SpaceX Falcon 9 : CRS-13 : Dec 15, 2017 : DISCUSSION

[Exastro]

I like to imagine the booster covered in soot, with the words "WASH ME" rubbed on it in huge letters.

[russianhalo117]

Also there is a claim the F9 will "look" a bit different than you'd expect. Nothing dramatic, more amusing (and practicable), but I want to "see" it before blurting anything else in public. I'll see if SpaceX want to confirm/comment on it before we see the booster rollout.

Did they decide not to wash the booster this time? Saving some money right there.

soot residue is added weight.

[vaporcobra]

Also there is a claim the F9 will "look" a bit different than you'd expect. Nothing dramatic, more amusing (and practicable), but I want to "see" it before blurting anything else in public. I'll see if SpaceX want to confirm/comment on it before we see the booster rollout.

Did they decide not to wash the booster this time? Saving some money right there.

soot residue is added weight.

For a first stage, the additional weight of soot is almost certainly a rounding error. Second stage is a different situation, but not the first stage.

[Exastro]

[size=78%]For a first stage, the additional weight of soot is almost certainly a rounding error. Second stage is a different situation, but not the first stage.[/size]

For a 10-micron thick layer of 2 gm/cm^3 soot covering a 10 meter length of a 3.7 m diameter cylinder, the mass would be around 5 kg.

[Exastro]

For a 10-micron thick layer of 2 gm/cm^3 soot covering a 10 meter length of a 3.7 m diameter cylinder, the mass would be around 5 kg.

Sorry guys, I messed up.  It's 2.5 kg, not 5 as I said.  (I put in 3.7 m as the radius rather than the diameter).

[BradyKenniston]

What would be the potential outcome of a government shutdown on CRS-13 if it was pushed past the 8th for whatever reason (scrub, slip, etc...)? With it being an NASA/ISS mission and not a commercial mission I would imagine they would get a pass to launch as MAVEN did back in 2013 but can't seem to find any hard evidence other than that.

[vaporcobra]

For a 10-micron thick layer of 2 gm/cm^3 soot covering a 10 meter length of a 3.7 m diameter cylinder, the mass would be around 5 kg 2.5kg.

About what I would have estimated Multiply by a factor of 10 and it might matter significantly for extreme margin cases to GTO, but 2.5kg is utterly irrelevant, and essentially means a payload reduction of 2.5kg total, even while including the upper stage, which is where the "tyranny of the rocket equation" really kicks in. where 5kg of soot might translate to ~50kg payload reduction. Wonderful MIT lecture on the topic (with algebra-based physics, too!) is attached.

Edit: oops, was a magnitude off. exastro notes that 2.5kg of soot on S1 would translate to a payload reduction of ~250 grams, whereas 2.5kg of soot on S2 would mean a reduction of ~2.5kg of payload.

[Exastro]

About what I would have estimated  Multiply by a factor of 10 and it might matter significantly for extreme margin cases to GTO, but 2.5kg is utterly irrelevant, and essentially means a payload reduction of 2.5kg total. For the second stage, that's where the "tyranny of the rocket equation" really kicks in, where 5kg of soot might translate to ~50kg payload reduction. Wonderful MIT lecture on the topic (with algebra-based physics, too!) is attached.

Doesn't mass added to the upper stage reduce the payload by 1:1, and mass on the lower stage by ~0.1:1?

[Herb Schaltegger]

Increased skin friction from the dirt is a MUCH bigger deal than weight of dirt for most flying vehicles, but that's because most of them are subsonic airliners, where a few gallons of jet fuel per flight can add thousands of dollars per year per plane in operating costs. Supersonic flight is whole different situation.

[deruch]

And potentially excess heating of propellants due to reduced emissivity or increased absorption, compared to pristine paint, after SpaceX has gone to all that trouble and exploded payloads to get subcooled LOX and RP-1 to work right.  But again, like the mass penalty it would all be a matter of margin.

[lrk]

But the LOX tank, which really is what needs to stay cold, always ends up with relatively little soot anyway. 

[Exastro]

And potentially excess heating of propellants due to reduced emissivity or increased absorption, compared to pristine paint

If the soot covers the tank along 10 m of its length and causes it to absorb an extra 1000 Watt/m^2 (~67% of the Solar Constant) for 5 minutes, it can heat 400 tons of propellant with a specific heat of 1.7 kJoule/(kg*Kelvin) by about 0.02 Kelvins (assuming I did this calculation right, of course).

[zubenelgenubi]

What would be the potential outcome of a government shutdown on CRS-13 if it was pushed past the 8th for whatever reason (scrub, slip, etc...)? With it being an NASA/ISS mission and not a commercial mission I would imagine they would get a pass to launch as MAVEN did back in 2013 but can't seem to find any hard evidence other than that.

NSF experts/KSC & CCAFS employees and contractors?

I don't know if this will make a difference, but the SLC, Falcon 9, Dragon, and the SpaceX processing and launch control facilities are on (or near) the Air Force base, not at KSC.

MAVEN was still being processed at the Payload Hazardous Servicing Facility (PHSF) at KSC on October 1, 2013.  Processing for flight was suspended for 3 days (?) until a waiver was procured.  Processing of the Atlas V, on the grounds of CCAFS, apparently continued uninterrupted.

See MAVEN launch thread, starting here: http://forum.nasaspaceflight.com/index.php?topic=31872.msg1104277#msg1104277

[Antares]

Astronauts and those directly supporting them are among the 85% of the federal government who still report for work when there is a lapse in funding.  The launch would proceed as scheduled.

[Antares]

Remember when people said that adoption of reused boosters would be slow and that NASA would be too conservative?

CRS has much more risk tolerance than other NASA flights.

I just don't understand government that is reflexively conservative.  If they're (or their team is) not looking at an objective measure of what is done to qualify before multiple flights and done to inspect between flights (and repair if necessary), are they doing anything else besides delaying progress?  What else should be done?  If we're going to demand that government look at everything, much less do everything, why do we have airlines and cars?  Are we going to say that hypervelocity and 8-9 figure payloads warrant a different approach?  If so, by what criteria do we retire those constraints?  Because if we don't, we're never getting off of this rock.

[jpo234]

I just don't understand government that is reflexively conservative.

It's the limited upside. If the mission succeeds, no one really cares. After all, it has been done many times before. But: If you try something new and it fails, you are in trouble. Everybody will scream about the waste of taxpayer money.

[abaddon]

Rollout of the CRS-13 booster. She's the CRS-11 booster and......now for the note I made earlier about appearance. She still has the soot from that landing. They've 'drawn' pinstripes in the soot. Asked SpaceX, comms people weren't sure, but the info was mentioned again by a local observation. Can't wait for photos!

So now we know!

I like to imagine the booster covered in soot, with the words "WASH ME" rubbed on it in huge letters.

Not a bad guess .

Really curious to see what this rocket looks like now.  And why the pinstripes?  Hopefully not because they are Yankee fans, that would be very sad.

[eeergo]

Really curious to see what this rocket looks like now.  And why the pinstripes?  Hopefully not because they are Yankee fans, that would be very sad.

Mentioned before: tank weld inspections.

[abaddon]

Mentioned before: tank weld inspections.

I hadn't seen it publicly mentioned before.  Link?

[drnscr]

Mentioned before: tank weld inspections.

I hadn't seen it publicly mentioned before.  Link?

Look for it in previous posts.