Ares I: vibration self-destruct?

[docm]

SpaceRef article....<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p><b>First Stage Design Problems Arise For NASA's Ares 1 Rocket</b><br /><br />Friday, November 16, 2007<br /><br />NASA has run into some problems with the design of its new Ares 1 launch vehicle - problems that could affect its ability (as designed) to safely launch its human cargo into space.<br /><br />The Ares 1 and the Orion capsule (also under development) are designed to replace the crew carrying function of the current Space Shuttle fleet which is due to be retired in 2010. The first flight of humans aboard an Ares 1 is planned for March 2015.<br /><br /><font color="yellow">According to NASA sources, the Ares 1 first stage, as currently designed, would produce a frequency of 25 Hz at liftoff. The concern is that this oscillation could shake the Ares 1 upper stage and Orion capsule designed to carry human passengers, causing considerable damage and that it could also adversely affect the Guidance, Navigation, and Control avionics in the rocket's Instrumentation Unit.</font><br /><br />When asked to comment on this development, NASA's Exploration System Mission Directorate (ESMD) Public Affairs Officer replied:<br /><br /><i>"The Ares Project Office identified Ares I thrust oscillation as a potential integrated stack challenge as a part of its system definition review which concluded in October. Thrust oscillation or resonant burning is a characteristic of all solid rocket motors. It is caused by vortex shedding inside the solid rocket motor, similar to the wake that follows a fast-moving boat. When the vortex shedding coincides with the acoustic modes of the motor combustion chamber, pressure oscillations generate longitudinal forces that may affect the loads experienced by the Ares I during the last phase of first-stage flight. NASA is assessing the analyses in more detail, looking for any poten</i></p></blockquote> <div class="Discussion_UserSignature"> </div>

 

[edkyle98]

Why the overwrought reactions? All rockets have resonances that must be accounted for during the development phase. (Remember Saturn V pogo?) This is not a show stopper, just an engineering challenge. <br /><br /> - Ed Kyle

 

[frodo1008]

Well, you and I are indeed having (a hopefully polite) discussion on the costs of the Ares I and Constellation systems on the next thread down.<br /><br />These kinds of problems might just be engineering challenges, but such challenges at the very least can cost lots of funding, and at the very worst can result in situations like the Challenger, and Columbia accidents for NASA!<br /><br />Is a new congress and President going to be happy with such increasing costs? Already NASA is saying that they might be losing lots of time off of the schedules, and they need more money to bring it back under control. <br /><br />I realize that compared to other government costs such as wars in the Middle East this is chump change. But this is EXACTLY the same kind of thing that gave us the STS system (in regard to the Viet Nahm war). Which while magnificent, was in the long run far too expensive. <br /><br />I lived through this kind of thing once, and I REALLY don't want to have to do it again!<br /><br />Also, besides what if the alt,space crowd can actually even do half of what they say they can (especially spacex and Elon Musk). Some ten years into the future they will be launching people into LEO for some $1,000 per pound, and NASA will then be stuck with a system that takes $5,000 to even the current $10,000+ per pound to LEO!<br /><br />Under those circumstances would ANY money be funded by a disgusted congress for NASA?<br /><br />I STILL believe in NASA, and don't want them to collapse in the long run!<br /><br />And so I am truly willing to have them really give possible cheaper alternatives to designing their own system a real look. But, I am afraid they might just be continuing to play politics here!<br /><br />And in the long run that could be fatal!

 

[nuaetius]

>"The Ares Project Office identified Ares I thrust oscillation as a potential integrated stack challenge as a part of its system definition review which concluded in October. Thrust oscillation or resonant burning is a characteristic of all solid rocket motors. It is caused by vortex shedding inside the solid rocket motor, similar to the wake that follows a fast-moving boat. When the vortex shedding coincides with the acoustic modes of the motor combustion chamber, pressure oscillations generate longitudinal forces that may affect the loads experienced by the Ares I during the last phase of first-stage flight. NASA is assessing the analyses in more detail, looking for any potential impacts to the integrated stack and ways to mitigate those impacts. Results are due in spring 2008. It is a normal part of the development process to identify, mitigate and track challenges such as this."<br /><br />Has anyone ever used a solid rocket to deliver a human or ICBM before?

