Tuesday, August 4, 2009

Spin Doctoring

Inverted logic. Once the domain of the Emperor, the minions have now taken to continuing the tradition of making confounding arguments intended for the uninitiated audience. As far as the public is concerned, if someone with a meatball on their shirt says it, it must be true. Unfortunately, the uneducated press propagates the confusion without challenge.

Take, for instance, one of the architectural concepts being considered by the 475nm Ribbon Panel. Instead of redeveloping an existing capability, it has been suggested that multiple EELVs be used to mount a mission to the moon. More successful flights (as opposed to paper excursions) also raises the confidence level in any given rocket's reliability. Even Bow Tie Joe would have to agree with that.

Enter the Spin Doctors, pointing to the downsides of the plan. "Rocket malfunctions are not uncommon, and the more launches are needed for each moon mission, the more likely it is that something will go wrong," says a former senior minion to New Scientist.

Duh.

Of course, this convolution fails to take into account the impact of any single failure that might occur. In reality (ours not theirs), should any single EELV fail, all is not lost as it might be if all eggs were placed in one ARES V basket. Launch teams are kept busy doing what they are supposed to do, launching, instead of sitting on their thumbs for the majority of a fiscal year, growing rusty.

Rest assured, this won't be the last oxymoron promoted by the mouthpieces being contracted for by the Italian Waiter to revise engineering textbooks. There are still 27 shopping days left in this crazy season.

12 comments:

Anonymous said...

Interesting speculation, but the maths don't agree.

Assume two extremes.

Single Ares V - Mission Reliability = 0.98

4 EELVs - Each with a reliability of 0.99

0.99^4 = 0.96 << 0.98

Add in the added complexity of docking, of launching 4 vehicles in a matter of weeks (EELVs can't launch that fast now), and the fact that your EELV may carry an "one of a kind" part of your mission (like crew) ...

While there are reasons to do multiple smaller launches as you suggest (and I even support this option for those reasons), the maths don't agree.

It is not as simple a choice as you make it out to be.

Anonymous said...

multiple launches actually reduce risk even if the total risks are higher. much of the launch mass is commodity propellant, which is trivial to insert into a launch processing stream. Lost modules are not hard to replace if you plan for more then one mission.
Consider a moon mission not as an Ares 5, but as
5 Modules (A,B,C,D,E) plus fuel, say 3 fuel launches.
You begin launching the modules and say Module B is lost. If you have another mission in plan, you take Module B from that stream and launch it earlier.

also say Module C develops a fault, while it's being integrated, additional parts can be sent up with Module D and perhaps an in flight repair can be conducted.

The NASA culture rejects this because it lacks a sufficient level of stupid to be interesting to the NASA managers.

Anonymous said...

I wonder how it is going to work out sending 17-19 EELVs and shuttles to ISS next year? Add up Soyuzes, Progresses, ATVs, HTVs, and STSs and that's what you get. Many more than a small launcher lunar mission model. If NASA adds that up they will no doubt call for the immediate splashing of ISS as it is logistically untenable. :)

kT said...

I wonder how it is going to work out sending 17-19 EELVs and shuttles to ISS next year? Add up Soyuzes, Progresses, ATVs, HTVs, and STSs and that's what you get.

You need to review your launch vehicle nomenclature and acronyms.

STS is shuttle. Everything else is EELV equivalents. It's all the same, just different providers.

The shuttle is roughly a 25 MT launch vehicle, the added 'value' is the vehicle and the astronauts.

Anonymous said...

The crew(NASA)upon sighting the iceberg, skillfully sank the ship in order to avoid collision!

When questioned by the Augustine panel, what was the first thing they did? Offer up Ares as a sacrificial lamb in order to save their miserable jobs!

On the subject of reliability, Ares V numbers are backed up with assumptions, wishes, random thoughts and animal sacrifices. The EELV's numbers are based upon fact. Now, which one would you ride???

They fired me for telling the truth but my out date is letting me see that all of the problems that I predicted are starting to show up right on time. Momma's don't let your babys grow up to ride Ares.....

Anonymous said...

Existing EELV's can support more ISS operations than the ISS can even execute. And it doesn't take dozens of launches. The ARCTUS proposal of some years back showed a system that could economically address pressurized cargo, vacuum cargo in the tons and more consumables than required for years. Just because you are used to ridiculous objects such as FRAMs which often weigh more than the payloads they support doesn't mean that other designers cannot address things more effectively.

Anonymous said...

Yes the maths do agree but you have to use real numbers and those have to do with DEMONSTRATED reliability. The flight proven reliability of any ARES vehicle will be less than .25 for years whereas by the time an EELV is used to fly any lunar payloads there will be nearly a hundred flown- without failures this implies a real world reliability of .99.

Anyone who believes these failure rate analyses of powerpoint rockets is simply ignorant of history. The Shuttle had quite an extraordinary predicted failure rate number. Which was two orders of magnitude off.

The only way to get high reliability and high crew safety is to fly them on machines that have the largest possible prior usage under more severe environments. The ESAS hardware will see the lowest utilization of any operational vehicle. Throw in the absurd gizmos trying to remedy starkly bad designs and you are into the realm of a contraption. Not a good springboard to reliability.

Anonymous said...

Anon1


this is Anon2, your calculation shows that
you would do very well a a NASA manager.
Are you by chance the Italian Waiter?

let's take your numbers and run an expected value calculation.

let's call the 4 EELV Launches (A,B,C,D)
Let's assume:
Mission A is the Lander Value $1B
Mission B is the Lander Propellant Value $50M
Mission C is the Transfer Stage Value $500M
Mission D is the Crew Value $2B

Lets take a 1% chance of loss
Sow e expect to lose $10M in Landers
$500K in Propellant
$5M in transfer stages
$20M in crews
or expected loss is $35.5M

now add those all up and stick them in
an Ares V
we have 3.5Billion in value on the Ares V.
we expect to lose $70Million in value on
the Ares V, plus we spend $30 Billion to build
the Ares V.

the Expected loss value of an A-5 leads to far more loss.

I don't expect a NASA Manager to know how to do probability or statistics, but, i'm sure you will do well in the future as a waiter.

Anonymous said...

As the other anonymous posters and my confrontation with the chief meat servo prove, statistics can be made to say anything and relied upon. Call me when
(cost of lost payloads on EELV + development and ops costs
) / EELV launches
exceeds
(total program cost of Ares / Ares launches).

Anyone who looks at reliability without considering cost deserves to be left behind.

Stevo Harrington said...

There are clearly two problems, one is jobs and one is mission architecture. As long as they are intertwined, it will be impossible to select a mission architecture over the objections of those who are worried about their jobs.
One way to solve the problem would be to have the NASA engineers who are not needed for the selected mission architecture work on energy projects, as was done in the late 70's.

Anonymous said...

What's sad and pathetic is that the NASA staff could work on enabling bits between EELV's and Orion. The JSC crew could restart X-38 and really make a reusable crew recovery bird. Orion would be the low risk option, X-38 would be the medium risk option
and both would fly on EELV the Zero Risk option.

The folks at Glenn could work on Altair.

Ames could work on a Lunar oxygen plant.

JPL could work on a Mars Polar Lander.

Langley could build a mars flyer


instead of the entire agency building the corn dog, they could be building useful long range hard things.

gravityloss said...

IF you don't have spare propellant launchers and assume a loss of mission for any failure, then launching many times is LESS reliable in total than a single launch with an equally reliable rocket.

IF you have one spare, it is MORE reliable to launch 7 (or 8 if there's one failure) times. (We're talking propellant launches as that is the majority of mass.)

IF you have two spares, multi-launch is EVEN MORE reliable.

With 98% failure probability of each rocket, having more than one failure in 8 launches is 1.03%. So clearly that's less than the 2% failure probability of the one big rocket.


The breakeven point for 98% single rocket reliability is about 10 launches, for many launches with one spare vs one launch.


With two spares you get to much much higher numbers naturally.

At 99% single rocket reliability, one spare multilaunch advantage cutoff is around 14 launches.


Gotta post on this as it seems many space blog followers' mathematics is not very strong.