ARES H - yet another ARES alternative configuration concept

[dwightlooi]

<p>This time we go back to 4-segment SRBs and 5 RS-68 engines. However, we use four SRBs and enlarge the upper stage to 400 tons with 2 J-2X engines. Overall, it yields better performance than a 6 engine ARES V with two 5.5 segment solids. In addition, we tender two lighter lift versions. One has two SRBs deleted, whereas the other has the upper stage as well as one core stage engine omitted.</p><p><br /> <br /> <img src="http://sitelife.space.com/ver1.0/Content/images/store/13/6/1d5dd410-06ab-49d7-86b1-c794b7ab6f6d.Medium.jpg" alt="" /><br /><br /></p><p>Full Resolution Illustration here...</p><p>&nbsp;</p><p>I added an accompanying ARES L to replace the ARES I. Honestly, the ARES I concept itself isn't bad. The problem is that it really doesn't make sense make it lift 26 tons and carry a big CEV packed full of equipment that isn't absolutely necessary for transporting humans to orbit to dock with the ISS or a big earth depature vehicle. The entire point of having the super heavy lift ARES H (or ARES V) and a separate crew launch vehicle is so you can have a simple, safe and relatively cheap CLV. All the fancy stuff, long endurance support gear and extended stay supplies should be stuffed into the ARES H launched package. Growing the CLV is a self-defeating proposition.</p><p>This concept is also very simple. We stick to the solid + hydrogen veritcal stack. We go back to the shuttle's 4-segment SRB and halved the size of the upper stage. We stick to the minimum number of engines possible -- an SRB, a single J-2X and a single AJ10-118 for the CTV's orbital maneuver engine. In doing so, we lose about 1/3 of the ARES I's LEO capacity, so the CTV has to be pared down to 16 tons from 25 tons.</p><p>A 16 ton CTV (including orbital maneuvers fuel load) is structurally about 20% heavier than Apollo. Add that to the fact that we are carrying a mere 4 tons of fuel in the CTV vs the 15.5 tons in Apollo, we can afford a crew capsule that is twice as heavy as the Apollo re-entry module. Instead of a 50/50 split between in mass between the crew capsule and service module structural masses, we have a 10 ton capsule and 2 ton propulsions section with a modest 67% fuel fraction. This should be enough for transporting six to orbit and at least equalling a an Ariane V as a cargo vehicle for re-supplying the ISS.</p><p><br /> <img src="http://sitelife.space.com/ver1.0/Content/images/store/12/9/bc19b403-39f1-42cd-993a-5d52d7574051.Medium.jpg" alt="" /></p><p>Full resolution illustration here...&nbsp;</p>

 

[Bytor_YYZ]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>This time we go back to 4-segment SRBs and 5 RS-68 engines. However, we use four SRBs and enlarge the upper stage to 400 tons with 2 J-2X engines. Overall, it yields better performance than a 6 engine ARES V with two 5.5 segment solids. In addition, we tender two lighter lift versions. One has two SRBs deleted, whereas the other has the upper stage as well as one core stage engine omitted. Full Resolution Illustration here... <br /> Posted by dwightlooi</DIV></p><p>&nbsp;</p><p>4 SRB vehicle is non viable.</p><p>The crawlerway, pad and VAB can't support it </p><p>&nbsp; There is nothing new under the sun when using SRB's, RS-68, J-2's etc.&nbsp; All combinations have been looked at already.</p><p>Even crazy <font face="Verdana" size="2" color="navy">Gaetano Marano can put together nonviable Ares configurations</font></p><p>http://www.ghostnasa.com/posts/034ares33.html </p><p>&nbsp;</p><p>Launch vehicles are not LEGO's </p>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>This time we go back to 4-segment SRBs and 5 RS-68 engines. However, we use four SRBs and enlarge the upper stage to 400 tons with 2 J-2X engines. Overall, it yields better performance than a 6 engine ARES V with two 5.5 segment solids. In addition, we tender two lighter lift versions. One has two SRBs deleted, whereas the other has the upper stage as well as one core stage engine omitted. Full Resolution Illustration here... <br />Posted by dwightlooi</DIV></p><p>Who did this design, and where are the calculations that support the design and performance projections ?<br /></p> <div class="Discussion_UserSignature"> </div>

 

