Load and Go

NASA is at least verbally sounding more encouraging about the SpaceX
'Load and Go' launch for manned vehicles. This is good because, while
they could do it the other way, there would be a performance hit due
to the propellants having time to warm up. Block 5 has some extra
performance over Block 4, so there may be some headspace there, but
why give it up?


--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw

"Fred J. McCall" wrote in message
...

NASA is at least verbally sounding more encouraging about the SpaceX
'Load and Go' launch for manned vehicles. This is good because, while
they could do it the other way, there would be a performance hit due
to the propellants having time to warm up. Block 5 has some extra
performance over Block 4, so there may be some headspace there, but
why give it up?



Yeah, I saw that the other day. I have mixed feelings about it. I think the
performance benefit is nice, but it is one more risk. I think over time
though we'll have enough data points to know exactly how big of a risk. Is
it 1 in 100 or 1 in 1,000,000 sort of thing... Time will tell.

--
Greg D. Moore http://greenmountainsoftware.wordpress.com/
CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net
IT Disaster Response -
https://www.amazon.com/Disaster-Resp...dp/1484221834/

"Greg \(Strider\) Moore" wrote on Fri,
25 May 2018 20:16:59 -0400:

"Fred J. McCall" wrote in message
.. .

NASA is at least verbally sounding more encouraging about the SpaceX
'Load and Go' launch for manned vehicles. This is good because, while
they could do it the other way, there would be a performance hit due
to the propellants having time to warm up. Block 5 has some extra
performance over Block 4, so there may be some headspace there, but
why give it up?


Yeah, I saw that the other day. I have mixed feelings about it. I think the
performance benefit is nice, but it is one more risk. I think over time
though we'll have enough data points to know exactly how big of a risk. Is
it 1 in 100 or 1 in 1,000,000 sort of thing... Time will tell.


I don't consider it a risk any more than doing it the other way.


--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world."
-- Mary Shafer, NASA Dryden

On May/25/2018 at 8:46 PM, Fred J. McCall wrote :
"Greg \(Strider\) Moore" wrote on Fri,
25 May 2018 20:16:59 -0400:

"Fred J. McCall" wrote in message
...

NASA is at least verbally sounding more encouraging about the SpaceX
'Load and Go' launch for manned vehicles. This is good because, while
they could do it the other way, there would be a performance hit due
to the propellants having time to warm up. Block 5 has some extra
performance over Block 4, so there may be some headspace there, but
why give it up?


Yeah, I saw that the other day. I have mixed feelings about it. I think the
performance benefit is nice, but it is one more risk. I think over time
though we'll have enough data points to know exactly how big of a risk. Is
it 1 in 100 or 1 in 1,000,000 sort of thing... Time will tell.

I wouldn't want to wait until we have enough data points to tell the
risk is 1 in 1,000,000. :-)

I don't consider it a risk any more than doing it the other way.

A SpaceX rocket went kaboom recently while filling the tanks. So there
is a risk with having astronauts on board while fuelling. What extra
risk do you see the other way?


Alain Fournier

Alain Fournier wrote on Sat, 26 May 2018
08:46:43 -0400:

On May/25/2018 at 8:46 PM, Fred J. McCall wrote :
"Greg \(Strider\) Moore" wrote on Fri,
25 May 2018 20:16:59 -0400:

"Fred J. McCall" wrote in message
...

NASA is at least verbally sounding more encouraging about the SpaceX
'Load and Go' launch for manned vehicles. This is good because, while
they could do it the other way, there would be a performance hit due
to the propellants having time to warm up. Block 5 has some extra
performance over Block 4, so there may be some headspace there, but
why give it up?


Yeah, I saw that the other day. I have mixed feelings about it. I think the
performance benefit is nice, but it is one more risk. I think over time
though we'll have enough data points to know exactly how big of a risk. Is
it 1 in 100 or 1 in 1,000,000 sort of thing... Time will tell.


I wouldn't want to wait until we have enough data points to tell the
risk is 1 in 1,000,000. :-)


It doesn't take all that many data points.



I don't consider it a risk any more than doing it the other way.


A SpaceX rocket went kaboom recently while filling the tanks. So there
is a risk with having astronauts on board while fuelling. What extra
risk do you see the other way?


Yes, various rockets have gone kaboom for various reasons. The root
cause of the incident you mention has been corrected.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn

In article ,
says...

NASA is at least verbally sounding more encouraging about the SpaceX
'Load and Go' launch for manned vehicles. This is good because, while
they could do it the other way, there would be a performance hit due
to the propellants having time to warm up. Block 5 has some extra
performance over Block 4, so there may be some headspace there, but
why give it up?

Agreed. Plus loading fuel after the pad is cleared of everyone but the
astronauts (who are strapped in a capsule with an escape system), the
risk to personnel is reduced over loading fuel then strapping the crew
inside.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

In article ,
says...

