Author Topic: DIRECT v2.0 - Thread 3  (Read 726833 times)

Offline robertross

  • Canadian Member
  • Senior Member
  • *****
  • Posts: 17801
  • Westphal, Nova Scotia
  • Liked: 462
  • Likes Given: 4071
Re: DIRECT v2.0 - Thread 3
« Reply #20 on: 01/14/2009 01:09 AM »
Incorrect, it is needed.  LH2 will not become stable in the tank without it

Does that mean it will be at a full rolling boil without it?  Would that cause foam or what (besides losses)?

Not just a rolling boil as a major issue, but the engine(s) rely on a stable flow of fluid for proper combustion. Having turbulence & vortices could cause major hiccups in the turbines, injector, and also creates line losses (restriction) which affects the expected movement of sufficient fuel. Lack of fuel destroys engines, which is why they run fuel rich.
Remembering those who made the ultimate sacrifice for our rights & freedoms, and for those injured, visible or otherwise, in that fight.

Offline Lee Jay

  • Elite Veteran
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 6668
  • Liked: 971
  • Likes Given: 139
Re: DIRECT v2.0 - Thread 3
« Reply #21 on: 01/14/2009 01:14 AM »
Lack of fuel destroys engines, which is why they run fuel rich.

I thought they also ran fuel rich to reduce the average molecular weight of the exhaust, which increases ISP.

Offline Will

  • Member
  • Full Member
  • ****
  • Posts: 902
  • Liked: 17
  • Likes Given: 1
Re: DIRECT v2.0 - Thread 3
« Reply #22 on: 01/14/2009 01:20 AM »

My guy tells me the latter should be true...but are these things that have all been absolutely accounted for?  Can we even know until a buildable blueprint for the new ET has been done?
*shrug*


Yes and yes.  Look at the NLS document Ross posted

Well, yes and no. The NLS showed that a particular Shuttle derived vehicle could be built, and doing that would require changes and choices that required over 600 pages even to summarize.

The Jupiter designs are quite different vehicles from NLS. Instead of a mere 80 ton payload atop the ET, they have to be able to support a honking enormous upper stage, with sometimes a massive payload atop that. So a similar design effort would be needed for the new assumptions.

Is the Jupiter core buildable? Absolutely. Is it just a matter of a few minor modifications to the existing ET? Well, read the NLS report and decide for yourself.

Now remember that the Jupiter proposal really hinges on the integrated Jupiter 232. Jupiter 120 is just the Jupiter 232 core and boosters with an RS-68 removed.

For the Jupiter 232 design to close, the ultralightweight upper stage has to meet the ambitious goals set by the Direct team and their anonymous engineers.

Before a contractor started building the Jupiter core, there would need to be a lot of detailed design work as NASA and the contractors figured out if the design could achieve its goals and what it would cost if it could.

That's the Achilles' heel of the Direct proposal. Ares now has a three year head start, and the gap is widening every day. A two launch solution was a fairly attractive option three years ago. Now, changing horses in midstream is a lot more expensive.






Offline Lars_J

  • Senior Member
  • *****
  • Posts: 6161
  • California
  • Liked: 665
  • Likes Given: 195
Re: DIRECT v2.0 - Thread 3
« Reply #23 on: 01/14/2009 01:43 AM »
Another reason not to scale down Direct is that everything smaller than the 120 could easily be replicated with the Delta IV. I remember the suggestion of a "Baby-Jupiter" with 1 RS-68, but it was found that at that point, the Delta IV Heavy would be much better.

It's kind of interesting that a Jupiter 110 would be *very* similar to the Ariane 5, both in look and payload capability.  :) (I'm not sure about the external dimensions, though)

But I certainly understand why you don't want to scale down the 120 further... and it would be nice to have a launcher that wouldn't have such tight mass margins.

Offline Lancer525

  • Full Member
  • **
  • Posts: 244
  • Liked: 1
  • Likes Given: 0
Re: DIRECT v2.0 - Thread 3
« Reply #24 on: 01/14/2009 01:54 AM »
I just wanted to jump in here, and say that I expect to have the plans and notes for the Jupiter Models ready to publish pretty soon.

