Author Topic: LIVE: Full Committee Hearing - A Review of NASA's Space Launch System  (Read 342132 times)

Offline MP99

It's a more complicated trade than you're making out.

Let's say you have an all-chemical transfer vehicle that can reasonably spare 5 km/s departure delta-V.  Hydrolox, with 4500 NĚs/kg; that's a mass ratio of 3.

This vehicle can go to L2 on its own, using 80% of its departure propellant.  Tanking up then requires the use of dedicated tankers delivering about 40% (cf. Zegler, Kutter, and Barr 2009) of their initial propellant load to L2.  This requires twice the departure propellant allocation to fill the transfer vehicle back up, so the propellant requirements triple.

You could do the same v_inf (~11,500 m/s) with a mass ratio of 6 from LEO, requiring a little over 80% as much total propellant.  But look what happened - you just doubled your departure mass ratio.  The transfer vehicle's IMLEO now includes a giant EDS, which eats into the available payload.

If you want to reuse a transfer vehicle that's already at L2, all the propellant goes by tanker, and the 20% advantage (in total propellant mass) of starting in LEO disappears...  and if you want more initial delta-V, the mass ratio for the LEO option climbs rapidly...

With all due respect, you're being disengenuous. Mass ratio is not a figure of merit. You have a higher mass ratio from LEO, but you didn't spend any mass on propellants used to deliver more propellant to L2. You should also count the mass of the tankers into the propellant side of your overall mission mass ratio, to the degree they're expended after they deliver propellant.

IOW, you never get something for nothing.

The transfer vehicle already at L2 is costing you resources to refurbish after its last mission.

I am not a fan of reuse for initial Mars missions, personally - too many things to go wrong on the second flight. Designing that out will add too much to the MTV's development costs. ISS has Soyuz as lifeboats, an MTV won't have that luxury.

Building the second MTV will be much easier than designing / building the first, and there are dV savings (ie launch mass) in not braking the first MTV back to EML that helps buy the launch for the new MTV.



But, to my main point, re "Mass ratio is not a figure of merit."

It is for a chemically-powered Mars mission. The total dV for TMI-from-LEO + MOI + TEI is pretty substantial. Assembling at EML allows you to drop nearly 3km/s from the dV budget, which means the vehicle you need to assemble can drop it's mass fraction reqts by about 1/2.

This is what a chemical-from-LEO vehicle looks like, and how much is that going to cost to develop? ISTM worthwhile to trade "commodity" launches delivering prop to EML (whether HLV or commercial) if it allows you to lose stages (ie get back into a sensible mass fraction range) for the MTV.

cheers, Martin

Edit: BTW, that's 5x Ares V launches.
« Last Edit: 07/28/2011 09:41 PM by MP99 »

Offline sergeante

  • Full Member
  • *
  • Posts: 117
  • SW Utah
  • Liked: 0
  • Likes Given: 0
But, to my main point, re "Mass ratio is not a figure of merit."

It is for a chemically-powered Mars mission. The total dV for TMI-from-LEO + MOI + TEI is pretty substantial. Assembling at EML allows you to drop nearly 3km/s from the dV budget, which means the vehicle you need to assemble can drop it's mass fraction reqts by about 1/2.

Singing the same old song here, just so my answer is complete: the industrial base is on Earth. That means you have to figure mission mass ratio from Earth, not any particular mission increment's mass ratio from somewhere else. That propellant at EML cost more propellant and tanker vehicles to get there. Those need to be figured into the propellant side of the overall mission mass ratio. When you do that, you find that you didn't save anything, and quite probably added to your overall mission mass with all of those intermediate vehicles.

Offline Prober

  • Senior Member
  • *****
  • Posts: 10313
  • Save the spin....I'm keeping you honest!
  • Nevada
  • Liked: 701
  • Likes Given: 728
{snip}

Which just brings up yet another one of those things I don't know.  Where do the meteorites keep their computers for figuring out their orbital mechanics?
I am sure that they use virtual computers. ::) ;D

They need new software, something that can handle planetary gravity wells without crashing.  8)

NASA computers should be able to do just about anything.  This still ticks me off.....

NASA has awarded HP a $2.5 billion contract over four years for desktop services and devices, HP said Thursday.

http://news.yahoo.com/s/zd/20110428/tc_zd/263749

read # 254 onward.....NASA waste of funds IMHO.   
http://forum.nasaspaceflight.com/index.php?topic=24821.240
Lets say these funds went into Commercial.  What could SpaceX etc have done 600 million a year?
or
Should these funds been assigned to the new launcher?


