Author Topic: DIRECT v2.0 - Thread 3  (Read 1123181 times)

Online DigitalMan

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Re: DIRECT v2.0 - Thread 3
« Reply #480 on: 01/21/2009 01:22 am »
I know the subject "what counts as a stage" has been talked to death many times here over the years, but...

Would it be reasonable to say a stage is any burn that is required to enable the spacecraft/payload to complete a full orbit ?

(regardless of the shape of the orbit)

Offline clongton

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Re: DIRECT v2.0 - Thread 3
« Reply #481 on: 01/21/2009 01:51 am »

We are if the original specification called for the capability. Originally, Orion was to make only 2 burns of the SM engine;
1) orbital insertion (same as Shuttle) and then
2) orbit circularization.
Now it has to make 3 because Ares-I can't get Orion to the point where it's 1st burn is orbital insertion. The SM's first burn completes the ascent and shuts down. Some time later, the 2nd burn does the orbital insertion. And later still, a 3rd burn circularizes the orbit.

Originally Ares-I was supposed to drop Orion off high enough and fast enough that only orbital insertion and later circularization was required. Not being able to actually accomplish that is called underperforming.

The SM has to perform an OMS-1-type insertion burn AND and OMS-2-type circularization burn? The original plan didn't call for a direct insertion trajectory?

No. The plan was always for the spacecraft to do the orbital insertion burn and then a circularization burn. This is the most efficient way to dispose of the upper stage. But the original plan did not call for the spacecraft to do an ascent burn BEFORE doing the insertion and circularization burns.
« Last Edit: 01/21/2009 02:02 am by clongton »
Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline kraisee

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Re: DIRECT v2.0 - Thread 3
« Reply #482 on: 01/21/2009 02:53 am »
I just wanted to announce that the plans for the models of the J-120 & J-232 are now publicly available for download and construction.

They can be found in three places (so far)

Jon Leslie's Lower Hudson Valley Challenger Center website.
http://www.jleslie48.com/gallery_models_real.html

As a side note, I find it immensely satisfying that they are listed under the "Real Spacecraft" section...  8)

Niels J. Knudsen's Paper Models site
http://www.nielspapermodels.com

and the Yahoo Space Paper Models Group.
http://groups.yahoo.com/group/Space-Paper-Models/

I hope those of you who build them enjoy doing it as much as I did.

Thanks

Well done with those!

And thanks for your own contribution too.

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 v2.0 - Thread 3
« Reply #483 on: 01/21/2009 02:57 am »
Could the Core be left in orbit, given that it will decay quickly?

No.   There are some parts which will not completely burn up when it re-enters.

The SRB Thrust Beam inside the Intertank, parts of the primary Thrust Structure are big & heavy, some of the larger cast parts of the engines and bits of the large valves may all come raining down from the heavens at Mach 2.

You want to be 100% sure they never come raining down on people.

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 v2.0 - Thread 3
« Reply #484 on: 01/21/2009 03:10 am »
The SM has to perform an OMS-1-type insertion burn AND and OMS-2-type circularization burn? The original plan didn't call for a direct insertion trajectory?

Actually it must make three burns:

At spacecraft separation (-11x100nmi 'insertion' at ~57nmi altitude) the Orion will actually spend between 20-30 seconds in free-fall while the Solar Arrays are deployed.

Burn 1 will raise the initial perigee (-11nmi) to 100nmi.

Burn 2, about 45 minutes later will raise the apogee to 220nmi for ISS or 130nmi for Lunar.

Burn 3, about 45 minutes later again, will raise the perigee to match.


The original plan was for the launcher to insert the spacecraft into an initial orbit which would actually have its apogee at the final intended orbit, so the spacecraft would only need to make a single circularization burn.

But the ESAS changed that and baselined a dual burn to better-suit the LV-13.1 CLV, which later became the Ares-I.   Unfortunately the current Ares-I hasn't got the available performance to do that any more, so CxP have slipped a third burn in without most people noticing.

Ross.
« Last Edit: 01/21/2009 03:13 am by kraisee »
"The meek shall inherit the Earth -- the rest of us will go to the stars"
-Robert A. Heinlein

Offline gladiator1332

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Re: DIRECT v2.0 - Thread 3
« Reply #485 on: 01/21/2009 04:20 am »
I just wanted to announce that the plans for the models of the J-120 & J-232 are now publicly available for download and construction.

They can be found in three places (so far)

Jon Leslie's Lower Hudson Valley Challenger Center website.
http://www.jleslie48.com/gallery_models_real.html

As a side note, I find it immensely satisfying that they are listed under the "Real Spacecraft" section...  8)

Niels J. Knudsen's Paper Models site
http://www.nielspapermodels.com

and the Yahoo Space Paper Models Group.
http://groups.yahoo.com/group/Space-Paper-Models/

I hope those of you who build them enjoy doing it as much as I did.

Thanks

Thanks for posting them!

I'll have to start building them once I can get some heavier paper. All I have in my room is computer paper, and that never works.

What kind of glue do you recommend?

« Last Edit: 01/21/2009 04:27 am by gladiator1332 »

Offline Yegor

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Re: DIRECT v2.0 - Thread 3
« Reply #486 on: 01/21/2009 05:08 am »
I finally got my copy of "Popular Mechanics" magazine with Direct article.

I got it at "Metro" grocery story which a very big chain of 573 stores in Canada. So Direct has got a great exposure with this article.


Offline zapkitty

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Re: DIRECT v2.0 - Thread 3
« Reply #487 on: 01/21/2009 09:21 am »
I just wanted to announce that the plans for the models of the J-120 & J-232 are now publicly available for download and construction.

An order to commence construction?... :)

Quote
They can be found in three places (so far)
Jon Leslie's Lower Hudson Valley Challenger Center website.
http://www.jleslie48.com/gallery_models_real.html
As a side note, I find it immensely satisfying that they are listed under the "Real Spacecraft" section...  8)

Cool! :) Direct is easily found and accessed...

Quote
Niels J. Knudsen's Paper Models site
http://www.nielspapermodels.com

The Direct models don't seem to be up there yet?

Quote
and the Yahoo Space Paper Models Group.
http://groups.yahoo.com/group/Space-Paper-Models/

Hmmm... members only.

Okay, I have the files from jleslie48.com and would  just toss them up on the mirror as a directory of separate files and a .zip of the directory for convenience in downloading.

In your notes with this release you spend quite some time explaining your sourcing but... no redistribution policy notice of your own?

(Something simple like "Mirror these if you want to but keep the files together and please don't change things without notice." would be nice ;) )
 
Edit: won't tell you what was edited or why
« Last Edit: 01/21/2009 09:24 am by zapkitty »

Offline MP99

Re: DIRECT v2.0 - Thread 3
« Reply #488 on: 01/21/2009 11:18 am »
I have a question regarding figures 20 & 21 from the V2.0.2 update doc (http://www.launchcomplexmodels.com/Direct/documents/DIRECT_Summary_v2.0.2.pdf).

This shows LSAM performing MCC / TCM burns (I presume MCC is Mid Course Correction, not sure what TCM stands for). The diagram shows the Isp as 448s, so this is using the RL-10's in the descent stage.

This burn is only 2m/s (a couple of seconds burn at minimum throttle, I think), so this seems like a pretty small burn to go through the whole complication of starting up the RL-10's.

Is there any reason why the CEV doesn't perform this burn? It is using hypergolic engines, which would use less mass of fuel (the RL-10 is more efficient, but wastes some fuel starting up). Also the hypergolic engines are considered more reliable.

The only reason I can see is that the LSAM cannot cope with an "upside down" burn, ie a burn with opposite thrust than produced by it's own engines.

Is this correct - LSAM can't be accelerated upside down?

If not, what is the reason why LSAM performs this manouvre instead of CEV?

cheers, Martin



Offline Jim

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Re: DIRECT v2.0 - Thread 3
« Reply #489 on: 01/21/2009 11:23 am »
I have a question regarding figures 20 & 21 from the V2.0.2 update doc (http://www.launchcomplexmodels.com/Direct/documents/DIRECT_Summary_v2.0.2.pdf).

This shows LSAM performing MCC / TCM burns (I presume MCC is Mid Course Correction, not sure what TCM stands for). The diagram shows the Isp as 448s, so this is using the RL-10's in the descent stage.

This burn is only 2m/s (a couple of seconds burn at minimum throttle, I think), so this seems like a pretty small burn to go through the whole complication of starting up the RL-10's.

If not, what is the reason why LSAM performs this manouvre instead of CEV?


Trajectory correction maneuver
This is how NASA planning and Direct is doing the same thing

Offline MP99

Re: DIRECT v2.0 - Thread 3
« Reply #490 on: 01/21/2009 12:04 pm »
I have a question regarding figures 20 & 21 from the V2.0.2 update doc (http://www.launchcomplexmodels.com/Direct/documents/DIRECT_Summary_v2.0.2.pdf).

This shows LSAM performing MCC / TCM burns (I presume MCC is Mid Course Correction, not sure what TCM stands for). The diagram shows the Isp as 448s, so this is using the RL-10's in the descent stage.

This burn is only 2m/s (a couple of seconds burn at minimum throttle, I think), so this seems like a pretty small burn to go through the whole complication of starting up the RL-10's.

If not, what is the reason why LSAM performs this manouvre instead of CEV?

Trajectory correction maneuver
This is how NASA planning and Direct is doing the same thing


DIRECT seem to be explicitly standing back from the post-TLI phase of the mission, and who could blame them - how many battles do they really need to fight at once?

I'd still like to know whether NASA do it this way because they must (LSAM is designed this way), or just because that's the option they happen to have chosen?

cheers, Martin

Offline clongton

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Re: DIRECT v2.0 - Thread 3
« Reply #491 on: 01/21/2009 12:26 pm »
After performing final ascent burn, orbital injection burn and orbital circularization burn, the remaining propellant in Orion's SM tanks needs to be reserved for the TEI burn to bring everybody home.
Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline MP99

Re: DIRECT v2.0 - Thread 3
« Reply #492 on: 01/21/2009 01:00 pm »
After performing final ascent burn, orbital injection burn and orbital circularization burn, the remaining propellant in Orion's SM tanks needs to be reserved for the TEI burn to bring everybody home.


It's only 2m/s !

It's my understanding that hypergolic engines are extremely reliable, start very easily, and I'd have thought were quite throttle-able, too.

Cryogenic engines have complex startup procedures, waste quite a bit of fuel spinning up their pumps, and the risk of non-starting or failure during operation is somewhat higher.

A hypergolic engine seems to be absolutely ideal for this type of manouvre. Have I missed something (about suitability of that type of engine, not whether fuel happens to be available).

As you've commented, if DIRECT is chosen Orion won't need to perform the ascent. Would it then make sense for NASA to use 2m/s of Orion fuel to perform the TCM/MCC burn? Does that have any appreciable effect on LOC/LOM numbers?

cheers, Martin

Offline clongton

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Re: DIRECT v2.0 - Thread 3
« Reply #493 on: 01/21/2009 01:09 pm »
After performing final ascent burn, orbital injection burn and orbital circularization burn, the remaining propellant in Orion's SM tanks needs to be reserved for the TEI burn to bring everybody home.


It's only 2m/s !

It's my understanding that hypergolic engines are extremely reliable, start very easily, and I'd have thought were quite throttle-able, too.

Cryogenic engines have complex startup procedures, waste quite a bit of fuel spinning up their pumps, and the risk of non-starting or failure during operation is somewhat higher.

A hypergolic engine seems to be absolutely ideal for this type of manouvre. Have I missed something (about suitability of that type of engine, not whether fuel happens to be available).

As you've commented, if DIRECT is chosen Orion won't need to perform the ascent. Would it then make sense for NASA to use 2m/s of Orion fuel to perform the TCM/MCC burn? Does that have any appreciable effect on LOC/LOM numbers?

cheers, Martin

The current lunar designs are all driven all the way back to the 1.5 architecture with an underperforming Ares-I. Ares-V is currently unable to entirely make up the difference to get everything thru TLI. Having said that, the burn allocations reflect this entire architecture approach, with both its benefits and its shortcomings. IF the DIRECT architecture is chosen to replace the 1.5 Ares, a lot of things *could* be reallocated, but it is way too premature to be going there. At this point, DIRECT's approach is to match the approaches of Ares for the lunar architecture, as it's the only way to do an apples to apples comparison.
« Last Edit: 01/21/2009 01:12 pm by clongton »
Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline Lancer525

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Re: DIRECT v2.0 - Thread 3
« Reply #494 on: 01/21/2009 01:11 pm »
I just wanted to announce that the plans for the models of the J-120 & J-232 are now publicly available for download and construction.

Thanks

Thanks for posting them!

I'll have to start building them once I can get some heavier paper. All I have in my room is computer paper, and that never works.

What kind of glue do you recommend?


You're very welcome!

I used (and recommend) two different glues, depending on what I needed at each step. YMMV.

For bonds that don't have to be "shifted around" a lot, that need to tack (set) quickly, and have to be sturdy, I used Aleen's Original Tacky Glue in the gold bottle. That stuff is amazing, but it tacks fast, and is impossible to separate joints if something isn't perfect. Use it sparingly!

For bonds where you need a little shifting or adjustment time, I recommend Tombow Mono-Aqua liquid. That's one of the best all-around glues I've ever used. It makes up about 90% of the bonds in the 1/4 scale Mercury spacecraft I am building. Great stuff.

If you have any questions about the build, my email address is on the last page of the notes section.


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

Offline Lancer525

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Re: DIRECT v2.0 - Thread 3
« Reply #495 on: 01/21/2009 01:34 pm »
I just wanted to announce that the plans for the models of the J-120 & J-232 are now publicly available for download and construction.

An order to commence construction?... :)

Hardly. I don't give orders. People tend to get cranky when you order them around...

Quote
Niels J. Knudsen's Paper Models site
http://www.nielspapermodels.com

The Direct models don't seem to be up there yet?

I'd give Niels a couple of days on that. He's got a real life, he's building, managing a very popular website, and so is a busy guy. I'm sure he'll get to it.

Quote
and the Yahoo Space Paper Models Group.
http://groups.yahoo.com/group/Space-Paper-Models/

Hmmm... members only.

So? It's a free group. If you have an interest in paper modeling space-related things, then it is an excellent resource, with knowledgeable, friendly, and exceptionally helpful people. Some of the best designers and builders in the world read and post there. They only have a membership requirement to keep posts about breast enlargement, penis enhancement, and Russian mail-order brides off the message board.  ::)

Quote
Okay, I have the files from jleslie48.com and would  just toss them up on the mirror as a directory of separate files and a .zip of the directory for convenience in downloading.

In your notes with this release you spend quite some time explaining your sourcing but... no redistribution policy notice of your own?

(Something simple like "Mirror these if you want to but keep the files together and please don't change things without notice." would be nice ;) )


Sure I have a redistribution policy. The models are always to remain free to everyone, and I trust that anyone who wants to host or build them has enough common sense to know that all the files have to be kept together and used to build it. One of the very best things about paper modeling is that someone out there, who is a much better builder than I am, is going to reskin (that means recolor and redesign parts to look more accurate) those pieces, and put together a much more realistic, and better model. That's part of what this hobby is all about. People can tweak a paper model in ways that plastic modelers never could.

I don't expect that anyone would, and in fact require, that no one may ever charge for access to these files. They are now, and are always to remain free of cost to the builder. I know I designed them, and its right there in the notes file how to get in touch with me, so if anyone really wants to ask, they can email me. I'm not worried about plagiarism, because I don't think anyone would bother to "steal" something that is free to the world anyway.  ;D

I appreciate your hosting them. The more distribution and exposure, the better!

Now, if I could just take that 3ds wire-frame of the XB-70 that I have, and figure out how to convert it to flat pieces, I can finally build that big 1/48 Valkyrie I've always wanted...  :D
"For some inexplicable reason, everyone seems to want to avoid simple schemes."   -John Houbolt

Offline simcosmos

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Re: DIRECT v2.0 - Thread 3
« Reply #496 on: 01/21/2009 02:29 pm »
Sorry all for opening this parenthesis here but, from some time that I'm not 'comfortable' (in lack of better word) with a few things. What will write next is related with recent posts:

In order to properly address what AresI (and EELV variants, etc) might or not be capable of doing when having an Orion spacecraft as main payload I really think that all starting assumptions need to be clearly stated. This is even more truth if / when making any kind of comparisons with a Jupiter vehicle variant.


Being more explicit - and remembering the readers (+ fellow DIRECT Team members) that I'm writing all this as a *personal note* - each launch vehicle is a separated case and its injection targets might be dependent of the specific launcher configuration vs trajectory / disposal constraints, etc, etc. 


Would like to note that - focusing only in the performance aspect - there have been several past discussions of what AresI might or not be able to do as well about what the ESAS CLV was or not intended to do: in some of recent posts in this thread, it seems that several people are saying different things and some might even being doing so thinking that are saying the same thing... What I wrote just now was confusing? Well, did it on purpose only because would like to end this parenthesis with a friendly and open suggestion...




So, will leave this suggestion in the air (for separated thread(s)): if anyone wishes to discuss the eventual capabilities of a specific launch vehicle I strongly suggest that perhaps it might be better if we do like in several past occasions at nasaspaceflight forums (like, in my case, some threads where have simulated AresI conceptual variants, CZ-2F ascent trajectory or, more recently, the thread that resulted in the Ares-IB exercise, etc, etc):

a) let's open a separated thread for a specific launch configuration musing (either it be AresI, Delta IV Heavy, an AtlasV variant, etc, etc): each thread could be called something like

[sim] launcher designation - payload

example: [sim] AresI - Orion


b) let's however agree first on a rough and – this is very important - common first order estimative for a CEV mass breakout (vs intended mission dV needs) as well lets agree in common mass values for LAS and for any other needed spacecraft adapters / covers (wich might be dependent of specific launch vehicle integration)… this might require a separated thread called [sim] Orion Specs or something like that...


c) then, once all the above (in b) is decided, we have  a minimum / maximum estimative for the launch vehicle payload at lift-off... next thing to do is to decide constraints for the jettison of LAS, covers, etc as well some other ascent rules (regarding staging / disposal events, aborts, payload / performance margins, etc)… some of such rules might be common, other might be specific of launcher configuration…


d) last but not least, it would be needed to agree in common numbers for the several components (masses of stages, thrust/ISP specs, engine thrust modes, etc) of a given launch vehicle brainstorm


Only then - with some basic assumptions and a common ground for important input data - can such input data be implemented into several independent tools / simulators and only then can the discussion about eventual divergence / convergence of 'results' be something more fruitful…

Else, without clearly showing starting assumptions and without defining common ground rules, people will always end up talking past each other… as already happened several times in the past and has it seems that it might be happening again...

António   
« Last Edit: 01/21/2009 02:31 pm by simcosmos »
my pics @ flickr

Offline MP99

Re: DIRECT v2.0 - Thread 3
« Reply #497 on: 01/21/2009 02:43 pm »
Only then - with some basic assumptions and a common ground for important input data - can such input data be implemented into several independent tools / simulators and only then can the discussion about eventual divergence / convergence of 'results' be something more fruitful…


António,

are any of these tools/simulators available as freeware? Can you point to them?

Is this one of those tools:- http://launchcomplexmodels.com/Direct/orbiter.htm

cheers, Martin

Offline clongton

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Re: DIRECT v2.0 - Thread 3
« Reply #498 on: 01/21/2009 03:02 pm »
How many people on this list actually have access to/own (and can use) software that does trajectory analysis?

For those of you that don't, I would suggest that you could get yourself a copy of Orbiter. It's a free sim tool and the results it produced closely match what we have obtained for Jupiter in POST. It's just a matter of making sure, like Antonio says, that the fundamental inputs are the same.
« Last Edit: 01/21/2009 03:06 pm by clongton »
Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline zapkitty

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Re: DIRECT v2.0 - Thread 3
« Reply #499 on: 01/21/2009 03:10 pm »
...

"Order to suspend construction" is a reference to an animated short feature from Japan. No reason you should be aware of it ;)

As for the notices... errrrrr... there are standardized variations of copyright notices used for such things that can cover every angle you might wish... in a much shorter format.

An ad hoc but very usable example.

"Permission is granted to redistribute these models as long as they made freely available at no charge. Permission is also granted to  modify and redistribute these models as long as you include a notice about the changes with the files."

Note the brevity... :)

As for yahoo... you wage valiant war against an opponent who's not there :D All I was doing was toting up the current availability of the files.

Now the files are also up here...
http://somedirectstuff.nekoslovakia.net
... and thank you for your hard work!

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