Author Topic: DIRECT v3.0 - Thread 1  (Read 1237991 times)

Offline MP99

Re: DIRECT v3.0 - Thread 1
« Reply #140 on: 06/02/2009 07:06 pm »
And no, the LOX tank is sized to precisely the same capacity as the current ET's Ogive tank.

We do still have an option to increase the capacity of both the LOX and LH2 tanks by ~7-9% (in the same way as NLS was going to), but right now, mostly for simplicity sake, we have simply chosen not to mess around with altering the capacities.   We can close all performance requirements comfortably without it.

I find it sad if the easy tankage structure changes that give lots of performace per kg of structure are not done when the hard ones are done. Why design a long engine thrust structure when you can elongate the LH2 tank and design a smaller thrust structure? What is the additional design work with making the LOX barrel section a little longer when you anyway redesign the tank for inline launch?

The only engineering reason for not doing this that I can think of is if you add to much tankage mass and no longer hit the sweet spot for the 3 SSME verison.

I find the political reason weak, who cares if the fuel load is aprox 8% larger when it looks the same on the pretty pictures? If you are that sensitive about looks you ought to have made the thrust structure design more expensive buy having two versions to center the mid engine. That would of course be a bad redesign from a system cost perspective.

Starting out in the "high end" of the tankage volume and mass sweet spot ought to be beneficial for future engine upgrades of the SSME:s or SRB:s.


Jupiter has multiple tweaks which could improve performance (5-seg SRB's & a core stretch give about 30% IIRC).

Apollo ended up needing a much larger vehicle than they'd expected. Since DIRECT is designed to close the mission without needing those tweaks, they make great growth options if it turns out extra performance is required. It's also quicker & cheaper to develop if you don't have to make unnecessary changes, and they can always be added in a block II or block III version.

DIRECT is littered with margins and growth options - one of it's strongest features.

cheers, Martin

Offline wannamoonbase

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Re: DIRECT v3.0 - Thread 1
« Reply #141 on: 06/02/2009 08:10 pm »
It'll be 30 years in April 2011, not 40.

I knew I should've taken off my shoes before attempting that calculation...

Depends if you count from the date of design or first flight.  I use to use first flight.  But the longer I'm an engineer the more I prefer design.  So I think your closer to 40 than 30. 

Some of the switches on the flight deck are probably closer to 50.

Can't not 100% right or wrong by going either way.
Wildly optimistic prediction, Superheavy recovery on IFT-4 or IFT-5 (Welp a little early on IFT-4, but still have a shot at 5)

Offline robertross

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Re: DIRECT v3.0 - Thread 1
« Reply #142 on: 06/02/2009 08:37 pm »
what % thrust are SSMEs being run at?
given  no re-use could they be pushed higher?

1) Currently the SSME runs at 104.5% thrust.

2) Somewhere back in the old Direct threads, Ross had indicated tests donw on the SSME which went up to at least 109% IIRC, and passed without issue. All that happens is you reduce life expectancy on certain components. Since they aren't destined to be reused anyway on Jupiter, they could easily attain that, probably more.

Offline tnphysics

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Re: DIRECT v3.0 - Thread 1
« Reply #143 on: 06/02/2009 08:57 pm »
What is the maximum power level the SSMEs could be run at,considering that they will not be reused?

Offline GraphGuy

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Re: DIRECT v3.0 - Thread 1
« Reply #144 on: 06/02/2009 09:00 pm »
What is the maximum power level the SSMEs could be run at,considering that they will not be reused?

Probably the standard 109% max, otherwise you would need to requalify them, etc.  Not worth it and Jupiter doesn't need the extra thrust in the first place.

Offline dlapine

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Re: DIRECT v3.0 - Thread 1
« Reply #145 on: 06/02/2009 09:02 pm »
The wikipedia article on the SSME has pretty good info on the throttle capabilities, as well as links to NASA's press kit. The press kit is pretty technical, and has detailed list of the upgrades to the SSME on page 4. The release is old enough that the Block II engines weren't in service at that time, however.

http://en.wikipedia.org/wiki/Space_Shuttle_main_engine

http://www.shuttlepresskit.com/scom/216.pdf

109% thrust is doable, and has been tested. In fact, the second reference document on the Wikipedia page is NASA's 1993 report of the SSME Assessment team, http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930012456_1993012456.pdf , and it states that 109% thrust is part of the design.

Unfortunately, the report also states that the failure rates when running at 109% thrust are significantly worse, with a critical engine failure (not a safe shutdown)rate  of 1 in every 20 flights.

So the maximum rate for the SSME's is not the same as the maximum safe rate.

Offline psloss

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Re: DIRECT v3.0 - Thread 1
« Reply #146 on: 06/02/2009 09:08 pm »
Unfortunately, the report also states that the failure rates when running at 109% thrust are significantly worse, with a critical engine failure (not a safe shutdown)rate  of 1 in every 20 flights.
Well, if that report was published in '93, then it probably didn't take into account a lot of the upgrades (such as to the high-pressure turbo pumps and main combustion chamber) that have gone into the engines since then.

Offline Jorge

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Re: DIRECT v3.0 - Thread 1
« Reply #147 on: 06/02/2009 09:57 pm »
Unfortunately, the report also states that the failure rates when running at 109% thrust are significantly worse, with a critical engine failure (not a safe shutdown)rate  of 1 in every 20 flights.
Well, if that report was published in '93, then it probably didn't take into account a lot of the upgrades (such as to the high-pressure turbo pumps and main combustion chamber) that have gone into the engines since then.


Indeed, the report lists the Pratt & Whitney turbopumps as "proposed improvements" in the table of contents, so it seems pretty clear to me that this assessment of 109% throttle was performed assuming the old turbopumps.
JRF

Offline tnphysics

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Re: DIRECT v3.0 - Thread 1
« Reply #148 on: 06/02/2009 10:04 pm »
Okay, so what is the maximum safe power for the Jupiter?

Offline tnphysics

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Re: DIRECT v3.0 - Thread 1
« Reply #149 on: 06/02/2009 10:18 pm »
One of the best 'alternative' mission profiles which we have been able to confirm so far is that of using the EDS to perform the LOI as well as the TLI.

Because the lander doesn't have to perform the LOI, it results in a lander which is considerably smaller and lighter than the current CxP design.   This solves almost all of the Altair's height/stability issues and might even allow the thing to fit inside an 8.4m PLF again too.   At this size and mass the LSAM & CEV will *easily* fit on a J-130, thus improving both costs and safety for each mission.   Also by having multiple engines on an RL-10-powered EDS you get high Isp and a great deal of engine-out capability for the LOI as well, which is nice.

With this profile we're seeing about 10% extra payload mass to the Lunar surface as well -- and that's the real point.

Ross.



Interesting. I thought that the extra mass that had to be carried through LOI would kill the performance.

Also, perhaps the easiest way to use the excess CLV capacity is to launch the EDS to an elliptical orbit and use the excess CLV performance to launch the LSAM and CEV to the same elliptical orbit. Less prop is available for TLI but this is more than compensated by the lower dV required.

Offline pierre

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Re: DIRECT v3.0 - Thread 1
« Reply #150 on: 06/02/2009 11:13 pm »
Also, perhaps the easiest way to use the excess CLV capacity is to launch the EDS to an elliptical orbit and use the excess CLV performance to launch the LSAM and CEV to the same elliptical orbit. Less prop is available for TLI but this is more than compensated by the lower dV required.

I may be wrong, but I think that circular orbits have the nice property that you can do the second launch every time the orbit is over your head, while elliptical orbits offer much less launch opportunities.
« Last Edit: 06/02/2009 11:13 pm by pierre »

Offline kraisee

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Re: DIRECT v3.0 - Thread 1
« Reply #151 on: 06/02/2009 11:22 pm »
tnphysics,
We are assuming 104.5% is the maximum for all Jupiter's.   That allows for emergency use of the 109% setting if ever required due to an in-flight anomaly.

It is possible that at some point in the future, the 109% setting might be sufficiently qualified for regular use on cargo-only flights though.

Ross.
"The meek shall inherit the Earth -- the rest of us will go to the stars"
-Robert A. Heinlein

Offline kraisee

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Re: DIRECT v3.0 - Thread 1
« Reply #152 on: 06/02/2009 11:42 pm »
I may be wrong, but I think that circular orbits have the nice property that you can do the second launch every time the orbit is over your head, while elliptical orbits offer much less launch opportunities.

You are exactly correct.

The only 'likely' use of such a profile would be in the unlikely, but not impossible, scenario of a dual launch occurring at the same time from both pads.

That's a 'difficult' proposition, to say the least, but is not completely unprecedented.   Here is an image showing Gemini 12 lifting off from LC-19 at the same time as an Atlas Agena lifts off from LC-14 a few miles away.   This was done specifically to enable a docking between the two spacecraft in LEO.



This sort of thing *has* been done before.

Ross.
« Last Edit: 06/02/2009 11:44 pm by kraisee »
"The meek shall inherit the Earth -- the rest of us will go to the stars"
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Offline mars.is.wet

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Re: DIRECT v3.0 - Thread 1
« Reply #153 on: 06/03/2009 12:08 am »
Any word when we will get to see the full ISDC presentation?  Or better yet, the new Direct 3.0 "proposal" with new costs and schedules?
« Last Edit: 06/03/2009 12:10 am by mars.is.wet »

Offline engstudent

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Re: DIRECT v3.0 - Thread 1
« Reply #154 on: 06/03/2009 12:40 am »
Any word when we will get to see the full ISDC presentation?  Or better yet, the new Direct 3.0 "proposal" with new costs and schedules?

Oooh - new thread partys over so soon? Back to buisness?  ;D
” …All of this. All of this was for nothing – unless we go to the stars.” - Sinclair

Offline psloss

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Re: DIRECT v3.0 - Thread 1
« Reply #155 on: 06/03/2009 12:49 am »
That's a 'difficult' proposition, to say the least, but is not completely unprecedented.   Here is an image showing Gemini 12 lifting off from LC-19 at the same time as an Atlas Agena lifts off from LC-14 a few miles away.   This was done specifically to enable a docking between the two spacecraft in LEO.
That's probably a composite.  The Gemini was launched more or less on the Agena's first pass over the launch site.

Offline gladiator1332

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Re: DIRECT v3.0 - Thread 1
« Reply #156 on: 06/03/2009 12:56 am »
My biggest worry is that the review panel does not go right to the source for information with regards to Direct. If they rely on numbers and data put out by NASA, then I fear it will not be a true Direct review.

Already their are rumors that Hawes has already tried to block any non-Contractors from providing official testimony information to the panel. From what I have read on here, Hawes will also provide data and analysis for the panel. I don't see him painting a pretty picture for Direct.

Either we cross our fingers and hope the panel sees through the bull, or hopefully the Team gets their shot to present to the panel so they can hear it straight.

Offline mars.is.wet

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Re: DIRECT v3.0 - Thread 1
« Reply #157 on: 06/03/2009 12:57 am »
My biggest worry is that the review panel does not go right to the source for information with regards to Direct. If they rely on numbers and data put out by NASA, then I fear it will not be a true Direct review.

Already their are rumors that Hawes has already tried to block any non-Contractors from providing official testimony information to the panel. From what I have read on here, Hawes will also provide data and analysis for the panel. I don't see him painting a pretty picture for Direct.

Either we cross our fingers and hope the panel sees through the bull, or hopefully the Team gets their shot to present to the panel so they can hear it straight.

If they were looking for data RIGHT NOW (for example) where would (they) look?

Offline gladiator1332

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Re: DIRECT v3.0 - Thread 1
« Reply #158 on: 06/03/2009 01:00 am »
Well once Direct 3.0 is officially launched, it is as simple as visiting Directlauncher.com and downloading the presentation. However, the best way to get the data they need to go right to the source, ie meet with the Direct Team in person.
« Last Edit: 06/03/2009 01:01 am by gladiator1332 »

Offline cixelsyD

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Re: DIRECT v3.0 - Thread 1
« Reply #159 on: 06/03/2009 01:11 am »
I'm not too worried about that since one of the members has a blog and many people have posted links and support comments for Direct. I'm pretty sure the commission won't ignore Direct if they know about it. Direct is quite clearly at the forefront of alternatives to Ares I/V, and will IMHO be a main subject of the panel.

I think the main questions the commission will face are the viability of switching, whether Direct or Ares will truly meet stated requirements. Perhaps it will even try to hammer out a compromise between the two teams. I'm very optimisitic about the commission.

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