Huh?   So are you saying NASA should have no PC's and networks for its workers?

Did I say that, No   Maybe you should re-read that linkhttp://forum.nasaspaceflight.com/index.php?topic=24821.240.  NASA employees don't need new computers every year do they? Clearly a few million a year spent on computers can keep NASA up and running.
 
By the way the left hand doesn't know what the right hand is doing.  Sure you saw where the WH is cutting back on Data centers.

Edit missing forum link
« Last Edit: 07/29/2011 02:39 PM by Prober »
2017 - Everything Old is New Again.
I have not failed. I've just found 10,000 ways that won't work. ~ by Thomas Alva Edison

Online clongton

  • Expert
  • Senior Member
  • *****
  • Posts: 10558
  • Connecticut
    • Direct Launcher
  • Liked: 2591
  • Likes Given: 962
Martin - the only problem I see with your mars spacecraft is there is nothing there for earth ED&L.
Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline HappyMartian

  • Senior Member
  • *****
  • Posts: 2714
  • Tap the Moon's water!
  • Asia
  • Liked: 15
  • Likes Given: 2
One final comment ...

If an Oberth effect leveraged TMI burn were executed on a dark clear night by a large spacecraft coming from EML-2 for a terrestrial gravity assist, that would be one heck of a photo opportunity.

Just saying . . .

Sorry, but I can't resist.

An LH2/LOX engine burning at a 100 mile altitude would be invisible, unless you were looking right at the engine bell. And then it wouldn't be much more than a small dot of bluish-white light.

Yep. Something like that. I've stood on a big hill in central Florida, west of the Kennedy Space Center, to watch a Space Shuttle night launch.

Now if we only had a TAN version of the J-2X hydrolox rocket engine that used kerosene and liquid oxygen to enhance its thrust during a terrestrial gravity assist burn in a night sky, that might be kind of pretty...   :)
"The Moon is the most accessible destination for realizing commercial, exploration and scientific objectives beyond low Earth orbit." - LEAG

Offline Jorge

  • Senior Member
  • *****
  • Posts: 6180
  • Liked: 32
  • Likes Given: 0
{snip}

Which just brings up yet another one of those things I don't know.  Where do the meteorites keep their computers for figuring out their orbital mechanics?
I am sure that they use virtual computers. ::) ;D

They need new software, something that can handle planetary gravity wells without crashing.  8)

NASA computers should be able to do just about anything.  This still ticks me off.....

NASA has awarded HP a $2.5 billion contract over four years for desktop services and devices, HP said Thursday.

http://news.yahoo.com/s/zd/20110428/tc_zd/263749

read # 254 onward.....NASA waste of funds IMHO.   

Lets say these funds went into Commercial.  What could SpaceX etc have done 600 million a year?
or
Should these funds been assigned to the new launcher?


Huh?   So are you saying NASA should have no PC's and networks for its workers?

Did I say that, No   Maybe you should re-read that link.

"Article not found or expired on Yahoo! News"

Quote
  NASA employees don't need new computers every year do they?

The contract won't provide new computers every year. If the article said that, it's wrong.
JRF


Offline Jorge

  • Senior Member
  • *****
  • Posts: 6180
  • Liked: 32
  • Likes Given: 0
Working link to the above:
http://news.yahoo.com/nasa-awards-hp-2-5b-contract-110517228.html

Thanks, Chris. As expected, the article makes no mention of new computers every year.
JRF

Offline MP99

Martin - the only problem I see with your mars spacecraft is there is nothing there for earth ED&L.

It's the "Chemical" option from Mars DRA 5.

Earth ED&L is performed by an Orion with minimal / no SM (though it doesn't seem to be shown).

cheers, Martin

Edit: quoting.
« Last Edit: 07/29/2011 11:35 AM by MP99 »

Offline MP99

But, to my main point, re "Mass ratio is not a figure of merit."

It is for a chemically-powered Mars mission. The total dV for TMI-from-LEO + MOI + TEI is pretty substantial. Assembling at EML allows you to drop nearly 3km/s from the dV budget, which means the vehicle you need to assemble can drop it's mass fraction reqts by about 1/2.

Singing the same old song here, just so my answer is complete: the industrial base is on Earth. That means you have to figure mission mass ratio from Earth, not any particular mission increment's mass ratio from somewhere else. That propellant at EML cost more propellant and tanker vehicles to get there. Those need to be figured into the propellant side of the overall mission mass ratio. When you do that, you find that you didn't save anything, and quite probably added to your overall mission mass with all of those intermediate vehicles.

