Fantastic detail. Much appreciated.
Quote from: dawei on 04/21/2013 03:02 pmFantastic detail. Much appreciated. I 2nd this, and would add thanks for taking your time to explain this.
Surface winds AT THE PAD affect the clearance during lift-off. Orbital has established a basic 15kts limit for ANY DIRECTION, waivable to 20kts by LD (Eberly). Eberly has a "pocket reserve" of a few kts if the wind direction is "away from the TEL." The range helps LD with the go/nogo decision (including computing its effect on POV) but this is not a range decision - it's Orbital's.
I hope this clarifies a bit what is admittedly a very complex situation.
All U.S. ranges agreed to add up the E sub C of each effect and use a composite criterion (100 per million) as a range go/no go criterion.
Quote from: meekGee on 04/17/2013 09:36 pmQuote from: Ben the Space Brit on 04/17/2013 03:35 pmIt's obviously a very different machine from the ULA launchers or Falcon-9. Would I be right in saying that the core will get almost all the way to orbit and the U/S is little more than a kick stage to get the perigee up?You know, I don't understand the choice of a solid U/S. It seems to have all the wrong attributes for an U/S.Solids, IIUC, have a high "dry" weight, since the entire "tank" is thick walled. And in an U/S, every pound wasted is 100% at the expense of payload.Also, it burns to depletion, so you can't control end-of-burn, so I'd think that precision insertion is problematic.Lastly, it is not a high ISP solution.I always thought that solids are good as either high-thrust boosters, or BEO kick stages since they are simple and can last a long time in orbit.Anyone familiar with why they went with a solid U/S?As Jim answered, the answer is "cost". The ultimate Antares second stage will be Castor 30XL, a stretched version that reportedly only cost $57 million to develop. That's probably not much more than it costs to build and fly one or two Centaur stages. Centaur, of course, cost far more than $57 million to develop, but that cost has been amortized over decades of flights by many stages now. Orbital did not have that luxury.Speaking of Centaur, Castor 30XL will have a better propellant mass ratio than that well-regarded and very successful liquid hydrogen upper stage. That "high dry weight" often associated with solid motors does not apply in this case, nor for many of the modern day solid motors.Centaur, of course will generate much more specific impulse than Castor 30XL, but the improved Antares second stage will still produce more than 75% as much total impulse as Centaur. Castor 30XL will produce 3.8 times more total impulse than the Delta 2 second stage while having a far better PMF than that pressure fed stage. Castor 30XL is a high performance graphite epoxy case solid motor with a huge nozzle designed to extract maximum performance. It provides that performance without need for any cryogenic propellant handling or loading at the pad. It is a good deal for Orbital, which is trying hard to develop a rocket that can make money flying only a few times per year. - Ed Kyle
Quote from: Ben the Space Brit on 04/17/2013 03:35 pmIt's obviously a very different machine from the ULA launchers or Falcon-9. Would I be right in saying that the core will get almost all the way to orbit and the U/S is little more than a kick stage to get the perigee up?You know, I don't understand the choice of a solid U/S. It seems to have all the wrong attributes for an U/S.Solids, IIUC, have a high "dry" weight, since the entire "tank" is thick walled. And in an U/S, every pound wasted is 100% at the expense of payload.Also, it burns to depletion, so you can't control end-of-burn, so I'd think that precision insertion is problematic.Lastly, it is not a high ISP solution.I always thought that solids are good as either high-thrust boosters, or BEO kick stages since they are simple and can last a long time in orbit.Anyone familiar with why they went with a solid U/S?
It's obviously a very different machine from the ULA launchers or Falcon-9. Would I be right in saying that the core will get almost all the way to orbit and the U/S is little more than a kick stage to get the perigee up?
Wall, all I can say is the the numbers are pretty harsh.The 30X has a mass fraction of 7.5% - I think even the first stage of F9 does better. (comparing it to old DII upper stage is not a good basis for comparison, is it?)The unit cost of the US is then going to be higher, right?Lastly, honestly, $57M doesn't sound that cheap for development cost.Shrug. The point is, after it flies, it needs to compete.
Quote from: meekGee on 04/21/2013 04:23 pmWall, all I can say is the the numbers are pretty harsh.The 30X has a mass fraction of 7.5% - I think even the first stage of F9 does better. (comparing it to old DII upper stage is not a good basis for comparison, is it?)The unit cost of the US is then going to be higher, right?Lastly, honestly, $57M doesn't sound that cheap for development cost.Shrug. The point is, after it flies, it needs to compete. Can't compare a first stage with a smaller upper stage. Different animals. And Falcon 9 is a bigger rocket in general. But sure, a LOX/RP stage can be more mass efficient than a solid stage, but it can also cost more - maybe much more, both to develop and to fly. How much do you think it will cost SpaceX to develop its v1.1 upper stage, which after all these years of engineering and testing has not yet flown? Billions of dollars will have flown into this company during this time.$57 million for a complete development program of an upper stage of this capability is cheap. Orbital is going to probably garner close to $200 million gross income per COTS mission, roughly speaking. If Antares flies 57 times, which is plausible, that development cost would amortize to $1 million per launch, but even less than that if inflation is considered. - Ed Kyle
Why is it counting up instead of down?
Orbital Sciences @OrbitalSciencesEven though it will consume close to 1ton of prop every second after lift-off, the early acceleration will be surprisingly slow.
Orbital Sciences @OrbitalSciences When the engines first ignite, the rocket will not lift off from the pad for two full seconds.
Orbital Sciences @OrbitalSciences At 10 seconds after Stage 1 engine ignition the vehicle will have accelerated to about 40 mph and climbed to 230 feet altitude.
Orbital Sciences @OrbitalSciences At 20 seconds after ignition, #Antares will be traveling at 100 mph at be about 1,250 feet above the pad.
Orbital Sciences @OrbitalSciences Even after 60 seconds, the vehicle will still be subsonic (about 460 mph) at just over 3 miles in altitude. #Antares
Orbital Sciences @OrbitalSciences#Antares achieves Mach 1 about 75 seconds after lift-off, when it will be at about 30,000 feet in altitude.
upstream just went offline for me too
Actually, the liftoff to 20 seconds data is surprisingly close to the Apollo 11 Saturn V numbers. Then the Saturn V looses mass percentage faster than Antares due to the 3 stages vs. Antares only
[Question:] What wind speeds are considered too high for launch?[Answer from Orbital:] Ground winds consistently above 20 knots (23 mph).