DIRECT v3.0 - Thread 1

[jarmumd]

The final results aren't in yet, but I have been told that this arrangement is more efficient to the tune of somewhere around 1,200-1,500lb or so.

The inline configuration would seem to have more control authority - which downrange could lead to removing the SRB TVC, which would seem to save more on cost and some on weight than this arrangement.

I suppose you should see if you have enough control authority with two engines to not need the SRB TVC.

[kraisee]

They ought to name a fairly large sized hole on the moon after you guys!
 

That can be taken multiple ways   I'm sure there is a group of Ares I folks that would like to more than put team direct's name in a hole on the moon ... Still great job, great job. They need to name the first return to the moon landing site after the team.

If we're talking naming stuff, just pick the Jupiter and keep the name

Then lets all just get on with going to the Moon, Mars and Beyond as quick as we can!!!

That would be the best reward of all.

Ross.

[kraisee]

The inline configuration would seem to have more control authority - which downrange could lead to removing the SRB TVC, which would seem to save more on cost and some on weight than this arrangement.

I suppose you should see if you have enough control authority with two engines to not need the SRB TVC.

That's actually been studied already and we are well in the green on that one.   There is plenty of control authority for just 2-engines on a Jupiter-130 to control the entire stack with margin to spare, and similarly a 3-engine Jupiter-24x works as well.

But we have some indications that removing the SRB's TVC and re-qualifying the SRB's without them would actually incur a fairly expensive up-front cost which we don't like, so we're putting this option on the back-burner for now.

Ross.

[zimdlg]

Hi Everyone, I have been lurking around here since DIRECT was in v2.0.

I’m  looking forward to Bolden announcing soon that NASA is changing its plans to a rocket more DIRECTly based on existing space shuttle hardware.

Just a question that occurred to me today. In various rocket launches I have seen the pay load flaring is dumped as soon as the rocket is out of the atmosphere, so as not to carry unnecessary weight up to orbit I assume. In the images of Jupiter it looks like Orion is attached to the core with the PLF, if so dumping the PLF is therefore not an option. If the PLF then has to be carried all the way up to orbit how is the PLF then deorbited so that it doesn't cause a debris problem? Now that I think of it how is the core deorbited? Would it be advantageous to attach Orion to the core with some kind of column so that the PLF could dumped as soon as possible? Just a thought.

I'm sure this has been considered before, I'm just curious. Thanks.

[kraisee]

You can see clearly which engine would be removed (in red) for the 3-engine Jupiter-130 arrangements.

Ross, why a diamond configuration instead of a triangular configuration with a engine in the center so that you could remove the center engine for the Jupiter-130? Is it because the diamond configuration provides optimal tapering of the thrust structure? Is the diamond shape better suited for the existing structure of the external tank?

I better volunteer that this issue is quickly getting out of my own personal depth with some of these questions, but my current understanding is that it's mostly about balancing the lateral thrust levels as much as possible in all "nominal" situations.   So even the default J-130 configuration works very well with the diamond arrangement in this regard.

It doesn't matter so much after SRB sep, but keeping the loads in check while those big powerful and heavy SRB's are attached is, apparently, an important factor.

Ross.

[kraisee]

Hi Everyone, I have been lurking around here since DIRECT was in v2.0.

I’m  looking forward to Bolden announcing soon that NASA is changing its plans to a rocket more DIRECTly based on existing space shuttle hardware.

Just a question that occurred to me today. In various rocket launches I have seen the pay load flaring is dumped as soon as the rocket is out of the atmosphere, so as not to carry unnecessary weight up to orbit I assume. In the images of Jupiter it looks like Orion is attached to the core with the PLF, if so dumping the PLF is therefore not an option. If the PLF then has to be carried all the way up to orbit how is the PLF then deorbited so that it doesn't cause a debris problem? Now that I think of it how is the core deorbited? Would it be advantageous to attach Orion to the core with some kind of column so that the PLF could dumped as soon as possible? Just a thought.

I'm sure this has been considered before, I'm just curious. Thanks.

Again, welcome to the site!

You are exactly correct.   When flying with an Orion, the PLF is carried all the way to orbit, but this is also what happened on the Saturn-V as well, if you recall.   The procedure is essentially exactly the same for Jupiter as for Apollo.

The only difference in this regard between Apollo and Jupiter, is that the PLF's will be disposed of in LEO before the TLI, rather than afterward.

The PLF "petals" don't stay in LEO for long though.   They are relatively lightweight structures and have a high area:mass ratio, so in a low Low Earth Orbit such as 130x130nmi, their orbit will naturally decay fairly quickly and they will re-enter within a few days, so they aren't much of a concern.


Of course, for Cargo-only flights, the PLF is disposed of normally during ascent, as soon as aerodynamic heating drops to 0.1BTU/sec/sq ft -- which is typically around 70-75nmi altitude.



As for missions which take the Core Stage to orbit, those will require an Attitude Control System of some sort.   Our current plan is to integrate systems from the EDS element (RCS & avionics) into the Core for such missions.

But we are 'generally' moving towards a recommendation that all payloads (except Lunar of course) are injected into a sub-orbital insertion and then make a circularization burn either using their own propulsion systems, or perhaps using a separate module like the Shuttle's PAM-D or PAM-D2 to perform the circularization burn.

Ross.

[luke strawwalker]

Hello all,

I have been following the Direct proposal for several weeks now and I have to say, as a pure layman that your proposal makes the most sense.

Thanks Mark, and welcome to the site.   Besides DIRECT-related materials you will find a wealth of other space-related information here, enough to satisfy all tastes!

I do have several questions that I have not been able to resolve by reading through the threads here on this site and reviewing the Direct website.  My questions are in regards to the ET - I see from the video that the Et is to be stretched -why is this necessary?

Actually, the ET's capacity remains exactly the same as at present.   But some new structures are needed at the top and bottom in order to place the engines at the bottom of the Core and to allow payloads to be stacked on the top.

One of the key differences is that the current LOX Tank (the Ogive (teardrop) shaped tank at the top of the ET) is not the right shape, nor is it actually strong enough to support the weight of much above it -- so we actually replace that entire tank with a design which can be built on the same manufacturing equipment which makes the lower LH2 tank.   The purpose of re-using that equipment instead of making brand-new tooling, is mainly to reduce costs and to minimize schedule impacts after Shuttle retires.


Having said that, we have looked at the possibility of a moderate Core Stretch as well (5ft stretch downwards towards the engines on the LH2 tank).   It really doesn't buy you much extra performance at all, in either Jupiter configuration -- perhaps 1.5mT more.   But it comes at additional development and manufacturing costs -- and there are more efficient ways to get that sort of performance boost if you ever needed it in the future.

Also, is there any increased loads caused by the in line thrust configuration that will cause the need for the ET to be strengthened?

Yes.   Not so much for our three-engine Jupiter-130 configurations, but certainly for the 4-engine Jupiter 24x systems.

The reality is that just about every panel and every ring-frame will change in some fashion or another compared to ET.   But those changes are relatively subtle and are all well within the manufacturing capabilities of the existing tooling at the Michoud Assembly Facility today.   The Jupiter Core Stage will be designed to cope with its own specific environments, but the design needs to be done with one eye firmly on the currently available facilities instead of assuming everything will need to be replaced.

Sorry, I am sure that this topic was probably one of the first issues that were discussed!

A few times, but its always worth covering ground again because there are so many new people coming around to this general approach every day.   So please, keep asking your questions!

Ross.

Quick question, Ross et al...

What are the ramifications of a barrel stretch to the ET on both O2 and H2 tanks to 'optimize' the system for the 5 seg SRB??  What kind of performance gain could be had with this??  I haven't seen any difinitive information about this, as to whether it would be advantageous or not or what kind of performance gains could be had from it. 

Of course that's assuming that the five segment SRB's are even adopted-- The fact that the Not-Shuttle-C proposal made use of the four segment shuttle SRB's as-is was quite telling, IMO, because you would think that if development is far enough along they'd at least have adopted the five segment boosters in place of the four segment, as I'm SURE that NSC could use the performance boost because of the side-mount inefficiency losses, but of course if you're proposing a budget-driven least-cost solution (which NSC appears to be) then spending additional development and integration money on five segment SRB's may be too costly for the program to absorb. 

Just curious performance wise what a five-seg and tank stretch does for Jupiter 130 and Jupiter 246 performance. 

Also, a bit of clarification-- I presume the reason no tank stretch is baselined even though the fourth SSME would be added to the tank (increasing fuel use per second by 25%, which would require a 25% tank capacity increase to sustain the same burn length of time) is that the core stages ~25% earlier, therefore not needing the extra fuel for the extra engine to maintain the same burn duration.  Is this correct??

Thanks!  OL JR

[Malderi]

The PLF "petals" don't stay in LEO for long though.   They are relatively lightweight structures and have a high area:mass ratio, so in a low Low Earth Orbit such as 130x130nmi, their orbit will naturally decay fairly quickly and they will re-enter within a few days, so they aren't much of a concern.

