For every extra kilogram of non-payload mass you carry to orbit, the payload must be decreased one kilogram to offset, and vice versa. Say for example the structural mass of the SM increases; you must then decrease the mass of the remaining payload an equal amount to compensate.
However if you experience mass growth or reduction in components that are jettisoned during ascent, the affect on deliverable payload is much less. For instance, if you save a ton on the LAS this does not mean you gain a ton of extra payload. According to my estimates, every 100 kg of mass saved on the LAS produces only about 8 extra kilograms of payload.
Let’s use your numbers and say the tower LAS has a mass of 6,100 kg and your LAS has a mass of 5,000 kg*. This gains you only 88 kg in payload mass. This 88 kg could easily be eaten up by SM structural changes to accommodate the abort motors, thus yielding no effective change in delivered payload.
(* I am not conceding that your LAS is lighter. I’m using this number as an example only.)
Carrying your abort motors all the way to orbit is the worst thing you can do. Adding a 5,000 kg LAS and jettisoning it during ascent costs you about 400 kg in payload, but carrying it all the way to orbit reduces the payload 5,000 kg.
No Gaetano, a pdf file is what you've seen of it. The design is the hard engineering work behind the results presented in the pdf file. The design isn't finished agreed, but the design process has been going on. Sure you can still alter things, but that doesn't mean it hasn't been thoroughly designed yet. Who knows they've already gone through all things you propose in the design phase. Calling the current Orion a ".pdf design" is failing to recognize the true engineering work behind that pdf. Unlike your articles, it is quite more than a "hey and how about this" design work.Originally Posted by gaetanomarano
Google is a nifty tool. Type in "orion parachute" if you want to know about Orion's parachutes. The first image that turns up is this nice, official, NASA schematic showing the current NASA parachute proposal. The first step reads: "jettison forward heat shield". Note again that the word "proposal" in this context does not mean "hey and what about doing this" but is the result of lots of engineering. It's more than Griffin's napkin. It's the part that survives after the engineering work that showed for example Griffin's napkin idea to be less than optimal. Currently, there are 2 possibilities on the chutes still open (this NASA proposal and Lockheed Martin's proposal), but they differ in drogue/mains methods, materials and 3 or 4 main chutes, not in the forward heat shield being above them. Apparently NASA's proposal has most chances, especially as L-M's proposal uses a material not commercially available. But it's a bit vague, as for example that article is dated next week...Originally Posted by gaetanomarano
No it was an error of reasoning, as explained in the following discussion with bob b and cjl. That discussion brought forth some nice nuances, such as the increased inertia pro/cons and the influence of a larger moment arm on the attitude system. Interesting.Originally Posted by gaetanomarano
I disagree. I don't see arguments allowing for the quantitative results you show. Plus stressing these quantitative results makes them look far more solid than they are.Originally Posted by gaetanomarano
Fine, in that case refrain from make quantitative statements derived from the lack of details.Originally Posted by gaetanomarano
Yes, the air. If you laugh at the idea of the air being a threat to a capsule, please stay very far away from any attempt at designing them. Dynamic pressure forces, friction forces, shock waves, turbulence, friction heat, stagnation heat... anything ring a bell? But hey, let's also not forget that the air isn't a problem for a capsule returning faster from lunar orbit compared to LEO because as you put it so nicely "that's true in first minutes, but the atmosphere quickly slows the capsule". Some more understanding on the subject wouldn't hurt here before proposing "BETTER" designs and slamming NASA who's struggling for a 1 mT cut with your thin air (pardon the pun) 3-4 mT figures.Originally Posted by gaetanomarano
That is only true if your other assumptions are also true, no proof of which is given. You don't know how much lighter IF lighter they will be, no matter how many number you pull out of your hat.since the abort motors in my design are lighter
Why is that a best suggestion? Exactly what is not possible with the tower LAS? Are impact damage chances indeed decreased when detaching engines in stable orbit, so is that indeed absolutely the safest option? What is the weight/performance penalty of bringing these engines (of which you don't know the weight compared to the tower) to stable orbit? And how many rockets have been launched with an escape tower in history, how many of them have had a problem with detaching the escape tower? What's the increased safety of proven concepts?the best suggestion (possible ONLY with my LAS) is to detach them (with the 2nd stage and teh Nose Cone) when the Orion is in its stable elliptical orbit
Yes that's a lot of questions, but a very strong statement needs very strong tests of its validity.
