DIRECT v3.0 - Thread 1

[MP99]

With that in mind you could add 25mT (maybe more?) of "debris retaining" structures to each SRB and still comfortably make orbit with margins intact.

I can answer that... no.

To terminate thrust the steel case must be unzipped. When that happens any addons that attempt to "contain" the debris will fail under the pressure of the still-burning fuel.

It seems to me the biggest problem is not that the SRB fails, but that debris is spread over such a wide area that once the LAS has burnt out the capsule must descend through the debris field.

Is there any chance that a structure could slow down the ejecta and reduce the spread of debris?

Not within a reasonable mass budget, no.

I'm not trying to labour a point, but what sort of unreasonable mass budget would be required?

50mT per SRB, a lot more?

cheers, Martin

[kraisee]

I think the question which really needs to be answered regarding exploding SRB's, is exactly *how* they come apart.

An SRB has a lot more area on the sidewalls than on the top/bottom.   My question is that in the event of a severe over-pressurization, do those 'sides' blow out sideways, or all around?

That report seems to suggest they make a large 'ball', but they also say that's just an assumption and that the camera angle doesn't really allow a precise analysis.

But I think we really need to see some real analysis before relying upon that assumption though.

If 80-90% of the structures is actually blown "sideways" instead of up/downwards, that will alter the danger levels.

Ross.

[Lancer525]

So Ross, will you ever offer Jupiter-130/246 models?  I might have to pick up one, although I can wait as you are understandably busy (I would love to see lego make a Jupiter model, dont ask why...)

Make it a model rocket and I'll buy two.    Altho technically you might be able to kitbash one using a shuttle kit.

Dr. Zooch is supposed to be coming out with a Jupiter model rocket... (user "zerm" here on the board)  Maybe PM him for more information...

Later!  OL JR

I've been fiddling with plans for a parallel staged J-130 for a while now, but I'm having some difficulty finding out enough information on how to separate the RSRMs from the core, and still have the core, RSRMs, and Orion recover separately. I'm also thinking about doing the J-246 as a paralell two stager, with the same recovery options.

It's not nearly as easy to design a flying model as it is to make a static one out of paper.

If any of you guys who are working on the flying model need any help with textures or skins, shoot me a PM and I'd be happy to work with you.

I should have the plans for the J-130 and J-246 in 1/144 scale out by the end of next week, I hope.

And if any of you guys build them, please share your photos and build experiences. I'm always looking at ways to improve the instructions sheets.

 

Check these out:

 http://www.rocketryforum.com/
http://forums.rocketshoppe.com/index.php?
http://www.rocketryplanet.com/forums/

You can search the forum for the specific information you're looking for.  There was a good post not long ago on this specific question of SRB seperation ideas for high power rockets.  There is an interesting "tube within a tube" design with capped ends that have a small charge of black powder installed in them that are electrically fired by a flight computer or timer at SRB burnout.  The small BP charges seperate the boosters.  The SRB's could use standard high-power motors with BP ejection charges or be more sophisticated with electronic deployment of the chutes.  I'd expect any upper stage would make use of a flight computer or timer to ignite the upperstage engines, be they either black powder motors or composite propellant.  The 1/70 scale would make an AWESOME rocket and be large enough to house the necessary electronics and large rocket motors. 

A smaller model with dropping SRB's deploying their own chutes and a staged core would be cool but probably more difficult, but DEFINITELY less expensive! 

There's an interesting Delta IV Heavy that drops its boosters after burnout, a fairly big model, and I'm not sure what method he used for the seperation-- I'm sure you can find it by searching the forum. 

Good luck!  OL JR

I've never built a model rocket before, so I can tell you on first inspection that some of these techniques are way beyond me. Flight computer? I don't have the first idea how that would work. All I've ever seen are the kits that you could get at Wal-mart, so I will probably give up the idea of making a flying model, or at least leave it to those who know more than I do.

Thanks for the links!

[Danny Dot]

I think the question which really needs to be answered regarding exploding SRB's, is exactly *how* they come apart.

An SRB has a lot more area on the sidewalls than on the top/bottom.   My question is that in the event of a severe over-pressurization, do those 'sides' blow out sideways, or all around?