"Greg \(Strider\) Moore" wrote on Fri,
25 May 2018 20:16:59 -0400:

"Fred J. McCall" wrote in message
.. .

NASA is at least verbally sounding more encouraging about the SpaceX
'Load and Go' launch for manned vehicles. This is good because, while
they could do it the other way, there would be a performance hit due
to the propellants having time to warm up. Block 5 has some extra
performance over Block 4, so there may be some headspace there, but
why give it up?


Yeah, I saw that the other day. I have mixed feelings about it. I think the
performance benefit is nice, but it is one more risk. I think over time
though we'll have enough data points to know exactly how big of a risk. Is
it 1 in 100 or 1 in 1,000,000 sort of thing... Time will tell.


I don't consider it a risk any more than doing it the other way.

Agreed. This is especially true for the ground crew which many people
seem to forget about (or at least they don't mention them).

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

In article ,
says...

On 2018-05-25 20:46, Fred J. McCall wrote:

I don't consider it a risk any more than doing it the other way.

From a performance point of view, isn't SpaceX concerned about having
the kerosene fuel as cold as possible? (aka: loaded only at last minute)

Doesn't LOX remain cold naturally once loaded and the only concern to
have it constantly refilled as some of it boils out?

No. SpaceX cools the LOX almost to the point where it would start to
become solid. They call it "sub-cooled". So if you load it and let it
sit, it warms up to the point that it's at the boiling point of LOX
instead of the much colder "sub-cooled" temperature. As you know from
physics, the colder it gets the more dense it gets. So, they can load
more LOX into the vehicle when it's sub-cooled than when it's at its
boiling point.

They also cool the kerosene for the same reasons. But I'd imagine the
LOX is going to heat up faster because conduction of heat depends on the
difference in temperature between the fluid and the outside ambient
temperature, which is far greater for the LOX than for the kerosene.

Seems to me that loading the He2 under pressure and LOX that surrounds
it is the higher risk part and could be done before they board, and then
load the kerosene at last minute so it is as cold as possible.

Can't do it that way and keep the LOX sub-cooled.

Note: comemrcial aircraft have various restrictions on fueling aircraft
when there are passengers on-board vs boarding/deplaning vs empty. (and
these vary depending on fuel being used).

Cite?

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

JF Mezei wrote on Sat, 26 May 2018
18:41:53 -0400:

On 2018-05-25 20:46, Fred J. McCall wrote:

I don't consider it a risk any more than doing it the other way.


From a performance point of view, isn't SpaceX concerned about having
the kerosene fuel as cold as possible? (aka: loaded only at last minute)


Well, not "as cold as possible", since that would mean it was frozen
solid, but I take your meaning and I already said just that an article
or two ago. Again, Block 5 has higher performance than Block 4, so
the performance difference from propellant density may be manageable.


Doesn't LOX remain cold naturally once loaded and the only concern to
have it constantly refilled as some of it boils out?


No. That would violate physics. There wouldn't be anything 'boiling
off' if it just remained cold.


Seems to me that loading the He2 under pressure and LOX that surrounds
it is the higher risk part and could be done before they board, and then
load the kerosene at last minute so it is as cold as possible.


Except LOX and helium don't violate the laws of physics, so they start
warming up the instant they hit the tanks.


Note: comemrcial aircraft have various restrictions on fueling aircraft
when there are passengers on-board vs boarding/deplaning vs empty. (and
these vary depending on fuel being used).


Note: Well, not really.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn

JF Mezei wrote on Sun, 27 May 2018
18:00:45 -0400:

On 2018-05-26 21:16, Jeff Findley wrote:

No. SpaceX cools the LOX almost to the point where it would start to
become solid. They call it "sub-cooled".


thanks. Knew about kerosene being cooled, didn't realize they did that
to LOX too.

How long does SpaceX take to load rocket with both LOX and kerosene? And
how long before launch does SpaceX expect crews to be strapped in, hatch
closed?

The "conflict" may exist because SpaceX wants the extra "cold"
performance to raise odds of successful landing whereas NASA isn't
inteested in that part, only interested in getting crew to ISS. (which I
assume is not straining performance and may not require the "extra cold"
fuel. (I have no data on this, just theory/speculation).


Well, NASA kind of cares, since it affects the price they get charged.


You raised ground crew safety. There is a corollary to this: it is safer
to have a rocket being fueled with no activity near pad, no equipment
moving, no motors starting/stoppiong, no cars/trucks etc. So it isn't
just the lived of ground crews, but also not having them there likely
reduces risks of things going kablouee.

Note: comemrcial aircraft have various restrictions on fueling aircraft
when there are passengers on-board vs boarding/deplaning vs empty. (and
these vary depending on fuel being used).

Cite?


Google FAA aircraft refueling regulations.


Do you know what a request for a cite to back up your claims means. I
can tell you what it does NOT mean. It does NOT mean telling someone
to go google something. Care to try again?


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn