Author Topic: Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)  (Read 66636 times)

Online clongton

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RE: Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)
« Reply #40 on: 01/14/2007 01:09 PM »
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Chris Bergin - 9/1/2007  3:18 PM

The DIRECT site appears to be down at the moment, I'm trying to find out why.
I'm told that Ross is in the process of switching to a different server.
Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline simcosmos

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RE: Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)
« Reply #41 on: 01/14/2007 02:51 PM »
Hello

I would like to start by thanking Dr. Doug Stanley for another Questions and Answers thread.

I would also like to note that my following questions / comments will be written in a spirit of *wanting to learn more* and, in that sense, nasaspaceflight forums have always been a great and very educative resource for all the persons wishing to learn about several space exploration related topics, thanks to the precious collaboration of persons linked to the several aerospace areas (NASA / Other Space Agencies, contractors, other private efforts, etc).


I have been implementing some conceptual designs about hardware mentioned in ESAS or current VSE related hardware (Ares I/V concepts, DIRECT, Atlas Phase II, etc) into Orbiter Space Flight Simulator – http://www.orbitersim.com - and as such my questions are more aimed for the technical / design aspects.

So, in that spirit, please have patience and allow me to do a few questions. I guess that the best should be to pack my comments by groups in a couple of structured posts. Here goes a try for a first one. Thanks in advance.


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Doug Stanley - 13/1/2007  10:20 PM

The second less major reason for the performance shortfall is in the assumptions about the amount of propellant that the core can actually hold.  Because of geometric and structural considerations, a core vehicle of this diameter cannot hold more than 1.6Mlbs of propellant due to tank clearance issues with the structure required to react SRB loads and thrust structure packaging considerations. A very detailed analysis of this was done during ESAS when we did the LV 24/25 concepts.  For a given diameter core, going to 5-segment solids has the added advantage of allowing you to make the hydrogen tank longer to hold more propellant.  


Quote
Doug Stanley - 14/1/2007  2:44 AM

Given the RS-68 engine length and required pad clearances, NASA designed and laid out an aft end with thrust structure/gimbal/lines and found that there really was no room left to drop the H2 tank by any useful degree...


A. ET derived cores for heavy lifter options, tanks capabilities (propellant quantities) and integration aspects

Please see the image that I will link to below (from temporary web space) and please look at it just as a kind of "clumsy" and far from perfect illustration about what I wish to ask:


(click to load larger picture)

At the left side is something more or less similar to the ESAS CaLV: ~8.4m diameter core for about 1004t of propellants assumed in ESAS, 2 x 5 segment SRB and 5 modified SSME.

At the right side is something more or less similar to DIRECT's proposal basic core: same 8.4m diameter, about 800t total propellants assumed, 2 x 4 segment SRB and twin modified RS-68 (first would be +/- normal versions, later would be regenerative nozzle engines; will try to ask a few extra questions about the engines later on, if having time to structure it in a post similar to this one.). All units are in SI.


A.1) At a first glance - and by comparing these two non-perfect but perhaps still capable of providing some hints representations of both launchers - there seems not to be any major problem when thinking in the tanks integration and relation with the solid boosters attachment points.

A.2) Regarding the integration with the propulsion structure, in the right side, for DIRECT core, I made a copy+paste of a +/- scaled RS-68 two dimensional representation from:

PropulsionForThe21stCentury-CostDrivenRS-68.ppt
(powerpoint about RS-68 development)
   
Again, at a first glance to the image above, the integration of RS-68 modified engines seem to be feasible for something like DIRECT core and with still a little of space left between the bottom tank and the top of the engine's thrust frame (DIRECT twin engines would also not be located directly below the lower part of the bottom tank like it seems in this 2D representation).

This seems to be more or less equivalent to the clearance assumed between old Soviet Union Energia core's bottom tank and the ~4.55m tall RD-0120, please see http://www.buran.ru/images/jpg/mtkkman2.jpg

Note: I'm making here a reference to Energia because, in some aspects (together with STS), it is probably one of the closer real life references we have for something like DIRECT basic core design.


Question A.1: Could you please extend a little more about integration issues regarding  DIRECT tank propellant quantities, propulsion structure, SRB attachment points, etc or perhaps even point directions for where I can learn about those aspects?


Question A.2: I know that the SSME is slightly shorter than RS-68 but when looking at the above simple comparison between ESAS CaLV and DIRECT basic core and when also using the linked Energia picture as a rough example there seems not to be any major (non workable, I mean) show stopper regarding geometrical integration of the propulsion structure with the rest of the core. Could you please also extend a little more about the studies / what are NASA's requirements / assumptions for the design of such propulsion structure(s) and, specifically how those requirements would make DIRECT infeasible from such point of view?

I mean, wouldn't a total propellant quantity of at least something like 790t really not be feasible in any possible and imaginable way? Might that information (about propulsion structures for heavy lifters) be made available for the "public" in a later moment (even if not in the near / middle-term)?


Questions A.3: Assuming that something like DIRECT core would be possible (~800t or 790t propellant) could you please share, if having it available, what would be your estimated empty mass for such core? (if possible by breaking up the mass in two main totals: one dedicated to the propulsion part and then the other mass for all the rest, with and without margins)?

Was, in your opinion, the dry mass assumed for the basic DIRECT core (~63t for a total prop. amount of 800t with core having  twin RS-68R engines) too much optimistic? Would it be closer to the 70t instead?


Please remember that I'm using this post to just ask about extra conceptual generic aspects or even about some details related with the analysis of DIRECT's basic core design / components integration and leaving out aspects related with specific choices for engine and related performance, other components (above the core, etc).


Thanks again,
(and sorry if wrote any nonsense :) )

António
my pics @ flickr

Offline Smatcha

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Re: Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)
« Reply #42 on: 01/14/2007 04:10 PM »
António, I think the aft SRB attach points should be moved down to the Thrust Structure/ET interface line that way the LH2 tank can just be a tank now.

“Do we want to go to the moon or not?”
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Question posed in Letter to Dr. Robert C. Seamans Jr, NASA Associate Administrator

Ralph Ellison “I was never more hated than when I tried to be honest”




Offline Smatcha

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Re: Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)
« Reply #43 on: 01/14/2007 04:18 PM »
Quote
braddock - 14/1/2007  3:43 AM

Quote
Doug Stanley - 13/1/2007  10:00 PM
What specific "hard dry math" did "he" show you.  I will try to get the same info.  Do you want C Star efficiencies, temperatures, pressures.  [...snip...]  JUst let me know...I will do my best to make it happen!

If only NASA Public Affairs would have facilitated this type of technical clarification, even just once, during the past year the Constellation program would be in far better standing.  The only solid NASA response to these many rumors (coming largely from within the program itself) has been a single "leaked" memo from Jeff Hanley, an interview this site arranged with Danny Davis, and Dr. Stanley's Q&A.

Are the following real problems with Constellation, and what can be done?

1) NASA PAO is unable or unwilling to support and defend the program effectively.
2) NASA Management is failing to communicate overall program health, progress, and direction to the rank-and-file engineers.
3) Program morale is low (I have seen almost none of the people involved attempt to defend the program on this site -- usually the opposite)
4) Contractors are attacking the program to boost their own alternatives - not necessarily unhealthy, but bad when NASA is silent and refuses to engage in the debate

Dr. Stanley, you are doing a world of good for the program here today.

Looks like Doug is NASA's unofficial Bruce Lee.





“Do we want to go to the moon or not?”
John C. Houbolt - November 15, 1961
Question posed in Letter to Dr. Robert C. Seamans Jr, NASA Associate Administrator

Ralph Ellison “I was never more hated than when I tried to be honest”




Offline Norm Hartnett

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Re: Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)
« Reply #44 on: 01/14/2007 09:54 PM »
Once again thank you for taking the time to address this forum Dr. Stanley.

I am very disheartened to find that the Direct concept is nonviable. I was an advocate of Direct because of what I have seen of the costs and schedule of the Constellation program. I jumped on the Direct bandwagon because I am of the opinion that without considerable numbers of launches and missions the American people will rapidly lose interest and spell the end of the VSE.

My question to you is, given that costs of the Constellation program will consume a major portion of the NASA budget and given that Constellation manned flights are unlikely to exceed four per year within those budget constraints, what is going to engage the American public’s interest and support that was not engaged by the Apollo program thirty five years ago?
“You can’t take a traditional approach and expect anything but the traditional results, which has been broken budgets and not fielding any flight hardware.” Mike Gold - Apollo, STS, CxP; those that don't learn from history are condemned to repeat it: SLS.

Offline Doug Stanley

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Re: Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)
« Reply #45 on: 01/14/2007 11:46 PM »
Quote
SMetch - 14/1/2007  11:01 AM

Quote
braddock - 14/1/2007  3:43 AM

Quote
Doug Stanley - 13/1/2007  10:00 PM
What specific "hard dry math" did "he" show you.  I will try to get the same info.  Do you want C Star efficiencies, temperatures, pressures.  [...snip...]  JUst let me know...I will do my best to make it happen!

If only NASA Public Affairs would have facilitated this type of technical clarification, even just once, during the past year the Constellation program would be in far better standing.  The only solid NASA response to these many rumors (coming largely from within the program itself) has been a single "leaked" memo from Jeff Hanley, an interview this site arranged with Danny Davis, and Dr. Stanley's Q&A.

Are the following real problems with Constellation, and what can be done?

1) NASA PAO is unable or unwilling to support and defend the program effectively.
2) NASA Management is failing to communicate overall program health, progress, and direction to the rank-and-file engineers.
3) Program morale is low (I have seen almost none of the people involved attempt to defend the program on this site -- usually the opposite)
4) Contractors are attacking the program to boost their own alternatives - not necessarily unhealthy, but bad when NASA is silent and refuses to engage in the debate

Dr. Stanley, you are doing a world of good for the program here today.

Looks like Doug is NASA's unofficial Bruce Lee.






I am back now and promise I will spend some time tonight getting to all of the current questions. I just have to put my kids to bed right now and will be back within an hour.  I was just scanning the questions and saw this one and had to respond!  This is the definitely the first time in my life I have ever been compared to Bruce Lee...HA...Steve Seagal maybe because of my pony tail...That is hilarious! I am showing it to my 6 year old daughter right now...See you in a little while!

Doug

Online Chris Bergin

Re: Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)
« Reply #46 on: 01/15/2007 12:48 AM »
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Doug Stanley - 15/1/2007  12:29 AM
This is the definitely the first time in my life I have ever been compared to Bruce Lee...HA...Steve Seagal maybe because of my pony tail.

And there was me struggling for a story tonight...

"Seagal In Shuttle Replacement Shocker"

Whatta Scoop ;)

[small]Thanks Nathan![/small]

Offline Generic Username

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Re: Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)
« Reply #47 on: 01/15/2007 01:29 AM »
Quote
Doug Stanley - 14/1/2007  5:29 PM
This is the definitely the first time in my life I have ever been compared to Bruce Lee...HA...Steve Seagal maybe because of my pony tail...

Let's hear it for my fellow rocket-industry long-hairs!

On Direct: do you know if there were any Direct or Ares V-type designs studied for ESAS featuring 5 SSME's or 5 RS-68s in an arrangement not like the S-ID, but like the S-I*D*? That Boeing proposal was for an SSTO version of the Saturn V first stage, and dropped the outer four F-1's much as the earlier Atlas dropped the outer two booster engines. This would leave only the central engine as a sustainer, and a lower-weight thrust structure.
Spacecraft and aircraft models, blueprints, documents:
http:www.up-ship.com

Offline Doug Stanley

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RE: Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)
« Reply #48 on: 01/15/2007 02:25 AM »
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MATTBLAK - 13/1/2007  10:30 PM

Quote
Doug Stanley - 14/1/2007  2:15 PM

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MATTBLAK - 13/1/2007  9:52 PM

Thanks! Yes, it would look sorta silly- like it needed a huge, celestial dartboard.

A follow-up if I may. I've heard of some concern over the prospective G-loads (>18-G!!) that might be placed on the crew if they used the LES during the Ares 1 first stage burn. Has there been any improvement in the LES or first stage designs that might ease these sorts of loads?

Where did that number come from???  The current abort g-loads are not that high and are within NASA's human-rating standards...the acceptable g's depend on the orientation and the time over which they apply, but never exceed 15 in any orientation...

Well, file that under the category of "Someone I know, who works for Nasa told me (true, they did) that it would be..."

I guess that is marginally better than "I read it on the Internet Alice so it must be true!" ;-)

Offline Doug Stanley

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RE: Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)
« Reply #49 on: 01/15/2007 02:37 AM »
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vt_hokie - 13/1/2007  10:35 PM

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Doug Stanley - 13/1/2007  11:18 PM

I have to go to bed now here on the East coast (do you people have lives??? ;-))  

I don't have much of a life these days, and I've been stuck working night shifts a lot, so my biological clock is all screwed up!   :)  I'd like to echo the comments of others here and just say thanks for taking the time to share your thoughts on this forum.

I do have one question that comes to mind.  You stated the following:

Quote
It is hard to get a safer system than a single 4-segment SRB with an SSME on top and a crew escape system.

In your opinion, if we had to start with a clean sheet design rather than adapting existing components and systems for this new launch vehicle, would a solid propellant first stage booster still get serious consideration over liquid fueled designs?  Can I assume from your statement that you believe starting with a clean sheet wouldn't necessarily allow for a safer overall design than this "shuttle derived" approach, which I have admittedly referred to as a kludge several times?

A KLUDGE!? Hmmm...

Definition (via Wikipedia): "a 'solution' for accomplishing a task, originally a mechanical one and usually an engineering one, which consists of various otherwise unrelated parts and mechanisms, cobbled together in an untidy or downright messy manner. A kludge is never elegant except ironically, nor, serviceability to the task at hand excepted, is it ever admirable ..."

Hmmm...I guess I can live with that....

I don't really like these hypothetical questions...I really don't know the answer, and I can't win either way.  It really depends a lot on other design factors...let's call it a tie!  For the second part...there is no immediate good substitute for proven, human rated hardware with a good safety record...



Offline Doug Stanley

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RE: Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)
« Reply #50 on: 01/15/2007 02:38 AM »
Quote
simonbp - 13/1/2007  10:36 PM

Quote
marsavian - 13/1/2007  9:38 PM

I must confess to not having fully read all of ESAS yet although I do intend to in time so if the answer to the question I'm about to ask is in there somewhere a page reference would be great. Could you please summarise what it is about Ares I compared to all the other alternatives looked at that give it such superior LOC and LOM figures ? Is it basically having only 2 stages with only 1 rocket in each stacked serially that give it the edge

Here's the chart:

Simon ;)

Section 6.8 has the discussion that he is searching for..not this chart...

Online Chris Bergin

RE: Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)
« Reply #51 on: 01/15/2007 02:53 AM »
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Doug Stanley - 15/1/2007  3:08 AM

I guess that is marginally better than "I read it on the Internet Alice so it must be true!" ;-)

I want to interject on this comment. The internet is made up of many different elements, from crap to media to educational resources.  Internet-based media is the new media that will replace print, magazine and one day TV - which itself is made up of all sort of elements, including crap.

Content is everything, as is availability. NASA.gov does a half arsed job - so seems the general consensus - in raising public interest in the space program, PAO doesn't seem interested in communicating with the media (that comes from some of the best space flight reporters around) so you end up seeing unofficial sites taking up the reigns.

Sure, some of it - including the above problems with official site media - leads to space industry workers providing information anomalously to sites like this, and when its documented information, it speaks for itself. The only reason they aren't named is to protect them from being sacked, as opposed to any other reason. I know who they are, and the readers either trust me or not. My job is to prove trust is deserved through the track record of our reporting.

Sure, sometimes the aforementioned people post information independent of the editorial processes of a site, and it risks being inaccurate, but I personally have more faith in the readership that they'll have their own filter and their own conclusions on the information provided, while assessing on the track record of the site they are reading the information.

Take it away and you'd likely be left with NASA trying to get its message across via the VSE truck that seemed to have more impact in annoying MSFC workers with its noisy generator in the car park.

And looky here, we're all chatting with Dr Stanley on here, rather than reading a semi-interesting press release, as one of about 50 examples from the past week alone that would not of been the case if there wasn't net coverage of NASA.

The net's not all bad, just depends which "channel" your tuned into. Ironically, the largest amount of crap in space flight media is via sites associated with major network channels and newspapers, that spew out the same wire report which is prone to lack an insight into the subject they are covering.

Offline Doug Stanley

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Re: Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)
« Reply #52 on: 01/15/2007 03:05 AM »
Quote
simonbp - 13/1/2007  10:53 PM

Smackdown! Thanks Dr. S for once again providing a wealth of real data, and dispelling a ton of myths in the process...

1) I noticed that the mean LOC for the baseline CLV had increased slightly with the fuller analysis; what aspects are deemed "safer" now than a year and a half ago?

2) If the Ares I does end up having an extra 3 mT of capacity, would there be any chance of adding something like the SIM bay on Apollo?

3) Gotta ask: are "green" (simple hydrocarbon) propellants still on the table for Orion/LSAM? Would they make it easier or harder on the launch vehicles?

Thanks again,

Simon ;)

This is NOT meant to be a "Smackdown".  I have great respect for Ross and the others on this site that have tirelessly and enthusiastically worked to improve human space as best they can.  I am simply trying to provide you all with the technical and NASA-related knowledge base possible from which to allow you to use your talent most productively...

Offline Smatcha

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Re: Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)
« Reply #53 on: 01/15/2007 03:12 AM »
Quote
Doug Stanley - 13/1/2007  6:44 PM

Quote
SMetch - 13/1/2007  7:14 PM

First Question:

Did you run a 4xRS-68Regen, 4 Seg SRB under a 8.4 meter core with an optimized upper stage?

Second Question:

Your “Maximum” Tank numbers for a 8.4m “is” the current SSTS tank capacity.  You could add about +60,000kg to tank by extending the LH2 tank down and LO2 tank up and still have room for the RS-68’s and Thrust structure.

Thanks for the questions...

Yes, NASA recently ran a number of different combinations of RS-68's, upper stages, 4 and 5 segment solids, at both diameters.  For the 4 segment boosters, ET diameter, and even 4 RS-68s, there was not enough payload to do the 2-launch solution with 10 percent payload margin and still fit within the VAB.  You reach diminishing returns by adding first stage engines with 4-segment boosters.  With 4 engines, the propellant just burns out twice as fast and you have higher lift-off and first stage accelerations.  The higher g's at lift off, coupled with dynamic loads, add additional compressive loads on the intertanks and H2 tank with a full O2 load on top, which adds structural weight.  Yes, th epayload goes up, but not by enough.  If you go to 5-segment solids (which allows additional first stage propellant and larger diameters, you can get RS-68-based vehicles that can do the two-launch solution...and this could still be on the table...

I would agree that the 4 RS-68’s don’t help without a true Second Stage like the Saturn V.  One of the biggest issues I have found with the current Ares V is the lack of a true second stage.  Concerning higher thrust loads = heavier tanks that’s usually what happens when you deliver more payload to orbit.  Run the dollars/kg number, more payload to orbit is almost always as a good thing.  Especially, when it’s a direct derivate of the current system and infrastructure.

Quote
Doug Stanley - 13/1/2007  6:44 PM
Given the RS-68 engine length and required pad clearances, NASA designed and laid out an aft end with thrust structure/gimbal/lines and found that there really was no room left to drop the H2 tank by any useful degree...

See attached picture, it sure looks like we have room.  Just how deep is this thrust structure going to be?

“Do we want to go to the moon or not?”
John C. Houbolt - November 15, 1961
Question posed in Letter to Dr. Robert C. Seamans Jr, NASA Associate Administrator

Ralph Ellison “I was never more hated than when I tried to be honest”




Offline Doug Stanley

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Re: Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)
« Reply #54 on: 01/15/2007 03:12 AM »
Quote
simonbp - 13/1/2007  10:53 PM

Smackdown! Thanks Dr. S for once again providing a wealth of real data, and dispelling a ton of myths in the process...

1) I noticed that the mean LOC for the baseline CLV had increased slightly with the fuller analysis; what aspects are deemed "safer" now than a year and a half ago?

2) If the Ares I does end up having an extra 3 mT of capacity, would there be any chance of adding something like the SIM bay on Apollo?

3) Gotta ask: are "green" (simple hydrocarbon) propellants still on the table for Orion/LSAM? Would they make it easier or harder on the launch vehicles?

Thanks again,

Simon ;)

1) NASA has done a more detailed probablistic risk assessment since ESAS (and changed the design somewhat) that has led to slightly different results...

