SpaceX: General Falcon and Dragon discussion (Thread 5)

[ugordan]

I would take that as FlightGlobal's artistic license and not based on any hard evidence from SpaceX. There have been raised eyebrows in the past about FlightGlobal's space reporting.

This alone should have raised question marks here:

"The Merlin 1D will offer up to 155,000lb (689kN) of thrust, an upgrade over the 140,000lb predecessor, the Merlin 1C"

[corrodedNut]

I would take that as FlightGlobal's artistic license and not based on any hard evidence from SpaceX. There have been raised eyebrows in the past about FlightGlobal's space reporting.

I'd have to agree until shown otherwise.

For instance: "The Merlin 1D will offer up to 155,000lb (689kN) of thrust, an upgrade over the 140,000lb predecessor, the Merlin 1C."

How'd they get that second number? Not much fact-checking.

Aww, beat me to it... What's the real number? 98k?

[ugordan]

What's the real number? 98k?

About 96 klbf, IIRC. The C1 demo press kit says 854 klbf total stage thrust, but cosine losses might have been factored in.

[Comga]

What's the real number? 98k?

About 96 klbf, IIRC. The C1 demo press kit says 854 klbf total stage thrust, but cosine losses might have been factored in.

There are no cosine losses. There are other effects from the close proximity of the 9 engines, but they all point along the same axis.

Edit: typo (and yes, ugordan, I am sure about that.)

[ugordan]

You *sure* about that?

[OpsAnalyst]

AvWeek on the difficulties faced by SpaceX re: schedule:

http://www.aviationweek.com/aw/generic/story_channel.jsp?channel=space&id=news/awst/2012/03/12/AW_03_12_2012_p49-431419.xml&headline=SpaceX%20Gleam%20Slips%20With%20Launch%20Plans

[ArbitraryConstant]

For instance: "The Merlin 1D will offer up to 155,000lb (689kN) of thrust, an upgrade over the 140,000lb predecessor, the Merlin 1C."

How'd they get that second number? Not much fact-checking.

I believe those numbers are the SL and Vac thrust for the 1D, Vac thrust being higher because of the greater pressure differential between the combustion chamber and outside.

You *sure* about that?

Yup.

Cosine losses are incurred when thrust is off-axis. Falcon 9's thrust isn't.

[ugordan]

Cosine losses are incurred when thrust is off-axis. Falcon 9's thrust isn't.

Err, F9 thrust is a sum total of the thrust of 9 engines. 8 of them do *not* lie on the vehicle axis.

Can you really say with authority that the outer 8 engines aren't canted to pass closer to vehicle CG for controlability reasons, Saturn I-style? Because all the images and footage *I've* seen, both pad static tests as well as exhaust plume after liftoff strongly suggest to me the outer engines aren't firing straight down, but with a slight sideways component.

[RocketmanUS]

and this.. not a direct quote:

SpaceX is in the midst of a variety of ambitious engine programmes, including the Merlin 2, a significant modification of the Merlin 1 series, and the Raptor upper stage engine. Details of both projects are tightly held.

I would take that as FlightGlobal's artistic license and not based on any hard evidence from SpaceX. There have been raised eyebrows in the past about FlightGlobal's space reporting.

I'd have to agree until shown otherwise.

Is SpaceX developing the Merlin 2?
Are they developing the Raptor?

[mmeijeri]

Can you really say with authority that the outer 8 engines aren't canted to pass closer to vehicle CG for controlability reasons, Saturn I-style?

Interesting, I didn't know that. So it isn't just some last-seconds checkout procedure?

[ArbitraryConstant]

Can you really say with authority that the outer 8 engines aren't canted to pass closer to vehicle CG for controlability reasons, Saturn I-style?

This practice was unknown to me, thanks for the information.

[corrodedNut]

Commercial Crew update:

http://www.spacex.com/updates.php

[RocketmanUS]

Commercial Crew update:

http://www.spacex.com/updates.php

Crew seats , liner custom fit for each crew member
Up to 6"5" 250lb person ( does not say how short a person could be )

How would a custom fit lined seat handle bringing back a different sized person?

Edit:
They have two great pics.
One with people in the seats.
And one with Elon and two others standing in the capsule showing how much space there is inside.

[corrodedNut]

Commercial Crew update:

http://www.spacex.com/updates.php

Crew seats , liner custom fit for each crew member
Up to 6"5" 250lb person ( does not say how short a person could be )

How would a custom fit lined seat handle bringing back a different sized person?

Like Souyz, I guess, every crewmember has their own liner.

[ugordan]

So it isn't just some last-seconds checkout procedure?

I don't believe so. They most likely perform steering checks earlier, but I think they lock the Merlins into flight position a couple of minutes before liftoff.

[Robotbeat]

So it isn't just some last-seconds checkout procedure?

I don't believe so. They most likely perform steering checks earlier, but I think they lock the Merlins into flight position a couple of minutes before liftoff.

Canting the engines so the line of thrust goes through the center of mass allows greater stability (such as in the case of sudden sub-standard performance of an engine or, in the worst case, engine-out), but I wonder if they are made more parallel if they need the performance margin.

[Blackjax]

Commercial Crew update:

http://www.spacex.com/updates.php

Crew seats , liner custom fit for each crew member
Up to 6"5" 250lb person ( does not say how short a person could be )

heh, gives me the mental image of this at the base of the launch tower...

[DavisSTS]

Aviation Week with a smackdown on SpaceX and their slips.

http://www.aviationweek.com/aw/generic/story.jsp?id=news/awst/2012/03/12/AW_03_12_2012_p49-431419.xml&headline=SpaceX%20Loses%20Gleam%20Slips%20With%20Launch%20Plans&channel=space

[Nate_Trost]

And one with Elon and two others standing in the capsule showing how much space there is inside.

I want to see the picture with how much space is left with a real ECLSS integrated...

[mmeijeri]

I don't believe so. They most likely perform steering checks earlier, but I think they lock the Merlins into flight position a couple of minutes before liftoff.

How about the Shuttle? Didn't the engines "wiggle" a couple of seconds before lift-off?