That report seems to suggest they make a large 'ball', but they also say that's just an assumption and that the camera angle doesn't really allow a precise analysis.

But I think we really need to see some real analysis before relying upon that assumption though.

If 80-90% of the structures is actually blown "sideways" instead of up/downwards, that will alter the danger levels.

Ross.

Keep in mind the SRB can rotate 90 before it is destroyed. 

Danny Deger

[mmeijeri]

That report seems to suggest they make a large 'ball', but they also say that's just an assumption and that the camera angle doesn't really allow a precise analysis.

The report is a bit vague, but it looks to me as if the "unconservative" assumptions made on page 5 include assuming the imparted velocity is purely radial. The debris also has forward velocity of course ("mothership velocity"), which is assumed to be unaffected. In other words, the debris is already moving forward and is then blown sideways. The report analyses the trajectories of the debris particles under the influence of gravity and aerodynamic forces.

[fotoguzzi]

If 80-90% of the structures is actually blown "sideways" instead of up/downwards, that will alter the danger levels.

Keep in mind the SRB can rotate 90 before it is destroyed. 

I know this has been covered before, but does the LAS have a concept of up, or does it merely head in the direction it was pointing when the switch was thrown?

Modify: verb tense; typo

[zapkitty]

I know this has been covered before, but does the LAS have a concept of up, or does it merely head it the direction it was pointing when the switch is thrown?

The LAS mini-stack has an attitude control system, a solid motor with 8 valved ports around its circumference, that's controlled by the LAS systems.

[Ronsmytheiii]

I think the question which really needs to be answered regarding exploding SRB's, is exactly *how* they come apart.

An SRB has a lot more area on the sidewalls than on the top/bottom.   My question is that in the event of a severe over-pressurization, do those 'sides' blow out sideways, or all around?

That report seems to suggest they make a large 'ball', but they also say that's just an assumption and that the camera angle doesn't really allow a precise analysis.

But I think we really need to see some real analysis before relying upon that assumption though.

If 80-90% of the structures is actually blown "sideways" instead of up/downwards, that will alter the danger levels.

Ross.

Well there is only one way to answer this question effectively, we need to blow up an SRB.  That would get people interested in spaceflight again....

[kraisee]

I think the question which really needs to be answered regarding exploding SRB's, is exactly *how* they come apart.

An SRB has a lot more area on the sidewalls than on the top/bottom.   My question is that in the event of a severe over-pressurization, do those 'sides' blow out sideways, or all around?

That report seems to suggest they make a large 'ball', but they also say that's just an assumption and that the camera angle doesn't really allow a precise analysis.

But I think we really need to see some real analysis before relying upon that assumption though.

If 80-90% of the structures is actually blown "sideways" instead of up/downwards, that will alter the danger levels.

Ross.

Well there is only one way to answer this question effectively, we need to blow up an SRB.  That would get people interested in spaceflight again....

LOL!

Actually Danny is right, there is no guarantee that when the booster goes pop, it sill still be flying 'straight up' -- it *could* blow at a relative angle of 90 degrees, so we need to be sure the Orion is even protected in that situation.

Anyway, here are my current results after a little more refinement...

Note that Orion continues for Approx 15 more seconds before the LAS/BPC are jettisoned.

Ross.

[Lee Jay]

Just FYI:   We are getting an analysis done into where the Orion ends up in relation to the debris field in the even of a worst-case SRB explosion.   It's going to take some time to complete though.

In the interim, I've tried running a very simple comparison and my own figures -- which HAVE NOT BEEN VALIDATED YET -- indicate that if an SRB detonated at Max-Q (T+50 sec) on a Jupiter-130 flight would result in the LAS getting the Orion CM away ahead of the debris field and out to a distance of some ~8,900 meters (~29,000ft) before the LAS/BPC is actually jettisoned from the CM.   This would be well outside of the debris field.

The crew gets exposed to roughly 16G during this abort.

Its still only a *very* rudimentary result, but I think it is a very encouraging preliminary result.

*IF* it can be validated, it would mean that this issue is not a concern for Jupiter.

I'll keep you all informed of the more detailed results as I receive them.

Ross.

