Author Topic: ASAP still has concerns over Commercial Crew LOC risks  (Read 45833 times)

Offline john smith 19

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #80 on: 01/18/2018 07:06 AM »

Expected loss standard procedure = 2*n*2*q*p = 4*n*p = 0.016
Expected loss SpaceX procedure = n*q*2*p = 0.008

What this shows is that the SpaceX procedure is safer because less people are exposed to risk and that the crew escape system is safer than having the ground and flight crew try and get away using slide wires. As the Space Shuttle did not have an escape system, the standard procedure is the safest way.
Which suggests (no proof, just suggests) that ASAP is thinking that programme vehicles don't have launch escape systems designed in, IE just like Shuttle.

This is simply bizarre, given they they know both capsules do (and DC will) and IIRC didn't they insist on them having such systems to begin with?

In aviation, loading passengers happens after the vehicle is fueled. This has (potentially) serious implications for ConOps with any future P2P BFS flights.
OTOH getting unstrapped from a capsule and running in a full pressure suit is a PITA.
However if you're in the same capsule with a finger poised over the Big Red Switch to fire the LES and watching any vehicle telemetry for anomalies that sounds quite a bit safer than being crew on the pad.

My instinct is go to the toilet, suit up and strap in then let the pad crew do their work, while being ready to punch out if anything looks off.
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Online rockets4life97

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #81 on: 01/18/2018 07:07 AM »
Sad part is SpaceX has already proved at least 38 times in a row they can safely fuel F9 without blowing it up, and that's with some flight-proven 1st stages in the mix.

That's 19 times in a row since the last fuelling explosion on 1 September 2016 with AMOS 6.

Negan is counting static fires. Should probably also count test fires at McGregor. So the number of successful fires with the current procedure is probably >50.

Online deruch

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #82 on: 01/18/2018 08:20 AM »
Sad part is SpaceX has already proved at least 38 times in a row they can safely fuel F9 without blowing it up, and that's with some flight-proven 1st stages in the mix.

That's 19 times in a row since the last fuelling explosion on 1 September 2016 with AMOS 6.

Negan is counting static fires. Should probably also count test fires at McGregor. So the number of successful fires with the current procedure is probably >50.

That makes some assumptions that aren't necessarily supported though.  Firstly, McGregor firings are of each stage individually and not of a combined stack.  Seems like this shouldn't really be a factor, but maybe there is some unexpected difference.  Secondly, while I have a hard time believing that this would be so, IIRC, we don't actually know that the loading process at McGregor is exactly the same as at the launch pad.  Slightly more believable is that environmental factors could be a factor. 

With the static fires, we absolutely know that it is being done the same as on launch day.  So, while you're probably right that there have been more successful firings with the current procedure, I don't think we can yet say so definitively.
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Offline Rocket Science

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #83 on: 01/18/2018 08:29 AM »

Expected loss standard procedure = 2*n*2*q*p = 4*n*p = 0.016
Expected loss SpaceX procedure = n*q*2*p = 0.008

What this shows is that the SpaceX procedure is safer because less people are exposed to risk and that the crew escape system is safer than having the ground and flight crew try and get away using slide wires. As the Space Shuttle did not have an escape system, the standard procedure is the safest way.
Which suggests (no proof, just suggests) that ASAP is thinking that programme vehicles don't have launch escape systems designed in, IE just like Shuttle.

This is simply bizarre, given they they know both capsules do (and DC will) and IIRC didn't they insist on them having such systems to begin with?

In aviation, loading passengers happens after the vehicle is fueled. This has (potentially) serious implications for ConOps with any future P2P BFS flights.
OTOH getting unstrapped from a capsule and running in a full pressure suit is a PITA.
However if you're in the same capsule with a finger poised over the Big Red Switch to fire the LES and watching any vehicle telemetry for anomalies that sounds quite a bit safer than being crew on the pad.

My instinct is go to the toilet, suit up and strap in then let the pad crew do their work, while being ready to punch out if anything looks off.
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Offline woods170

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #84 on: 01/18/2018 09:17 AM »
Because the highest danger is during fueling.  It's a dynamic process both in terms of the propellants themselves flowing but also the vehicle hasn't reached thermal stasis.  The danger that something goes wrong and causes an accident is much higher during this period than that it is during the relatively static period of topping-off/replenishment.  So, that added risk has to be weighed against the lower risk of fewer man minutes of exposure to a loaded rocket.  Exactly which one turns out to have the true lower risk is dependent on the variables: number of astronauts and ground crew exposed, loading duration, etc.

Emphasis mine.

"Relative" is the right word here. You see, there is nothing static about topping-off/replenishment:

- Valves are opening and closing, both on GSE and the launch vehicle. Propellant flow intermittently starts and stops, causing small, but significant rises and drops in propellant pressure in both GSE and the launch vehicle.
- Intermittent instances of venting, the result of a rise in tank-pressure. The venting results in a dropping tank-pressure. So, the tanks are constantly "breathing" which results in continues cycles of expanding/shrinking.
- People sometimes cite thermal equilibrium as the thing being "static". But that is not correct either. Temperature of parts of the launcher continue to drop well after topping-off/replenishment has started. The STS ET, for example, continued to "shrink" for almost an hour into the stable replenishment cycle because that first hour into the replenishment-cycle there was no thermal equilibrium.

Offline jak Kennedy

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #85 on: 01/18/2018 09:56 AM »
I wonder what ASAP had to say about fuel transfers to the ISS? And next fuel depots in space. Although a different environment it will become SOP (or has) one day with crew onboard.

Offline envy887

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #86 on: 01/18/2018 01:19 PM »
Sad part is SpaceX has already proved at least 38 times in a row they can safely fuel F9 without blowing it up, and that's with some flight-proven 1st stages in the mix.

That's 19 times in a row since the last fuelling explosion on 1 September 2016 with AMOS 6.

Negan is counting static fires. Should probably also count test fires at McGregor. So the number of successful fires with the current procedure is probably >50.

That makes some assumptions that aren't necessarily supported though.  Firstly, McGregor firings are of each stage individually and not of a combined stack.  Seems like this shouldn't really be a factor, but maybe there is some unexpected difference.  Secondly, while I have a hard time believing that this would be so, IIRC, we don't actually know that the loading process at McGregor is exactly the same as at the launch pad.  Slightly more believable is that environmental factors could be a factor. 

With the static fires, we absolutely know that it is being done the same as on launch day.  So, while you're probably right that there have been more successful firings with the current procedure, I don't think we can yet say so definitively.

Prop load during WDRs are also done the same as launch day, and Zuma did two of those and FH at least 1.

Seven Block 5 flights will be at least 42 stage loads (2x stages, 3x loads each counting McGregor), and probably >50 loads because each FH gets 12 stage loads, and Block 5 might get extra tests or WDRs.

Offline spacenut

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #87 on: 01/18/2018 02:12 PM »
I don't like that NASA required SpaceX to remove the landing legs and go with water landings.  Yet Boeing can use air bags and do land landings.  Seems like a waste of innovation.

Does anyone think SpaceX will eventually go back to landing legs for non-NASA flights?

« Last Edit: 01/18/2018 02:13 PM by spacenut »

Online kevinof

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #88 on: 01/18/2018 02:33 PM »
Nope. Dragon2 is not their end-game. BFR is where they want to be and why waste the money and time getting legs on a Dragon?

Online abaddon

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #89 on: 01/18/2018 03:03 PM »
That's 19 times in a row since the last fuelling explosion on 1 September 2016 with AMOS 6.
Wrong, static fires fully fuel the vehicle, and every launch has been preceded by a static fire.  The originally cited 38 is correct.

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #90 on: 01/18/2018 03:08 PM »
As an aside, whatever risk there is in Astros needing to use the Boeing crew escape system (the slide wire) from the pad must be accounted for.  I would assume the estimated level of risk in using the system itself is generally considered to be low.  Presumably the window of time where it would be used is also low, as once the Astros are in the craft and buckled in, the LES should take over responsibility rather than using the slide wire.

Also worth noting that SpaceX has no equivalent system because of their plans to board unfueled.  If at some point those plans change, they will presumably have to implement a crew escape system similar to Boeing's.

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #91 on: 01/18/2018 03:44 PM »
As an aside, whatever risk there is in Astros needing to use the Boeing crew escape system (the slide wire) from the pad must be accounted for.  I would assume the estimated level of risk in using the system itself is generally considered to be low.  Presumably the window of time where it would be used is also low, as once the Astros are in the craft and buckled in, the LES should take over responsibility rather than using the slide wire.

Also worth noting that SpaceX has no equivalent system because of their plans to board unfueled.  If at some point those plans change, they will presumably have to implement a crew escape system similar to Boeing's.

Which will add delay. Which will be the fault of SpaceX even if NASA or congress mandates it.

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Online gongora

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #92 on: 01/18/2018 03:55 PM »
Also worth noting that SpaceX has no equivalent system because of their plans to board unfueled.  If at some point those plans change, they will presumably have to implement a crew escape system similar to Boeing's.

I thought SpaceX is also going to have a slide wire system on 39A?

Online DigitalMan

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #93 on: 01/18/2018 04:03 PM »
Also worth noting that SpaceX has no equivalent system because of their plans to board unfueled.  If at some point those plans change, they will presumably have to implement a crew escape system similar to Boeing's.

I thought SpaceX is also going to have a slide wire system on 39A?

There already was a slide wire system.  I donít know what state it was in but I can probably dig up pictures from just before 39A handover

Offline woods170

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #94 on: 01/18/2018 06:00 PM »
I wonder what ASAP had to say about fuel transfers to the ISS? And next fuel depots in space. Although a different environment it will become SOP (or has) one day with crew onboard.

ASAP has nothing to say about that, given that fuel transfer to the ISS is already happening, on a regular basis, on the Russian Segment. It was done on five (5) ATV missions and Progress freighters also regularly transfer fuel into the tanks of the Zvezda module.

Offline woods170

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #95 on: 01/18/2018 06:03 PM »
Also worth noting that SpaceX has no equivalent system because of their plans to board unfueled.  If at some point those plans change, they will presumably have to implement a crew escape system similar to Boeing's.

I thought SpaceX is also going to have a slide wire system on 39A?

That was the plan once. But plans may have changed when they switched to fueling after the crew has boarded. Don't know if the slide wires will still be there.

Offline Robotbeat

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #96 on: 01/19/2018 04:11 AM »
Wow this thread is like Deja vu all over again from AMOS-6... :o

Sorry if I'm annoying people. I just can't wrap my head around the idea that working around, riding an elevator beside, climbing into etc. an empty shell might be considered more dangerous than doing the same things when the empty shell has been transformed into a very large bomb.

It's statistical analysis.

It's the same reason it's fine for them to store large amounts of fuel and oxidizer on site for months and have people working around them, but why no extraneous personnel can be around when it's transferred from the trucks.
Statistical analysis? I doubt it.

NASA likes to do things like not count, say, the LAS as part of the safety situation when analyzing such things because "LAS is only for last resort." (Oh, and treating pad crew separate from astronaut.) That's not very statistically sound and can end up being MUCH, MUCH less safe. For example:

Let's say, not counting LAS, that loading the astronauts in the capsule, then fueling it up, is twice as dangerous to the astronauts as fueling the vehicle and THEN loading the astronauts.

"LAS is a last resort, so we can't count it." Uh huh. However, pad abort is something the LAS should be particularly good at since the vehicle isn't even moving, but let's give it just a 9/10 chance of success.

That means that, if you count the system as it ACTUALLY is, with LAS and everything, it's fully FIVE TIMES safer the put the astronauts in the LAS-equipped capsule before fueling than after.

Not only that, but it's like (nearly) infinitely safer for the pad crew to evacuate them before fueling the rocket!

This sort of rule-based safety culture, which can ignore actual full resultant risk when making decisions, seems pervasive at NASA just by talking to people. But Gerstenmeier (who always impresses me) in his testimony said that NASA won't play those word games and instead will do a fair safety assessment.

I hope so.
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Offline A_M_Swallow

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #97 on: 01/19/2018 08:27 AM »
Nope. Dragon2 is not their end-game. BFR is where they want to be and why waste the money and time getting legs on a Dragon?

Because SpaceX will want to get the BFR's launch escape system (LES) to a high technology readiness level (TRL) before they build it into a BFR. This includes the guidance system software for the LES and landing from space. SpaceX does not a BFR yet but it will soon have some used Dragon 2s to which legs can be added.

Online kevinof

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #98 on: 01/19/2018 08:40 AM »
So let me understand this. Currently, during even a static fire, they close off the pad, put up road blocks , remove everyone to a distance to 50,000 miles and then do the static fire.

What Nasa are proposing is the same process, but then stick their prized Astos and employees (and Spacex) in a bus, drive back to the pad, climb the gantry, out on the crew arm , open the hatch and get the crew seated (and if I remember from the Shuttle days this took forever) all the while standing a couple of metres away from this fully fuelled and loaded , hissing and grumbling rocket.

Are they serious? Seems to me it's lack of logic and more "we've always done it this way and therefore there is no other way" thinking.

Offline woods170

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #99 on: 01/19/2018 09:30 AM »
So let me understand this. Currently, during even a static fire, they close off the pad, put up road blocks , remove everyone to a distance to 50,000 miles and then do the static fire.

What Nasa are proposing is the same process, but then stick their prized Astos and employees (and Spacex) in a bus, drive back to the pad, climb the gantry, out on the crew arm , open the hatch and get the crew seated (and if I remember from the Shuttle days this took forever) all the while standing a couple of metres away from this fully fuelled and loaded , hissing and grumbling rocket.

Are they serious? Seems to me it's lack of logic and more "we've always done it this way and therefore there is no other way" thinking.

This.

This is exactly why.

NASA has a very substantial database on everything involved in putting the crew on the vehicle AFTER it has been fueled.
They have NO knowledge on everything involved in putting crew on the vehicle BEFORE it is fueled.

Plain-and-simple it is this: NASA is afraid of change.

That's why NASA shot down propulsive landing for Crew Dragon: it is a radical break from the traditional way to land a capsule (parachute).

That's why SLS is basically a modern-day implementation of a 1970s-based launch vehicle design (RS-25, SRBs, external foam insulation, etc, etc.)

That is why NASA is still using the 1970's EMUs for EVAs because they don't dare completing and certifying their half dozen newer suit designs.

That is why NASA has the US Navy involved in post-landing crew-egress and recovery of Orion, in stead of using (much cheaper) commercially available assets.

That is why NASA is designing its monster rocket by itself, in stead of having the industry do it for them.

That is why the huge success of COTS/CRS model was not repeated for CCP: it upset their established way-of-doing-things too much when applied on a bigger scale.

Etc, etc, etc.

But I digress.
« Last Edit: 01/19/2018 09:32 AM by woods170 »

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