:)
"For some inexplicable reason, everyone seems to want to avoid simple schemes."   -John Houbolt

Offline gladiator1332

  • Mike Majeski
  • Senior Member
  • *****
  • Posts: 2429
  • Fort Myers, FL
  • Liked: 4
  • Likes Given: 4
Re: DIRECT v2.0 - Thread 3
« Reply #25 on: 01/14/2009 02:49 AM »
Another reason not to scale down Direct is that everything smaller than the 120 could easily be replicated with the Delta IV. I remember the suggestion of a "Baby-Jupiter" with 1 RS-68, but it was found that at that point, the Delta IV Heavy would be much better.

It's kind of interesting that a Jupiter 110 would be *very* similar to the Ariane 5, both in look and payload capability.  :) (I'm not sure about the external dimensions, though)

But I certainly understand why you don't want to scale down the 120 further... and it would be nice to have a launcher that wouldn't have such tight mass margins.

It would make a nice "What If?" scenario, where NASA is able to develop a launch vehicle that can be used commercially. I would like to see how a Jupiter-110 would have fared against the EELVs and Ariane V.

Offline Ronsmytheiii

  • Moderator
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 22455
  • Liked: 767
  • Likes Given: 286
Re: DIRECT v2.0 - Thread 3
« Reply #26 on: 01/14/2009 02:58 AM »
It would make a nice "What If?" scenario, where NASA is able to develop a launch vehicle that can be used commercially. I would like to see how a Jupiter-110 would have fared against the EELVs and Ariane V.

NASA is forbidden by law to compete in the commercial area. Shuttle pretty much wiped out the US commercial launch industry, no reason to do so again.
"Every vision is a joke until the first man accomplishes it; once realized, it becomes commonplace." - Robert Goddard

Offline Lee Jay

  • Elite Veteran
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 6668
  • Liked: 971
  • Likes Given: 139
Re: DIRECT v2.0 - Thread 3
« Reply #27 on: 01/14/2009 03:13 AM »
For the Jupiter 232 design to close, the ultralightweight upper stage has to meet the ambitious goals set by the Direct team and their anonymous engineers.

I may not be reading these numbers right, but what's so ambitious about it?  According to the baseball cards it weighs 47,367 pounds, and carries under 800,000 pounds of propellant, while the ET weighs 58,500 pounds (23% more) and carries over 1,600,000 pounds (over 100% more) of propellant.  It sound's as if the current ET is much more ambitious from those numbers, and it has to side-mount the orbiter, support the beam from the SRBs, and it's not a common-bulkhead design.

What am I missing?

Offline gladiator1332

  • Mike Majeski
  • Senior Member
  • *****
  • Posts: 2429
  • Fort Myers, FL
  • Liked: 4
  • Likes Given: 4
Re: DIRECT v2.0 - Thread 3
« Reply #28 on: 01/14/2009 03:17 AM »
It would make a nice "What If?" scenario, where NASA is able to develop a launch vehicle that can be used commercially. I would like to see how a Jupiter-110 would have fared against the EELVs and Ariane V.

NASA is forbidden by law to compete in the commercial area. Shuttle pretty much wiped out the US commercial launch industry, no reason to do so again.

I know this. I meant, this in a "what if?" where that law does not exist. Just an apples to apples comparison between the vehicles.

Offline Lars_J

  • Senior Member
  • *****
  • Posts: 6161
  • California
  • Liked: 665
  • Likes Given: 195
Re: DIRECT v2.0 - Thread 3
« Reply #29 on: 01/14/2009 04:11 AM »
I don't think a Jupiter 110 could compete very well in such a hypothetical scenario... It would be a bit over-engineered for the purpose. It's parts cost would probably exceed the EELVs by quite a margin. Then add in all the extra workforce...
(but it would look cool) :D
« Last Edit: 01/14/2009 04:12 AM by Lars_J »

Offline kraisee

  • Expert
  • Senior Member
  • *****
  • Posts: 10481
  • Liked: 408
  • Likes Given: 19
Re: DIRECT v2.0 - Thread 3
« Reply #30 on: 01/14/2009 05:12 AM »
I understand the ET won't leave LEO, but it was never designed to carry a load that would like it will be used for now.
Like I said, maybe it's not a major obsticle.  Just pointing out some  other consideration that people might not be thinking about, especially when they all get excited about their own ideas.

