Fifth is the fact that the SRB's were never designed to be utilized in this fashion with hundreds of tons of stage and payload on top. They just weren't designed for these loads.
Quote from: kraiseeFifth is the fact that the SRB's were never designed to be utilized in this fashion with hundreds of tons of stage and payload on top. They just weren't designed for these loads.Why are these loads a big issue for the SRB, but not for Jupiter's ET-based core stage? Is it because the core (being mostly tanks holding the liquids) can be redesigned to handle the loads, but the SRB can't be modified similarly?
... If you want a reasonably detailed description of the sorts of changes required, I refer you to this public document:-http://hdl.handle.net/2060/19930007493The first 600 pages or so detail all the changes which are required to make each part of an ET into an NLS Core Stage.But from page 611 onwards there is a really *great* description of how NLS was planning to modify the existing tooling -- and that gives you a glimpse into what's really involved in what they do day-to-day at Michoud...Ross.
Those wikipedia numbers represent the gross performance numbers without margin, and to the sub-orbital -11x100 "injection" point, not to the final orbit.If you work it out that way (which is a plain stupid way I might add) Ares-I is supposedly able to lift 23,151kg for ISS missions and 25,573kg for Lunar -- but only to "injection", and without accounting for any performance margins at all.Once you apply industry-standard margins and deduct the propellant used by the SM to achieve full orbit, you aren't delivering anything like that amount of actual payload to a useful orbit (220nmi circular, 51.6deg for ISS and 130nmi circular, 29.0deg for Lunar).The 23mT and 25mT are really just meaningless "sales speak" figures. Yeah, your car might be rated by the manufacturer at "125mph maximum", but if you need five miles of dead-straight downhill road to ever actually achieve it is that really an accurate statement?The Ares-I will never, ever, ever be able to lift that amount of mass to stable orbit in practice. No way, no how.Every other rocket in the world quotes its final delivered performance to stable orbit, and states it after the routine margins have been accounted for.
But Ares-I keeps on deliberately conning everyone because they hope nobody understands what they're actually looking at. They refuse to reveal the apples-to-apples comparisons and instead persists in this practice of only ever publishing the "theoretical maximum" which they know the system will never actually be able to achieve in the real world.Why is that?
Because once you knock the industry-standard 10% margin off those figures and once you account for the propellant which the Orion needs to burn in order to achieve its final orbit, the final delivery performance is no better than the Delta-IV Heavy.
And CxP daren't risk anyone noticing that they're spending $14 billion of your tax dollars on a rocket which can't actually match our existing capability!
So lets actually work it out and see what the truth REALLY is...***The result is that the maximum *REAL WORLD* mass delivered by the Ares-I/Orion system is no more than 19,628kg to 220x220nmi, 51.6deg.
Delta-IV Heavy can directly insert the Orion spacecraft straight into that 220nmi circular orbit without Orion having to perform any of those extra burns. And DIVH can actually deliver a little over 21,000kg to that exact same orbit in its Crew-launch configuration *after* it has successfully accounted for all its margins too. That's the real apples-to-apples comparison 19.6mT for Ares vs. 21.0mT for Delta.
But Ares keeps on claiming "23 metric tons" or "25 metric tons". They are successfully pulling the wool over many people's eyes with that claim because nobody understands the rocket science sufficiently well enough to disprove the claim.
They can try all they like to make it appear that Ares-I is more capable than the existing Delta system. But the physics don't lie. It is clearly not the truth.
1. Negative 11 nm x 100 nm is not an orbit - it's a crash and it's not useful for anything. It takes you 11 nautical miles beneath the surface of the earth.
Quote from: kraisee on 01/13/2009 04:25 amFifth is the fact that the SRB's were never designed to be utilized in this fashion with hundreds of tons of stage and payload on top. They just weren't designed for these loads.Why are these loads a big issue for the SRB, but not for Jupiter's ET-based core stage? Is it because the core (being mostly tanks holding the liquids) can be redesigned to handle the loads, but the SRB can't be modified similarly?Steve
[...] all remind me of a certain Italian that needs to stay off the internet.
Quote from: Lobo on 01/12/2009 11:41 pm The SSMT was never designed to carry payload on it's nose, or have rocket engines under it, with all the avionics that entails. Modifying to to do that could be as expensive and problematic as building a new chasis from scratch that -is- designed for it.Not true.The ET (not MT) to Direct core is not the same as F-15 to stealth fighter.It is more like F-15 C/D to F-15E.The same assembly jigs and tooling can be used for both. Skin thicknesses are the basic differences. New domes on the LO2 and LH2 tanks are basically the same as the remaining ones on the tank. The thrust structure and forward adapter are not hard items to build. Avionics has no bearing, new avionics is being designed for Ares I which would be adapted
The SSMT was never designed to carry payload on it's nose, or have rocket engines under it, with all the avionics that entails. Modifying to to do that could be as expensive and problematic as building a new chasis from scratch that -is- designed for it.
Quote from: mrbliss on 01/13/2009 02:51 pmQuote from: kraisee on 01/13/2009 04:25 amFifth is the fact that the SRB's were never designed to be utilized in this fashion with hundreds of tons of stage and payload on top. They just weren't designed for these loads.Why are these loads a big issue for the SRB, but not for Jupiter's ET-based core stage? Is it because the core (being mostly tanks holding the liquids) can be redesigned to handle the loads, but the SRB can't be modified similarly?Steve, and comments of the "truth" all remind me of a certain Italian that needs to stay off the internet.Marc
Those wikipedia numbers represent the gross performance numbers without margin, and to the sub-orbital -11x100 "injection" point, not to the final orbit.If you work it out that way (which is a plain stupid way I might add) Ares-I is supposedly able to lift 23,151kg for ISS missions and 25,573kg for Lunar -- but only to "injection", and without accounting for any performance margins at all.Once you apply industry-standard margins and deduct the propellant used by the SM to achieve full orbit, you aren't delivering anything like that amount of actual payload to a useful orbit (220nmi circular, 51.6deg for ISS and 130nmi circular, 29.0deg for Lunar).The 23mT and 25mT are really just meaningless "sales speak" figures. Yeah, your car might be rated by the manufacturer at "125mph maximum", but if you need five miles of dead-straight downhill road to ever actually achieve it is that really an accurate statement?The Ares-I will never, ever, ever be able to lift that amount of mass to stable orbit in practice. No way, no how.Every other rocket in the world quotes its final delivered performance to stable orbit, and states it after the routine margins have been accounted for.But Ares-I keeps on deliberately conning everyone because they hope nobody understands what they're actually looking at. They refuse to reveal the apples-to-apples comparisons and instead persists in this practice of only ever publishing the "theoretical maximum" which they know the system will never actually be able to achieve in the real world.Why is that?Because once you knock the industry-standard 10% margin off those figures and once you account for the propellant which the Orion needs to burn in order to achieve its final orbit, the final delivery performance is no better than the Delta-IV Heavy.And CxP daren't risk anyone noticing that they're spending $14 billion of your tax dollars on a rocket which can't actually match our existing capability!So lets actually work it out and see what the truth REALLY is...ISS:-23,151kg is Ares-I's maximum theoretical performance. So start by knocking this down to 90% to cover regular 10% margins: 20,836kg is therefore the actual *practical* maximum payload mass which the system can insert to -11x100nmi, 51.6deg.Orion must then circularize to 100x100nmi or it will be heading straight back to Earth. Using a Hohmann Transfer, that requires a 62.241m/s burn, assuming Orion masses the full 20,836kg at the start and that its engine is 326.0s vac Isp, and ignoring any wasted propellant used during the engine start sequence, Orion will use 402kg of propellant to perform Burn #1. Total mass now drops to 20,434kg to 100x100nmi, 51.6deg stable initial orbit.Now the Orion needs to boost its orbit ready for a rendezvous with the ISS which usually has a nominal orbital altitude of 220nmi circular. Another two Hohmann burns are therefore required. Burn #2 is 64.603m/s and uses another 409kg of propellant leaving 20,025kg total Orion mass. Burn #3 is then a 64.068m/s burn using another 397kg of propellant.The result is that the maximum *REAL WORLD* mass delivered by the Ares-I/Orion system is no more than 19,628kg to 220x220nmi, 51.6deg.Not quite as impressive as the 23 metric tons they keep telling us, is it? In fact the true apples-to-apples comparable performance of the system is actually only 85% of the figure which they keep telling us. I think deliberately and continually over-quoting things by 15% is rather deceitful myself.There are laws in most industries clearly saying that if you market a product as one thing, say a bar of Milk Chocolate clearly marked as 1kg in weight, and the customer takes it home and finds there's only 850 grams of chocolate inside they have a legal claim to get their money back. I consider this a very similar situation, albeit at a much more expensive level.Delta-IV Heavy can directly insert the Orion spacecraft straight into that 220nmi circular orbit without Orion having to perform any of those extra burns. And DIVH can actually deliver a little over 21,000kg to that exact same orbit in its Crew-launch configuration *after* it has successfully accounted for all its margins too. That's the real apples-to-apples comparison 19.6mT for Ares vs. 21.0mT for Delta.But Ares keeps on claiming "23 metric tons" or "25 metric tons". They are successfully pulling the wool over many people's eyes with that claim because nobody understands the rocket science sufficiently well enough to disprove the claim.They can try all they like to make it appear that Ares-I is more capable than the existing Delta system. But the physics don't lie. It is clearly not the truth.Anyway, I digress. That was totally off-topic...Ross.
There are actually over 160 other documents like that one publicly available on ntrs.nasa.gov dealing with similar Shuttle derived systems, be those NLS, ALS, Shuttle-C and whatever.Not one of NASA's studies prior to 2004 ever mentioned a "Stick" configuration like Ares-I. And none ever tried to propose a Shuttle-derived configuration as ridiculously large as Ares-V has become.It is my opinion that a Shuttle-derived solution needs to at least retain the 4-seg SRB's and the 8.4m tank to qualify as "Shuttle Derived". If there's less than 25% of the system actually with real heritage back to Shuttle, its not very honest to try to claim its Shuttle Derived any more.If you bought a car from a dealer and later found that only 10% of it was actually the original car identified by the VIN plate, you'd have an open-and-shut case for getting your money back.I believe we represent the evolution of the "horse we are riding" today -- which I will remind everyone is *Shuttle*, not Ares.Ross.
Quote from: Jim on 01/13/2009 12:13 amQuote from: Lobo on 01/12/2009 11:41 pm The SSMT was never designed to carry payload on it's nose, or have rocket engines under it, with all the avionics that entails. Modifying to to do that could be as expensive and problematic as building a new chasis from scratch that -is- designed for it.Not true.The ET (not MT) to Direct core is not the same as F-15 to stealth fighter.It is more like F-15 C/D to F-15E.The same assembly jigs and tooling can be used for both. Skin thicknesses are the basic differences. New domes on the LO2 and LH2 tanks are basically the same as the remaining ones on the tank. The thrust structure and forward adapter are not hard items to build. Avionics has no bearing, new avionics is being designed for Ares I which would be adaptedIf you want a reasonably detailed description of the sorts of changes required, I refer you to this public document:-http://hdl.handle.net/2060/19930007493The first 600 pages or so detail all the changes which are required to make each part of an ET into an NLS Core Stage.But from page 611 onwards there is a really *great* description of how NLS was planning to modify the existing tooling -- and that gives you a glimpse into what's really involved in what they do day-to-day at Michoud.It should be noted that NLS had the additional complication that they were planning to manufacture up to 14 NLS Cores at the same time as continuing production of up to 9 Shuttle ET's every year -- all occurring in parallel. We don't have that same complication.The details are a little out of date because this is all dealing with LWT structures, not SLWT. Most of the general principles all still apply, as does quite a large portion of the same tooling actually, just not all.I find it amazing that they believed they were able to do this in 1993, so much so that the program passed its PDR. Yet 'some' people are trying to tell us its 'too hard' to do these days, all the while promoting an option which requires everything to be 100% replaced. That argument holds no water for me.Ross.
The SRB has no problem holding up the loads of the Ares upper stage, since two of them have to jointly hold up the entire fueled ET and Shuttle with payload in bending. Ares US is ~400,000 lbs fueled, nothing close to the 1.6 million+ lbs of fueled ET alone. And in flight, they can only apply a force in similar magnitude to the force they are creating.
Quote from: jarmumd on 01/13/2009 05:08 pmThe SRB has no problem holding up the loads of the Ares upper stage, since two of them have to jointly hold up the entire fueled ET and Shuttle with payload in bending. Ares US is ~400,000 lbs fueled, nothing close to the 1.6 million+ lbs of fueled ET alone. And in flight, they can only apply a force in similar magnitude to the force they are creating. Forgive any mistakes in my math henceforth. I don't exactly have a PhD in aerospace...Orbiter + Payload = Total Weight of Orbiter68,585 + 25,061 = 93,646SSME Thrust x 3 = 400,000 x 3 = 1,200,0001,200,000 - 93,646 = 1,106,354So 1,106,354 pounds of positive thrust from the orbiter.1,600,000 - 1,106,354 = 493,646493,646 / 2 = 246,823So each 4 segment SRB would support 246,823 pounds of external fuel tank, not 400,000. Let's assume we get a 5/4 improvement in thrust with an additional segment:246,823 x (5 / 4) = 308,529That's still almost 100,000 pounds short. Granted, my reasoning is probably flawed, but I think I've sufficiently illustrated that the mass of the tank itself is not proof of an SRB's capacity to lift weight on its own.
Lobo, it is technically conceivable to strap on more SRBs. Early on in the DIRECT conversation (first thread?), someone (maybe Antonio) mocked up a version as you describe-- but it was only done to amuse the geeks on the forum.That said, it would lose all commonality with launch infrastructure (pads, MLPs, etc.). As I understand DIRECT's goal, they want to keep the same launch footprint. If you increase the diameter of the ET, then you're starting to talk about ARES V territory. At that point, it probably makes more sense to pursue ARES V or a clean-sheet launch system.
Quote from: mrbliss on 01/13/2009 02:51 pmQuote from: kraisee on 01/13/2009 04:25 amFifth is the fact that the SRB's were never designed to be utilized in this fashion with hundreds of tons of stage and payload on top. They just weren't designed for these loads.Why are these loads a big issue for the SRB, but not for Jupiter's ET-based core stage? Is it because the core (being mostly tanks holding the liquids) can be redesigned to handle the loads, but the SRB can't be modified similarly?SteveThe SRB has no problem holding up the loads of the Ares upper stage, since two of them have to jointly hold up the entire fueled ET and Shuttle with payload in bending. Ares US is ~400,000 lbs fueled, nothing close to the 1.6 million+ lbs of fueled ET alone. And in flight, they can only apply a force in similar magnitude to the force they are creating. Ross, I'm sure this will upset you, but I think you need to take it down a notch. Passion is good, but in all honesty your post above with the bold text and italicizing, and comments of the "truth" all remind me of a certain Italian that needs to stay off the internet.Marc
And it seems to me there is some mixup kg vs lb