[dwightlooi]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Who did this design, and where are the calculations that support the design and performance projections ? <br /> Posted by DrRocket</DIV></p><p><br /> <img src="http://sitelife.space.com/ver1.0/Content/images/store/12/9/6ce7a80d-1988-4046-b99d-379e3353a366.Medium.gif" alt="" /></p><p><br />Full resolution chart here...&nbsp;</p>

 

[kyle_baron]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>This time we go back to 4-segment SRBs and 5 RS-68 engines. However, we use four SRBs and enlarge the upper stage to 400 tons with 2 J-2X engines. Overall, it yields better performance than a 6 engine ARES V with two 5.5 segment solids. In addition, we tender two lighter lift versions. One has two SRBs deleted, whereas the other has the upper stage as well as one core stage engine omitted. Full Resolution Illustration here... <br />Posted by dwightlooi</DIV></p><p>YEAH!&nbsp; I LIKE IT!&nbsp; Although it's probably&nbsp;not official, I've been saying all along, 4 4-segment SRB's.&nbsp; You do realize it will require new crawlers, new crawlerway, and a new launch pad.&nbsp; Not to mention several&nbsp; $Billion in additional funds.<img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-smile.gif" border="0" alt="Smile" title="Smile" /><img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-wink.gif" border="0" alt="Wink" title="Wink" /><br /></p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'> Full resolution chart here...&nbsp; <br />Posted by dwightlooi</DIV></p><p>That looks like a nice summary, but it does not tell me how the figures were calculated, what assumptions were made&nbsp;or what method was used to calculate them&nbsp; Is this your design, or NASA's or someone else's ?<br /></p> <div class="Discussion_UserSignature"> </div>

 

[dwightlooi]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>That looks like a nice summary, but it does not tell me how the figures were calculated, what assumptions were made&nbsp;or what method was used to calculate them&nbsp; Is this your design, or NASA's or someone else's ? <br /> Posted by DrRocket</DIV></p><ul><li>The calculations for each stage's Gross Delta Vwas calculated using the standard <strong>Tsiolkovsky's Ideal Rocket Equation:&nbsp; </strong><em>IpSec x 9.8 x LN (Initial_mass / Final_mass)</em></li><li>Weights are in tons.</li><li>The IpSec of the SRBs and the core stage burn period during the SRBs' burn duration were taken as the average of Sea Level and Vaccuum Specific Impulse of the motors.</li><li>The IpSec of the upper stage and the post SRB separation Core stage burn were taken at the Vaccuum values of the respective engines.</li><li>A correction factor of <strong>0.80</strong> was applied to the final gross number to arrive at the net number to account for aerodynamic and gravity losses. A factor of 0.80 was chosen because applying it to the Shuttle's gross numbers -- calculated using the aforementioned method -- yields ~7700 m/s.</li><li>Burn time was estimated using the specific impulse of the engines, their full thrust levels and the propellant load plus about 10~15 seconds to account for throttling down periods during MaxQ transitions and pre-separation throttling. Basically, it goes like this: <em>(Propellant_load x IpSec / Engine_Thrust) + 10</em></li><li>Checks were performed to ensure that lift off thrust and post staging thrust at the lower portions of the ascent were greater than vehicular mass at that instant.</li><li>A criteria was set that the upper stage thrust to weight ratio has to match or exceed that of the Ariane V ECA's upper HM7-B upper stage (0.20:1). In this particular instance it is more than twice as good (0.46:1), which indicates that even one J-2X will do on the upper stage. However, this will result in a 1220 second burn time which seems excessive even on a regeneratively cooled engine. </li></ul><p>&nbsp;</p><p>&nbsp;</p>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The calculations for each stage's Gross Delta Vwas calculated using the standard Tsiolkovsky's Ideal Rocket Equation:&nbsp; IpSec x 9.8 x LN (Initial_mass / Final_mass)Weights are in tons.The IpSec of the SRBs and the core stage burn period during the SRBs' burn duration were taken as the average of Sea Level and Vaccuum Specific Impulse of the motors.The IpSec of the upper stage and the post SRB separation Core stage burn were taken at the Vaccuum values of the respective engines.A correction factor of 0.80 was applied to the final gross number to arrive at the net number to account for aerodynamic and gravity losses. A factor of 0.80 was chosen because applying it to the Shuttle's gross numbers -- calculated using the aforementioned method -- yields ~7700 m/s.Burn time was estimated using the specific impulse of the engines, their full thrust levels and the propellant load plus about 10~15 seconds to account for throttling down periods during MaxQ transitions and pre-separation throttling. Basically, it goes like this: (Propellant_load x IpSec / Engine_Thrust) + 10Checks were performed to ensure that lift off thrust and post staging thrust at the lower portions of the ascent were greater than vehicular mass at that instant.A criteria was set that the upper stage thrust to weight ratio has to match or exceed that of the Ariane V ECA's upper HM7-B upper stage (0.20:1). In this particular instance it is more than twice as good (0.46:1), which indicates that even one J-2X will do on the upper stage. However, this will result in a 1220 second burn time which seems excessive even on a regeneratively cooled engine. &nbsp;&nbsp; <br />Posted by dwightlooi</DIV></p><p>That is probably a pretty decent first cut. </p> <div class="Discussion_UserSignature"> </div>

