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I find it all very distracting and difficult to read.
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it's true (in part) if you read the text with an LCD screen (I use an CRT screen that don't "cuts the pixels" but paste them)

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Getting the components into orbit is no more time critical than missions to the ISS
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the probem is not the lenght of each launch window, the ISS don't have only a few day for the launch or an EDS/LSAM max loither time (that reduce the launch windows to about 30 per missions), the ISS can wait a launch for years and, when the rocket is ready, every day (exactly, every launch window in a day) is good for the launch

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The CEV will make only about 12 lunar orbits per day, not 50. And the Moon does rotate, once every 27.3 days.
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I accept the correction about lunar orbits (I don't know any different figure) despite the number of orbits depends of CEV altitude

but the moon that rotate is "the scoop of the millennium"!!!

seriously, the moon rotates around the earth not around itself (you know that the little launch windows from earth are not due to the earth rotation around the sun...)

without any rotation on itself, each lunar launch window (12 or more) is good

...but... just a moment... if the orbits of the LSAM/EDS around the earth at 250 km are about 15 per day... how can be less around the little moon at around 100 km? speed? gravity? ummmmh... I need to make some research about lunar orbits...

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Can you provide a quantitative analysis to back up this claim? If not, then I suggest you not randomly throw out numbers that cannot be supported.
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the number was based on 50 orbits and on the max orbital life of the CEV in stand-by (for long missions or aborted lunar departure that need a rescue, both with a cargo-LSAM already on the moon with sufficient life support):

50 orbits (all good to launch) per day x 30 days (all good to launch) x 6 months (CEV max stand-by) = 9000 launch windows from the moon

the earth launch windows (in 95 days) of the CEV may be 30 max but only without any delay (if the delays are many the launch windows will be a few...)

then, the launch from the moon may be from 300 times to 9000 times the earh launch windows

the first figure (earth launch windows) means a success of the mission or not, the second (lunar) figure means the possible rescue of the astronauts on the moon (and is greater)

of course, in real flights the number of lunar launch windows in 7-10 days (for emergency or normal departure) will be up to 500 (with 50 orbits per day) or up to 120 (with 12), in both case they are much more of the (real) CEV earth launch windows!

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But in your article you argue that launch vehicle size is not indicative of reliability. If you are now arguing the CaLV is more likely to have problems than the CLV then you are contradicting yourself. And what evidence do you have to say the LSAM is more complex than the CEV?
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my article is about missions failure due to the "one-and-half" launch architecture, NOT about a CEV and/or LSAM failure while the moon mission (this is another problem that need other analysis and other solutions, redundancy, etc.)

about reliability... there is no contradiction, all rockets may have similar reliability

the missions' fail may happen due to the 1.5 launch architecture (with an SLV months of delays don't means a mission fail!)

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I agree with the other users who say you need to support your argument with numbers. You are arguing subjectively about something that requires a quantitative analysis.
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my opinions is that the number I've posted in this therad (only 30 launch windows of a few minutes) are sufficient to demonstrate the risk of the 1.5 launch architecture

I can't add number about CEV/CLV reliability and failures, but, since they are built with "shuttle-derived" technology.......

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The ISS's orbit was selected to permit access to it from both Cape Canaveral and the Baikonur Cosmodrome in Kazakhstan. Placing the ISS in a lower inclination orbit would have made access by the Space Shuttle more efficient, but it would have prohibited Russian participation in launching components, crews, and supplies. In the wake of the Columbia accident, this turned out to be a very wise decision.

Space Shuttle flights to the ISS are launched into a high inclination orbit (51.6 degrees), but this reduces the amount of payload that can be carried versus a due east launch into an orbit with an inclination of only 28.5 degrees. Therefore, prior to the Columbia accident, flights not going to the ISS were always launched into more efficient orbits, but this made subsequent access to the ISS impossible. I believe the recommendation following Columbia is that all future Shuttle flights be able to reach the ISS in case of an emergency. (I believe this is why NASA decided to abandon the Hubble Space Telescope, though I'm not sure that decision is absolute. Any future repair mission to HST will place the Shuttle in an orbit prohibiting ISS access.)

Future lunar missions will surely be launched into as low an inclination orbit as is practical. This will maximize the lift capacity of the launch vehicles and provide a longer window for launch of the second component.

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gaetanomarano, just for your information:

I'm a little bit colourblind, and I can hardly read the orange letters you used on the grey background in your last post.

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The ISS cannot wait for years. It must be periodically re-supplied and the emergency escape vehicle (a Soyuz capsule) must be replaced every 6-months. You are also missing the point that it has never needed to wait for years because the re-supply ships have always gotten off the ground on or near to schedule. Yet you are arguing that it is a virtual certainty a CEV will not get off the ground on or near to schedule. I don’t believe that argument is supported by statistical evidence.


The moon most certainly does rotate. It must complete one full rotation per revolution around the Earth in order to keep the same hemisphere facing Earth. The Moon’s periods of revolution and rotation are both 27.3217 days.


Because the Moon is less massive than Earth, an orbiting satellite doesn’t need to travel as fast to keep from being pulled in by the weaker gravity. This makes the period of revolution in a low orbit around the Moon about 2 hours versus 1.5 hours around Earth.

P = SQRT(4*pi^2*r^3/GM)

Let’s say we’re in a 100 km orbit above the Moon, then r = 1,838,000 meters and, for the Moon, GM = 4.902794E+12 m^3/s^2. Therefore,

P = SQRT(4*pi^2*1,838,000^3/4.902794E+12) = 7,071 sec = 1.964 hours


I disagree. First, the launch windows can be as long as two hours, not just a few minutes. The following document discusses launch windows starting on document page 371 (or page 11 of the PDF):

http://users.wpi.edu/~aiaa/esas/ESAS.REPORT.06.PDF
(WARNING: Large document, 9.6 MB)

For a 29-degree inclination orbit, the launch window exceeds 2 hours for a maximum payload penalty of 500 pounds. On the other hand, note that the launch window for ISS access is only a few minutes.

Second, you haven’t provided any statistical evidence to support your contention that long delays are inevitable. The reliability of launch systems to regularly re-supply the ISS and provide crew rotation on schedule within a very tight launch window speaks to me that meeting the launch requirement of the CEV is most definitely doable and not cause for unwarrented concern.

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I've changed the color, I hope it's better to read now.

.

The comment I was referring to was made while you where arguing against my suggestion that the CEV be launched first. Your argument was that the CaLV/LSAM/EDS is more complex than the CLV/CEV and would therefore likely result in more delays than if the CEV is launched second. This seems incompatible with your argument that the reliability of large and small launchers is the same.

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The ISS cannot wait for years
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it's unnecessary that you explain me what is obvious about the ISS

it's clear that "can wait years" is not "without re-supply"

simply (you know) the re-supplied ISS can wait in its orbit for years (and every day is good to launch a Soyuz or a Progress or a Shuttle) while the LSAM/EDS will have only 30-40 launch windows (in 95 days), then, DIES (and can't be "re-supplied" ...or "resurrected"...)

note: two grammar corrections in my text about moon rotation etc.

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Because the Moon is less massive than Earth, an orbiting satellite....
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the 12 orbits per day (all good for a launch from the moon) of your previous post mean: 72 (normal or emergency) launch windows for a 7-days moon mission, 120 l.w. for a 10 days mission, 360 l.w. for an one month mission (with cargo-LSAM resupply) and over 2000 l.w. for a (re-supplied) very long mission (or to wait a rescue) while the CEV runs six months' stand-by in orbit

very good numbers if compared with the 1.5 launch architecture's l.w. of the CLV/CaLV!!!!

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I disagree. First, the launch windows can be as long as two hours...
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36 minutes (like in my previous posts' calculation) or 2 hours don't change so much the problem because the risk is NOT due to the length of the l.w. but on the number and length of DELAYS

the 1.5 launch moon missions may fail due to a "sum of (little and big) DELAYS"

see recent the story of the Shuttle... months to modify a tank, weeks to change an SSME (external in the Shuttle, but, while the J2X is INTERNAL if it need to be changed the entire rocket must be deassembled and reassembled!), two months for a simple ECO sensor malfunction, etc. etc. etc.

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Second, you haven’t provided any statistical evidence to support your contention that long delays are inevitable...
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the precise statistical evidence of the 1.5 launch failures will be given by NASA chiefs in 2020 to a Congress' commission that will investigate about the giant VSE moon missions' fiasco

in my next post I will give a "visual opinion" of the risk with the 1.5 launch architecture

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no

please read my previous post about this argument

the main problem is that each CaLV delay of more than 2 weeks (the life of the CEV with the astronauts) need to launch another crew and another, another, another for "n" 2-weeks delays

a giant cost and a big risk for the astronauts

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If not for re-supply then what is it you claim the ISS is sitting around waiting for? If you acknowledge the re-supply vehicles are launching regularly on or near schedule, then I fail to see your point. You’ve yet to demonstrate that launching a CEV on time is any different than launching an ISS re-supply ship on time.

But you haven’t provided any evidence to demonstrate that 30-40 launch windows over 95 days is inadequate. You simply handwave and say it is self-evident, but history (such as regular and mostly on-schedule ISS re-supply) seems to contradict your conclusions.

On days when the landing site lies in or near the plane of the orbiting CEV, there will be ample launch opportunities. However, there can be periods of days at a time when the landing site lies well outside the CEV’s orbital plane. (In fact, it can be as much as 90-degrees out of plane.) Unless the CEV, LSAM, or both are provide with the extra propulsion capability to perform a very large plane change (as much 2.3 km/s delta-v), then there will be extended periods when no launch windows are available.

Of course the length of the launch window is important. For delays such as those caused by unsatisfactory cloud or wind conditions, a short window will almost certainly result in postponement of the launch until the next available window. However, a long window greatly increases the chance the unsatisfactory condition will correct, thus permitting the launch to proceed within the window.

The Space Shuttle is a very complicated and, in many ways, flawed machine. The CLV/CEV is a much safer configuration that eliminates many of the problems that has plagued the Shuttle. For instance, the tank problem you mention is a non-issue with the CLV/CEV. Furthermore, the problem was discovered during a launch and did not stop that particular mission from proceeding – only those that followed. Likewise, if a similar problem occurred with the CLV/CEV it would not result in the loss of a LSAM/EDS; it would only result in the postponement of future LSAM/EDS launches until the problem is corrected.

The other delays you speak of do occasionally occur, but they’re only a problem when they begin to compound. It should be possible to perform a statistical analysis and calculate, based on past experience, the probability of a lunar mission abort due to the inability to launch a CEV within the allotted time. For instance, on average how many launch attempts have been required to get a Shuttle off the ground, a Soyuz, what is the standard deviation? What was the cause of each delay and the time required to correct the problem? Etc. etc. Without this kind of data we’re really just guessing at whether the odds are acceptable or not. I cannot support your conclusions without more complete data and analysis.

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OK, BobB is surely correct; I see his point. Still, launch pads, as well as space stations can be moved. Don't the Russians have a southern little colony in California or by the Black Sea or something where they could set up a launch pad?

And if latitude is such an important consideration, then why are we launching from Cape Kennedy? The US has even more southern possessions (Brownsville, TX, or Guam) or better yet, why not outsource the launch pad to a place like Singapore (1 degree north).

Too bad Carter gave away the Canal Zone. . . .

Well, the US prefers to launch off the east coast (launch over the ocean so that if anything goes wrong there's nothing to hit). That eliminates Texas. Shipping stuff to Panama or Singapore would be prohibitively expensive. The floridian coast is a good compromise that still allows one to take advantage of most of the earth's rotational benefit.

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If not for re-supply then what is it you claim the ISS is sitting around waiting...
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since I'm italian probably my english is not clear, I try again to explain

the ISS runs in orbit and (with resupply) its life will be of 10, 15, 20 years or more

if it needs a resupply, EVERY DAY is good for a launch (no need to wait the moon night) and, with three space-ports, will be available 3+ launch windows per day, over 1000 launch windows per year

if the Shuttle can't fly for a year or more, the ISS' resupply can be sent with a Progress and in future the vehicles for crew rotation and ISS' resupply will be MANY

the LSAM/EDS will have only 95 days of total life (not 20 years!), only 30-40 of them usable, then only 30-40 launch windows in total, from only one space-port

if the "sum of delays" will exceeds 95 days, the LSAM/EDS dies and the moon mission fails

and you can't send any Shuttle/Progress/ATV/Shenzhou to the LSAM/EDS to "resupply" it so it can survive six months or one year!

it's DEAD

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But you haven’t provided any evidence to demonstrate that 30-40 launch windows over 95 days is inadequate...
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I can't claim that 70%, 80%, 90% of missions will fail and you can't claim that 90%, 100%, 110% of missions will be successful, because we can't know the real figures before the real launches

the problem is that the 1.5 architecture BORNS WITH THIS BIG RISK while the single launch architecture BORNS WITHOUT THIS BIG RISK

three monts of delays of the "1.5" means a mission fail and $6+ billion lost

six, nine, twenty months or more delays with the single-launch NEVER mean a mission fail!

