Quote from: woods170 on 08/17/2016 09:35 amQuote from: kevinof on 08/15/2016 03:30 pmIs the issue with Nasa and densified propellant related to the late loading of the prop and they don't want their people sitting on top during fueling?The point is that with regards to flying crew on rockets NASA doesn't like to change the way they have done things for the past four+ decades. Most, if not all, of their experience is with the crew getting aboard a fully fueled vehicle. And then comes SpaceX proposing to do it the other way around. Given how risk adverse NASA in general, and the astronaut office and ASAP in particular are, it is no surprise they feel uncomfortable with this new approach to things.And my guess is that, prior to prop densification, NASA might have thought that they could convince SpaceX to load props and only then insert the crew, but what with the densified prop requirement to launch as shortly after fueling as possible, this just can't be done? So NASA has two choices -- don't launch their crews on Falcon, or get comfortable with prop loading while the crew is inside the spacecraft?Am I apprehending this issue correctly?
Quote from: kevinof on 08/15/2016 03:30 pmIs the issue with Nasa and densified propellant related to the late loading of the prop and they don't want their people sitting on top during fueling?The point is that with regards to flying crew on rockets NASA doesn't like to change the way they have done things for the past four+ decades. Most, if not all, of their experience is with the crew getting aboard a fully fueled vehicle. And then comes SpaceX proposing to do it the other way around. Given how risk adverse NASA in general, and the astronaut office and ASAP in particular are, it is no surprise they feel uncomfortable with this new approach to things.
Is the issue with Nasa and densified propellant related to the late loading of the prop and they don't want their people sitting on top during fueling?
I was under the impression that manned rockets are also being topped off while the crews are aboard before liftoff. If so then fuel is always being pumped aboard although at a much lower rate. Am I correct in this assumption?
Quote from: jak Kennedy on 08/17/2016 05:41 pmI was under the impression that manned rockets are also being topped off while the crews are aboard before liftoff. If so then fuel is always being pumped aboard although at a much lower rate. Am I correct in this assumption?No, you're correct. The Shuttle topped off until right before launch, when the top ET access arm would rotate away. I don't know about earlier manned rockets, though.
The Commercial Crew Program continues to face multiple challenges that will likely delay the first routine flight carrying NASA astronauts to the ISS until late 2018 – more than 3 years after NASA’s original 2015 goal. While past funding shortfalls have contributed to the delay, technical challenges with the contractors’ spacecraft designs are now driving the schedule slippages. For Boeing, these include issues relating to the effects of vibrations generated during launch and challenges regarding vehicle mass. For SpaceX, delays resulted from a change in capsule design to enable a water-based rather than ground-based landing and related concerns about the capsule taking on excessive water.
More delays:Quote from: OIGThe Commercial Crew Program continues to face multiple challenges that will likely delay the first routine flight carrying NASA astronauts to the ISS until late 2018 – more than 3 years after NASA’s original 2015 goal. While past funding shortfalls have contributed to the delay, technical challenges with the contractors’ spacecraft designs are now driving the schedule slippages. For Boeing, these include issues relating to the effects of vibrations generated during launch and challenges regarding vehicle mass. For SpaceX, delays resulted from a change in capsule design to enable a water-based rather than ground-based landing and related concerns about the capsule taking on excessive water.https://oig.nasa.gov/audits/reports/FY16/IG-16-028.pdf
Quote from: yg1968 on 09/01/2016 09:43 pmMore delays:Quote from: OIGThe Commercial Crew Program continues to face multiple challenges that will likely delay the first routine flight carrying NASA astronauts to the ISS until late 2018 – more than 3 years after NASA’s original 2015 goal. While past funding shortfalls have contributed to the delay, technical challenges with the contractors’ spacecraft designs are now driving the schedule slippages. For Boeing, these include issues relating to the effects of vibrations generated during launch and challenges regarding vehicle mass. For SpaceX, delays resulted from a change in capsule design to enable a water-based rather than ground-based landing and related concerns about the capsule taking on excessive water.https://oig.nasa.gov/audits/reports/FY16/IG-16-028.pdfIIRC water landing for D2 wasn't SpaceX's idea...
Quote from: Lar on 09/01/2016 10:54 pmQuote from: yg1968 on 09/01/2016 09:43 pmMore delays:Quote from: OIGThe Commercial Crew Program continues to face multiple challenges that will likely delay the first routine flight carrying NASA astronauts to the ISS until late 2018 – more than 3 years after NASA’s original 2015 goal. While past funding shortfalls have contributed to the delay, technical challenges with the contractors’ spacecraft designs are now driving the schedule slippages. For Boeing, these include issues relating to the effects of vibrations generated during launch and challenges regarding vehicle mass. For SpaceX, delays resulted from a change in capsule design to enable a water-based rather than ground-based landing and related concerns about the capsule taking on excessive water.https://oig.nasa.gov/audits/reports/FY16/IG-16-028.pdfIIRC water landing for D2 wasn't SpaceX's idea...Correct. D2 was to land on land under parachutes with propulsive assistence for cushioning purposes. But NASA didn't agree. NASA wanted full parachute landings, something SpaceX cannot do on land, for lack of a alternative cushioning system (like the one CST-100 has). As such, the only other way of doing full parachute landings is at sea.So basiscally, this is NASA causing this particular delay to the D2 portion of CCP.The delays for CST-100 come from a changed launch environment (from 'clean' booster to one sporting 1 or 2 solids) and the need to adjust for that. The change in booster configuration resulted from the on-going overweight issue that's been hampering CST-100 development for quite some time now.
Quote from: woods170 on 09/02/2016 07:17 amQuote from: Lar on 09/01/2016 10:54 pmQuote from: yg1968 on 09/01/2016 09:43 pmMore delays:Quote from: OIGThe Commercial Crew Program continues to face multiple challenges that will likely delay the first routine flight carrying NASA astronauts to the ISS until late 2018 – more than 3 years after NASA’s original 2015 goal. While past funding shortfalls have contributed to the delay, technical challenges with the contractors’ spacecraft designs are now driving the schedule slippages. For Boeing, these include issues relating to the effects of vibrations generated during launch and challenges regarding vehicle mass. For SpaceX, delays resulted from a change in capsule design to enable a water-based rather than ground-based landing and related concerns about the capsule taking on excessive water.https://oig.nasa.gov/audits/reports/FY16/IG-16-028.pdfIIRC water landing for D2 wasn't SpaceX's idea...Correct. D2 was to land on land under parachutes with propulsive assistence for cushioning purposes. But NASA didn't agree. NASA wanted full parachute landings, something SpaceX cannot do on land, for lack of a alternative cushioning system (like the one CST-100 has). As such, the only other way of doing full parachute landings is at sea.So basiscally, this is NASA causing this particular delay to the D2 portion of CCP.The delays for CST-100 come from a changed launch environment (from 'clean' booster to one sporting 1 or 2 solids) and the need to adjust for that. The change in booster configuration resulted from the on-going overweight issue that's been hampering CST-100 development for quite some time now.Only partly true in the case of SpaceX, aborts will land in the water so D2 has to be designed for that. However, aborts are assumed to be rare so a small additional risk on a water landing might be acceptable, but a similar additional risk every flight is too great.
My understanding was that CST-100 always was to launch with one SRB. Weight issues caused the possible addition of a second SRB but they said they want to get back to one SRB.SpaceX landing under parachutes with propulsive cushioning was suggested by SpaceX and they mentioned that propulsion failing would make the landing as hard as Soyuz landing, but not threaten the astronauts life. As hard as Soyuz with or without those thruster pods, I don't know. Those pods have failed occasionally and crew survived though with some injuries. I remember SpaceX claimed no injuries though hard when propulsion fails.
No, it's now 2 SRB but even that was not enough as they had to find ways to cut down on the weight of the CST-100 Starliner.
Can SpaceX launch the F9FT without propellant densification and take the hit on performance? It isn't like the latest version of the F9 needs it's full performance to put a DragonV2 into orbit.
Quote from: Brovane on 09/03/2016 01:10 amCan SpaceX launch the F9FT without propellant densification and take the hit on performance? It isn't like the latest version of the F9 needs it's full performance to put a DragonV2 into orbit. Are you thinking they might have to, if the fault is found to be densification related? Or ?
I'm not really sure which is safer. Loading the crew with the vehicle fully fueled puts a lot of people at risk. Vehicles have exploded after they have been fueled, although this is less likely to occur after propellant loading. The LAS can not be armed while loading the crew and thus the crew are not safe until the check out crew have left and the LAS armed.However, loading the crew before fueling has the least risk for the closeout crew and the crew themselves. Once the closeout crew have left, the LAS can be armed and propellant loading commences.
If you trust your launch abort system, it makes sense to me to load the propellents after. Get the crew safety in the vehicle and they'll be okay. I wouldn't want people caught on the pad, but not in the vehicle when something went wrong because then the launch abort system is useless.
SpaceX’s launch vehicle, the Falcon 9, hasbeen upgraded to improve its performanceby increasing engine thrust and using densifiedpropellants. Among the risks associated with theupgraded vehicle is SpaceX’s planned concept ofoperations for launching using densifiedpropellants. SpaceX plans to load crew into theDragon and then fuel the rocket to keep thedensified propellants chilled. The program hasreported that loading the crew prior to thepropellant is a potential safety risk. SpaceXstated that its approach will improve safetyby minimizing personnel exposure to a fueledrocket. It has also identified safety and hazardcontrols to mitigate any risks associated withthis approach.
Boeing’s CCtCap contract initially included 23 milestones ranging from the establishment of an original requirements baseline to the final vehicle certification. Within the first 2 years of the contract, Boeing and NASA modified the contract to separate three of the milestones into multiple segments, replace one milestone, and add seven milestones related to NASA-imposed software upgrades, landing qualification tests, and hardware modifications.18 These modifications increased the number of milestones to 34 and the total contract value by approximately $46 million. As of June 2016, Boeing had completed 15 of the 34 milestones (44 percent) necessary to achieve certification and was scheduled to receive up to $1.067 billion (25 percent) of the total contract value in payment.
SpaceX’s CCtCap contract initially included 18 milestones ranging from establishment of the original requirements baseline to final vehicle certification. During the first year of the contract, SpaceX and NASA agreed to separate SpaceX’s Propulsion Module Testing and Critical Design Review into multiple segments, which increased the total milestones to 21.20 As of June 2016, SpaceX had completed eight milestones (38 percent), five less than planned under the original schedule, and received $469 million (18 percent) of the total contract value.
NASA Program officials anticipate SpaceX will encounter additional delays on the path to certification. For example, in January 2015, the tunnel that provides a passageway for astronauts and cargo between the Dragon and the ISS was reported to have cracked during the heat treatment phase of the manufacturing process. As a result, SpaceX delayed qualification testing by approximately one year to better align the tests as SpaceX moves toward certification. SpaceX has also experienced ongoing issues with stress fractures in turbopumps that must be resolved prior to flight.
Propulsive Descent Test Complete. This test of the Pad Abort Test Vehicle to perform controlled propulsive burns in a dynamic environment was completed in December 2015 after a 3-month delay.