Last edited by gaetanomarano; 2007-Feb-13 at 12:29 PM.
OK here's one for you (but don't try this at home! Intended as a mental exercise only ). Stand on your chair and jump off. *pof*. OK very well. Now stand on your chair again and jump off, but this time stand make sure you land on your head. *splat*. oooooouch.a capsule built to survive a VERY HOT reentry can't be damaged by "aerodynamic forces" or "hot air" in the first 20 km. of the flight
The point is: the capsule returns with its large, nice, thick, ablative lower heat shield first. But it ascends with its top first. And that is why it has a smaller upper heat shield on top. Because you can have all the heat shield you want below you, if the heat's above you it won't help a thing.
The upper heat shield is something different than the BPC. The BPC is there to protect you against the LAS tower firing, against ascent and pre-ascent strikes, to improve the aerodynamic specs of the capsule and as a large (= safer! as you like to put it) protection of the capsule and all its exterior components against all these things, and aerodynamic forces and heating...
Your velocity claim is wrong and incomplete. Let's take saturn V -the only other moon rocket- as comparison.
Saturn V reaches 500 m/s, or 1800 km/h, already at 2 km altitude. That is already as fast as a concorde, which starts having some very intriguing heat problems at that velocity, better aerodynamical shape and 20 vs 2 km altitude. Do I need to point out the difference in aerodynamic pressure between 20 and 2 kilometers altitude? The hottest part of an object moving through air is the nose, in this case the location of the upper heat shield. Apollo got a maximum aerodynamic pressure of 36.000 N/m². That's the same as the maximum an SR-71 Blackbird got. When an SR-71 landed, it was still so hot you couldn't touch it. Max Q was limited by the windows blowing out due to the expanded hot metal of the cockpit (!). We're talking about several hundred degrees Celcius here, 400°C is a good estimate. That is just stgnation temperature of the air at 3300 km/h. Note that Saturn V went faster during part of the ascent. It may be clear that the upper heat shield located on the nose of the capsule can be very useful in preventing this top heat from penetrating to deep into the capsule. Max Q can be taken as an indication of stagnation heat and as it is velocity dependent also gives a rough indication of friction heat.
The fact that you put "aerodynamic forces" and "hot air" in brackets is a striking example of your underestimation of the issue. Learn first, and tell NASA how to improve things later. A wild guess that turns out to be correct is worth less than understanding why something is wrong.
'nuff said and pardon for the long edit time.
Last edited by Nicolas; 2007-Feb-13 at 03:14 PM.
Nicolas has also provided some excellents reasons for the inclusion of a BPC.
I've changed a units mistake in my previous post. Point remains that during ascent, the stagnation temperature of the outside air becomes 400°C already at 3300 km/h.
you don't need to post the obvious... the SAFEST option (detach the abort motors in orbit) can be adopted ONLY if (thanks to a lighter Orion+SM+LAS) Ares-I will be able to put in orbit ALL THE REQUIRED PAYLOAD and (also) the small LAS motors ...of course, if Ares-I can't do that, the small abort motors must be detached in-flight a few seconds after the 2nd stage engine ignition (as planned in the current Ares-I flight) ...the giant mass' saving of my Orion+SM+LAS design can be used to... a) add more payload, or... b) increase the Orion's safety... well, since the payload launched will be sufficient, I suggest to use this huge mass' saving to increase the Orion's SAFETY...every extra kilogram of non-payload mass you carry to orbit, the payload must be decreased one kilogram...
no, this is not the weight of "my" LAS ...its only the mass of a tower-LAS for my (8 mT) TBS-Orion ...the weight of "my" LAS may be around 2.5-3.5 mT and the total (TBS-Orion + new-LAS + smaller-SM) mass may be around 20-21 mT (less than the max payload the Ares-I can lift to orbit) then, the Ares-I can send in orbit (both) "my Orion AND "my" LAS...use your numbers and say the tower LAS has a mass of 6,100 kg and your LAS has a mass of 5,000 kg...
worst but SAFESTCarrying your abort motors all the way to orbit is the worst thing you can do.
"my" LAS may weigh 2.5-3.5 mT and it's main purpose is NOT to carry more payload, but (thanks to smaller Orion and SM) to launch Orion with a smaller and cheaper rocket ...now the total (Orion+SM+propellent+LAS) mass is over 27 mT ...with my design the total mass may fall under 22 mT to launch the LUNAR-TBS-Orion with a smaller Ares-I or a Delta IV Heavy or an Ariane5 or a new AtlasV or a future Falcon or, or, or, or... (and an ORBITAL-TBS-Orion with a much smaller rocket!)...a 5,000 kg LAS...
no, despite the animation may suggest it, the protection panel never is detached ...only the four small motors are detached...a TPS protection panel that appears to detach along with the abort motors...
no, I've used the "panel" just as example ...the abort motors can be (simply) joined to the structure between the Orion and SM (so far we don't know how exactly it will be, so, I can't give any detailed suggestion)...then its mass reduces the payload...
Last edited by gaetanomarano; 2007-Feb-14 at 03:27 AM.
Nose cone with attitude control system
Attitude control propellant mass
Boost protective cover
TPS protection panel
Abort motor mass
Abort motor propellant
Jettison motor mass
SM structural modifications
agreed! ...it's a nice image! ...for schools... (and press releases) ...like other images I've seen, it's only the (official) sketch of a proposal... NOT a project... the final design CAN be different...first image that turns up is this nice, official, NASA schematic showing the current NASA parachute proposal...
the Attitude Control Motors can be placed in another position (IF necessary) like (e.g.) the top of the abort motors...on the attitude system...
just imagine that everything in a tower-LAS is made of similar materials... then, cut 40-60% of the tower-LAS volume (and mass...)...don't see arguments allowing for the quantitative results you show...
why? ...we don't have detailed specs ...but we know (at least) the tower-LAS dimension and mass ...it's sufficient to do some evaluations...refrain from make quantitative statements...
forces/problems aerospace engineers must face (an solve) everytime they design a supersonic jet or a spacecraft...dynamic pressure forces, friction forces, shock waves, turbulence, friction heat, stagnation heat..
what is uncorrect in my claim? ...the atmosphere slows the lunar capsule from 40,000 km/h to 500 km/h in a few minutes ...never said that a capsule can do that without be properly designed for a direct reentry from the moon...as you put it so nicely "that's true in the first minutes, but the atmosphere quickly slows the capsule"...
correct (and my opinion is that my assumption are very close to reality)...true if your other assumptions are also true...
that's true... I can give more accurate evaluations/calculations when NASA and LM will release DETAILED specs of the tower-LAS...don't know how much lighter...
in my opinion it's less risky to detach the LAS motors Orion in orbit than in-flight (it's SAFER like exit from a car when it stops rather than running at 200 mph...)Why is that a best suggestion?
because "my" Orion AND "my" LAS (with a smaller SM and less propellent) are under 21 mT (the Ares-I payload) while, to carry in orbit the tower-LAS, the Ares-I payload-to-orbit must be over 27 mTExactly what is not possible with the tower LAS?
Concorde or less than 65% of the max [Mach 2.5] speed of an F-15 Eagle or less than 60% of the max [Mach 2.83] speed of a MiG 25...) at 12 km. of altitude while it will reach Mach 6.08 (less than 90% of the max [Mach 6.85] speed of the '50s X-15...) at 60 km. of altitude... and I'm sure that NASA and LM engineers will be able to build (with to-day's advanced materials and alloys) an Orion as good as a '50s X-15...
Which is even closer to the cg, requiring even more performant engines.the Attitude Control Motors can be placed in another position (IF necessary) like (e.g.) the top of the abort motors
Nothing is uncorrect in your claim, it's just very strange to use the "slowing down very fast in the atmosphere" as an argument why heating would not be a problem compared to LEO, as your original argument seemed to be.what is uncorrect in my claim? ...the atmosphere slows the lunar capsule from 40,000 km/h to 500 km/h in a few minutes ...never said that a capsule can do that without be properly designed for a direct reentry from the moon
Well, you'd better be a tad bit more sure about it as reality doesn't care about opinions and assumptions. You come with extreme mass figures, far better than anything NASA can do, it would only be polite to give them some basis. But Bob B already asked a question on that.correct (and my opinion is that my assumption are very close to reality)
Then, as I said over and over again, refrain from throwing quantitative estimates as semi-facts.that's true... I can give more accurate evaluations/calculations when NASA and LM will release DETAILED specs of the tower-LAS
Again reality doesn't care about opinions. WHY is it safer? And how about the track record of tower LAS detachments, how's the safety of thoroughly tested and proven hardware compared to new hardware?in my opinion it's less risky to detach the LAS motors Orion in orbit than in-flight (it's SAFER like exit from a car when it stops rather than running at 200 mph...)
Again this is an argument (the new LAS is safer) based on an assumption (the new LAS is lighter, 6 tons lighter(!) ) which you haven't verified yet, and in this case you haven't even verified the "safer" argument itself. You just think it's safer with no argument other than a car analogy (?) and for that you take a mass assumption as a given. BTW I can butcher your car analogy easily to prove the opposite: lightly throw a can out of the roof window of a car at 200 mph. bye-bye can. Lightly throw a can out of the roof window of a car standing still. Good chance it hits the roof. So please provide arguments that are based on the actual physics of ascent detachment versus in orbit detachment and show the latter is safer, indeed that much safer that it justifies the weight penalty (and don't fall back on unproven quantitative mass assessments to say in the end it's still lighter, as you DON'T KNOW that).because "my" Orion AND "my" LAS (with a smaller SM and less propellent) are under 21 mT (the Ares-I payload) while, to carry in orbit the tower-LAS, the Ares-I payload-to-orbit must be over 27 mT
[I'm glad quoting removes the bulk of formatting]as you can see from the flight profile image (below) the Ares-I will reach Mach 1.61 (less than 80% of the max [Mach 2.04] speed of a Concorde or less than 65% of the max [Mach 2.5] speed of an F-15 Eagle or less than 60% of the max [Mach 2.83] speed of a MiG 25...) at 12 km. of altitude while it will reach Mach 6.08 (less than 90% of the max [Mach 6.85] speed of the '50s X-15...) at 60 km. of altitude... and I'm sure that NASA and LM engineers will be able to build (with to-day's advanced materials and alloys) an Orion as good as a '50s X-15...
Thanks for posting that graph, I didn't find it so based myself on Saturn V data.
OK so let's take mach 6 at 60 km. Let's take NASA's X-15 measurements. At Mach 6, the stagnation temperature was around 2500°C. This is the temperature that would exist were the flow slowed down to standstill. This doesn't happen -the slowdown isn't complete- but still there will be a huge temperature increase. 650°C has been probed at mach 6, and that is for a nice aerodynamic design. The windshield has cracked due to the heat. The X-15 had an advanced heat protection system, in case of model 2 even an ablative one. They don't put on an ablative heat protection system just for fun. The leading edges had a different, even more heat resistent material. This setup indeed makes you think of the upper heat shield on Orion.
This is a nice NASA quote:
Don't you think this is an excellent argument for the BPC? Don't you think the high temperatures -650°C skin temperature for X-15 at mach 6- are what requires a top heat shield, and the chutes -a very critical system featuring gaps in the surface- are protected behind that heat shield because they need to be protected against heat channeling as described in the quote?An important lesson learned from the X-15 was that small gaps or protrusions on the surface of the aircraft can get extremely hot and can act like a blowtorch, channeling high-temperature gas into areas that could be damaged, like the wells around the landing gear.
This is what was the importance of the discussion: the need of a BPC and upper heat shield. You've provided the relevant flight conditions, but you didn't draw the conclusion.
Yes they will be able to build it. But they will require the BPC and upper heat shield.
Honestly, the reason I prefer NASA's solution over Gaetano's is because NASA has a proven track record of successful aerospace analysis, design, and operations. I think they've earned the right to simply publish a .pdf of their conclusions, without having to show their work, and have it accepted provisionally by the rest of us.
Gaetano has no such track record, so I would very much like to see the work that led to his conclusions.
It is my impression you have seen it.
I do hope to be corrected on this one.
heating is not a problem for a (properly designed) Orion or TBS-Orion (that is mainly a resized lunar-Orion with lunar-TPS)...heating would not be a problem...
a tower-LAS is not made of titanium in some parts and of cotton in other parts... starting from the known tower-LAS' dimensions and mass, I've just made some reasonable evaluations...extreme mass figures...
(reasonable) "semi-facts" are better than nothing to evaluate and discuss a proposal...semi-facts...
my opinion is that it's safer to detach the abort motor without any (LAS or rocket) engine burning (and the example of the car explains why I think that)WHY is it safer?
as I've said many times, carry the small LAS motors can happen only if the max mass reduction will be possible, of course...you haven't verified yet...