Okay, so they're out of the atmosphere, but do any pieces survive to the ground? Wouldn't want even a small piece to land on someone's house. Any studies on this?

[kraisee]

I have just been told to prepare for a new round of FUD from CxP regarding our Altair > EDS docking arrangement.

Apparently they're about to try to attack DIRECT for this "fatal flaw".

I just thought I would pre-empt their attack by putting this information "out there" well ahead of their attempts.

Ross.

[Mark S]

Also, a bit of clarification-- I presume the reason no tank stretch is baselined even though the fourth SSME would be added to the tank (increasing fuel use per second by 25%, which would require a 25% tank capacity increase to sustain the same burn length of time) is that the core stages ~25% earlier, therefore not needing the extra fuel for the extra engine to maintain the same burn duration.  Is this correct??

Thanks!  OL JR

Actually, adding the fourth engine would increase the fuel consumption rate by 1/3, or 33.333%.  The J-246 core ends up in the middle of the Atlantic ocean (instead of in orbit) due to its faster rate of fuel consumption, it lower speed at burn out, and its lower altitude.

Mark S.

[MP99]

But we have some indications that removing the SRB's TVC and re-qualifying the SRB's without them would actually incur a fairly expensive up-front cost which we don't like, so we're putting this option on the back-burner for now.

The 5-seg programme presumably includes re-qualification.

If 5-seg can't or simply isn't cancelled, could the TVC change be qualified within the same budget (ie pay for the development, and re-qual comes along for free).

I know that you recommend staying with 4-segs, but NASA may be committed, or simply be happy to pay for the performance boost.

cheers, Martin

[kraisee]

The 5-seg programme presumably includes re-qualification.

If 5-seg can't or simply isn't cancelled, could the TVC change be qualified within the same budget (ie pay for the development, and re-qual comes along for free).

I know that you recommend staying with 4-segs, but NASA may be committed, or simply be happy to pay for the performance boost.

Absolutely.   It's one of the many options which are available if we simply choose to go down this path to start with.

The key is getting that choice made now though...

Ross.

[clongton]

I have just been told to prepare for a new round of FUD from CxP regarding the Altair > EDS docking arrangement.

Apparently they're about to try to attack DIRECT for this "fatal flaw".

I just thought I would pre-empt their attack by putting this information "out there" well ahead.

Ross.

Imagine what would have happened if instead of executing witch hunts and trying to discredit DIRECT, all that energy were directed instead into implimenting the VSE. IMHO we might be in orbit with test vehicles already, with Shuttle still flying. Sigh. Here we go again.

[Mark S]

I have just been told to prepare for a new round of FUD from CxP regarding the Altair > EDS docking arrangement.

Apparently they're about to try to attack DIRECT for this "fatal flaw".

I just thought I would pre-empt their attack by putting this information "out there" well ahead.

Ross.

Such an attack, if successfully carried out, would also preclude any NASA-originated two-launch solutions, unless the Gargantua-V Ares-V remains in its current configuration.  Anything smaller would require the Altair be launched with the Orion, just like DIRECT.  Only an Ares-V with a fully loaded EDS and a pre-attached Altair would obviate this "fatal flaw".

If docking two vehicles in space is a "fatal flaw" now, then NASA is in deep doo-doo.

Mark S.

[Pheogh]

I have just been told to prepare for a new round of FUD from CxP regarding our Altair > EDS docking arrangement.

Apparently they're about to try to attack DIRECT for this "fatal flaw".

I just thought I would pre-empt their attack by putting this information "out there" well ahead of their attempts.

Ross.

An idea in which direction this attack will come from? "One if by land, and two if by sea" or where?

[zapkitty]

... If docking two vehicles in space is a "fatal flaw" now, then NASA is in deep doo-doo.

Negative margins coupled with ever-increasing performance deficits added to 100% fatal "black zones" joined with years of flightless "Gap" all bundled together with still-ballooning budget overruns in the billions... this is not deep doo-doo already?

How low can they go?

[fotoguzzi]

I have just been told to prepare for a new round of FUD from CxP regarding our Altair > EDS docking arrangement.

Calling Dr. Pietrobon!  Dr. Pietrobon to the launchpad - Stat!

[zapkitty]

... Any idea in which direction this attack will come from? "One if by land, and two if by sea" or where?

Oh noes! NASA's learned about teh EDS Docking Black Zone!!! What are we going to do?! 

[kraisee]

I really hope somebody has sufficient spine to make a real "example" of these idiots.

Augustine?   Bolden?   Garver?   Obama?   Holdren?   Anyone?

Ross.

[Paul Adams]

Ross,

Do you know how they will 'attack' - what media and what means?