I thought the report concluded that it was *radiative* heating that destroyed the chutes.  If so, being ahead of the debris cloud doesn't necessarily bring you to safety.  A large and hot debris cloud can radiate a lot of heat.

Better make sure the chutes are white.

[fotoguzzi]

I'd love to have local get-togethers to hoist a pint in celebration of reaching the long-standing goal...

As we get closer to the 30th, I'll get everyone to confirm so that we can book a table large enough at a restaurant in the area.

Has John Shannon accepted?

[luke strawwalker]

So Ross, will you ever offer Jupiter-130/246 models?  I might have to pick up one, although I can wait as you are understandably busy (I would love to see lego make a Jupiter model, dont ask why...)

Make it a model rocket and I'll buy two.    Altho technically you might be able to kitbash one using a shuttle kit.

Dr. Zooch is supposed to be coming out with a Jupiter model rocket... (user "zerm" here on the board)  Maybe PM him for more information...

Later!  OL JR

I've been fiddling with plans for a parallel staged J-130 for a while now, but I'm having some difficulty finding out enough information on how to separate the RSRMs from the core, and still have the core, RSRMs, and Orion recover separately. I'm also thinking about doing the J-246 as a paralell two stager, with the same recovery options.

It's not nearly as easy to design a flying model as it is to make a static one out of paper.

If any of you guys who are working on the flying model need any help with textures or skins, shoot me a PM and I'd be happy to work with you.

I should have the plans for the J-130 and J-246 in 1/144 scale out by the end of next week, I hope.

And if any of you guys build them, please share your photos and build experiences. I'm always looking at ways to improve the instructions sheets.

 

Check these out:

 http://www.rocketryforum.com/
http://forums.rocketshoppe.com/index.php?
http://www.rocketryplanet.com/forums/

You can search the forum for the specific information you're looking for.  There was a good post not long ago on this specific question of SRB seperation ideas for high power rockets.  There is an interesting "tube within a tube" design with capped ends that have a small charge of black powder installed in them that are electrically fired by a flight computer or timer at SRB burnout.  The small BP charges seperate the boosters.  The SRB's could use standard high-power motors with BP ejection charges or be more sophisticated with electronic deployment of the chutes.  I'd expect any upper stage would make use of a flight computer or timer to ignite the upperstage engines, be they either black powder motors or composite propellant.  The 1/70 scale would make an AWESOME rocket and be large enough to house the necessary electronics and large rocket motors. 

A smaller model with dropping SRB's deploying their own chutes and a staged core would be cool but probably more difficult, but DEFINITELY less expensive! 

There's an interesting Delta IV Heavy that drops its boosters after burnout, a fairly big model, and I'm not sure what method he used for the seperation-- I'm sure you can find it by searching the forum. 

Good luck!  OL JR

I've never built a model rocket before, so I can tell you on first inspection that some of these techniques are way beyond me. Flight computer? I don't have the first idea how that would work. All I've ever seen are the kits that you could get at Wal-mart, so I will probably give up the idea of making a flying model, or at least leave it to those who know more than I do.

Thanks for the links!

Oh, ok...  now I know more of where you're at...

The Electronics are sold for mostly high-power rockets using ammonium perchlorate composite propellants.  There are lots of suppliers for electronics-- most are rather simple accelerometer-based or pressure-transducer based (some a combination thereof) altimeters that sense when the rocket has reached apogee and ignite a black powder charge to eject the drogue, and then continue sensing the descent altitude and eject the main chute with another BP charge at a pre-programmed altitude, say 800 feet.  Some of the more advanced electronics systems can also perform other flight 'events' like airstart motors and such.  A lot of staging is performed with simple electronic timers programmed to ignite the upperstage motor after a given pre-programmed time after liftoff is detected (usually by an accelerometer). 

Starting out you want a simple rocket and can go from there... the Dr. Zooch Space Shuttle is fairly simple and like Direct itself can easily be tranformed into a Jupiter.  As I said, Dr. Zooch (zerm) is supposed to be coming out with a Direct Jupiter soon, or so he's said on the rocket boards in the recent past.  They aren't THAT difficult to build and are a blast to fly!  I have a build thread on the shuttle on the rocketry forum, crossposted to ye old rocketry forum and rocketry planet as well, including an 'upgraded' shuttle orbiter made to look like "Moonraker 5" from the Bond film of the same name. 