I suggest the SLV to avoid that ALL moon missions will born with a "BUILT-IN FAILURE OPTION"

the second launch delays may be little, medium or big

ONE big-delay (also due to a little problem like the ET's ECO sensor change) of two months can "EAT" 2/3 of ALL launch windows available and TWO medium-delays will "EAT" the ENTIRE set of launch windows available!

then, the real number of launch windows available with every mission (net of delays) may be 3, 5, 11, not 30+

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On days when the landing site lies in or near the plane of the orbiting CEV, there will be ample launch opportunities...
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the CEV/SM will be remote-controlled to change its orbit, if it will runs in the same orbit the number of LSAM launch windows equals the number of orbits per day (12, you say)

if the CEV will change its orbit (via remote-control) the number of launch windows may be more or less than 12 per day (but I don't think it will be necessary to do)

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Of course the length of the launch window is important....
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true, but only to solve little problems

unfortunately, I think that (like with the Shuttle) the main problems and delays will not come from wind or rain but from one or more of the thousands critic parts of the very complex (and new) CLV/CEV/SM

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The Space Shuttle is a very complicated and, in many ways, flawed machine....
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not true, the '70s' Shuttles (orbital-only) electronics, computers, software and mechanics is incredibly simply (and WELL known, thanks to 25 years of good and bad experiences) if compared with to-day's an 2020 technology (that will be completely new, with hundreds unknown problems that may happen!) made for beyond LEO navigation, etc.

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the tank problem you mention is a non-issue with the CLV/CEV...
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the CLV and the SM will have many tanks... but the problems that will give big delays don't need to come from tanks, the full system will have thousands of parts that may fail of may need to be changed (with weeks or months of delay)

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if a similar problem occurred with the CLV/CEV it would not result in the loss of a LSAM/EDS....
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true, but if the problems persist (like with the Shuttle) the entire VSE/ESAS plan will be DELETED and NASA must restart from ZERO with a new and more reliable mission architecture (that mean billions lost and the first new moon landing in 2030...)

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Without this kind of data we’re really just guessing at whether the odds are acceptable or not...
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I agree with you, but I prefer (and I suggest) an architecture WITHOUT a possible fail-option "BUILT-IN" (like with the "1.5")

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All of Russia's launch sites are far north, though I've hear rumors they're working with the European Space Agency to build a Soyuz launch complex at the Kourou launch facility in French Guiana. I don't know any of the details of this.


Cjl has already provided a good answer to this part. Cape Canaveral/Kennedy Space Center provides a good compromise between all the important considerations -- good access and infrastructure, open ocean downrange for safety, and fairly close to the equator.

Being at N 28.5 deg latitude is actually pretty good. At the equator the amount of velocity gained from Earth's rotation during a due east launch is 465 m/s. At other latitudes the velocity is 465*cos(latitude). Thus at 28.5 degrees we have, 465*cos(28.5) = 409 m/s. Compare this to launching from 50 deg latitude, 465*cos(50) = 299 m/s.

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There are plans currently in motion to have Soyuz et al launches from the Ariane site in French Guiana. That would solve the orbit inclination issue.

To a previous poster: no shuttle has "blown up". Columbia was torn apart by aerodynamic stresses during its entry into the atmosphere. The stresses were due to a foam-impact-created hole in its left wing's RCC leading edge, which led to the structural deterioration of the wing. NASA managers decided that, despite video evidence of the foam impact, this anomaly was not worth pursuing.

Challenger was destroyed by aerodynamic stresses caused by the break-up of the launch stack at a high speed low in the atmosphere, due to a faulty SRB whose field joint had failed as a result of conditions already known by NASA and Thiokol managers.

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They mainly have Baikonour (though that's Kazachstan in fact, rented by the Russians) and Pletesk. Pletesk is very northerly.

They are building a Soyuz(2) launch pad in the ESA Kourou base (which is in French Guiana, French overseas territory). That's no longer a rumour, but an official contract. This will allow Russia to launch from the equator other than Sea Launch. Of course, they have the same problem as with Baikonour that the base is not located in Russia, but I thought the contract for Kourou was financially interesting for Russia.

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The ISS orbits at an altitude of about 350 to 407 km (it occasionally requires boosts from the Shuttle to raise its altitude). If we assume the maximum altitude, then its orbital velocity is about 7,665 m/s. If we were to move it from its current inclination of 51.6 degrees to 28.5 degrees, then we're looking at a plane change of 23.1 degrees. The velocity required to make this plane change is,

delta-V = 2*7,665*sin(23.1/2) = 3,069 m/s

Let's say we move it with a propulsion system using LOX/liquid hydrogen with a specific impulse of 450 seconds, then the required propellant mass ratio is,

Mass ratio = e^(3069/(450*9.807)) = 2.00

This means the mass of propellant needed to move the ISS to the lower inclination is equal to the mass of the ISS plus the dry mass of the attached propulsion system. The fully assembled ISS would require over 400 tonnes of LOX/LH2 to move.

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Gaetanomarano, I think you're basing your expectation of launch delays too much on the Shuttle programme, which because of its fragile tiles and wings has a lot of weather constraints that other vehicles don't. Most Saturn V launches went on time, most Soyuz launches still do.

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the new vehicles may be more or less reliable (I don't know) without any comparison with the past

the problem is that an 1.5 l.a. BORNS with a "sum-of-delays-failure-option" BUILT-IN while the SLV may have years of delays without any missions' fail because it borns WITHOUT any "sum-of-delays-failure-option" built-in

.

My point is that the new vehicles lack features of the Shuttle that are the major causes of Shuttle delays, so should be less likely to be delayed. In addition, several of the delay causes you mention are long-term ones like the current Shuttle sensor problem that will be detected before the target vehicle is launched and thus will not affect the rendezvous. It is only the last-minute problems that occur after the target launch that are a problem.

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true, the new vehicle lacks some old problems but may have hundreds of new and unknown problems

the single-launch may COMPLETELY avoid ALL missions' failures due to a "sum of delays" (that, I think, is a GIANT advantage!)

-----------------------------------

since "images worth 1000 words", I post here my "visual opinion" about the 1.5 launch architecture

the 30-40 max (and short) launch windows available for the 1.5 l.a. (before the LSAM/EDS' death) remember me "something"... THE ROULETTE!!!

the 1.5 l.a. REALLY is a sort of "MOON-ROULETTE" with only "36 numbers" (launch windows) to bet!

if NASA wins, all is ok!

but, if NASA bets on the wrong number, they lose $104,000,000,000 (or more!)

can NASA risks all its funds and credibility on a single number? (1.5)

moonroulette.jpg
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So on the equator, we would gain 56 m/s, only a 14% improvement, probably not worth pursuing.

Still, Kourou, French Guiana, has a latitude of about 5.1 degrees, which yeilds a rotational velocity of 463 m/s. Moreover, Kourou is a lot closer to Florida than it is to Europe and Russia. If the Europeans and Russians can make it work over such long distances, so could the US. Manned spaceflight is hugely expensive. Any savings in launch costs have to be considered.

In this vein, how many people who work at Cape Canaveral are actual Ph.D. rocket scientists, and how many are maintenance types who do jobs that could be filled by Guianians for a tenth of the wage? The operational costs of relocating to Kourou might actually be lower than the Cape. I would also guess that being so close to the equator there would be fewer hurricanes.

Will this happen? Probably not, since most NASA types are comfortable in their lives in Florida, and relocating to a miserable place like Kourou would not appeal to them.

(Which, incidently, is another argument for handing NASA's lunar exploration project to the US Space Command. Military types are used to living in miserable parts of the world.)

Gaetanomarano's basic point is valid. The 1.5 architecture will be born with the extra risk of delays causing missions to be scrubbed. Nevertheless, coordinating multiple launches is something we'll all have to get used to if the human race is ever to get more than a toehold into space. The delay risk could be reduced if all manned activity in LEO, including the ISS, took place within an orbital inclination band of 5 degrees. Moreover, the delta-v's for space rendezvous would be negligible for everyone. It's called standardization.

How to move the ISS? Well, for one thing it would be a lot easier if it were moved sooner, rather than later. 180 tons is a lot less mass to move than 400+ tons. Also, the ISS has to be periodically boosted in its orbit due to atmospheric drag. So we just hook up one of the last space shuttles and burn however much fuel it takes. If necessary, put a spare fuel tank in the cargo bay. The long term rocket fuel savings would be worth it.

Using Bob's formulas to figure the fuel required to move the ISS to a 5.1 degree inclination (a 46.5 degree move):

delta-V = 2*7,665*sin(46.5/2) = 6,051 m/s

Mass ratio = e^(6051/(450*9.807)) = 4

So it would take over 400 tonnes of oxygen / hydrogen to move the ISS to a 5.1 degree inclination as it is now, and over 800 to move it once it's fully loaded.

Unbelievable. . . .

If the ISS was intended to be a permanent outpost, why didn't someone think about this before?

Mulitple launches have been done in the past - Gemini, Skylab - the tradeoff is between the added complexity and having to make a larger vehicle for a single-launch mission.

As to putting all activity in one orbital plane, this doesn't work because orbits precess at different rates depending on altitude, so you may start close but before long you drift away unless you spend fuel on frequent adjustments.

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How can NASA lose several years' budget on one launch? Your numbers need checking.

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And 56 m/s is only about 0.6% of that needed to achieve orbit. So moving to the equator gains a little bit but not much.

You also must consider that all new facilities would have to be built at Kourou to accommodate the US vehicles. KSC already has launch pads and a vehicle assembly building.

Another advantage of being in a near-zero inclination orbit is the frequency of launch windows. A launch could take place at just about any time.

The only engine the Shuttle has that can be used for this is the OMS engine, and it has a specific impulse of only 313 seconds. This means the required mass ratio jumps to 2.72 to move to 28.5 degrees (and 7.18 to move to 5.1 degrees). It would therefore take 310 tonnes of propellant to move the 180-tonne ISS as currently assembled. If you used the Shuttle’s 25-tonne cargo capacity to carry the propellant required to accomplish this, it would take 13 launches. And as soon as we begin to move it we eliminate the Russian launch option (at least until the Kourou facility is operational), which means the Shuttle is then responsible for all re-supply and crew rotation and there is no Soyuz option for emergency crew return. We also delay any further ISS assembly until after the move is completed. And all this is going on while NASA is planning to retire the Shuttle fleet in four years. There is no way this could ever be worth the effort, cost, and risk.

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It's actually worse than that. Mass ratio is the fully fueled mass divided by the dry mass. Thus a mass ratio of 4 means you have 3 parts propellant and 1 part dry mass, (3+1)/1 = 4. You therefore need 540 tonnes of LOX/LH2 to move 180 tonnes, or 1,200 tonnes of LOX/LH2 to move 400 tonnes.

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because, if many 1.5 launches will fails, NASA will lose all the money spent for R&D, hardware, etc. in next 10-15 years and will have a big cut of the VSE funds (or the privatization of the agency)

I see your point. There is absolutely no way the shuttle can move the ISS to a more practical orbit. The only way would be with the new Cargo Launch Vehicle (CaLV) that's supposed to be developed alongside the new CEV. The upper stage of the CaLV is envisioned to be equipped with two J-2 rocket engines. Each of these would have a specific impulse of 418 s, for a total of 836 (correct me if I'm wrong about this please--I'm obviously no expert on space navigation). Applying this figure to Bob's formulas:

Mass ratio = e^(6051/(818*9.807)) = 2

for the full move to a 5 degree inclination. By the time the CaLV will be operational, the ISS is supposed to be completed (yeah right). So we're back to 400 tonnes of propellant. Each CaLV could carry an extra 100 tonnes of fuel as a special payload. So on this scenario, it would "only" take about four CaLV launches to move the ISS to an equatorial inclination, and perhaps two launches to move the ISS to the Cape's inclination.

So you're saying that if NASA go for 1.5, every single launch for the next 15 years will fail? Even the Shuttle managed quite a few on-time launches. Why will NASA suddenly have much less success with a technique which worked reasonably well in the past?

Your point is obviously one that needs to be considered, but in taking such an extreme position you do your cause little good.

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I think that move the ISS is interesting but not possible

it need a special CaLV and some $billions

the lunar-CaLV will be available only in 2018-2020 and special "orbital & probes" CaLV will be available only in the next two-three years

15 years are too much for the ISS to expand, move and use it for different purposes

in 2020-2025 the better choice will be to build a new space station, in another orbit and with cheap technologies

.