Quote from: TrevorMonty on 03/18/2015 11:35 pmQuote from: Rocket Science on 03/18/2015 10:57 pmQuote from: Comga on 03/18/2015 10:45 pmThe wing hinges fold so that the mechanisms have to hold them against the drag. Sounds difficult.The fairing simplifies the aerodynamics but adds cost and mass, which could mean extra solids on Atlas and even more cost.The X-38 was to have folding wings so the idea is not "too off the wall"...Aircraft carrier fighter airplanes have been using them for decades. It ain't rocket science.Yeah, but the carrier airplane wings are folded by ground crews. They don't have to be folded autonomously in space.Nobody is arguing that it's impossible, just that it adds mass and complexity and cost. None of those things helps Dream Chaser cargo compete against the other proposals, none of which have to deal with folding wings.
Quote from: Rocket Science on 03/18/2015 10:57 pmQuote from: Comga on 03/18/2015 10:45 pmThe wing hinges fold so that the mechanisms have to hold them against the drag. Sounds difficult.The fairing simplifies the aerodynamics but adds cost and mass, which could mean extra solids on Atlas and even more cost.The X-38 was to have folding wings so the idea is not "too off the wall"...Aircraft carrier fighter airplanes have been using them for decades. It ain't rocket science.
Quote from: Comga on 03/18/2015 10:45 pmThe wing hinges fold so that the mechanisms have to hold them against the drag. Sounds difficult.The fairing simplifies the aerodynamics but adds cost and mass, which could mean extra solids on Atlas and even more cost.The X-38 was to have folding wings so the idea is not "too off the wall"...
The wing hinges fold so that the mechanisms have to hold them against the drag. Sounds difficult.The fairing simplifies the aerodynamics but adds cost and mass, which could mean extra solids on Atlas and even more cost.
Quote from: A_M_Swallow on 03/18/2015 08:18 pmQuote from: adrianwyard on 03/17/2015 11:26 pmQuote from: TrevorMonty on 03/17/2015 10:58 pmThe is video on web showing the thrusters, 3 small ones on each side.Can't compete with Dragons trunk for bulky unpressurized cargo.Hmmm, if you ask me it looks like those thrusters are aimed at the solar panels...To use the tail thrusters to slow down I would expect the Dream Chaser to be flying backwards. It would turn around after the burn.Boosting the station! How? The thrusters point to wards to station. Unless there is an additional set of thrusters somewhere that point towards the nose of the spacecraft.I'm not following. The solar panels are in the way of the thrusters regardless of whether you're flying forwards or backwards WRT the ISS. Also, you need the ability to brake/abort the approach in the last few moments before docking, i.e. you need these station-facing thrusters to be available. I think the obvious answer is the graphics are just wrong; in reality the panels would be hinged at a different location, and can be folded out of the way of the thruster plume during docking.
Quote from: adrianwyard on 03/17/2015 11:26 pmQuote from: TrevorMonty on 03/17/2015 10:58 pmThe is video on web showing the thrusters, 3 small ones on each side.Can't compete with Dragons trunk for bulky unpressurized cargo.Hmmm, if you ask me it looks like those thrusters are aimed at the solar panels...To use the tail thrusters to slow down I would expect the Dream Chaser to be flying backwards. It would turn around after the burn.Boosting the station! How? The thrusters point to wards to station. Unless there is an additional set of thrusters somewhere that point towards the nose of the spacecraft.
Quote from: TrevorMonty on 03/17/2015 10:58 pmThe is video on web showing the thrusters, 3 small ones on each side.Can't compete with Dragons trunk for bulky unpressurized cargo.Hmmm, if you ask me it looks like those thrusters are aimed at the solar panels...
The is video on web showing the thrusters, 3 small ones on each side.Can't compete with Dragons trunk for bulky unpressurized cargo.
If they chose a third Cargo contractor, then they might even desire that the third contractor uses IDA.
Quote from: ChrisWilson68 on 03/19/2015 06:24 amI can't see why they would build a carrier aircraft with wings that can be folded by the pilot from the cockpit. It would be like designing a car that lets you remove the wheels from the driver's seat. It seems obvious to me it's better to require someone to physically go up to the wheel with a lug wrench and unbolt the wheel, both because it prevents accidental, catastrophic removal of the wheel while driving and because it would be a bunch of extra complexity that's not needed because there's no reason to remove the wheel except when the vehicle is stopped and you can physically access it.While I might have supposed something similar...We don't need suppositions when we have facts. Ladies and gentlemen, the E-2C, the EA-6B, the V-22, and the F/A-18. The last one is now the base platform for the vast majority of USAF carrier aircraft.
I can't see why they would build a carrier aircraft with wings that can be folded by the pilot from the cockpit. It would be like designing a car that lets you remove the wheels from the driver's seat. It seems obvious to me it's better to require someone to physically go up to the wheel with a lug wrench and unbolt the wheel, both because it prevents accidental, catastrophic removal of the wheel while driving and because it would be a bunch of extra complexity that's not needed because there's no reason to remove the wheel except when the vehicle is stopped and you can physically access it.
Dreamchaser was already going to have aerosurfaces for maneuvering that would have to move properly. Shuttle had elevons, a body flap, and a rudder that had moving surfaces under load with tps. Folding the whole stablizier isn't really breaking much new ground.
Quote from: Burninate on 03/19/2015 06:44 amQuote from: ChrisWilson68 on 03/19/2015 06:24 amI can't see why they would build a carrier aircraft with wings that can be folded by the pilot from the cockpit. It would be like designing a car that lets you remove the wheels from the driver's seat. It seems obvious to me it's better to require someone to physically go up to the wheel with a lug wrench and unbolt the wheel, both because it prevents accidental, catastrophic removal of the wheel while driving and because it would be a bunch of extra complexity that's not needed because there's no reason to remove the wheel except when the vehicle is stopped and you can physically access it.While I might have supposed something similar...We don't need suppositions when we have facts. Ladies and gentlemen, the E-2C, the EA-6B, the V-22, and the F/A-18. The last one is now the base platform for the vast majority of USAF carrier aircraft.That's interesting!As always, evidence trumps what we suppose would be the case. :-)I'm really curious now why they chose to do it that way.
Quote from: baldusi on 03/19/2015 02:39 pmIf they chose a third Cargo contractor, then they might even desire that the third contractor uses IDA.They might select a cargo contractor in spite of them using IDA, but I don't think they'd prefer it. They have two of each kind of port and a third cargo contractor would mean two crew and two other cargo vehicles. Do they really need three cargo vehicles at the same time? Probably not. And redundancy is probably more important for crew than for cargo, so they'd probably rather keep the IDAs clear for crew vehicles so if one is down they still have the other for another crew vehicle.
While the CRS-2 RFP talks about docking (IDA) and berthing (CBM) being options, it also says that they need a CBM solution in the mix because of its width. See Answer 20 here: https://prod.nais.nasa.gov/eps/eps_data/160022-OTHER-003-001.pdf so that implies that at least SpaceX or Orbital ATK will get chosen.
Quote from: adrianwyard on 03/19/2015 02:56 pmWhile the CRS-2 RFP talks about docking (IDA) and berthing (CBM) being options, it also says that they need a CBM solution in the mix because of its width. See Answer 20 here: https://prod.nais.nasa.gov/eps/eps_data/160022-OTHER-003-001.pdf so that implies that at least SpaceX or Orbital ATK will get chosen.CRS-2 RFP calls for (among other things) pressurized cargo up/down per-flight range of: M01 bag 0-10; M02 bag 10-TBP; M03 bag 0-6. How those bags fit with respect to NDS, Cygnus mini-CBM and CBM is shown in the attached figure below.
Quote from: Burninate on 03/18/2015 06:04 amIs a CBM even an option, or is NDS implicitly mandated?LM's proposal seems to use the CBM.Besides, the ISS will only have 2 NDS ports. At least one will have a commercial crew vehicle attached to it at all times. The other has to remain available for contingency and crew rotations. I don't see how an NDS-equipped commercial cargo vehicle can fit into that scheme.
Is a CBM even an option, or is NDS implicitly mandated?