Good luck and don't be intimidated... they're really cool and no more difficult to build than any other model kit...   OL JR

[MP99]

Actually Danny is right, there is no guarantee that when the booster goes pop, it sill still be flying 'straight up' -- it *could* blow at a relative angle of 90 degrees, so we need to be sure the Orion is even protected in that situation.

Anyway, here are my current results after a little more refinement...

Note that Orion continues for Approx 15 more seconds before the LAS/BPC are jettisoned.

Ross.

Orion is carried well away from the debris during LAS burn, but the elements of debris represented by the blue ring were imparted a wholly lateral velocity in the explosion, whilst the capsule has continued to accelerate in the direction of ascent (mostly upwards, small lateral component).

As a result, they have very similar lateral velocities.

Also, the capsule has higher total velocity and is much less dense than the debris, so I wouldn't be surprised if it suffers more deceleration, further decreasing the lateral separation (rate of increase, at least).

Whilst it looks like the capsule will remain above the debris throughout the descent, it doesn't seem that it would take much of an adverse wind during the parachute phase to make the capsule land amongst the debris.



Is there any way that the LAS can steer to impart a much larger lateral component to the velocity after T+51? Would that be desirable?

cheers, Martin

[zapkitty]

Whilst it looks like the capsule will remain above the debris throughout the descent, it doesn't seem that it would take much of an adverse wind during the parachute phase to make the capsule land amongst the debris.

What's needed now is data on the radiated heat  outside the debris field as a function of the field dispersion over time and what effects the thermal updraft might have  (if any effect at all)

So how long would it take to set up an SRB to fly solo with just enough ballast to keep TO within the tolerance range of instruments?

One that's instrumented to unzip itself as it passes through the range of Ares I's max-Q...

... and if Ares I has been sensibly shelved before that can be done then have it unzip at the max q of the next highest q'd contender...

[marsavian]

You have finally found a real use for Ares I-X, LAS design validation for Jupiter/Ares V .

[Danny Dot]

I think the question which really needs to be answered regarding exploding SRB's, is exactly *how* they come apart.

An SRB has a lot more area on the sidewalls than on the top/bottom.   My question is that in the event of a severe over-pressurization, do those 'sides' blow out sideways, or all around?

That report seems to suggest they make a large 'ball', but they also say that's just an assumption and that the camera angle doesn't really allow a precise analysis.

But I think we really need to see some real analysis before relying upon that assumption though.

If 80-90% of the structures is actually blown "sideways" instead of up/downwards, that will alter the danger levels.

Ross.

Well there is only one way to answer this question effectively, we need to blow up an SRB.  That would get people interested in spaceflight again....

LOL!

Actually Danny is right, there is no guarantee that when the booster goes pop, it sill still be flying 'straight up' -- it *could* blow at a relative angle of 90 degrees, so we need to be sure the Orion is even protected in that situation.

Anyway, here are my current results after a little more refinement...

Note that Orion continues for Approx 15 more seconds before the LAS/BPC are jettisoned.

Ross.

18 meters is way too close to be setting off the range package.  The blast from the ET would kill Orion.  Make sure you have a good model for drag on every thing (numerical integration?) and then probably need to monte carlo the attitude and time of destruct of the post abort Jupiter.  Also 75 m/sec for debris might be too small.  I think the Air Force had faster debris.  Also, Orion has a steerable LAS.  It doesn't have to burn straight ahead.  This might help.

I am thinking if the debris field is 7,900 foot radius, the impulse from the LAS will need to be increased even at the smaller dynamic pressure of Jupiter.  The good news is Jupiter can carry a bigger LAS.

Danny Deger

[Lab Lemming]

That's the height the capsule sits at on the rocket- he's assuming the SRB blows with no warning here.

Is it really a good idea to do lots of steering at Max Q?

18 meters is way too close to be setting off the range package.  The blast from the ET would kill Orion.  Make sure you have a good model for drag on every thing (numerical integration?) and then probably need to monte carlo the attitude and time of destruct of the post abort Jupiter.  Also 75 m/sec for debris might be too small.  I think the Air Force had faster debris.  Also, Orion has a steerable LAS.  It doesn't have to burn straight ahead.  This might help.