 

[vogon13]

Anyone considered using prototype ballute material to make an accumulator (a device used in hydraulics) to attach to the solid fuel combustion chamber ??<br /><br />Seems like it could dampen vibration 6 dB or so, and that would be quite a help.<br /><br />Accumulators in hydraulic circuits are light weight and effective.<br /><br /><br />I also recall an ellipsoidal chamber used on (IIRC) the Boeing 757 hydraulic pump. With no moving parts, just a specific shape in the flow path, pressure pulsation dampening was acheived. At the top of the SRB chamber might we affix a suitably shaped chamber made from refractory materials to attenuate the problem ??<br /><br />Or, how about slightly 'foaming' the solid fuel with helium ?? If the fuel in the combustion chamber was even slightly compressible, it could dissipate considerable acoustic vibrations. Helium would have virtually no effect on combustion, and entrained 'bubbles' might increase fuel volume by a percent or so.<br /><br /><br />To my severely out of date engineering mind, this seems like a very minor problem, I've just come up with 3 contenders in 5 minutes for fixing the problem.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[docm]

<font color="yellow">Has anyone ever used a solid rocket to deliver a human or ICBM before?</font><br /><br />A hybrid (solid fuel, liquid oxidizer) was used in SpaceShipOne and its fuel is solid and AFAIK virtually all or all ICBM's are solid. In both cases the trajectory is sub-orbital, and the power is small fraction of that needed for orbiting Orion. <div class="Discussion_UserSignature"> </div>

 

[j05h]

along with SS1, a 260" diameter monolithic solid rocket was tested as a possible Saturn first stage. There are examples of liquid-fuel ICBMs - Dnepr (Satan/SS-19 ICBM) rockets use hypergolics that can sit in their tanks for years. This is probably the exception, though. Solids for humans, no, no one has ever gone beyond the concept range, AFAIK. <br /><br />Ares I is a solution looking for a problem. It is a square peg for a round hole. There are already rockets to lift the craft - the world market for rocket launch is depressed and could use a customer. Another medium-lift rocket with even worse economics will not help make spaceflight more accessible. None of the proposed ESAS components are out of the mass-to-LEO range of the various ELVs, if unfueled. The majority of planned lunar mission mass is highly divisible fuel. Even the proposed landers are only around 20t mass, unfueled. All of this requires not being afraid of orbital caching, assembly and forward basing at Lagrange and lunar orbital sites.<br /><br />Once they deal with the 25hz vibration, they can deal with the "hotdog on a pencil" balance issues because of the oversized second stage. If it gets to first flight, I give Ares I a 50/50 chance of snapping during ascent. This is another vibration issue, but is more yaw/pitch intensive. <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[h2ouniverse]

in reply to<br />-------<br />Why the overwrought reactions? All rockets have resonances that must be accounted for during the development phase. (Remember Saturn V pogo?) This is not a show stopper, just an engineering challenge. <br />----------<br /><br /><br />indeed. Ariane 5 had pogo issues too. Still considered for manned missions (a man-rated version might be developped).

 

[radarredux]

> <i><font color="yellow">Why the overwrought reactions? All rockets have resonances that must be accounted for during the development phase.</font>/i><br /><br />The problem is that the Ares I was largely sold on how fast and cheap it would be to deliver and that it was already man-rated. Now its schedule keeps slipping, it is billions of dollars over budget already, they keep having to downsize Orion, and there have been so many proposed changes that it would be silly to consider this "already man-rated."<br /><br />If I worked for the Delta or Atlas rocket groups I would be pretty pissed that a group sold NASA that a strap-on booster that had never been launched stand-alone would be so much better and easier for the Ares I than existing commercial rockets.</i>

 

[frodo1008]

It would seem as if most of the people on here are now of the opinion that NASA has goofed. Even those such as myself that supported NASA originally (when they were going to use either no modifications or at worst slight modifications to at least the propulsion of Ares I) have now become almost bitterly disillusioned.<br /><br />I do not feel anger, just disappointment!

 

[j05h]

Even if successful, ATK and NASA will take longer to field the Ares I it took to go from no spaceflight to landing on the moon. This is using an "existing booster" and known mold-line for the crew capsule. I'd laugh if it wasn't so tragic. <br /><br />Please notice that Lockmart, developing the Orion capsule, is on time and budget. Since they just signed the upper stage contract, we'll have to wait and see on that performance. <br /><br />The thing that doesn't make sense, not even in the semi-false context of early Ares V development, is that the SRB descendant is competing against an already depressed launch market. If they really, really want to develop the strap-on boosters for Ares V, just buy the Zenit. It exists, it works, and was developed in both contexts (booster and own rocket). Copy the Energia core using Shuttle components. Even then, everything we want to do in space can be started with existing medium ELVs.<br /><br />In theory the current SRB casings can take the latitudinal stress, but it has never been tried. This could have been tried already with an existing SSRM and a boilerplate upper stage, but even that is years away. At this rate, Dragon will be flying people in orbit before the Ares/Orion boilerplate flies. NASA used to be very can-do, in that old-school "demo or die" way that good teams of engineers naturally have. They have become cloistered and risk-averse. <br /><br />On top of all of this, the best, achievable solution, the EELV-based Orbital Space Plane OSP was canned in the aftermath of Columbia. Those craft, if pursued, would be in test flights or operational now.<br /><br />Does Lockheed get to keep their part of the Orion design if ESAS collapses? That is valuable intellectual property if they want to field a capsule through ULA. <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[baktothemoon]

Any chance you can lift an Orion on a Falcon 9?

 

[docm]

Last I heard Ares I was listed at ~25,000 kg to LEO and Falcon 9 can only do 9,900 kg from the Cape. Falcon 9 Heavy is listed as 27,500 kg to LEO, so it's theoretically possible. So is Delta IV Heavy.<br /><br />That Falcon 9 is to lift Dragon to LEO shows you how overweight/overdone Orion really is. <div class="Discussion_UserSignature"> </div>

 

[j05h]

Dragon - same number of seats to LEO for half the mass. (or is that one more seat for half the mass?) <br /><br />Falcon 9 is only 10t to LEO - but Falcon 9 Heavy can indeed handle the planned Orion. There are plenty of existing rockets that could do it, too. Atlas, Proton, Ariane. <br /><br />Ares I is a solution looking for a problem.<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[usn_skwerl]

they have two options if they keep the set-up they want; Keep the 5-seg SRB, and you must decrease the Orion module mass.<br /><br />Decrease the Orion, you decrease crew capabilities and capacities.<br /><br />If a third stage were added, as an intermediate one between SRB and a non-compromised Orion system, the SRB wouldn't be able to get as much deltaV and altitude, but a liquid intermediate stage would be able to compensate for it, I would assume. <div class="Discussion_UserSignature"> </div>

 

[docm]

Making it even longer and more likely to flex at critical junctures. Wouldn't that worsen the problem? <div class="Discussion_UserSignature"> </div>

 

[josh_simonson]

Dragon doesn't contain enough OMS fuel for a TEI burn from lunar orbit, it also isn't large enough to support crew for the duration of lunar missions - dragon packs folks in tight like Soyuz, but lacks the on-orbit room of the soyuz SM.<br /><br />However, CEV could fly with less fuel for ISS missions and get down in weight to 15-20t, which is well within the range of several potential LVs. <br /><br />Also note that STS uses SRBs and it doesn't shake itself apart. This problem is almost certainly surmountable.

 

[vogon13]

Well . . .<br /><br />To a certain degree, it shook itself to pieces twice.<br /><br /><br /><br />{I am considering pressure 'spiky' nature of solid combustion in opening up clevis joint and scorching o-rings, and vibration may have played at least some part in dislodging bipod ramp}<br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[thereiwas]

Videos taken inside the orbiter certainly show a lot of vibration. And astronaut accounts report a smoother ride after SRB separation.

 

[j05h]

I'm only discussing Block 1 Orion (orbital) - AFAIK the Lunar-capable Orion is still to heavy for Ares I. Good point on crew space in Dragon, it is really a crew-exchange vehicle. Let me emphasize that Dragon on F9 (not heavy) competes comfortably with Block 1 Orion, and has room to expand with service/Hab modules on F9H, unlike Orion/Ares. <br /><br />The only people that seem to be talking about Orion on anything but the Stick is us space cadets. I find it hard to believe that Lockheed and ULA aren't looking into that possibility. Time will tell.<br /><br />Actually, SRB vibrations and seal issues are exactly what destroyed Challenger and contributed to Columbia's destruction. Enough money will make any pig or Spruce Goose fly. The real question is when is the fiscal pain to much? <br /><br />They should have dropped the Ares I as soon as it went out of the original specs. The original idea was interesting, but the current version (while working slowly towards flight) is an entirely new rocket. <br /><br />The sensible thing is to use existing EELVs and other LVs for crew, payload and cargo launch. Nothing in ESAS is "Shuttle-derived" anymore - so scrap the Ares V and build a monolithic HLV if the need arises, but work with the tools at hand for now. Don't mess around with side boosters, the Saturn V was a single stack of stages. NASA could have spent the last 3 years working on the moon and tug hardware instead of these paper rockets, if they had gone with existing rockets. <br /><br />It would make sense to build "X" rocket if it promises to change the economics of spaceflight. Falcon is an attempt like this, as was DC-X and X-33. Ares I/V are not. They exist for a different purpose, and it's not about landing on the Moon.<br /><br />i feel like a broken record on this subject, but ESAS is running backwards.<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[steve82]

"Let me emphasize that Dragon on F9 (not heavy) competes comfortably with Block 1 Orion"<br /><br />It's an apples to oranges comparison if Dragon doesn't have a Launch Abort System-that's the big weight penalty Orion has in return for a zero-zero abort capability. Dragon is a water lander too, Orion is nominally land.