2) Having done this sort of thing before...I can pretty much guarantee you the ARES will NOT have much "extra" payload.  I can count the number of times that has happened in our industry on one hand...

3) Green is off the table for Orion, but now baselined for the LSAM. We just completed an extensive study of this matter and I did a Q&A on it here:

http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=5419&posts=100&start=1




Offline Doug Stanley

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RE: Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)
« Reply #55 on: 01/15/2007 03:15 AM »
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Korea.Rogers1 - 14/1/2007  3:10 AM

Good morning, Doug and colleagues, and in addiiton to going to church, I wonder what plans you have to celebrate today, the third anniversary of President Bush's speech announcing the VSE?

By answering your questions so you can help us actually accomplish that vision thing...

Offline Doug Stanley

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Re: Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)
« Reply #56 on: 01/15/2007 03:17 AM »
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JIS - 14/1/2007  3:42 AM

So the -30x100 nm mystery seems to be solved too. Disposing of US. Propellant from US was also transferred to Orion which makes it heavier. But it is somewhat unapropriate to compare performance of original ESAS vehicle (26mT to 60x100, 28deg) to Ares 1 (25mT to -30x100, 28deg). It really looks like performance went down by few tons. More massive LAS could partially explain this.

They are working as we speak to make the LAS lighter...It is way overdesigned...

Offline general

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Re: Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)
« Reply #57 on: 01/15/2007 03:31 AM »
Would NASA ever consider backups to the current Ares 1/Orion plans, in case of funding or technical problems?  I'm mostly concerned about the "Gap" which seems to be at even greater risk recently due to funding problems.  For example, what about doing Orion risk reduction flights on an Atlas?  Bigelow and Atlas seem to be making progress on commercial human spaceflight.  It would seem prudent for NASA to hedge it's bets and see if there's some synergy to be had.  I would think that if a Bigelow, (backed up by LM/ULA), were able to get people to orbit before NASA, heads would roll at the Agency.

Offline Doug Stanley

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Re: Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)
« Reply #58 on: 01/15/2007 03:43 AM »
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CuddlyRocket - 14/1/2007  4:53 AM

Thank you for doing this, Dr Stanley. Hearing from people like you is why this site is at the top of my favourites list. (And is really a credit to Chris.)

Slightly O/T, but can you comment on who came up with the Ares IV proposal, and why NASA decided to give it some development money? (If you don't know, might I prevail upon you to ask? :) )

As for Ross, and other proponents of DIRECT. Well (misquoting somebody), they may have been wrong, but at least they were interesting! :)

Sure...I can say a few words about it...NASA has been looking a wide variety of HLLV architecture trade studies.  In particular, revisiting the ESAS trades on two vs. 1.5 launches (as I described at the beginning of this thread) and LOR vs. EOR rendezvous.  Given the changes that were made in HLLV max diameter and engine type (RS-68s), they needed to re-look to see if the trade results were still valid.  The definition of this vehicle is simply a part of the that process.  It is not any new "baseline", just one of the trade vehicle designs...

The FI article has a quote from Jeff that describes this status as well: "Ares IV is a study-level effort and not formally part of our baseline today. No definitive decisions have been made, and no specific requirements for such a mission defined. It will remain under study for the foreseeable future, but does represent an interesting capability," says NASA Constellation programme manager Jeffrey Hanley.

This is simply a revisit of the two-launch "LOR split" mission architecture that was our "Initial Reference Architecture" in ESAS and that I originated when I was at Orbital Sciences a few years back.  You could also use the same vehicle to do the two-launch LOR/EOR mission from ESAS.  As I mentioned in my intro at the beginning of this thread, a two-launch option could still be considered, but the 1.5 launch is still the baseline for the reasons I mentioned above...

As an aside...the 90-day loiter requirement has since been changed back to 15 days...

Offline kevin-rf

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Re: Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)
« Reply #59 on: 01/15/2007 03:59 AM »
Dr. Stanley

Thankyou your for taking time out of your sleep scedule to answer our questions.

One quick question, all the safety seem to focus on the risk to the crew. Where any similar studies (with numbers) made on risk to the ground crew for the different designs. For instance if heaven forbid something like a solid segment ignited while being stacked, similar to what happened in brazil a few years back. Or a pressure stabilized design loosing pressure while being stacked on the pad.
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