There's more cost to a Mars mission than buying the launches to lift the necessary mass to LEO!

To restate my premise, it is that it may be cheaper to buy additional launches rather than pay the costs to develop a "monster" MTV.

cheers, Martin

Offline JohnFornaro

  • Not an expert
  • Senior Member
  • *****
  • Posts: 9167
  • Delta-t is the salient metric.
  • Planet Eaarth
    • Design / Program Associates
  • Liked: 620
  • Likes Given: 324
Quote from: Sarge
What I mean by "investing payload capacity" is allocating payload capacity that can be bought to a certain task.

Which is another way of putting what I mean as well: Well, Orbital, SpaceX and the several other players, are "allocating payload capacity that can be bought to a certain task".  Are they not?

Quote
There's no side trip around an energy requirement in orbital mechanics.

It is an apt analogy, but only up to a certain point.  As you say, there is a minimal energy requirement in orbital mechanics, say, that lazy spiral, which eventually gets you to L1.  You can also shoot the Moon, so to speak.  I read a text from the sixties [search my posts for when I brought it up.]  which featured a 36 hour impact trajectory to the Moon, available to the then current tech.  Not much of a payload, and all you got was an impact crater for your work.  Within these energy ranges are Hohman transfers and other orbits.

So for a robotic interplanetary mission, which is all you appear to be interested in, there is a perfect launch/orbit envelope.  The idea of a prop depot would take a more "generic" approach to missions of this sort, sacrificing delta-vee efficiencies somewhat.  Unfortunately, I am but an egg in the orbital mechanics department, so I can't provide much math here, but others have been pointing this out as well.

Quote
I've never heard somebody with a science or engineering education assert that papers demonstrate anything. In science, experiments demonstrate things.

So true.  Here's the rewrite:

The theoretical utility of an EML assembly point has been substantiated to a certain extent for decades in older papers.

Quote from: Prober
NASA computers should be able to do just about anything.  This still ticks me off.....

NASA has awarded HP a $2.5 billion contract over four years for desktop services and devices...

Since the vast majority of this, the casual observer would note, appears to be support for Windows 7, it suggests also that operating systems are hampering work to a greater extent than ever before.  Plus, I have followed the upgrades to CAD software very closely since 1988.  When I read NTB on the CAD update issues, all the talking heads are still saying the same things now that they did then: "Access to legacy data continues to be a sticking point with new CAD systems."  They've been saying this since 1988, and the vendors have not been providing this access.  So much time has been wasted in re-drawing, re-engineering, and re-justaboutanything that it makes the head spin.  The vendors are so busy trying to compel customers to use their product exclusively, that they have forgotten how to make the products useful.  But I digress.

Quote
So are you saying NASA should have no PC's and networks for its workers?

Everybody is capable of making incorrect grand conclusions from a faulty interpretation of one data point. Except me, of course.
Sometimes I just flat out don't get it.

Offline Prober

  • Senior Member
  • *****
  • Posts: 10313
  • Save the spin....I'm keeping you honest!
  • Nevada
  • Liked: 701
  • Likes Given: 728
Working link to the above:
http://news.yahoo.com/nasa-awards-hp-2-5b-contract-110517228.html

Thanks, Chris. As expected, the article makes no mention of new computers every year.

Sorry my mistake the link I wished you to read is this
http://forum.nasaspaceflight.com/index.php?topic=24821.240

=========

For me this contract just doesn’t pass the smell test.       Some areas within NASA are nickel and dime cost cuts, while other projects are pure waste.

http://forum.nasaspaceflight.com/index.php?topic=26200.0      Can’t say how old some of these servers are, but sure in these tight money times spending over 2 billion dollars on new computers, when you’re laying off employees, and ending programs just doesn’t sit well.

Wasn’t going to bring this point up but maybe someone from Houston can tell us what’s going on?    I’ve seen some signs of “manned” infrastructure being dismantled.   

« Last Edit: 07/29/2011 03:00 PM by Prober »
2017 - Everything Old is New Again.
I have not failed. I've just found 10,000 ways that won't work. ~ by Thomas Alva Edison

Offline deltaV

  • Full Member
  • ****
  • Posts: 1538
  • Change in velocity
  • Liked: 165
  • Likes Given: 480
$2.5 billion for 60,000 users is $42k per user (total over 4 years). I don't see why NASA would need to spend $10k per year on computers and services. Does that include really expensive licenses for CAD software or something?

Offline madscientist197

  • Regular
  • Full Member
  • ****
  • Posts: 1014
  • Liked: 2
  • Likes Given: 0
Does the $2.5 billion include the provision of heavy-duty supercomputing power, or is it just for running normal desktops and basic servers?
John

Offline JohnFornaro

  • Not an expert
  • Senior Member
  • *****
  • Posts: 9167
  • Delta-t is the salient metric.
  • Planet Eaarth
    • Design / Program Associates
  • Liked: 620
  • Likes Given: 324
Windows 7 is really, really complicated.  We can't begin to tell you how complicated, but consider that with this OS, you can actually do email, a powerful new way to communicate, a way to communicate which has only recently begun to be generally used.  With all this complication, tho, it is really really easy to use.  For only $10K/year/seat you can realize that this is great value, because it's so easy.  True, some people will have to be let go, and some rockets will have to be canceled.  But that's not the fault of the OS, is it? 

I better go now.
Sometimes I just flat out don't get it.

Offline Proponent

  • Senior Member
  • *****
  • Posts: 5475
  • Liked: 990
  • Likes Given: 653
Is it possible for a mere peasant such as myself to obtain items that Administrator Bolden submitted for the record?

There are two items I'm thinking of.  The first is a budget profile requested by now-former Rep. Wu:

Rep. Wu (0:44:43):  "... I do ask this of you to ... give this committee, a high-end number, not what the administration has asked for, not what the Congress has authorized, but what is a high-end number for what NASA, what NASA needs to fully fund a deeper-space human exploration program...."

Admin. Bolden (0:45:48):  "Congressman, I don't have a number in my head today, and I'll take it for the record...."


The other relates to a question about propellant depots posed by Rep. Rohrabacher:

Rep. Rohrabacher (2:11:00):  "The development costs of actually achieving a refueling capability, which would give us further capabilities in space, how does that match up with the cost, the new cost, of developing a new, huge rocket?..."

Bolden (2:11:23):  "Congressman, I'll have to take that for the record, because that, that is a study that I'm certain is somewhere, you know, over in the headquarters building, but I'm not aware of it, I've not asked for that information, but I'll get it to you."
« Last Edit: 08/18/2011 04:40 AM by Proponent »

Offline deltaV

  • Full Member
  • ****
  • Posts: 1538
  • Change in velocity
  • Liked: 165
  • Likes Given: 480
Is it possible for a mere peasant such as myself to obtain items that Administrator Bolden submitted for the record?
Try the "contact us" link at http://science.house.gov/hearing/full-committee-hearing-review-nasa%E2%80%99s-space-launch-system ?

Offline Prober

  • Senior Member
  • *****
  • Posts: 10313
  • Save the spin....I'm keeping you honest!
  • Nevada
  • Liked: 701
  • Likes Given: 728
$2.5 billion for 60,000 users is $42k per user (total over 4 years). I don't see why NASA would need to spend $10k per year on computers and services. Does that include really expensive licenses for CAD software or something?

The next part of the story.
HP plans PC spinoff

http://news.yahoo.com/hps-ceo-needs-convince-wary-wall-street-041211229.html
2017 - Everything Old is New Again.
I have not failed. I've just found 10,000 ways that won't work. ~ by Thomas Alva Edison

Offline Proponent

  • Senior Member
  • *****
  • Posts: 5475
  • Liked: 990
  • Likes Given: 653
Is it possible for a mere peasant such as myself to obtain items that Administrator Bolden submitted for the record?

There are two items I'm thinking of.  The first is a budget profile requested by now-former Rep. Wu....

The other relates to a question about propellant depots posed by Rep. Rohrabacher....

Try the "contact us" link at http://science.house.gov/hearing/full-committee-hearing-review-nasa%E2%80%99s-space-launch-system ?

Well, thanks for the suggestion, deltaV, which I did try.  I've received no reply at all, but I'm feeling a little less miffed about it now that Space News reports that Rep. Rohrabacher himself is still waiting for the study that Administrator Bolden promised to provide.
« Last Edit: 09/14/2011 01:52 PM by Proponent »

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 32377
  • Cape Canaveral Spaceport
  • Liked: 11063
  • Likes Given: 329
$2.5 billion for 60,000 users is $42k per user (total over 4 years). I don't see why NASA would need to spend $10k per year on computers and services. Does that include really expensive licenses for CAD software or something?

The next part of the story.
HP plans PC spinoff

http://news.yahoo.com/hps-ceo-needs-convince-wary-wall-street-041211229.html

Wrong.

unrelated to the NASA contract
« Last Edit: 09/14/2011 01:58 PM by Jim »

Tags: