not all, of course, but may be many

one Shuttle mission costs around $600M

one moon mission may cost (including shared R&D, etc,) $6+ billion

I think it's too much money to risk!

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Specific impulse (Isp) is not additive like that; it is a measure of efficiency and tells us how much thrust can be obtained from a given mass of propellant. Using two engines doubles the thrust but it also doubles the propellant flow rate, therefore the efficiency remains the same. the calculation should be,

Mass ratio = e^(6051/(418*9.807)) = 4.38

The upper stage of the CaLV is called the Earth Departure Stage (EDS). Let's suppose we can lift a fully fueled EDS into orbit and attach it to the ISS. After the fuel is depleted, we jettison the EDS and attach another, and so on until the ISS is moved to the final orbit. The burnout mass of the EDS will be about 22 tonnes and it will carry about 208 tonnes of usable propellant.

The total mass to be moved is the 400-tonnes of the ISS plus the burnout mass of the EDS, for a total of 422 tonnes. With a mass ratio of 4.38, we will require a total propellant mass of 1,426 tonnes. It will therefore require 7 EDS to complete the move.

Also note that the ISS was never designed to handle the stresses that will develop during such a maneuver. There is no guarantee it would ever survive the move.

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Wow. . . .

Well, maybe if the French Guiana deal works out with the Russians and they start doing many of their launches there: if the ISS were in the 28.5 degree inclination orbit, would it be practical for Russian spacecraft launched from Kourou to reach the ISS? In which case it would be a lot more convenient for US craft and would only take about 3 EDS to move it optomistically speaking.

What about a specially designed ion engine module that would be attached to the ISS? The low level of acceleration wouldn't stress the structure much. If it were powerful enough, it would eliminate the need for periodic boosting of the ISS, and though it might take a long time, it would take a lot less fuel to change the ISS's inclination due to the higher specific impulse of ion engines. Indeed, the ion engine wouldn't even need to be powerful enough to eliminate the need for periodic boosting. These could still be accomplished while the weak ion engine continously nudged the ISS into a new orbit.

But gaetanomarano is probably right that it would be cheaper to just build a new space station, one specially designed to serve as a way station while assembling craft for lunar insertion. 7 CaLV's could build a sweet station!

It appears to me that launching a Soyuz into a 28.5-degree orbit from Kourou should be feasible, but that’s unconfirmed.


Although ion engines are very fuel efficient, they require much electrical power. Since a finite amount of power is available, ion engines are very limited in how much thrust they can provide. In the following post,

Here's an idea

I performed precisely this calculation for another problem we were discussing (someone was proposing sending the ISS to the Moon.) If 100% of the ISS’s electrical power were used for propulsion (an impractical figure) it would take 10.8 years to produce a delta-v of 3,100 m/s (essentially the same number needed to transfer from a 51.6 deg orbit to a 28.5 deg orbit). In reality only a relatively small amount of the available power could be diverted to propulsion, thus it would take decades to complete the transfer.


I don’t know if we need another space station or not, but I agree with gaetanomarano that it would be better just to build a new one. I don’t think the ISS is going anywhere from its current orbit.

It is my understanding NASA plans to use the CLV/CEV for ISS access once it becomes operational. NASA should therefore have a considerable amount of launch experience with the CLV/CEV before the start of the lunar missions. I’m not sure this is something gaetanomarano has taken into consideration in making his pessimistic assessment of the 1.5 launch architecture.

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you are too optimist about the CEV and its use for ISS because:

- due to the changes in its design (5-seg., etc.) and other possible delays I don't think that an orbital-CEV will fly before 2014-2015

- in 2015 the orbital-CEV will be only one of many crew vehicles available for the ISS (Digital-Soyuz, Shenzhou, Kliper or a new russian vehicle)

- the ISS' crew will remain of 3 for great part of its time

- since the ISS is international, only 1/3 of the crew will be american (and many times will fly with the Soyuz, like to-day)

- Europe, Russia and China can't spend $200+ million per seat for the CEV (and don't want to spend it, since one Soyuz-seat costs $20M)

the sum of these points is that an orbital-CEV will fly only for the crew rotation of american astronauts, then, in 2014-2018 (when the moon missions begin), the CEV will (probably) fly 3-5 times max, not a great amount of launch experience

consider also, that, a big launch experience, don't means to avoid all problems and delays (see the 25y. experience of the Shuttle...)

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The ISS orbital inclination was selected so that it would be accessible to launches from Baikonur. Having a second launch site has provided continued access following the temporary loss of Shuttle support. If you reduce the inclination, you must provide an alternative to Baikonur. Korou will provide this once the Soyuz pad is built there. However, reducing the inclination to near-equatorial will mean that it is no longer accessible from the Cape. In this case a second equatorial launch site for the US supply vehicles will be required.

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While I understand the Russians are building a launch pad for Soyuz rockets at Korou, I haven't seen anything that says they're planning on building the facilities needed to launch Soyuz capsules there. It takes a fair amount of specialized infrastructure to prepare a Soyuz capsule for launch. Being able to launch Soyuz rockets is only part of the equation.

qwiz is right about changing the inclination of the ISS - if we lowered the inclination, then almost immediately, you couldn't launch anything from Baikonur to the ISS without requiring an energy (propellant) intensive delta-I maneuver.

If we decide we need a space station for orbital assembly, perhaps a single inflatable habitat module with solar arrays and docking ports would be sufficient. It wouldn't have to be nearly as elaborate (or expensive) as the ISS.

gaetanomarano,

I don’t think history bears out your dire predictions. Unless you can provide real statistical evidence to support your estimations, rather than anecdotal evidence, I am under no obligation to accept your claims about the inevitability of future lunar mission failures.

I’m not saying you don’t have a point, and I’m not saying failures of the type you describe will not happen. I just think before either method – 1.5 launch or single launch – is favored, a detailed statistical analysis has to be performed to determine what the real probability of failure is and compare that risk against the other pros and cons of the two architectures. Only then can one determine whether the risk associated with the 1.5 launch architecture is an acceptable risk or not.

So far I’ve seen mostly handwaving and alarmist tactics, and what numbers you have provided I don’t believe are adequate to support your conclusions. Your proposal may have merit, but you seem to be overselling the idea with insufficient quantitative support for it.

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the problem is very simple

the ESAS plan needs 13-15 years and an incredible quantity of money to send the first (new) mission on the moon

when the time is ended and the money spent ALL must be PERFECT

if the "statistical analysis" suggest that an 1.5 l.a. is reliable but the PRACTICE of REAL launches will be different, a giant quantity of time and money will be lost and NASA must restart from ZERO

consider that each moon mission will be very very expensive (about 10 times one Shuttle launch) and that only 12 moon missions are planned in 2020-2025

then, "only" two-three missions fails (due to the 1.5 l.a.) will be an economical catastrophe, like lose 20-30 shuttles!

this is my opinion

do you think that NASA, politics and public opinion can accept this risk?

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If I read your numbers correctly, you are essential predicting about a 20% failure rate due to the inability to achieve an Earth orbit rendezvous. This is absurdly pessimistic in my opinion.

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no

I can't predict (and no one can predict now) the "number" of missions fail

if the CLV will be sufficiently reliable may be 1-2 fails of 12 missions

but, if the CLV (made with "shuttle derived" technology and MANY new systems and electronics), will have an high number of (little and big) delays (like to-day's Shuttles... one year of delays, then, "lift-off!"), the number of missions' fails may reach 100%!

and this is NOT the only risk of the 1.5 l.a.!

don't forget that a mission may fails also due to a ROCKET failure!

with the 1.5 l.a. each moon mission will have a TRIPLE risk of failure:

1. failure of the CaLV, or...

2. failure of the CLV, or...

3. failure due to a "sum of delays" of the second launch

with the SLV the risk of mission failure may come ONLY from the failure of the SLV

then, the risk of an SLV based mission is only 33% of the 1.5 l.a. (or, if you prefer, the risk of failure of the 1.5 l.a. is THREE TIMES than with SLV)

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Okay, perhaps "predict" was the wrong word. But you are certainly assigning a probability to the outcome when you say 1-2 missions, or 2-3 missions (you keep changing the number), out of 12 will likely fail. If we go with the median number of 2 failures, then you're talking a 17% failure rate in simply getting two payloads to link up in orbit.

Can two failures occur? ... Absolutely. But I think any reasonably calculated probability will show the odds are much closer to there being zero failures out of twelve.

I don't deny that there is an inherent risk in the 1.5 launch architecture, nor have I ever denied it. I just think you're grossly overselling the risk factor and promoting inflated numbers to make your case.

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you ask me a reliability figure that is IMPOSSIBLE to have before the rockets will really fly!

but the problem is very simple:

with 1.5 l.a., moon missions CAN fail for a "sum of delay" while, with the SLV, they CAN'T

if the problem will happen in 2020 the ENTIRE program will be DELETED and NASA (if will "survive" as space agency) must restart from ZERO

and, don't forget the risk of failure of the mission due to the failure of one of two rockets (that, with TWO rockets is TWICE than with one!)

I explain my point of view in a simpler way

just imagine 1000 cars WITH airbags+belts and 1000 cars WITHOUT them

with no accidents, no passengers dies (with both kind of cars)

but in case of accidents (launch delays), that may happen, the passengers of the unsafe cars will die, while many of the safe cars will survive

the 1.5 l.a. is like a car without airbags and belts!

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Let's look at the historical record for NASA dual launches:
Gemini 6: Target vehicle launch failure
Gemini 6A: Launch delayed, successful rendezvous at second attempt
Gemini 8: Success
Gemini 9: Target vehicle launch failure
Gemini 9A: Launch delayed, successful rendezvous at second attempt
Gemini 10: Success
Gemini 11: Success
Gemini 12: Success
Skylab 1: Launch delayed due to target problem, successful rendezvous at second attempt
ASTP: Success

The two complete failures were both due to target problems. None of the delays in launching the second vehicle were long enough to prevent a successful rendezvous.

Why should things be so much worse in the future?

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my impression is that you want only demonstrate that I'm wrong, no matter if the 1.5 l.a. will fails!

the problem is different because:

1. the Gemini was very simple vehicles with very simple rockets while the LSAM, CEV, etc. are very complex (especially the electronics will be thousands times more complex than Shuttles, that, since are much more complex than a Gemini, have had much more and much longer delays and problems)

2. the success to rendez-vous an Agena is not the same, a capsule like the Gemini (or the Soyuz) can fly every day and have many delays before reach an Agena, the CEV will have only 30 brief launch windows before the LSAM/EDS death

3. the moon missions will be only 12 in 2020-2025 (if the funds will be sufficient...) and each mission will cost $6+ billion, then, lose the hardware of ONE moon mission will be like lose the hardware of 100+ Gemini/Titan!

however, this is only my opinion

if NASA wants to risk with the "1.5" it's not my problem

also... why NASA (aka WERNHER VON BRAUN...!!!!) have NOT used the 1.5 l.a. in '60s (since the technology was available from Gemini...) for the Apollo missions if it's so good, reliable, cheaper, safe, smart, etc. etc. etc.?????

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I just want to see your proposal accompanied by what I feel is realistic risk analysis.

Simple by today’s standards but high-tech for the time using ‘primitive’ 1965 technology.

You keep saying this but you fail to grasp the point that none of these other missions that “can fly any day and have many delays” have ever needed to do that. Mission after mission after mission has lifted off and successfully completed its rendezvous on or within days of the originally scheduled launch time. You expect us to just forget about the success of the past and accept that the CLV/CEV will suddenly be plagued by problems and delay after lengthy delay. I see no historical basis on which to draw that conclusion.

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You scoff at my request for a reliability estimate citing it is impossible to do so for a vehicle that has yet to fly, and yet you have no problem whatsoever stating affirmatively that the CLV/CEV will be more complex and have a worse record for delays than any vehicle that preceded it. If it is impossible for you to provide the former, it is likewise impossible for you to conclude the latter.

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"simple" is used literally, not only "simpler than to-day technology", but "simple" as "made of less and simpler parts"

like the "simple" '70s Voyagers that have worked well for a very long time or the '60s Lunakods, etc. (while HALF of the "modern", complex and hi-tech Mars probes have failed!)

or the "simple" (but perfect!) Apollo and SaturnV that was successful (with only one fail of a little part of one module of one mission) in the very complex moon missions (with '60 technology!) compared with the problems of the, much more complex (and updated) orbital-only Shuttle

etc.

the new vehicles will perform better missions but will be incredibly more complex and with hundreds more parts, chips, sensors, etc. than ALL past vehicles

then, like all complex machine may fails MORE than "simple" machines

Gemini was like a 4-functions pocket calculator... it works or not works

CEV, LSAM, etc. will be like a to-day's PC, with Win XP, hundreds of thousands files, thousands bugs, virus, internet attaks, spywares, HDD failures, damaged CDs, etc. etc. etc.

the new PC performs much more than a pocket calculator but its problems are multiplied n-times and, each problem (launch delay), may need hours or days to find and solve, but, many times it's impossible to repair and vital data (moon missions and hardware) are LOST

that may happen (and will happen) with future vehicles, compared with the old but "simple" gemini, Apollo, Voyager, etc.

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the 1.5 l.a. (+ two rockets that may fail, instead of one) don't become "safe" and "reliable" if you demonstrate here that I'm wrong!

the only way to have safe and reliable launches is to avoid to use the 1.5 l.a. with the "sum-of-delays-failure-option" BUILT-IN

it's better an architecture (single rocket and single launch) that DON'T HAS this (bad) "option" BUILT-IN for the same reason that a car with airbags and belts is better than one without them

do you prefer to drive a car with airbags and belts, or not?

your choice!

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Apollo and Saturn V were far from perfect. The first test launch of the Saturn V, for instance, had several major problems and the vehicle nearly shook itself apart. And during the launch of Apollo 13 the rocket was headed toward a catastrophic failure had the center engine of the S-II stage not been shut down early. All the Apollo missions except #13 achieved their primary objectives but not without a great many problems along the way.

Bad analogy. The pocket calculators I used in college back in the late 1970s were always wearing out and breaking down. Just about every year I had to buy a new one. Today’s far more complex PCs, if properly maintained, can work reliably for several years with little problem. PCs usually become obsolete before they wear out, unlike those simple old calculators I once used.

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the missions results of the SaturnV-SLV was 100% perfect: all CM/LM launched in orbit and toward the moon! (all things have problem in tests)

I know the apollo13 problem with the 2nd stage central J-2 engine failure (but with successful orbital insertion) ........just imagine what may happen if the "central" J-2x CLV engine will fails.......... (in the 11 manned apollo launches the "central" SaturnV-2nd stage J-2 have failed 1 time... how many times will fails the "central" J-2x CLV engine in the 12-only new $6+ billion moon missions.....?????)

PC/calculators: bad example but TRUE

the first calculators was like the first airplanes, cars, clocks, etc.

to-day, if a (simple) pocket calculator works don't give any problem while near all PCs have problems every day

probably you think that only "BIG" problems counts, a spyware and virus to remove, one or more PC "freezing" per day (that need to restart the PC with all unsaved work lost), newly installed programs that don't work (or damage other softwares), disinstalled softwares that changes PC configuration or delete files used in other softwares, etc. etc. etc. etc. etc.

one day I've disinstalled a program on my PC that have damaged so much the PC files that I was unable to reinstall the Windows in its own folder (I've saved the files in my PC without format the hard disk only with a little trick: change the windows folder name with the dos from floppy and reinstall in a new windows folder, but losing the registry configuration of many softwares)

in my experience (and of great part of PC users), the number of (little and big) problems with PCs (including simple freezing) are hundreds per year, and around two dozens times I've saved my PC without format the HDD only because I have a good experience from MS-DOS days!

then, my example not only is good... it is PERFECT!

just imagine how many delays may happen on the CLV/CEV, etc. with hundreds unknown problems in its thousands chips, computers, electronics, sensors, cables, etc. etc. etc.

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Do you think NASA's CEV contactor is going to stick a consumer built PC running Windows XP into their capsule? All the problems you described are commonplace on poorly maintained general purpose comsumer PCs. Embedded computer systems are an entirely different animal. How often have you had to reboot your washing machine or microwave oven? These devices are microprocessor controlled but aren't suseptable to viruses and crashes.

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please don't say obvious things or treat me like an ignorant, I know many of these arguments from when they was invented

it's clear that all systems will be the best, space-grade, double and triple redundancy, etc.

but we know many "high-grade" products (airplane, military, supercomputers, medical, etc.) that fails in its first versions/units, need big changes, upgrades, delays, redesign, new tests, etc. (just see the 2.5 years of extra-research after the Columbia accident to solve the foam's problem... without solve it!)

we have had hundreds of unknown problems on commercial airplanes (made with the best technologies and enginneering procedures available) discovered only examining the debris of the plane crash (with hundreds deads)

the most advanced vehicles have had problems... gemini, apollo, soyuz, rockets, satellites, probes (the single most expensive and advanced vehicles humans have made), SHUTTLES

that happen because they are made by humans, and humans are not prerect, nor can imagine the unknown!

I don't understand why do you think that so many vehicles, so new and so complex, like the CEV, CaLV, etc. (THIS TIME and ONLY this time!) will be ABSOLUTELY PERFECT!!!

the new vehicles will have hundreds of unknow problems like ALL new products (consumer or hi-grade)

some will be little and not dangerous, some may cause brief delays, some may cause big or multiple delays and (unfortunately) some may be lethal for astronauts, like happen two times with the Shuttle and Soyuz

the 1.5 l.a. and the use of two rockets can only MULTIPLY by THREE the risks, because they add problems that (simply!) DON'T EXIST with the SLV

with the SLV a mission will NEVER fails due to a "sum of delays" of the second launch and one rocket will have TWICE the probability to work than TWO

it's simply the probability's law... if twice the cars runs on an highway there is (statistically) twice the probability of accidents and twice the passengers dead

I don't know how many single-launches will fail, but, TWICE launches, will mean TWICE probability of failure

e.g. if with one rocket per mission the risk will be 1 fail every 30 launches (may be, due to the "central" J-2x CLV engine failure...), with two rockets per mission the risk will be 1 fail every 15 launches

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If you knew better, why did you made the invalid comparison to a general-purpose consumer PC? How am I to know you know otherwise?

This is not the first time I’ve tried to correct or elaborate on something you said only to have to respond defensively with something like “don’t state the obvious” or “that’s not what I meant”. I’m sorry but I’m not a mind reader. If you don’t make yourself clear then please don’t blame me for misinterpreting. Also bear in mind that I sometimes clarify things for the lurkers who might be reading. Not all my comments are intended solely for you.

This is the second time today that you’ve called the Shuttles advanced and/or complex vehicles, yet yesterday when I called them very complicated machines you responded by saying the “electronics, computers, software and mechanics is incredibly simply”. So what are they: complex, simple, or whatever you need them to be at the moment to emphasize the point you are trying to make?

I challenge you to find one place were I’ve said the new class of vehicles will be absolutely perfect. I’m sure I can find several places were I’ve said or implied otherwise.

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Gaetanomarano, you still haven't addressed my point that the majority of Shuttle delays have been weather related. Because it is a winged vehicle, it has extra limits on wind levels during ascent and it must have low cross winds for landing not only at the launch site in case of a return abort, but also at the airfield in Europe or Africa selected for a trans-Atlantic abort. Because of the fragile tiles, it cannot fly in rain, again giving a weather limit for both launch and trans-Atlantic sites.

A non-winged vehicle is less sensitive to launch winds. A parachute lander is less sensitive to landing site weather.

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probably some misunderstanding are due to my english, I'm sorry

1st point: the calculator and PC are used only as an example (like... the LEM was complex like a pocket calculator while the LSAM is complex like a PC, etc.) I don't say that NASA will use a consumer PC for the CEV

2nd point: there is no contradiction, the Shuttle is very complex if compared with a Gemini, etc. (then, it has n-times more problems and delays) and incredibly simply if compared with future vehicles (then, the new vehicles may have n-times more problems and delays)

3rd point: the claim that the new vehicles will not have problems (then, no "sum of delays" missions' fail due to 1.5 l.a.) implies that they will be perfect, because, if they will be NOT perfect (like all past vehicles) you must agree with me that the 1.5 l.a. (due to "delays-failure" built-in) may produce many missions' fail

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as I've explained in my previous posts, the 1.5 l.a. and the use of TWICE the rockets (with TWICE the probability of rocket's fail) TRIPLE the risk of a missions' fail and, the fact that these rockets may fly with the rain, don't reduce so much the probability of fail that come from l.a. and twice rockets

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You keep saying that new vehicles will be more complex and thus more likely to be delayed. However, there is no evidence that the Apollo-Saturn V was more likely to be delayed than the much simpler Mercury-Atlas or Gemini-Titan, rather the reverse in fact. The main reason the Shuttle is delayed more is that it's configuration is more sensitive to weather conditions.

You have only your opinion, absolutely no evidence, that the CLV will be any more prone to delay than earlier non-winged vehicles, and on the historical record these never missed a rendezvous.

Most technical delays are resolved by changing an item of equipment. If the CLV is designed, as it should be, to make this process relatively easy, there is no reason it should experience your postulated month-long delays.

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when you make a travel with your family, do you prefer to drive a car with airbags, belts, etc. or an old and dangerous car without any airbag, etc.?

of course, if no accidents happen, no matter if you drive the first or the latter, but, if an accident will happen, the car with airbags may save your life!

well... TWO rockets mean TWICE the risk to fail and the 1.5 l.a. adds a further risk (that, with an SLV, simply, don't exists!)

the choice to NASA

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I don't see the relevance. The crew is only on one of the vehicles, and they have a launch escape system, which the Shuttle doesn't. It should be safer.

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