SpaceX News

[Maui]

Hey, hey, hey! Exciting!

Where do you work now, if you don't mind me asking...

[paperburn1]

MCAS cherry point.
Flight simulation/crew training
Filled out the form on a whim.
I doubt this will lead anywhere but crews do need to be trained, simulators need to be maintained

[NotAPhysicist]

Nice one, good luck!

[NotAPhysicist]

They reckon good weather is only 40% for the launch today.
Also, the range is apparently down for maintainence/upgrade, which explains some of the slow down in launch candence. That is probably a good thing!..
Link: https://arstechnica.com/science/2017/07 ... on-sunday/

[Tom Ligon]

Is the Falcon Heavy finally going to fly this year?

Its all just talk until it is on the pad, but we'll be watching. Ought to be a good show.

http://www.spaceflightinsider.com/organ ... arly-fall/

[ladajo]

Tom,
They have been rolling it right all since last year. While I would love to see it fly tomorrow, I am willing to wait for them to get it right.
Should be a spectacular launch, and I have considered a couple of times to make the run down. The 'All-D' experience looks promising...

On another note, I had long chat with Jaeyoung this weekend. He is doing well, and the sims are progressing well.

[paperburn1]

Major problem is having the pad ready on time and also they can not start all 27 engines at once for fear of sonic rapid disassembly. But they are working on a plan to sequence start the engines all within a second or two.

[krenshala]

Is that sonic issue even with the (water) sound suppression system going?

[ladajo]

I can imagine that simultaneous start on all 27 would make quite the pop!

Have to find an old video from the Saturn Vs to see if the was a slight stagger in lights on the five engines.

I know during my time at Stennis, that there was a good pop from a single STS ME light off. Of course the ground rumble felt for miles and miles was pretty cool too. Even out in the swamp.

[paperburn1]

Is that sonic issue even with the (water) sound suppression system going?

Yep. with the Saturn five rocket the center engine ignited first, followed by opposing outboard pairs at 300-millisecond intervals to reduce the structural loads on the rocket. When thrust had been confirmed by the onboard computers, the rocket was "soft-released" in two stages: first, the hold-down arms released the rocket, and second, as the rocket began to accelerate upwards, it was slowed by tapered metal pins pulled through dies for half a second. The engines actually were started of a full 8 seconds before liftoff to allow the engines to come up to full thrust.
There is a web site and YouTube channel called "vintage space" that has a dudette that does engineering breakdowns of the tech used during that time and why they did it that way. I highly recommend it if you were not of the age to see things first hand because she also goes into how they overcame certain problems due to limits of technology back then.

[ladajo]

Thanks for the link, I will check it out. Sounds cool.
Looks like the Falcon Heavy will need to follow a similar approach. Shouldn't be too hard to manage. Especially given the comparatively exquisite throttle control and range they enjoy over the original school guys.

[Tom Ligon]

That answers my question ... why not start them out at a low throttle setting and then run them up. Apparently they do.

So, a little reverse engineering of the numbers. The Saturn V first stage burn was 165 seconds and it carried 203,400 gallons kero and 318,000 gallons of LOX, or a burn of 1233 gallons/sec of kero and 1927 gal/second of LOX. Divide by five to get the burn of the individual engines.

245 gps kero, 385 gps LOX.

So if one started at 1% throttle, what kind of explosive power do you get from 2.45 gallons of kerosene and 3.85 gallons of liquid oxygen.

Ah, I think I see the problem. Even a soft start on those engines would be a blast that would level the average home, sending bits flying for a mile.

[ladajo]

2.45 gals kerosene at about 6.82 lbs /gal at 10% tnt equivalent gives 1.67lbs tnt.
3.85 gals LOX at 9.52lbs/gal at 60% tnt equivalent gives 22lbs tnt.
Grand total: 23.67lbs tnt.

That will level a house for sure.
It is akin to a Hellfire hit, which has an equivalent warhead of about 23lbs tnt (20lbs slightly higher energy explosive)
Hellfire House Boom

Just for fun, here is a link to an explosive energy calculator. 23lbs of tnt is about 0.0115 tons of tnt.

Boom Convertor

Edit: Added Convertor Link and comment/link on battlefield equivalent.

[Tom Ligon]

Boom Converter. Gotta love it! That went straight into my favorites list, right under Engineering Toolbox and the Little Machine Shop drill size charts.

[ladajo]

Yay! Another launch and recover. Successful CRS-12 boost for IST Resupply. Really nice day on the Cape, and great video of the first stage boost, and fly back to the dirt pad. Starting to look routine...