So you think people, which are working on DIRECT project for 2 years now, somehow "might not be thinking about" whether it is feasible of making ET-derived tank to support this weight.

Surprise! They did think about it, and found out that it is possible, and not even hard.

Easy mater! :)

Many of us have been over this question before, but Lobo's question *is* still a valid one for all those folk who weren't here 6 months ago -- or 24+ months ago.

We have spent a great deal of time investigating the procedures, facilities and design involved in converting the ET into a Core Stage.

Back on the old Thread 2 I posted a link to one of the many hundreds of documents about the NLS -- a system which bears a lot of similarity to Jupiter.   That document certainly requires updating, but it shows precisely how MSFC wanted to perform precisely this sort of modification to the ET back in 1993.   The document is part 1 of three, making a complete set of Trade Studies which were together, completed within the 9 month period from May 1991 to January 1992.   This was the "Structures" book.   The other two parts of the set are Avionics and Systems and Propulsion.

Our small group has been gradually trying to update this study and create something similar for Jupiter.   We're in a position today where we have plans for implementing the first DAC and have almost got a fully-integrated baseline design ready to enter that process "running" -- although we also acknowledge that none of our work will actually ever be used.   It will all have to be redone "officially" anyway, but we have at least helped 'clear the path' and we've already tackled a number of the hurdles so we know it can be done.

Without doubt, this is most definitely "rocket science", or perhaps more precisely "rocket engineering".   We (and I'm talking about our engineers, not myself here -- While I'm a quick learner, I've still got a long way to go myself!) are fully-aware of what's involved to get this right.

We do have the benefit that a lot of what we're proposing has its roots firmly in existing flight hardware.   But even with that advantage, nobody is claiming that this is "simple", "easy" or "minor" -- nothing in this business ever qualifies for those terms except when it is used exclusively a relative statement.

The design of any new rocket is a major effort, an engineering challenge, a costly endeavor and a careful balance of risk.   But, like with many things in life, there are comparatively easier paths and comparatively more difficult ones which can be taken.   We are convinced that DIRECT's Jupiter launcher represents a much simpler and less costly approach than the Ares duo.   We are also convinced that Ares is not fiscally responsible enough and that it will ultimately lead the way to joining so many other NASA projects which have been canceled prematurely due to cost.   It is DIRECT's hope to change direction before that happens and prevent the Vision For Space Exploration from becoming yet another wasted effort to reach for the stars.


The DIRECT approach attempts to reuse as much existing proven flight hardware, with the least possible number of changes, to create a new fiscally-responsible system able to perform the tasks which we are planning to do.

What we're proposing is still a major project.   Jupiter-120 is a $9.5 billion development program -- but that's roughly $5 billion less than Ares-I will cost.

Where we really save money though, is by removing the full development of the second launcher (Ares-V) from the equation.   We remove the need for another set of SRB's and the requirement for manufacturing and launch infrastructure for all that too.   Of course, we still need the EDS, but the total cost savings of re-using the Core of the J-120 again as the basis for the J-232 saves over $10 billion more in development costs.   That's some really serious money we're talking about there.


While I started out really simply some ~30-something months ago, the initial very rudimentary concept has been seriously fleshed-out over the last few years by the hard volunteer efforts of a group of experienced professionals from across the whole industry.   Today The DIRECT Team have a very mature proposal with a lot of substance behind it.

Ross.
« Last Edit: 01/14/2009 07:25 AM by kraisee »
"The meek shall inherit the Earth -- the rest of us will go to the stars"
-Robert A. Heinlein

Offline Lampyridae

  • Veteran
  • Full Member
  • ****
  • Posts: 1662
  • Liked: 77
  • Likes Given: 138
Re: DIRECT v2.0 - Thread 3
« Reply #31 on: 01/14/2009 05:50 AM »
Lack of fuel destroys engines, which is why they run fuel rich.

I thought they also ran fuel rich to reduce the average molecular weight of the exhaust, which increases ISP.

Yes and no. Running stoichiometric (burn everything equally) means maximum energy is extracted from the chemical reaction. Running fuel or oxidiser rich means you are chucking more mass overboard for less chemical energy per unit mass... hence a lower collective exhaust velocity. However, it also means that the thermal energy is more efficiently distributed amongst molecules. It's easier to plunk thermal energy into H2 because it has one bond. H2O has 3 bonds so it gets squished out in the interactions.

(Real rocket engineers please feel free to correct me wherever I foul up).

Tankage is also an issue. I believe US rockets run a tankage ratio of 4.5 to 1 for LH/LOX combos when stochiometric is like 8 to 1 (mass ratio). It's all very fuzzy really. That's why you see the LH tank is something like 4x the size of the LOX tank instead of 2x the size.

edited for accuracy and spelling. stoichiometric! always forget the i!!
« Last Edit: 01/14/2009 05:59 AM by Lampyridae »
SKYLON... The League of Extraordinary Gentlemen's preferred surface-to-orbit conveyance.

Offline madscientist197

  • Regular
  • Full Member
  • ****
  • Posts: 1014
  • Liked: 2
  • Likes Given: 0
Re: DIRECT v2.0 - Thread 3
« Reply #32 on: 01/14/2009 07:21 AM »
I think it's closer to 6:1 oxidiser/fuel for most LH/LOX engines today. 4:1 is approximately the ratio for the maximum possible ISP, but it takes too much tanking to be worth it.
John

Offline kraisee

  • Expert
  • Senior Member
  • *****
  • Posts: 10481
  • Liked: 408
  • Likes Given: 19
Re: DIRECT v2.0 - Thread 3
« Reply #33 on: 01/14/2009 07:30 AM »
I'd have to go look it up to be certain, but I'm pretty sure J-2X uses a 5.5 : 1 mixture ratio.

Ross.
« Last Edit: 01/14/2009 07:30 AM by kraisee »
"The meek shall inherit the Earth -- the rest of us will go to the stars"
-Robert A. Heinlein

Offline gospacex

  • Senior Member
  • *****
  • Posts: 3028
  • Liked: 536
  • Likes Given: 604
Re: DIRECT v2.0 - Thread 3
« Reply #34 on: 01/14/2009 08:26 AM »
That's the Achilles' heel of the Direct proposal. Ares now has a three year head start,

...during which it has slipped four years to the right. Today Ares is looking far worse than three years ago.

Offline gospacex

  • Senior Member
  • *****
  • Posts: 3028
  • Liked: 536
  • Likes Given: 604
Re: DIRECT v2.0 - Thread 3
« Reply #35 on: 01/14/2009 08:35 AM »
Lack of fuel destroys engines, which is why they run fuel rich.

I thought they also ran fuel rich to reduce the average molecular weight of the exhaust, which increases ISP.

Yes and no. Running stoichiometric (burn everything equally) means maximum energy is extracted from the chemical reaction. Running fuel or oxidiser rich means you are chucking more mass overboard for less chemical energy per unit mass... hence a lower collective exhaust velocity. However, it also means that the thermal energy is more efficiently distributed amongst molecules. It's easier to plunk thermal energy into H2 because it has one bond. H2O has 3 bonds so it gets squished out in the interactions.

(Real rocket engineers please feel free to correct me wherever I foul up).

I think you are wrong. Energy is not important, impulse (speed) is. Running LOX/LH non-stoichiometric gives you free H2 in the exhaust, which has highest possible speed of all gases at any given temperature. Thus, even though energy per kg of exhaust is not maximized, impulse (Isp) is.

IIRC Isp-optimal ratio for LOX/LH is 4:1 by mass, IOW, to use twice as much hydrogen compared to stoichiometric (which would be 8:1). Due to LH tankage inefficiencies, in practice ratios close to 6:1 are used.

Offline Kaputnik

  • Extreme Veteran
  • Senior Member
  • *****
  • Posts: 2825
  • Liked: 466
  • Likes Given: 437
Re: DIRECT v2.0 - Thread 3
« Reply #36 on: 01/14/2009 08:40 AM »
For the Jupiter 232 design to close, the ultralightweight upper stage has to meet the ambitious goals set by the Direct team and their anonymous engineers.

I may not be reading these numbers right, but what's so ambitious about it?  According to the baseball cards it weighs 47,367 pounds, and carries under 800,000 pounds of propellant, while the ET weighs 58,500 pounds (23% more) and carries over 1,600,000 pounds (over 100% more) of propellant.  It sound's as if the current ET is much more ambitious from those numbers, and it has to side-mount the orbiter, support the beam from the SRBs, and it's not a common-bulkhead design.

What am I missing?

Discussed extensively in the old thread. But arguments for/against the feasibility of the Jupiter Upper Stage are as follows:

For:
- Less ambitious than ET mass fraction
- LM Centaur engineer says it is possible, even conservative (see Popular Mechanics article) (this pretty much convinces me :) )

Against:
- more ambitious than SII, SIVB, or Ares-V EDS
- NASA are squeezing more performance from Ares-V yet have not suggested such a high-performance upper stage as part of this
- Steve Cooke says it isn't possible.
Waiting for joy and raptor

Offline ugordan

  • Senior Member
  • *****
  • Posts: 7504
    • My mainly Cassini image gallery
  • Liked: 1725
  • Likes Given: 376
Re: DIRECT v2.0 - Thread 3
« Reply #37 on: 01/14/2009 08:45 AM »
For the Jupiter 232 design to close, the ultralightweight upper stage has to meet the ambitious goals set by the Direct team and their anonymous engineers.

It doesn't get any more anonymous than Bernard Kutter, Manager of Advanced Programs at ULA - Lockheed-Martin publicly saying the JUS is verging on conservative, does it?

I suppose that once you make up your mind about something, no amount of authority in the field will convince you otherwise. You wouldn't be forgetting this point that was brought up to you earlier otherwise. Sure, believe Steve Cook, he's an expert on cryo upper stages.

Offline Nathan

  • Member
  • Full Member
  • ****
  • Posts: 701
  • Sydney
  • Liked: 14
  • Likes Given: 2
Re: DIRECT v2.0 - Thread 3
« Reply #38 on: 01/14/2009 09:28 AM »
For the Jupiter 232 design to close, the ultralightweight upper stage has to meet the ambitious goals set by the Direct team and their anonymous engineers.

It doesn't get any more anonymous than Bernard Kutter, Manager of Advanced Programs at ULA - Lockheed-Martin publicly saying the JUS is verging on conservative, does it?

I suppose that once you make up your mind about something, no amount of authority in the field will convince you otherwise. You wouldn't be forgetting this point that was brought up to you earlier otherwise. Sure, believe Steve Cook, he's an expert on cryo upper stages.

I think we all just want to know why the tech used in the JUS isn't used in the Ares-V vehicle and if it was then what would the performance of the Ares-V be? NASA does consullt with Boeing & Lockheed regularly so the tech cannot be unknown to them.
Given finite cash, if we want to go to Mars then we should go to Mars.

Offline MP99

Re: DIRECT v2.0 - Thread 3
« Reply #39 on: 01/14/2009 09:41 AM »
I have a question about the EDS.

It will have been sitting in orbit for a while when LSAM / CEV comes to dock with it. Is there any possibility that it will be tumbling by this point?

If so, how does the EDS stablise itself to allow docking to proceed? I don't see any thrusters in the EDS diagrams, nor any mass allocation (eg in figure 36 of http://www.launchcomplexmodels.com/Direct/documents/AIAA-2007-6231-LowRes.pdf).

cheers, Martin

Tags: