Quote from: oldAtlas_Eguy on 02/05/2016 04:52 pmQuote from: nadreck on 02/05/2016 03:28 pmQuote from: Robotbeat on 02/05/2016 03:00 pmYes, you must actually calculate performance to a reference orbit of your choosing. That's better than Wikipedia (obviously), SpaceX (doesn't provide full orbit parameters and reserves some undefined amount of performance for reuse, according to Shotwell), and spaceflight101 (which isn't a primary source).And because it gives you performance numbers to many different orbits, you can use it to calibrate your model much better than just giving a couple reference orbits (especially when it's "GTO" without specifying 1500 or 1800m/s-to-go)But it does not give me the information I need to calculate anything. How can I use the calculation on this page to check my model of calculations if I don't know the masses they are assuming? Is the reference model in their calculations one with legs? Back when the first TMI numbers went up on the SpaceX website I could use that with the data on SII engine performance and SII masses (wikipedia, spaceflight 101 and also the SpaceX website) to backwards calculate the speed the FH lofted the 2nd stage to in fully expendable mode. That gave me one point of sanity check for my model of FH operation. This doesn't really give me any without knowing the numbers they used.The values given by the orbit query is based on no margins (including no legs). No margins means no engine out either. The 1350 LEO and GTO values for v1.1 given by SpaceX included engine out margins + maybe a little more as well as attached legs and other recovery hardware margins. The two values gives the percentages or delta V/energy values for the stage deltas for no margins vs ASDS recovery for the v1.1. Now for FT we do not have any values.Plus I do not think the numbers in the NASA query model will give you any answers since they are most likely a polynomial algorithm that given certain inputs returns an output. They may have no relationship to masses of stages or engine thrusts ISPs or anything else just a complex curve equation.Or sure, but you can use it to back out realistic values for all those things and to test your model. If you know lift-off mass, Isp, thrust, and payload to multiple orbits, you could actually back out dry masses, especially for a simple vehicle.
Quote from: nadreck on 02/05/2016 03:28 pmQuote from: Robotbeat on 02/05/2016 03:00 pmYes, you must actually calculate performance to a reference orbit of your choosing. That's better than Wikipedia (obviously), SpaceX (doesn't provide full orbit parameters and reserves some undefined amount of performance for reuse, according to Shotwell), and spaceflight101 (which isn't a primary source).And because it gives you performance numbers to many different orbits, you can use it to calibrate your model much better than just giving a couple reference orbits (especially when it's "GTO" without specifying 1500 or 1800m/s-to-go)But it does not give me the information I need to calculate anything. How can I use the calculation on this page to check my model of calculations if I don't know the masses they are assuming? Is the reference model in their calculations one with legs? Back when the first TMI numbers went up on the SpaceX website I could use that with the data on SII engine performance and SII masses (wikipedia, spaceflight 101 and also the SpaceX website) to backwards calculate the speed the FH lofted the 2nd stage to in fully expendable mode. That gave me one point of sanity check for my model of FH operation. This doesn't really give me any without knowing the numbers they used.The values given by the orbit query is based on no margins (including no legs). No margins means no engine out either. The 1350 LEO and GTO values for v1.1 given by SpaceX included engine out margins + maybe a little more as well as attached legs and other recovery hardware margins. The two values gives the percentages or delta V/energy values for the stage deltas for no margins vs ASDS recovery for the v1.1. Now for FT we do not have any values.Plus I do not think the numbers in the NASA query model will give you any answers since they are most likely a polynomial algorithm that given certain inputs returns an output. They may have no relationship to masses of stages or engine thrusts ISPs or anything else just a complex curve equation.
Quote from: Robotbeat on 02/05/2016 03:00 pmYes, you must actually calculate performance to a reference orbit of your choosing. That's better than Wikipedia (obviously), SpaceX (doesn't provide full orbit parameters and reserves some undefined amount of performance for reuse, according to Shotwell), and spaceflight101 (which isn't a primary source).And because it gives you performance numbers to many different orbits, you can use it to calibrate your model much better than just giving a couple reference orbits (especially when it's "GTO" without specifying 1500 or 1800m/s-to-go)But it does not give me the information I need to calculate anything. How can I use the calculation on this page to check my model of calculations if I don't know the masses they are assuming? Is the reference model in their calculations one with legs? Back when the first TMI numbers went up on the SpaceX website I could use that with the data on SII engine performance and SII masses (wikipedia, spaceflight 101 and also the SpaceX website) to backwards calculate the speed the FH lofted the 2nd stage to in fully expendable mode. That gave me one point of sanity check for my model of FH operation. This doesn't really give me any without knowing the numbers they used.
Yes, you must actually calculate performance to a reference orbit of your choosing. That's better than Wikipedia (obviously), SpaceX (doesn't provide full orbit parameters and reserves some undefined amount of performance for reuse, according to Shotwell), and spaceflight101 (which isn't a primary source).And because it gives you performance numbers to many different orbits, you can use it to calibrate your model much better than just giving a couple reference orbits (especially when it's "GTO" without specifying 1500 or 1800m/s-to-go)
Algebra gives us that given two solutions with two equations you can solve for 1 unknown. With three solutions you can solve for 2 unknowns ... Pick orbits that give you solvable for unknowns equations and you can back out all the data to the same level of accuracy that the solutions are given (looks to be 3 significant digits, maybe 4). You can do the back out analysis with a simple Basic program that iterates the unknown values until it matches up with the given solutions.
Quote from: oldAtlas_Eguy on 02/05/2016 05:48 pmAlgebra gives us that given two solutions with two equations you can solve for 1 unknown. With three solutions you can solve for 2 unknowns ... Pick orbits that give you solvable for unknowns equations and you can back out all the data to the same level of accuracy that the solutions are given (looks to be 3 significant digits, maybe 4). You can do the back out analysis with a simple Basic program that iterates the unknown values until it matches up with the given solutions.One unknown can be solved per simultaneous equation.
Quote from: fthomassy on 02/05/2016 06:18 pmOne unknown can be solved per simultaneous equation.Thank you, I got carried away with the plethora of unknowns. Having the extra equation/answer helps in unknown value solution validation. [snip]
One unknown can be solved per simultaneous equation.
One thing to keep in mind with all this discussion of larger payload fairings is road transport. I doubt anything over the current size is going to be able to fit on the road in halves. Will quarter slices get you back to small enough? That adds more complexity. Of course, there has been no mention of any actual payloads out there requiring larger than what is available now so much of this discussion is just burning pixels for fun.
Quote from: Robotbeat on 02/05/2016 02:21 amAlso, where the heck would you TEST such a huge fairing? As it is, 5m fairings barely fit at Plum Brook, which has the largest vacuum chamber in the world.Isn't the vacuum chamber 100' in diameter and taller than that? The acoustic facility is smaller...
Also, where the heck would you TEST such a huge fairing? As it is, 5m fairings barely fit at Plum Brook, which has the largest vacuum chamber in the world.
Also, you have to actually test separation dynamics, and then you have to carefully slow down the fairing so it doesn't bang into your expensive thermal vacuum chamber.Look at the tests they do with 5m fairings. There's not exactly a ton of extra room.
Quote from: Robotbeat on 02/10/2016 05:09 pmAlso, you have to actually test separation dynamics, and then you have to carefully slow down the fairing so it doesn't bang into your expensive thermal vacuum chamber.Look at the tests they do with 5m fairings. There's not exactly a ton of extra room.They have done bigger shrouds in the past (Skylab shroud seen in Plum Brook below)http://grin.hq.nasa.gov/ABSTRACTS/GPN-2000-001462.html
Looks like they've lost the Viasat-2 launch due to the FH delays It has been redirected to Arianespace
What about building a fairing test rig on a reused first stage, and trying out the new fairing on a suborbital flight?
Quote from: Nilof on 02/11/2016 05:12 pmWhat about building a fairing test rig on a reused first stage, and trying out the new fairing on a suborbital flight?Only if the test can replicate the same conditions as the regular flight
In addition, you would also need to expend a brand-new second stage. We're starting to talk about a very expensive test by this point.
That is likely the main issue. To be comparable to a thermovac chamber, the stage would have to provide a similar altitude profile to the actual launch. I don't know exactly how much delta-v would be necessary for that and if it's feasible for a reusable stage. Acceleration doesn't necessarily need to be simulated too closely though, since vacuum chambers don't simulate that at all.