probably the "airbag" is not a good example

of course, the crew is safe thanks to the LAS, parachutes, etc.

but I suggest to use the SLV to greatly reduce the so called "LOM" (Loss Of Mission)

if the new family of rockets will have an "n" factor of reliability, "two rockets per mission" means "n" missions' fail, while, "one rocket per mission" means n/2 missions' fail

in other words, with TWO rockets you have TWICE the risk that a mission may fails due to a rocket failure

also, the two-rockets (or "1.5") launch architecture, adds the risk of a mission's fails due to a "sum of delays" of the second launch

the single-launch architecture dont't have these two big risks, then, it is more reliable "by design"

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You are still talking absolutes, while real engineering is always a matter of trade-offs.

For a single launch, the cargo vehicle must be bigger, and it must be man-rated. This increases the costs, and you still need the CLV for ISS missions.

The question is whether the cost of losing missions with a dual launch is more or less than the extra cost of a single launch system.

Looking at the historical record suggests that the risk is acceptable, certainly a lot less than your idea of losing the whole ten-year programme.

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no matter which is the reliability of a rocket... twice launches of a rockets' "family" mean twice possible failures

if a rockets' family has a 95% rate of success that mean:

> one rocket lost every 20 launches

> two rockets lost every 40 launches

> five rockets lost every 100 launches

then, HALF rockets used for each mission, means TWICE the reliability and success of the missons

and this is a FACT

the 1.5 l.a. BORNS with a "second-launch's-sum-of-delays-failure-option" BUILT-IN (no matter if this "option" will really happen or not, IT EXISTS as option!) while the single-launch architecture borns WITHOUT this additional risk

and this is another FACT

the SLV don't double man-rating costs (very very very low if compared with the R&D + hardware costs of TWO rockets!!!!) because the man-rated rocket is one, not two

the SLV don't need to be bigger but smaller, building 25% smaller vehicles for 3 astronauts and 10 days moon exploration (same exploration time than 7 days with 4 astronauts)

the risk is to lose 25 years (15 for the 1.5 l.a. VSE + 10 to restart from zero with a new program and land on the moon in 2030) not 10, and the money lost may be twice than VSE funds (the first FAILED 1.5 l.a. VSE and the "new VSE")

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I realize you weren't saying a consumer PC was going to be used in the CEV; I'm sorry if I implied that. I was simply trying to demonstrate that the embedded computer systems used in a spacecraft will be far more reliable and not prone to all the problems associated with a general-purpose PC.

Furthermore, I don't think it’s appropriate to draw an analogy between a PC and a modern day pocket calculator when comparing the reliability of a complex modern spacecraft versus Gemini. I think a better analogy is between a modern day computer and a, comparatively simple, 1960s era computer. I think in this case you will see the old computer, although perhaps simpler, is not necessarily more reliable because of the more primitive technology used.

I've never said the new vehicles will not have problems. In fact, I've even acknowledged that a "sum of delays" failure is possible. My complaint is that you're grossly exaggerating the likelihood these events will occur while ignoring other factors that may make the risk of a "sum of delays" failure an acceptable trade-off.

Gwiz brought up one of these trade-offs when he spoke of man-rating. Your single large launch vehicle must be rated to carry a human crew, while the CaLV need not be. One must analyze the extra cost of man-rating a large booster versus the likelihood of losing a LSAM/EDS due to a “sum of delays” failure. It becomes an economics decision – just like deciding whether or not to buy collision insurance for my automobile. If I buy insurance and never have an accident then I wasted the money, but if I don’t buy insurance and have an accident I could be out even more money. It comes down to analyzing the cost of insurance, the value of my car, and the likelihood I’ll have accident.

You’ve promoted the single-launch architecture like it is a cure to all that ails us, but it is not nearly that simple. There are many other economic factors that must be considered and I don’t believe you’ve done this.

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Your single launch vehicle is still much larger than the CLV, so you still need two man-rated vehicles, and I very much doubt if you'll save that much launch mass by reducing the crew from 4 to 3.

On your figures, you're likely to lose one mission out of a ten-mission programme. This is hardly losing 25 years. If the dual-launch works out more than 10% cheaper, you're ahead.

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95% is way too low. NASA calculates the reliability of the Space Shuttle at one loss in 200, or 0.995 reliability. There have been 114 Shuttle launches with only one failure, and tragically that one failure was avoidable and never should have happened. Thus the 1/200 estimate seems reasonable. NASA initially put the loss rate of the CLV at 1/2,000 but I think they may have backed off that number somewhat. Nonetheless, the in-line configuration and simple capsule design of the CEV should make the CLV/CEV much more reliable than the Space Shuttle.

To be conservative, let’s go with the 0.995 figure. The probability of completing 12 successful launches (single-launch architecture) without failure is,

0.995^12 = 0.9416

And the probability of successfully completing 24 launches (1.5-launch architecture) is,

0.995^24 = 0.8867

We therefore see the odds of a launch failure increasing from 5.84% to 11.33% with the 1.5-launch architectural. I agree this is not insignificant, but it must be weighed against other economic factors. Accepting the occasional loss of a vehicle may be more economical than absorbing the cost of increasing reliability.

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the risk of failure due to a "sum of delays" is absolutely NOT acceptable if its cost is of $6+ billion every time it will happen (I think that, with these very high costs, ONE failure already is TOO MUCH)

the economic factors are LARGERLY IN FAVOUR of the SLV because you spend (maybe) $200 million more to man-rate a bigger rocket but you save:

$5 billion of (planned) R&D costs for the CLV

$2 billion of (announced) extra R&D costs for the 5-segments SRB (I suggest to build a smaller SLV with 4-seg. SRBs)

$6+ billion for the CLV "hardware" of the first 20 moon missions

$15+ billion of standard NASA budget (because you save 3 to 5 years of time and work before the first moon mission: 2015 instead of 2020)

$5+ billion of extra costs for a big 4-astronauts-SLV (with 5-seg. SRB, more engines and 33% bigger LSAM, SM, EDS, tanks, etc.) in the first 20 moon missions

also... you save the costs of two launch pads, two specialized assembly and launch teams, two manufacturing lines and buildings, twice air and surface transport of parts, two assembly costs, two launch's earth support, two SRB after-launch-recovery teams (and costs), etc. etc.

not only you can make the first moon missions sooner (3 to 5 years BEFORE planned!!!) but, with the same VSE funds, you can make from +50% to TWICE moon missions!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

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Here's another trade-off. You're proposing smaller and shorter missions for increased reliability. You're conceding capability for reliability, thus the single-launch architecture does not come without a price. It comes down to a decision of whether larger, longer, and more capable missions are worth the increased probability of failure. You apparently believe so, but I'm certainly not convinced of that.

It seems to me that if we are to return to the Moon we must significantly increase our capabilities there over what they were during the Apollo days. I question whether a single-launch architecture provides the increased capability necessary to warrant a return to the Moon.

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[QUOTE=gwiz]Your single launch vehicle is still much larger than the CLV, so you still need two man-rated vehicles, and I very much doubt if you'll save that much launch mass by reducing the crew from 4 to 3.
QUOTE]

the mass saving with 3 astronauts is not only the weigth of the 4th astronaut... but 25% less weight thanks to a 25% smaller CEV, SM, LSAM, EDS, tanks, SRB, fuel, only four main engines instead of five, etc. etc. etc.

you save also on life support weight because 3 astronauts need 3 more days of life support for the 10 days moon exploration (instead of seven) but 7 less days of life support in the earth-moon-earth travel, that mean TONS of water, food, oxigen, tanks and stores, spacesuits, electronics, etc. etc. etc.

no

because, this time, "the plan" includes the cargo-LSAM that may send of the moon the hardware and life support for months

with the cargo-LSAM, build a CITY on the moon will be only a problem of funds!

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only ONE mission's fail due to rocket fail already is too much at these costs, if you add 1-2 fail due to sum of delays the costs and risks become unacceptable

with the SLV you have only HALF of the first risk (thanks to HALF rockets launched!) and ZERO RISKS to fail for a sum of delays

why risk so much time and money with the 1.5 l.a.???

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So you must also reduce the amount of equipment you take to the moon by 25%. You're scaling the mission down so you need to fly more missions to regain the lost payload. This is going to negate your cost saving.

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It sounds like you're proposing abandonment of CLV development. But if we do that and focus only on your proposed SLV, then the USA no longer has access to low Earth orbit after retirement of the Shuttle fleet. Are you willing to abandon USA manned access to LEO? We need something smaller than the SLV or CaLV to launch the CEV for LEO missions.

One possibility might be to man-rate the Delta IV-Heavy, which I think is capable of boosting the CEV. Of course this is also a potential cost savings for the 1.5-launch architecture. Whatever path is pursued, the parallel development of a CEV to LEO launcher must proceed along with the heavy-lift vehicle.

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absolutely not

because the total payload weight of a 4 astronauts mission and 7 days moon exploration is over 150 tons (125 with the CaLV and 25 with the CLV) but only TWO TONS of them are of "scientific and moon exploration hardware"

then, if you save (maybe) 30+ tons with a 3x mission, you can send all the hardware for a 4x moon exploration

however, since I think that 2 tons (of the 4x plan) are too little for a good exploration, in my article (and here) I suggest to send the moon-hardware (and extra life support for emergency) for 5+ missions separately, before the first manned landing, with a (planned) cargo-LSAM

that means an extra saving of weight for the next five manned SLV launches (but not a big money saving, since the cost of the cargo-LSAM is shared on the 5 manned)

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Wait a minute… does your plan include both a CaLV and a SLV? If so, how the heck is that going to have a lower development cost the a CaLV and CLV?

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If you factor down the total payload, you have to factor down the surface equipment, you can't have it both ways. Two tonnes is a lot more than one astronaut and his life support for ten days.

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as I write in my article...

1. the orbital-CEV is completely unnecessary because it will fly only a few times to the ISS

2. for the ISS there are (and will be) many cheaper (10-15 times cheaper!) cargo and crew vehicles (I don't think that NASA can spend 10-15 times for the same "service"!)

3. the 1.5 l.a. has the ISS orbital-CEV option but with the risk to lose the (much more important and expensive!) moon missions (due to twice launch per mission and 1.5 l.a. risks)

4. the SLV can be used to send mixed heavy payloads to the ISS with a single launch, like... one CEV + one new module + ISS' resupply ...less time, less launches, less costs, less risks for the astronauts

5. if NASA absolutely need an orbital launch (for RARE military strategic reason where the cost don't count) of a CEV (without cargo) they can use the SLV (it's not so cheap or efficient to use an SLV to launch a CEV only in orbit, but I don't see so much probabilities that a similar "secret" mission may happen... with the Shuttles, military-missions was possible thanks to its cargo-bay for spy-satellites, etc., a little caspule is useless)

6. I think that man-rate an EELV to launch the CEV may be possible and cheap but completely unnecessary

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no

only a 100-110 tons payload SLV to be used to launch cargo-LSAMs or manned moon missions with 3 astronauts

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no

2 tons of moon-hardware needs (about) 1 ton of extra LSAM propellent for LOI and landing and (about) 2 tons of extra EDS propellent for earth departure (I forget the acronym...)

but I suggest to launch the hardware for 5+ missions before the manned launches with a cargo-LSAM, this option is much more efficient and cheaper

also, it's safer for astronauts, because you can send on the moon extra life support hardware to survive 2-3 months (if something goes wrong) to have the time to launch a rescue mission

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Just so you don’t think I’m needlessly coming down hard on you, gaetanomarano, let me reiterate that I don’t think your proposal is totally without merit. I’m just having a hard time accepting the numbers you’re throwing around. I’m unconvinced your analysis is sufficient to conclude unquestionably that the single-launch architecture is the best option. I’m not arguing with you just to prove you wrong or to blindly support the 1.5-launch architecture. I just need to see, or produce for myself, an analysis that I can feel confident in. Whichever method that analysis says is best will be the one I support.

(I may not be able to post much more today, I've got work to do.)

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TLI (Trans-Lunar Injection).

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So why do you quote a much bigger difference for removing one of the crew?

I must admit I couldn't read your web page on the subject, all the colours and caps hurt my eyes.

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for me (and for the ESAS plan) 2 tons are the hardware for lunar science and exploration... rovers, experiments, etc.

the main saving with a 3x launch is a 3x CEV, 3x SM, 3x LSAM, 3x EDS, 3x CaLV, etc.

the total saving (without the moon-hardware) may be up to 40 tons, then, a 110 tons payload SLV will be sufficient

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right, thank you

Several points: A lot of the equipment won't scale with crew size, eg communications and navigation. You can only scale down your launch vehicle by 25% if you also cut your surface hardware. You can't just account for the fuel required for hardware and scale the whole vehicle for the crew size. The amount of useful surface work depends on the surface hardware. If you have less per launch, you must carry out more launches for the same programme results.

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with to-day's (and 2015) technology, the comm & navigation hardware will be so small and light that we can't imagine... probably less than 0.000001% of the SLV weight!

about the exploration-hardware... I've already posted the answer

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You can't just base this on the way consumer electronics has scaled down over the years. You still need antennae, radar, electrical power, star tracker optics, plus all the supporting structure and fuel that you scale for the crew size but ignore for anything else. Why do you think a modern communications satellite has a mass of several tonnes?

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you're right but the weight still remain marginal (the CEV/LSAM don't need to transmit 500 TV channels...)

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NASA has (unfortunately) decided to use the 5-segments SRB and the RS-68 for its CaLV

that choice needs many extra-billion$ of R&D and tests

my proposal of an SLV-light, made with to-day's SRB and SSME, is a GIANT saving of money and a GIANT saving of TIME, since the new 5-seg.SRB will needs up to THREE years of research and tests

also, the SLV-light don't need so much time and money to man-rate the rocket, since the 4-seg.SRB and the SSME already are man-rated and have made 100+ successful (manned!) flights with the Shuttles!

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From what I hear, the 5-segment booster should be ready to fly by 2012. That’s well before the LSAM will be ready, so I don’t see there being a scheduling problem.

The CaLV doesn't need to be man rated at all, though I believe there has been consideration given to doing so.

Gaetanomarano, have you performed the calculations to see if your proposed SLV can lift the payload you say it can?

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