I really WONDER you don't see HOW MUCH SAFER is throw your can when the car stops! (especially if your car will be damaged by a can throw out at 200 mph...)...lightly throw a can out of the roof window of a car at 200 mph. bye-bye can. Lightly throw a can out of the roof window of a car standing still...
why? ...your "car and can at 200 mph" example is fine......please provide arguments that are based on the actual physics...
true, I can't know it now, but I suggest to adopt this (safer, in my opinion) option ONLY if the final TBS-Orion will be very light and the Ares-I can lift that (unused) extra-payload...mass assessments to say in the end it's still lighter, as you DON'T KNOW that...
until burn the 2nd stage engine at 80 km. of altitude, the Orion will fly just A FEW SECONDS (probably less than 30 sec.) at (both) Mach speed AND dense atmosphere (to have more friction and high temperatures) while the X-15 flight (from B-52 drop) duration was up to 11 MINUTES at speeds near Mach 7 and GREAT PART in the dense atmosphere plus (probably) also with more inclination (since the X-15 was a winged rocketPLANE, not just a rocket) ...but, assuming that your "650°C" figure for the peak Orion temperature may really come true, it will be LOWER than the max external temperature the Orion (including the parachutes' shell) will reach (for much more time) at reentry, due to the hot plasma... and I'm sure that NASA and LM engineers (with 2010's [X-15 + 50 years] advanced technology) will be able to give a proper protection to your (so far, just supposed) "capsule gaps" (a pure guess, since the Orion doesn't exist) WITHOUT build for it a second, larger and useless (1-2 mT) metallic capsule duplication that covers the Orion like a giant (and heavy) space-condom......650°C...
Last edited by gaetanomarano; 2007-Feb-14 at 10:28 PM.
Boost Protective Cover ...... kg.
Adapter Cone ...... kg.
Abort Motor ...... kg.
Abort Motor propellent ...... kg.
(each) Interstage ...... kg.
Jettison Motor ...... kg.
Canard Section ...... kg.
Attitude Controls Motors ...... kg.
Nose Cone ...... kg.
As I’ve attempted to explain, the mass penalty of carrying the abort motors to orbit is dramatic compared to jettisoning them during ascent. If your goal is to save weight, carrying the abort motors to orbit is certainly counter to that objective.
Last edited by Bob B.; 2007-Feb-14 at 11:48 PM. Reason: spelling
that's true, infact I suggest to add that extra-safety ONLY if the TBS-Orion and the new-LAS will be adopted AND the mass' saving will be over 6 mT AND the Ares-I will be able to lift the planned 22+ mT payload to carry in orbit BOTH the required (lighter but full functional) Orion's paylaod AND the smaller new LAS ...if one of these conditions can't be achieved, the suggested extra-safety can't be added...If your goal is to save weight, carrying the abort motors to orbit is certainly counter to that objective.
In fact, your proposal is far riskier from a detachment standpoint because you have at least two components that must be jettisoned while the tower is only one piece.
That does not go into the remark that when placed closer to the cg, the performance needs to increase.rockets, LEM, LAS and SM all have attitude control jets and, for every kind of vehicle (and cg) the engineers can put them where they think (and tests showes) is the right place
You've only showed that the cars "analogy" can be used to prove anything (safer/not safer). I ask you again, work with the actual physics of being in stable orbit versus ascent. There are some important arguments to be made that are quite lost in the car "analogy".cars cars cars
-re-entry works on the bottom of the capsule. Ascent on the top. I've explained that before. Assume the max skin temperature is for example 400°C instead of 650°C. Still requires an upper heat shield in any case, and depending on the capsule design it could use a BPC against heat channeling.until burn the 2nd stage engine at 80 km. of altitude, the Orion will fly just A FEW SECONDS (probably less than 30 sec.) at (both) Mach speed AND dense atmosphere (to have more friction and high temperatures) while the X-15 flight (from B-52 drop) duration was up to 11 MINUTES at speeds near Mach 7 and GREAT PART in the dense atmosphere plus (probably) also with more inclination (since the X-15 was a winged rocketPLANE, not just a rocket) ...but, assuming that your "650°C" figure for the peak Orion temperature may really come true, it will be LOWER than the max external temperature the Orion (including the parachutes' shell) will reach (for much more time) at reentry, due to the hot plasma... and I'm sure that NASA and LM engineers (with 2010's [X-15 + 50 years] advanced technology) will be able to give a proper protection to your (so far, just supposed) "capsule gaps" (a pure guess, since the Orion doesn't exist) WITHOUT build for it a second, larger and useless (1-2 mT) metallic capsule duplication that covers the Orion like a giant (and heavy) space-condom...
-inclination is not the most relevant for the max temperature. Maximum slowdown of air is more relevant. This will be less for X-15, which is nicely aerodynamically shaped, than for Orion, which is a simple cone.
-Please refrain from rebouncing arguments used against your claims when not applicable. Addressing the danger of possible heat channeling for Orion is not "a pure guess", as any capsule has small and large gaps, protrusions and the like. From the top of my head some possibilities:
* venting holes
* parachute outlets
* attitude control systems
In short, anything other than a smooth, flat, seamless shape is a candidate for heat channeling problems. That's why the shuttle is loaded with filler materials (and we've seen the safety of those...). That 's why a BPC is handy (along with other reasons in favor of a BPC): it temporarily makes the capsule more smooth and seamless, without making the design of the capsule itself more difficult and heavy (the shell will be heavier than the nomex system it features now), and on top of that is a heat protection layer in itself. A realistic capsule design, especially one that should be light while in space, has loads of things that could trigger heat channeling or shouldn't become too hot in general. That is not a "pure guess" or "just supposed", but the reality as seen in any capsule designed thus far. Yes, a capsule could be designed to perform fine without a BPC. This means that the capsule itself has to be designed such that there were no heat channeling problems or parts prone to overheating, and all additional weight from these features would have to be carried all the way to the moon, unlike a BPC which is used when required and then gotten rid of. Your aptly called space condom, also called fairing or in this case BPC, is what is seen in all launchers I could think of, except for the shuttle (which works with the tile mess). That may be because it's a good (as in feasible) approach, no? After all, when having a BPC (you need an upper heat shield on the capsule anyway, unless you would totally decouple the capsule, as sats inside a fairing are), you can design your capsule less stringent, hence have less package weight going to the moon, and who knows even end up with a lighter design in total. Where in your reasoning do I see the capsule weight penalty of designing a capsule such that it can withstand ascent without BPC? A weight penalty that goes all the way to the moon. Where do you address the other advantages of having the BPC, such as the previously summed up protective features and aerodynamic improvement it offers, such as impact protection? The BPC is not ONLY there to protect against the tower firing. Let's not forget that Griffin's proposal, which did not have a BPC, was found less optimal than a tower with BPC. Not saying this is solely due to the BPC or even despite the BPC. But it is something to remember.
Again a huge lack of pro/con in your argumentation. Your proposals are presented as pro/pro/pro only (or con/con/con the other alternative). A good designer thinks of the cons of his own design as well, and is willing to present them.
I don't know the numbers on mass penalty of a BPC, a capsule that has to take care of heat channeling issues itself, and the overall penalty of taking this mass all the way versus only durin ascent for the BPC. NASA has far more data on this and knowledge to assess this, and in the end they decide to go for a BPC. If they had seen ways of saving 1 to 2 mT just by redesigning to a non-BPC craft, they would have done so. Apparently they found no such way. And assuming that is because they're not smart enough to come up with any general idea remotely like your proposal is less likely and more arrogant than assuming your proposal does not live up to the advantages it seems to offer on first sight. The same goes for the other tons of savings you propose. Sure the Orion can be designed lighter. But the simple multiton saving proposals of yours are far likely unrealistic than simply not thought of by the NASA engineers. Though unlikely, one person can come up with an idea a whole team overlooked. 5-6 tons worth of overlooked ideas on the capsule and LAS alone, is more than extremely unlikely though.
Last edited by Nicolas; 2007-Feb-14 at 11:57 PM.
You have yet to show your assumptions are reasonable before they're fit for any evaluation.(reasonable) "semi-facts" are better than nothing to evaluate and discuss a proposal
And then there's things such as ease of initial separation and continued separation, which you didn't address at all.also, the risk doesn't come from the rocket's speed but from the relative speed between the Orion-"car" and the LAS-"can"
Note that the 1-2mt "space condome" Gaetano speaks of in reality will be closer to 700-1000 kg (majority of the thermal protection system + part of the strucural weight, I assumed 20-50%, thoug hI think 50% is quite a large estimate). Apollo's BPC was 318 kg, for Orion's LAS it's a bit hard to tell at the moment as the total system's weight assessment is split in things such as "thermal protection" and "structure".
I read too much articles, blogs, posts, documents, webpages, .pdf, etc. ...and sometime my CPU goes to overload...
I've (and download every day) dozens of links, images and pages, so, I've too much files to remember and consult...
when I've made the newLAS' article, I've searched in my database the image of a detailed LAS, found in a .pdf file...
but the LAS' image I've found was without any data about the mass of parts and I've founded my article only on it...
that despite I've the RIGHT image (below) from six months on a .pdf file of the Aug. 2006 Orion's press conference... :surprised
so, I've guessed, guessed and guessed about the LAS parts' mass, while, the full (or sufficient) data was available...
then, after the Bob B. "remember bell" I've searched on the web and found the image that already was on my HDD... (smile/image #9 not allowed: rolleyes)
ok, I'm sorry ...then... << REWIND...
from the (standard Orion) tower-LAS image we have these specs:
tower-LAS GLOW: 6,176 kg.
tower-LAS dry mass: 3,696 kg.
tower-LAS propellent: 2,480 kg. (that include the Jettison Motor propellent)
from the tower-LAS propellant mass we can do an evaluation of the four small Abort Motors GLOW (including motors' case & nozzle) for the STANDARD 9.5 mT Orion, by comparison with other solid rockets like the Delta GEM-60 that has:
33.8 mT GLOW
29.5 mT propellent
3.85 mT dry mass (about 10% the weight of the full rocket)
then, the four motors of "my" LAS for a standard Orion may weigh 2,480 kg. + 248 kg. = 2,728 kg. in total
while, the four motors of "my" LAS for a (15% lighter) 8 mT TBS-Orion may weigh less than 2.3 mT (only!!!)
of course, we must include the LAS/Orion Nose Cone and LAS Attitude Jets dry mass (maybe, 0.5 mT) and we have that...
>>>>>>>>>> "my" LAS weight is 2.8 mT <<<<<<<<<<
EXCELLENT RESULT !!!
...and excellent mass' saving over the 6.1 mT tower-LAS !!!
Last edited by gaetanomarano; 2007-Feb-16 at 01:28 AM. Reason: text fix
I’ve been thinking about the two LAS proposals and I can find absolutely no way to justify Gaetano’s outrageous mass saving claims. Gaetano’s design is more or less a simple reconfiguration of the LAS components. Claiming a mass reduction of 50% is just not credible.
Here is a breakdown of the major components of the tower LAS and my evaluation of how they measure up to the comparable parts of Gaetano’s underside LAS…
Both systems require a nose cone, but the tower nose cone is much smaller than the Gaetano’s capsule nose cone.
Both systems require attitude control but the tower configuration is favorable due to its longer moment arm. The tower can achieve the same torque with smaller thrusters and less propellant.
Extending the canard provides drag that causes the capsule to turn around and stabilize into a blunt end forward attitude. Gaetano has eliminated this, thus the same function has to be performed by the attitude control system. I’ll call the mass of the canard versus the extra propellant a wash, but I’ll give the advantage to the canard for simplicity and reliability of design.
See post #364 for revisions and/or additional comments.
The tower includes several interstage adapters that Gaetano’s design does not require, however the underside configuration will require a small enlargement of the Service Module to accomodate the abort motors. I’ll call it a wash.
Gaetano’s design does not require the adapter cone, though it does need a larger nose cone (see nose cone above).
BOOST PROTECTIVE COVER
Despite Gaetano’s denial regarding the need for a BPC, both designs will require it as nicely explained by Nicolas.
Gaetano claims no jettison motors are required but I cannot accept this. The abort motors will have to be thrown clear of the launch vehicle at jettison to avoid a possible collision. This might be achieved by spring mechanisms, but the issue cannot be simply ignored.
See post #364 for revisions and/or additional comments.
I’m seeing no clear overall mass advantage to either design; therefore both will require essentially the same amount of abort propellant. Both designs have four nozzles and I see no edge to either in casing weight (one large vs. four small casings).
Furthermore, let’s consider the following…
TPS PROTECTION PANEL
This is something Gaetano has added to his design that is not required in the tower design. Since this panel cannot be jettisoned it must be carried to orbit and all the way to the Moon. This results in a significant weight penalty to the underside design.
I see the tower as the more stable configuration due to its higher moment of inertia and the respective locations of the center of mass and center of pressure.
Last edited by Bob B.; 2007-Feb-15 at 02:27 PM. Reason: as noted