 

[docm]

<p>Great!!</p><p><strong>Now</strong> try to convince NASA to use the H420 instead of the Ares 1, putting back all the size & capability they stripped off because it was a weakling POS. ONE rocket instead of two, but with different configurations depending on the mission requirements and with plenty of reserve capability.</p><p>Neh....they'll never do it - too much common sense involved for them.&nbsp;</p> <div class="Discussion_UserSignature"> </div>

 

[rocketscientist327]

<span style="font-size:3pt;font-family:Verdana"><font size="2">... but I still like Direct 2.0 over this.&nbsp; This seems more complicated and does not use the KISS principle.&nbsp; However, that being said, I would take Aries H over what we have now.</font></span> <p><span style="font-size:3pt;font-family:Verdana"><font size="2">I think NASA has a lot of awesome engineers who are slaves to the leadership of NASA and political leaders from both parties who view NASA and it's budget as a cashcow instead of a national treasure.&nbsp; If this kind of thinking continues to permeate NASA and our nation's politicians, NASA will be passed by the private sector or another nation IE China.</font></span></p><p><span style="font-size:3pt;font-family:Verdana"><font size="2">And do not think that China cannot pass the United States and Russia (FSU).</font></span></p><p><span style="font-size:3pt;font-family:Verdana"><font size="2">Respectfully,</font></span></p><span style="font-size:3pt;font-family:Verdana"><font size="2">Rocket Scientist 327</font></span> <p>&nbsp;</p>

 

[trailrider]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>YEAH!&nbsp; I LIKE IT!&nbsp; Although it's probably&nbsp;not official, I've been saying all along, 4 4-segment SRB's.&nbsp; You do realize it will require new crawlers, new crawlerway, and a new launch pad.&nbsp; Not to mention several&nbsp; $Billion in additional funds. <br />Posted by kyle_baron</DIV><br /><br />What is the tank diameter of the Ares H series?&nbsp; If it is 8.4m, then you better write the President and request he issue an Executive Order to HALT dismantling of the Shuttle ET tooling at Michoud.&nbsp; Likewise, if the Shuttle is to be extended, they will probably need additional ET's!</p><p>We need time to rethink this whole U.S. manned space effort beyond the election!</p><p>Ad Luna! Ad Ares! (Mars) Ad Astra!</p>

 

[dwightlooi]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Great!!Now try to convince NASA to use the H420 instead of the Ares 1, putting back all the size & capability they stripped off because it was a weakling POS. ONE rocket instead of two, but with different configurations depending on the mission requirements and with plenty of reserve capability.Neh....they'll never do it - too much common sense involved for them.&nbsp; <br /> Posted by docm</DIV></p><p>Personally, I think that using a 50 ton vehicle to launch a 4~6 person capsule is a waste. This is especially so when it is a vehicle with 4 hydrogen engines, two SRBs and the same risk factor of having SRBs next to the hydrogen tank which&nbsp; did the Challenger in. The ARES I idea of a single SRB and a sngle engine Hydrogen upperstage isn't a bad one. What we need to do is to stop making the CEV bigger and bigger, then enter into a vicious cycle of needing more and more lift capacity. This is what lead to the upper stage growing from 100 ton 125 tons, the launch escape system growing to 2~3 tons and the SRB needing the 5th segment with its potential thrust oscillation issues.</p><p>The idea is not adding spices and condiments to th CEV, all the non-essential stuff should be thrown on the package going up with the ARES V (or whatever it becomes)! I have added an illustration of a 16 ton ARES L vehicle with a 4-segment SRB and a very modest 60 ton upper stage (<strong><em>See the revised opening post</em></strong>). </p>

 

[docm]

Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>What we need to do is to stop making the CEV bigger and bigger, then enter into a vicious cycle of needing more and more lift capacity. <br /> Posted by dwightlooi</DIV><br />That's not the history of Orion/Ares I.&nbsp; The history is that Orion has had to be shrunk several times to compensate for power insuffiiciencies in the Ares I. Not to mention the thrust oscillation problem that almost literally turns Orion into an oversized paint mixer. <div class="Discussion_UserSignature"> </div>

 

[Bytor_YYZ]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'> This is especially so when it is a vehicle with 4 hydrogen engines, two SRBs and the same risk factor of having SRBs next to the hydrogen tank which&nbsp; did the Challenger in. <br /> Posted by dwightlooi</DIV></p><p>That is not an issue for vehicles with an LAS.&nbsp; It is not the same risk factor</p><p>&nbsp;</p><p>&nbsp;</p><p>&nbsp; </p>

 

[Bytor_YYZ]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>This is what lead to the upper stage growing from 100 ton 125 tons, the launch escape system growing to 2~3 tons and the SRB needing the 5th segment with its potential thrust oscillation issues.The idea is not adding spices and condiments to th CEV, all the non-essential stuff should be thrown on the package going up with the ARES V (or whatever it becomes)! I have added an illustration of a 16 ton ARES L vehicle with a 4-segment SRB and a very modest 60 ton upper stage (See the revised opening post). <br /> Posted by dwightlooi</DIV></p><p>&nbsp;</p><p>You have it wrong. &nbsp;</p><p>1.&nbsp; First of all any stick vehicle is just plain wrong.&nbsp; It is a bad design.&nbsp; The velocity split between the stages is skewed.&nbsp; </p><p>2.&nbsp; The 5th segement is not the cause of the&nbsp; thrust oscillation issues. 4 segment SRB's have it too.&nbsp; It is inherent in all solid motors</p><p>3. &nbsp; a "6 ton ARES L vehicle with a 4-segment SRB and a very modest 60 ton upper stage" does not meet Orion's requirements.&nbsp; Also Why build it when EELV's can do the job</p><p>4. &nbsp; Orion is a minimal spacecraft.&nbsp; It does depend on other spacecraft for support.&nbsp; .&nbsp; The Orion doesn't have a real EVA capability (only contingency).&nbsp; The Orion is a parasite on the LSAM for the outbound flight.&nbsp; The LSAM does the LOI </p><p>&nbsp;</p><p>You are making gross assumption about Orion without backing them up </p>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>That's not the history of Orion/Ares I.&nbsp; The history is that Orion has had to be shrunk several times to compensate for power insuffiiciencies in the Ares I. Not to mention the thrust oscillation problem that almost literally turns Orion into an oversized paint mixer. <br />Posted by docm</DIV></p><p>You quote that thrust oscillation "problem" as though it is an established fact.&nbsp; That problem is an analytical projection, based on an extrapolation from 4-segment motors of a 1 psi oscillatioin, using computer modeling techniques that have not been particularly accurate in the past.&nbsp; I think we need real data before we conclude that it is a real problem.<br /></p> <div class="Discussion_UserSignature"> </div>

 

[Bytor_YYZ]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>You quote that thrust oscillation "problem" as though it is an established fact.&nbsp; That problem is an analytical projection, based on an extrapolation from 4-segment motors of a 1 psi oscillatioin, using computer modeling techniques that have not been particularly accurate in the past.&nbsp; I think we need real data before we conclude that it is a real problem. <br /> Posted by DrRocket</DIV></p><p>&nbsp;</p><p>It is a fact as far as that they are modifying the booster and spacecraft&nbsp; </p>

 

[docm]

Absolutely, but given the amount of concern NASA is showing over TO it may well be more "real" than not.&nbsp; It certainly has caused a huge amount of concern among those involved. <div class="Discussion_UserSignature"> </div>

 

[vulture4]

The payload would well below that of the Delta IV-H, which is in srvice, has an existing launch pad, and is seriously underutilized at present, as wellas avoiding some of the potential failure modes of the solids.<br />

 

