Quote from: Jim on 05/12/2016 03:06 amQuote from: king1999 on 05/12/2016 01:00 amDid you mean that out of the more than 3700 pounds of down mass, more than 2700 pounds is trash? Why don't they use the Cygnus for trash?"Hundreds of pounds" goes up to 1900lb before it becomes a ton. And multiple vehicles are used for trash, including Dragon.I guess it is a case of lost in translation. In my language (non-English), "hundreds" only goes up to 999. More than that we call it "thousand(s)".
Quote from: king1999 on 05/12/2016 01:00 amDid you mean that out of the more than 3700 pounds of down mass, more than 2700 pounds is trash? Why don't they use the Cygnus for trash?"Hundreds of pounds" goes up to 1900lb before it becomes a ton. And multiple vehicles are used for trash, including Dragon.
Did you mean that out of the more than 3700 pounds of down mass, more than 2700 pounds is trash? Why don't they use the Cygnus for trash?
So now Elon's providing a contract laundry service to NASA?!??
Quote from: Mike_1179 on 05/13/2016 02:01 amQuote from: king1999 on 05/12/2016 01:00 amDid you mean that out of the more than 3700 pounds of down mass, more than 2700 pounds is trash? Why don't they use the Cygnus for trash?Getting rid of trash is a challenge for ISS, you can't just throw something out the window or wash and reuse clothes. Any vehicle leaving gets trash in it, otherwise you have to store it and wait.So now Elon's providing a contract laundry service to NASA?!?? It never occurred to me before that maybe it's really the smell of dirty laundry that awaits the lucky first to open Dragon after splashdown. "The laundry basket's over on the left there, under those science experiments."
Quote from: king1999 on 05/12/2016 01:00 amDid you mean that out of the more than 3700 pounds of down mass, more than 2700 pounds is trash? Why don't they use the Cygnus for trash?Getting rid of trash is a challenge for ISS, you can't just throw something out the window or wash and reuse clothes. Any vehicle leaving gets trash in it, otherwise you have to store it and wait.
Quote from: king1999 on 05/12/2016 03:21 amQuote from: Jim on 05/12/2016 03:06 amQuote from: king1999 on 05/12/2016 01:00 amDid you mean that out of the more than 3700 pounds of down mass, more than 2700 pounds is trash? Why don't they use the Cygnus for trash?"Hundreds of pounds" goes up to 1900lb before it becomes a ton. And multiple vehicles are used for trash, including Dragon.I guess it is a case of lost in translation. In my language (non-English), "hundreds" only goes up to 999. More than that we call it "thousand(s)". Even the total mass is "hundreds" as in 37 hundred lbs.
Quote from: Jim on 05/13/2016 12:37 pmQuote from: king1999 on 05/12/2016 03:21 amQuote from: Jim on 05/12/2016 03:06 amQuote from: king1999 on 05/12/2016 01:00 amDid you mean that out of the more than 3700 pounds of down mass, more than 2700 pounds is trash? Why don't they use the Cygnus for trash?"Hundreds of pounds" goes up to 1900lb before it becomes a ton. And multiple vehicles are used for trash, including Dragon.I guess it is a case of lost in translation. In my language (non-English), "hundreds" only goes up to 999. More than that we call it "thousand(s)". Even the total mass is "hundreds" as in 37 hundred lbs.To be fair, the original comment was "couple of tons" so hundreds of pounds vs a couple of (short) tons would definitely break at 1999 pounds.
This discusses a waiver SpaceX requested for CRS-8 having to do with ship-borne impact hazard but also mentions the previous ASDS landings and a USAF evaluation of the overall launch hazard. https://www.federalregister.gov/articles/2016/05/10/2016-09685/waivers-of-ship-protection-probability-of-impact-requirement
Quote from: acsawdey on 05/12/2016 01:03 pmThis discusses a waiver SpaceX requested for CRS-8 having to do with ship-borne impact hazard but also mentions the previous ASDS landings and a USAF evaluation of the overall launch hazard. https://www.federalregister.gov/articles/2016/05/10/2016-09685/waivers-of-ship-protection-probability-of-impact-requirementWould someone who's read it kindly do a TL:DR for the busy, busy. Thanks.
I can see how in the past, the FAA would have a risk threshold for a possible ship impact hazard, but now the object of the test is that SpaceX "AIMS" to hit the ship.
I can see how in the past, the FAA would have a risk threshold for a possible ship impact hazard, but now the object of the test is that SpaceX "AIMS" to hit the ship.Times change...
The point for me is that the stage is re-entering under control. SpaceX know where they want it to go, and they clearly have at least an 80% chance of putting it exactly there, which should reduce the remaining area risk by a factor of at least 5.
Hmmm... not sure about that "80% chance of putting it exactly there..." (where does that come from?).
The FAA found that small boats (too small to have AIS required) located close to the launch point should not produce significant individual risks, given conditions expected in the vicinity of Cape Canaveral. Specifically, sufficient surveillance with other means (e.g., radar, and/or using Coast Guard ships or aerial assets) will be used to ensure individual risks comply with the FAA requirement in § 417.107(b)(2). In addition, Notices to Mariners will continue to be issued for the areas where the probability of impact on a ship would exceed 1 × 10 −5, which is current practice at the ER, and required by §§ B417.3 and B417.11. Since the FAA's current requirements allow launches to proceed with unquantified residual collective risks to people in waterborne vessels, as long as the collective risk for people on land from each source of hazard (i.e., debris, toxics, or distant focusing overpressure) does not exceed 30 × 10 −6 E C, and because the launch will not exceed the 30 × 10 −6 E C with the inclusion of persons on water borne vessels, the FAA finds that the Falcon 9 CRS-8 launch will not jeopardize public health and safety or safety of property, and waives 14 CFR 417.107(b)(3) and Appendix B to part 417, paragraph 417.5(a)'s requirement not to initiate flight absent evacuation.
To be clear: THIS WAIVER IS NOT DIRECTLY RELATED TO LANDING ON ASDS. If it was for ASDS landings, then similar waivers would have been needed for every previous ASDS landing attempt.
A more nuanced reading, and the part that could be relevant for ASDS landings, is that it might allow them to stage the recovery support vessels (Go Quest and tug) closer to the ASDS during landings. i.e. Instead of making them wait 5-7miles away, they might only have to wait 2-3 miles. This would reduce the time needed to return landed stages to port. But, without reading SpaceX's actual application, it's hard to understand exactly what they were arguing. The gist from the Federal Register is that AIS and ship tracking data is sufficient now to determine the Ec including shipboard persons as opposed to just trying to determine the odds of hitting a ship with debris. And, SpaceX would like to do that as they feel like they're less likely to be forced to scrub a launch by a late intrusion into the hazard area unless the ship in question happens to be a large, passenger carrier.
Quote from: Arb on 05/13/2016 11:06 pmQuote from: acsawdey on 05/12/2016 01:03 pmThis discusses a waiver SpaceX requested for CRS-8 having to do with ship-borne impact hazard but also mentions the previous ASDS landings and a USAF evaluation of the overall launch hazard. https://www.federalregister.gov/articles/2016/05/10/2016-09685/waivers-of-ship-protection-probability-of-impact-requirementWould someone who's read it kindly do a TL:DR for the busy, busy. Thanks.TL:DR: Previously calculating the actual probability of impact on a ship and subsequent loss of life was difficult, so the rule was written as "no launching if there are ships in a hazard zone". The USCG mandate to have AIS transponders on ships above a certain size has allowed the range to develop a more sophisticated approach, where you can compute in real time the probability of human casualty using the known maximum human capacity and location of the AIS-carrying ships and some assumptions about small non-AIS-carrying ships. This allows a uniform treatment of potential casualties on land and sea.SpaceX requested a general waiver back in January to use this new casualty-estimation process. They were then encouraged to request a specific exemption for CRS-8 after the tug boat scrubbed the launch of SES-9, since presumably in that particular case the launch would not have been scrubbed under the new rules since the tugboat had a very small crew and so the risk of casualty would have been sufficiently low.There seems to be more general rulemaking in progress to make this new standard the default, but the FAA seems willing to give individual flights waivers to use it for now.