO) or Geosynchronous Earth Orbit (GEO) or even boost it to escape, given enough time and propellant (at least the super-high efficiency of ion thrusters would help here!) The station would make many long extended passes through the Van Allen radiation belts, which is very detrimental to electronics and precludes any chance of having crew aboard. Technically it's possible, but not particularly valuable or worthwhile. The thermal environment in deep space is MARKEDLY different than it is in LEO, which means that ISS, which was designed for the LEO thermal environment, would have difficulties with thermoregulation in deep space. There is no large, warm planet radiating heat at night at the station, despite it being in Earth's shadow... nor radiating and reflecting heat back at it during orbital "day"... the station would have a lot of trouble thermoregulating, and would probably ice up badly. (if it was not to be inhabited, this might not be much of a problem). The other issue is, what to do with it once you DID accelerate it to Earth escape velocity or a higher orbit. We don't presently have any vehicles capable of reaching it with crews, and it would be VERY expensive missions if we did (requiring at the least SLS and ICPS/Orion on the US side, or specially outfitted Soyuz's with propulsion stages added, launched by Proton on the Russian side).

Quote:
Originally Posted by airdave View Post
Or put it into orbit around the Moon?
Turn it into an orbiting Moon platform..
You'd have to have a LOT of delta-V to get it there... as previously mentioned... which creates a whole lot of expenses to create and implement.
The other issue is, if you're sending it to one of the Lagrange points, say L1 or L2 between Earth and Moon, (EML1 or EML2 behind the moon) then you have to decelerate it into a halo orbit at the L points... and keep it there. Or, if you're sending it to Low Lunar Orbit (LLO) you have to decelerate it into LLO, and provide reboost propellant on an ongoing basis to account for lunar mascons degrading the orbit. HLO might be better from this point of view, but again, the thermal issues will be considerable. Accelerating and decelerating such a MASSIVE object creates a WHOLE lot of headaches... it just isn't worth the effort. Nothing remotely the size of ISS will be needed in LLO or EML1 or 2 for many many decades, if ever... by which point ISS will be as antiquated as the Wright Flyer...

Quote:
Originally Posted by airdave View Post
Crash it into the Sun...to see how close it gets.
Have it take photos and send back data right up to the point of incineration?
Imagine the closeup views of the Sun we could get!.
Accelerating it into the orbits necessary to do this would be absolutely prohibitive... the delta V is enormous... it would literally take YEARS of continuous thrusting by ion engines to put it into a transfer orbit and get it there... it basically takes all the rocket propulsion we have just to get a probe weighing just a few tons to the outer solar system... getting to the inner solar system is even harder, from a delta-V standpoint, and requires some EXTREMELY complicated planetary fly-by trajectories to actually LOSE momentum enough to lower the orbit to even get to Mercury... actually getting to the sun is actually extremely difficult... not as simple as they make out in Star Trek... point the ship at it and go... everything has angular momentum and equates to energy that must be "gotten rid of" through braking, or accelerating in a different direction with a gravity assist... it's EXTREMELY complicated. Basically getting Messenger to Mercury took everything we had to get it there, because of the difficulties and energy levels involved... and it was just a small unmanned probe. Flying an enormous multi-hundred ton space station there... impossible without Star Treknology... IF there was a need for a such a mission, we could do it MUCH cheaper with a simple automated probe, kept as light as possible to minimize the expense and delta-V requirements to get it there...

Quote:
Originally Posted by airdave View Post
I am fully aware of the reasons not to salvage it...salvage costs quite often outweigh the values.
I guess I am just having a big problem with the idea of just crashing it into the Ocean and throwing it away so easily.
Salvage isn't going to be possible either. IF shuttle were still flying, say if Columbia disaster never happened, and the US continued with the shuttle for the foreseeable future, as the plans were prior to the 2003 loss of Columbia, and the shuttle DID manage to continue operating safely until the ISS was decommissioned, it would NEVER be cost effective to salvage any of that hardware... the delta-V cost of going there to get it back is simply too expensive. Perhaps, if the Congress was willing to drop a billion dollars on such a mission, ONE of the US modules could have been returned for the Smithsonian or something, but the likelihood of that ever being funded was zero. Same thing with recovery of Hubble... even if shuttle was still flying, it would never happen just because of the expense! With shuttle retired, there's nothing flying or going to fly even remotely capable of going and retrieving it... maybe some "bits-n-pieces" will come back via Dragon one day for museums when ISS's decommissioning time nears, but that'll be all... no major components like modules will ever come back "alive" in one piece. Removing a module and bringing it back, even if it were possible, would complicate the deorbiting manuever anyway, because it would change the station's center of gravity and mass and surface area (air drag) and all that, which you need to know PRECISELY to calculate the exact time of reentry and amount of propulsion needed to deorbit it.

When ISS eventually is decommissioned, it will be decrewed and put in a standby power-down mode. The propulsion, guidance, stabilization, and communications telemetry systems will have all been put in top working order to facilitate the eventual deorbit. Once the crew has left, the station will be left to orbit, as it's orbit will naturally and predictably decay due to the continual miniscule air drag that it encounters from Earth's outer atmosphere (which will eventually get Hubble too, BTW-- Hubble has no ability to boost it's own orbit, unlike ISS via its Russian Service Module or a visiting Progress cargo ship). Without reboosts, ISS's orbit will gradually decay until it's near an uncontrolled reentry. At some point, a deliberate manuever will put the service module flying backwards to the orbital direction, to provide retrograde thrust. The SM will be commanded to burn its reboost rockets in retrofire mode to lower its orbit to intersect Earth's atmosphere at the desired entry point, to put the debris footprint and impact points of any surviving bits into an unpopulated part of the ocean... Just as was done for Mir, so will ISS follow...

Later! OL JR
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