 

[josh_simonson]

>"Also note that STS uses SRBs and it doesn't shake itself apart. "<br /><br /> />That is a totally different case. The other ET, Orbiter and ET change the resonance of the vehicle.<br /><br />Indeed, but the problems were still overcome. As for vibration causing the two LOVs, I think we could place as much blame on dynamic pressure, wind shear, atmospheric conditions.... In the case of Challenger they were operating outside the SRBs specifications! <br /><br />Ares V WILL be a vehicle that changes the economics of spaceflight for NASA if it is built. It's launch will cost about the same as that of STS, but it has FIVE times the payload. That's an 80% drop in per-pound launch costs - hardly something to sneeze at. The only pity there is that NASA is so overpriced that even an 80% reduction only makes it about twice as good as the existing domestic LVs.

 

[docm]

Pertinent post froms NSF's thread;<br /><br />Thread page #8.....<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p>clongton - 20/11/2007 10:57 AM<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p>Crispy - 20/11/2007 5:05 AM<br /><br />I think that's a question that could only be answered with some detailed analysis. It would certainly be a curious looking launch vehicle!<p><hr /></p></p></blockquote><br /><font color="yellow">Hundreds of thousands of analysis man hours have already been expended on this question by the original STS design team. <b>Their answer was if solids must be used, they should fly in pairs in combination with a liquid core, connected by a common horizontal thrust beam that would direct the resonant into the liquid propellant for dissipation. But for some largely unknown reason, the Ares-1 design team has not availed itself of that data. I am hoping that there was a specific reason for it, and not that it was an error or an oversight.</b></font>p><hr /></p></blockquote><br /><blockquote><font class="small">In reply to:</font><hr /><p>clongton - 20/11/2007 11:17 AM<br /><blockquote><font class="small">In reply to:</font><hr /><p>brihath - 20/11/2007 11:16 AM<br /><br />I would imagine that the resonance can be resolved through design changes, but more design changes take the vehicle further away from Shuttle heritage, which was supposed to be justification for selecting Ares I in the first place. On top of that is cost and schedule impact, potentially lengthening the post Shuttle gap which places us in the position of buying manned space launches from the Russians for longer. With the higher costs, longer gap, etc, etc, NASA suffers.<p><hr /></p></p></blockquote><br /><font color="yellow">There is always a design solution. The question is will that design solution drive the design outside the imposed design paramet</font></p></blockquote> <div class="Discussion_UserSignature"> </div>

 

[j05h]

<i>> It's an apples to oranges comparison if Dragon doesn't have a Launch Abort System</i><br /><br />Dragon uses it's service module engines for launch-abort, plus has the added safety advantage of being able to shut down main propulsion in emergency. It does this in less than half the mass of Orion. And it'll be commercially available for anyone with the cash. Block 1 Ares is going to be competing with Dragon, even if it's not for sale, in mind-share.<br /><br />Orion's landing method is up for reassessment. Seemingly along with everything else about the project. Flux is good early on, but it seems like a lot of earlier decisions were in error. Especially items like deciding on a single-source provider of a specific rocket before any other aspects of the project were decided. <br /><br />Ares is a pork-derived rocket.<br /><br />When the first Ares I snaps in half mid-flight, people are going to ask "why is it so long and skinny?" The answer will be simple: because they send the segments by train from Utah, so they have to be small enough to fit through the tunnels. <br /><br />ATK is talking about new fuel grains among other upgrades. Ares I will be a new rocket compared to the SSRM. The fuel changes automatically mean extensive qualifications. If ATK's knowledge is really so necessary, why not build a wider booster near the launch site? It's compeletely new, except that it still retains all the weaknesses of the older booster, while requiring Billion$ to qualify, if at all. <br /><br />Will Orion fly? I think so. Will Ares I fly? Not so sure.<br /><br />On top of all this, there is a 50/50 chance that ESAS is completely out the window in 2009. Which probably means back to flying circles until 2012, when INA kicks in, then what for American spaceflight? Hopefully SpaceX and Bigelow succeed. <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[vulture2]

The Delta IV Payload Planner's Guid gives the max vibration for the Delta at just over 1G. The recent launch looked pretty darn smooth; certainly it doesn't have anything close to the vibration of a solid, even the Shuttle while the SRBs are burning. <br /><br />If anyone has details or sources for the statement that the D-IV trajectory is unacceptable for human launch due to "lofting", "black zones" etc. I hope you'll post them. We should try to pin down the facts.<br />