[dwightlooi]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The payload would well below that of the Delta IV-H, which is in srvice, has an existing launch pad, and is seriously underutilized at present, as wellas avoiding some of the potential failure modes of the solids. <br /> Posted by vulture4</DIV></p><p>Solids in have far less failure modes than liquids. Even an O-ring leakage, like that which caused the challenger accident, is not in and of itself a catatrophic failure. The reason it was a mission ending failure was because of the hydrogen tank next to the SRB. If the plasma jet was away from the LH2 tank for instance the mission would have been successful.</p><p>In terms of sheer number of failure modes, having three parallel liquids is far worse. You have three engines, three sets of turbopump, three hydrogen tanks side-by-side. In terms of costs, three RS-68s and one RL10B-2 is surely more expensive from a bill of materials standpoint than one SRB and one J-2X.</p><p>An all hydrogen lift off wasn't a good idea to begin with. LH2/LOX propulsion is great for maximizing specific impulse. But the tanks are HUGE and the thrust from hydrogen engines of a given size is about 2/3rds to 1/2 that of a kerosene engine and an entire magnitude lower than solids. An all hydrogen rocket can hardly get off the pad! That is why LH2/LOX is typically used in upper stage motors with a hydrocarbon first stage (Saturn V, Atlas, etc), or employed in a 1.5 stage arrangement where by they are assisted by solid strap ons (Ariane V, Shuttle, etc).</p><p>The Delta IV Heavy used three CBCs side by side not because it is efficient, but because it is cheaper due to commonality than using one CBC and a pair of large solids or RP-1 boosters alongside it. </p>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Absolutely, but given the amount of concern NASA is showing over TO it may well be more "real" than not.&nbsp; It certainly has caused a huge amount of concern among those involved. <br />Posted by docm</DIV></p><p>Actually this sort of thing is pretty common.&nbsp; Before you have hard test data a lot of analysis is performed.&nbsp; People are paid to look for problems, the idea being that if you find them early you can correct them before they cause a real failure.&nbsp; That is a good thing.&nbsp; The by-product is that people are not&nbsp;only encouraged to find these problems they are highly motivated to find something.&nbsp; The result is that a lot of potential problems are identified that turn out not to be real.&nbsp; That is not bad, but if you are not used to that environment it makes things sound a lot worse than they probably are.</p><p>Acoustics happens to be an area in which the tools are not all that good.&nbsp; They tend to make predictions that don't turn out to match reality.&nbsp; But until you have test data they are all that is available, so you have to pay attention to the predictions and prepare for the worst.&nbsp; So the designers are doing the right thing, paying attention to the predictions and working on potential solutions.&nbsp; But the problem is probably not as serious as it sounds at the moment.&nbsp; There is always the possibility that the problem is real and serious, and that is why they are identifying design solutions to handle the problem.</p><p>In my experience nearly all the problems like this that are identified come to nothing.&nbsp; The stakes are high enough though that you cannot be complacent and you have to address each one completely.&nbsp; The launch business is not forgiving of failures so you can leave no stone unturned.&nbsp; The level of activity is not indicative of the level of reality of the problem.&nbsp; </p> <div class="Discussion_UserSignature"> </div>

 

[vulture4]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Solids in have far less failure modes than liquids. Even an O-ring leakage, like that which caused the challenger accident, is not in and of itself a catatrophic failure. The reason it was a mission ending failure was because of the hydrogen tank next to the SRB. If the plasma jet was away from the LH2 tank for instance the mission would have been successful.In terms of sheer number of failure modes, having three parallel liquids is far worse. You have three engines, three sets of turbopump, three hydrogen tanks side-by-side. In terms of costs, three RS-68s and one RL10B-2 is surely more expensive from a bill of materials standpoint than one SRB and one J-2X.An all hydrogen lift off wasn't a good idea to begin with. LH2/LOX propulsion is great for maximizing specific impulse. But the tanks are HUGE and the thrust from hydrogen engines of a given size is about 2/3rds to 1/2 that of a kerosene engine and an entire magnitude lower than solids. An all hydrogen rocket can hardly get off the pad! That is why LH2/LOX is typically used in upper stage motors with a hydrocarbon first stage (Saturn V, Atlas, etc), or employed in a 1.5 stage arrangement where by they are assisted by solid strap ons (Ariane V, Shuttle, etc).The Delta IV Heavy used three CBCs side by side not because it is efficient, but because it is cheaper due to commonality than using one CBC and a pair of large solids or RP-1 boosters alongside it. <br /> Posted by dwightlooi</DIV></p><p>The burn-through in the Challanger booster resulted in separation of the booster at the aft attach ring, not a failure mode that occurs in liquids, which can also shut down in a contingency. Second, unlike solids, liquids can be test-fired prior to use and shut down in a contingency. Third, the size of the tanks has little effect on cost. The entire DIV-H can be integrated horizontally with no crane lifts and rolled out to the pad on a rubber tired carrier lighter than the one used for the Orbiter; the SRB powered ELVs required the VAB and crawler, and involve multiple hazardous operations for stacking the booster.. The EELV launches are carried out with a small fraction of the personnel required for SRB-derived vehicles. The recurring costs with either of the EELVs are much lower, and that's what ultimately determines what can be done in a program. </p><p>&nbsp;As to the launch payload, it's difficult to claim the D-IV is hobbled by low thrust when it is in fact capable of launching about 25 metric tons into LEO. While traditionally LH2 fueled engines were considered low in thrust, the RS-68 is by far the most powerful LH2 engine ever built, with a thrust of 3.3 MN, three timed the thrust of the 1.5 meter SRBs used on the Atlas, which of course have a much lower Isp, and twice the thust of the SSMEs, though it has only about 10% as many parts. The use of the common booster core does reduce cost; this is the goal, after all.<br /> </p><p>But the most obvious point is that we already have two _operational_&nbsp; medium-lift ELVs. There is simply no rational explanation to paying the multibillion dollar development cost on yet another, e.g. the Ares I, which must be amortized across a very limited number of launches. The amortizaiton of development costs, the massive support facilities, the complex and hazardous booster stacking, and the number of man-hours required to prepare the vehicle for launch make the Ares much more expensive. </p><p>I cerainly agree that the weight of the CEV could easily be trimmed to be within the payload capability of the Delta IV, or the Atlas V for that matter.&nbsp;</p>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The burn-through in the Challanger booster resulted in separation of the booster at the aft attach ring, not a failure mode that occurs in liquids, which can also shut down in a contingency. Second, unlike solids, liquids can be test-fired prior to use and shut down in a contingency.&nbsp;... <br />Posted by vulture4</DIV></p><p>Yes you can shut down liquids.&nbsp; And then you crash.<br /></p> <div class="Discussion_UserSignature"> </div>

 

[dwightlooi]

<p>Solids and liquids have different failure modes, but liquids have more of them which are catastrophic.&nbsp; For instance, you can grenade the turbomachinery and send a sharpel through the tank causing an immediate explosion. You can also have a sudden loss of thrust during lift off and crash back down and blow up. You can have boil off related overpressure failures. You can have cavitation failure in the fuel lines.</p><p>On solids the only real safety issue that is not matched by similar problems on liquids is that you can't shut it off. But you never want to shut off a rocket once it leaves the pad. If you have to abort, you'll use your launch abort system to blast clear of the vehicle whether it is shut off or not so the ability to shut down an engine is practically irrelevant for safety. As for burn through of the casing or O-rings, you are just as likely to burn through the chamber or nozzle in a liquid engine so that is not really a downside.</p><p>Solids give you a lot of thrust is a very small package. This is what you want on a 1st stage, whose perpose is basically to loft a big enough upper stack off the pad and onto a staging event at a high alitude while being compact enough to have a managably sized vehicle with good aerodynamics during the initial ascent. This is why lower stages focus on thrust density not specific impulse and are usually either Kerosene or Solids. A popular arrangement is to use an oversized hydrogen core stage whose engine thrust is less than the weight of the stage. You strap solids onto it and such that the hydrogen engine can burn off enough fuel so the vehicle is light enough for its thrust level after solid separation. This is the mos efficient 1.5 stage to orbit solution and is used by the Shuttle and the Arianne V.</p>

 

[BrianSlee]

Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Yes you can shut down liquids.&nbsp; And then you crash. <br />Posted by DrRocket</DIV><br /><br />not if your launch system is lighter than air. <div class="Discussion_UserSignature"> <p> </p><p>"I am therefore I think" </p><p>"The only thing "I HAVE TO DO!!" is die, in everything else I have freewill" Brian P. Slee</p> </div>