"Direct" Alternative

[Mark Dave]

I know. My question was why not use engines just as powerful for AresV?

[Jim]

Because the RS-68 exists and therefore cheaper.  No development program

[meiza]

In a way, the shuttle solids are F-1:s successors, and provide the low-isp high-t/w bulk thrust for the early flight.

[kraisee]

Meiza, its a bit of a stretch, but I know what you mean.

They do the same basic job, getting the second stage up to speed and altitude to do it's work, but they allow the second stage to be lit on the ground - which ought to be safer.

Ross.

[pierogoletto]

JIS - 11/9/2006  7:45 PM


I think there is no point for NASA to develop manned vehicle for LEO.
Maybe even more important is to have capability to deliver some significant cargo to the Moon, libration points, close asteroids or Mars in one shoot. And its Ares V.  

Although LEO or Moon may be stepping stones to go beyond, that's not at all the base idea of ESAS.

[kraisee]

A question for someone more familiar with LM's proposals (maybe Kayla?), but I'm wondering about the performance benefits of using a "Centaur approach" to making an EDS...

In short, the Centaur basically works by being a very light-weight stage, which only flies in space.   Because it doesn't need hardware to support atmospheric flight, it can be built down in mass to the barest possible minimum.

Normally a Centaur stage will fly inside the payload shroud to provide it with protection during the atmospheric phase of a launch.

Now, obviously DIRECT would need something plenty bigger than an existing Centaur, but the same approach might result in performance benefits.

What I'm really asking is this:   If there were something like a 7.8m diameter Centaur, with a single J-2X engine, fitted inside the DIRECT's 8.4m diameter payload fairing, what sort of benefits could that offer over the "aero-EDS" approach currently being proposed?

Currently the aero-EDS increases performance from 70.9mT to 98.2mT to 60x160nm 28.5deg insertion orbit.   Would this approach be able to improve performance significantly?

TIA for any explanations.

Ross.

[Jim]

The Centaur is only in the fairing because it is only 10' in diameter and the spacecraft is bigger, not because it needs protection.  The Centaur for the 4m fairing  (which is outside) is the same as the one inside the 5m fairing.    Atlas did this to keep the number of configurations down (only one is needed).  A fatter Centaur just like the Atlas V Phase two options, using the same diameter as the booster is better.  It has less surface area and the equivilent fairing is shorter and therefore lighter.   Also the ground ops is easier and less with less work with the wider stage (don't have the extra steps of encapsulating the stage)

[kraisee]

Jim,
   Little wonder then why I was continually scratching my head to figure out why it wasn't being looked at

Ross.

[rumble]

Ok.  Let's combine them then.

Would the centaur design transfer to a stage as wide as, say, the ET?  If the engine used was a J-2X instead of an RL-10, would it still be a centaur?

It makes some sense to me for LM to build the US/EDS for DIRECT and just use a J-2X as the power plant instead of a cluster of RL-10's or RL-60's.

How would a centaur-based design differ from something MSFC would create?

[Jim]

EDS is only bigger than the Centaur or the D-IV second stage.  Either design can be used

[simcosmos]

Yes, that is my goal when making the EDS for NASA VSE SC and Direct SDLV Orbiter addons

From my flickr photo set (please click image to directly load the specific EDS page / description):




The above EDS still needs work in several components and, for Direct use, I might still have to change its dimensions (to accommodate extra propellants).

I used Apollo / Centaur and also First Lunar Outpost images as inspiration to model it:

Already widely known in these forums, but here goes a link for a page where people can read more about Lockheed-Martin studies regarding Centaur Extensibility to Long-Duration In-Space Applications


Specific FLO image that used as inspiration for the external look (although it seems that its EDS design would not have a common bulkhead):
http://aerospacescholars.jsc.nasa.gov/HAS/cirr/Images/flo2.jpg

See:
http://www.abo.fi/~mlindroo/Station/Slides/sld051f.htm
http://www.astronautix.com/craft/firtpost.htm


Also used a few pre-ESAS images, like:
New Cryo US for CaLV
New Cryo US for CLV

(both from SDLV/CEV - JULY AIAA Joint Propulsion Conference Document)


To end, a clumsy photo where I'm playing with the EDS internal layout, just for *rough* visualisation purposes; it might not be 100% correct. Just went to one of the previous pictures and made a bit of copy+paste to size the tanks for a given amount of hydrogen / oxygen, please see attachment)

António

 

[rumble]

Excellent stuff.  I think the common bulkhead design makes all kinds of sense on an EDS for weight AND cryo storage purposes.

Concern with your last image on the page:  The RCS nozzles look dangerously close to the interstage...  I know you're just working on concepts (work in progress), but I see it being possible the interstage could slide off "less than perfectly" and damage one or more of those nozzles, and possibly that entire RCS structure.

Thanks for sharing all your visual work...

[simcosmos]

Thanks,

Yes, still playing with RCS (and other parts ). There are about 2 or 3 options for the RCS:

a) in the bottom of the EDS, +/- like in the previous pictures (but still have to fine tune a good position / attachment method when thinking about control and clearances)
b) internal, I mean, something similar to some of the recent CLV representations  (RCS for upper stage / interstage)
c) external pods, like in Apollo

All approaches should have its advantages and disadvantages: I would prefer to make them in the bottom and/or somehow *internal* (at least from a purely cosmetic point of view ). Still have to better research about the subject as well how it is (or would be) done in Centaur derived hardware.

António

[kraisee]

I would suggest integrating them into an 'aft skirt' area.   There will have to be one anyway for the lower umbilical connections to be attached to.   I would use the basic design from the Ares-V myself.

Can you calculate the real-world volumes of the individual tanks?

Ross.

[simcosmos]

kraisee - 23/10/2006  2:04 AM

I would suggest integrating them into an 'aft skirt' area.   There will have to be one anyway for the lower umbilical connections to be attached to.   I would use the basic design from the Ares-V myself.

Will try to introduce some alterations in that regard (must first study umbilical connections).

kraisee - 23/10/2006  2:04 AM
Can you calculate the real-world volumes of the individual tanks?

It is a bit harder for common bulkhead designs, much easier if assuming separated tanks: for common bulkhead I kind of *visually* extrapolate from separated tanks volumes / shapes. The above EDS is 8.4m width (other dimensions can be known by comparison, short in time now to take the dims from the 3D model) for a total propellant quantity (LH2+LO2) of about 105.2mt / 106mt or so. Still need to do some flight tests / math. Depending of a few hardware / mission design assumptions Direct might (or not) need a bigger EDS (will also implement something like the "official" EDS Direct numbers and something in-between and then compare results between the 3 versions, maybe next weekend)

António

[publiusr]

Your artwork just keeps getting better and better.