I am thinking if the debris field is 7,900 foot radius, the impulse from the LAS will need to be increased even at the smaller dynamic pressure of Jupiter.  The good news is Jupiter can carry a bigger LAS.

Danny Deger

[MP99]

The 2896kg listed as Ascent Flight Performance Reserve is the same as the Pre-TLI Overboard mass, is that right?  Also, CLV values are identical except for the Usable Post-Ascent Propellant value?

Yep.   You don't want to be carrying any additional mass thru TLI which you don't have to.

So a 'nominal' mission should arrive in LEO with that 2.9mT of extra mass.   You will want to dump it before the TLI.

Ross.

Interesting - your AIAA 2007 paper talks about using depot to overfuel the EDS for a 10% margin on the TLI.

I guess later analysis has shown more benefit in reducing stresses on the TLI engines by keeping the burn as short as possible?

cheers, Martin

[Michael Bloxham]

Hey guys. I was looking at the DIRECT article on wikipedia and read this section:

Payload capacity
The payload capacity of Ares V to low earth orbit, according to NASA, is 188,000 kg. This is more than the largest proposed Jupiter rocket (J-246 Heavy with 5 segment SRBS) which is claimed to lift about 120,000 kg to LEO [33]. For potential Mars missions the currently envisioned Ares V would have a significant advantage for any mission architecture[citation needed].

Which prompted me to add this:

Although in the case of a Mars mission it can be argued that the internal payload fairing diameter is the limiting factor, not mass, due to Mars EDL limitations. The DIRECT team have studied payload fairings of up to 12m diameter and even beyond for the Jupiter launch vehicles[citation needed]. The Jupiter rockets are also shorter in height than the Ares V, permitting very long payload fairings and thus greater total internal volume than possible with the taller Ares V which quickly encounters restraints due to height limitations within the Vehicle Assembly Building at KSC.

Any help with citations please?

[anonymous1138]

Actually Danny is right, there is no guarantee that when the booster goes pop, it sill still be flying 'straight up' -- it *could* blow at a relative angle of 90 degrees, so we need to be sure the Orion is even protected in that situation.

Anyway, here are my current results after a little more refinement...

Note that Orion continues for Approx 15 more seconds before the LAS/BPC are jettisoned.

Ross.

Orion is carried well away from the debris during LAS burn, but the elements of debris represented by the blue ring were imparted a wholly lateral velocity in the explosion, whilst the capsule has continued to accelerate in the direction of ascent (mostly upwards, small lateral component).

As a result, they have very similar lateral velocities.

Also, the capsule has higher total velocity and is much less dense than the debris, so I wouldn't be surprised if it suffers more deceleration, further decreasing the lateral separation (rate of increase, at least).

Whilst it looks like the capsule will remain above the debris throughout the descent, it doesn't seem that it would take much of an adverse wind during the parachute phase to make the capsule land amongst the debris.



Is there any way that the LAS can steer to impart a much larger lateral component to the velocity after T+51? Would that be desirable?

cheers, Martin

There are qbar*alpha limits to what the LAV assembly can withstand. Which leads me to thinking about MLAS ... I don't think MLAS would have the same problem. A thought experiment I've been considering (and I haven't thought this through entirely) is that with MLAS you might be able to get off the booster, gain some lateral separation, and then turn completely around ... putting on the brakes, so to speak. I would think that you might prefer to be behind the booster when it is destructed. The problem would be that you may not be able to gain enough lateral separation to avoid the SRB plumes. You'd maybe need a bigger MLAS to do this. That's where DIRECT comes in. :-)

Ascent abort in some regions is a very complicated effort. But, even with the well developed aircraft ejection seat technology being what it is, sometimes it still doesn't work. There isn't any 100% safe ascent abort system that will work for all cases. The idea is to spend the effort on prevention of the need for aborts in the first place, and give the crew at least a fighting chance for safely aborting throughout the entire ascent.

FYI, awareness of the problem of max q aborts and separation distance has been known at JSC for a long time, and it's been getting attention.

Edit: Spelling correction.