SpaceX Falcon 9 : Intelsat 35e : July 5, 2017 : DISCUSSION

[M.E.T.]

To those with more insight into these matters, is the profitability of a launch significantly affected by a scrub?

I assume things like range costs would double, staff need to be paid overtime etc. Can the fuel be reused or does it pick up dirt or other contaminants that affect its suitability for reuse the next day?

Basically, does SpaceX lose a lot of money each time a launch is stopped late in the count?

And yes, before someone says it, I'm fully aware that any such financial loss is minimal compared to the potential loss of a vehicle and payload. I'm merely trying to understand how a scrub affects the profitability of a launch, from the launch provider's point of view. Is it a 1% hit to the profit margin, or is it closer to 10%, or perhaps more?

[saliva_sweet]

My recollection is that we were told that there were more serious consequences to aborting after T-10 rather than before.
(With some sincerity I hypothesized that Musk, who had been watching something out-of-family since about T-60 min, waited until T-15 seconds to call an abort so that it WOULDN'T go under T-10.)
Does anyone have any information on what systems change at T-10 and what those consequences could be?

IIRC the consequences aren't necessarily more serious, but there is no way to manually abort after T-10. It's all automatic then. This used to be recited out on the countdown net on earlier streams, something like "operator shall not call a hold after t - 10 seconds". So if you wanted to manually hold the count you had to do it before then.

[drzerg]

as i remember from one of the webcasts after -10 you can not manually abort launch. only rocket itself can do this. so final 10s go / go checks are fully automated.

[Dante2121]

as i remember from one of the webcasts after -10 you can not manually abort launch. only rocket itself can do this. so final 10s go / go checks are fully automated.

Could any of these checks be performed much earlier in the count too?  Obviously some can only be performed in last few seconds as everything turns on and pressurized for launch, but guidance not working seems like something you could additionally check at T60 minutes before even loading fuel.  You'd still want to check again in final seconds to be safe.

TL/DR why can't they find more of these scrub causes sooner in the count.

[smoliarm]

as i remember from one of the webcasts after -10 you can not manually abort launch. only rocket itself can do this. so final 10s go / go checks are fully automated.

Could any of these checks be performed much earlier in the count too?  Obviously some can only be performed in last few seconds as everything turns on and pressurized for launch, but guidance not working seems like something you could additionally check at T60 minutes before even loading fuel.  You'd still want to check again in final seconds to be safe.

TL/DR why can't they find more of these scrub causes sooner in the count.

>>...but guidance not working seems like something you could additionally check at T60 minutes

- well, IIRC, GNC stands for "Guidance, Navigation and Control".
So, my guess would be - some of the CONTROLS do not comply with your formula quoted above.

[mn]

Not actually official yet, but the way KSC is acting on the notes of roadblocks and preps suggests they are deep into activating the 24 hour scrub turnaround, so another attempt today. Caveat is they can take it down to polling points, so yeah - but let's go with another attempt until we hear different.

So is the update posted earlier by Steven from http://www.spacex.com/webcast not official?

SpaceX update.

"Following scrub for a guidance abort on the first attempt, SpaceX is now targeting launch of Intelsat 35e from Launch Complex 39A (LC-39A) at NASA’s Kennedy Space Center in Florida on Monday, July 3, at 7:37 p.m. EDT, or 23:37 UTC. The launch window will remain open for 58 minutes and the satellite will be deployed approximately 32 minutes after launch."

[LouScheffer]

We know this is a burn to depletion, targeting 26^o.  What should we expect?

Compare to Inmarsat.  That put 6086 kg into a 70K km apogee, 24.5^o orbit, needing minimal GTO+377m/s.

Plugging in the new mass of 6761 kg, second stage estimates (ISP=348, empty mass 4.5t, fuel 111.5t), plus  a small first stage loss, gives a total delta V of 202 m/s less.  So it should still reach GTO, but with only 175 m/s left over.  Adding in the final inclination of 26^o, we get an apogee of 48K km, with a delta-V remaining to GEO of about 1700 m/s.

Of course since this is a burn to depletion, dispersions could be quite large  (the apogee spec is 31K km, or greater).  But if it performs as well as the last one, it will be super-synchronous and Intelsat will get a good deal.

[Rocket Science]

In the count timeline at T-0:00:10 Latest VC Abort. Perhaps at this point was the conflict noted and required abort. So the system performed as it should...

[Wolfram66]

In looking at the images of the F9 on SFN, No grid-fins of course, but do they remove the Cold Gas N2 thrusters or just not load the Nitrogen?

https://spaceflightnow.com/2017/07/03/spacex-scrubs-sunday-launch-attempt-with-intelsat-relay-satellite/

[LouScheffer]

Falcon 9 does it with just two stages, and no fancy business (RP fuel and straight GG engines).  It seems like black magic or something.

I see this not as black magic, but a sign that conventional wisdom about maximizing ISP needs adjusting.  CW says that high ISP = high performance.  But it's known that hydrogen is very light, so the mass fraction is worse, and the thrust is low, so gravity losses hurt.  The ISP boost is commonly thought to out-weigh this, but maybe it's not so, especially if you enhance the density benefit of RP-1/LOX with sub-cooling.

Likewise, staged combustion helps ISP.  But the engines are significantly heavier, which cancels some of this benefit.

So I think the drawbacks of these technologies are perhaps under-estimated.  Careful engineering of simpler solutions can apparently be more than competitive.

Finally, I suspect a psychological (confirmation bias) component.  Both hydrogen and staged combustion are expensive and hard to master.  So they must be good, right?   Especially to those that have taken the time and effort to master them. 

[edkyle99]

Falcon 9 does it with just two stages, and no fancy business (RP fuel and straight GG engines).  It seems like black magic or something.

I see this not as black magic, but a sign that conventional wisdom about maximizing ISP needs adjusting.  CW says that high ISP = high performance.  But it's known that hydrogen is very light, so the mass fraction is worse, and the thrust is low, so gravity losses hurt.  The ISP boost is commonly thought to out-weigh this, but maybe it's not so, especially if you enhance the density benefit of RP-1/LOX with sub-cooling.

We should probably take this to another thread.  I'll point out that a Falcon 9 with an LH2 upper stage would only really need to be a "Falcon 7".

 - Ed Kyle

[DecoLV]

Isn't one of the very last things any rocket does is take a snapshot of its relative position in space, for tracking purposes? This is because of the earth's rotation, so the closer to liftoff the better, right? So do we know when F9 does that? I'm imagining that that final GNC box get not get ticked, causing the abort. What would have fouled that?

[Rocket Science]

Isn't one of the very last things any rocket does is take a snapshot of its relative position in space, for tracking purposes? This is because of the earth's rotation, so the closer to liftoff the better, right? So do we know when F9 does that? I'm imagining that that final GNC box get not get ticked, causing the abort. What would have fouled that?

Yes, that happens at T-0:02:00    Flight Control to Self Alignment per the timeline...

[Lars-J]

From the update thread:

I assume they have to unload the LOx? Also do they need to unload the RP1? Then they probably have tovrechill the Oxygen and pump it back?

Fingers crossed for tonight.

Yes. But that unloading was done yesterday after the scrub. A 24hr turn-around is not a problem for the propellant chilling.

[Eagandale4114]

Is there any way to listen to the LD loop?

[The Roadie]

Is there any way to listen to the LD loop?

Yes, if you're an accredited journalist. You should have gotten an email.

[Herb Schaltegger]

Is there any way to listen to the LD loop?

Yes, if you're an accredited journalist. You should have gotten an email.

It might have been a bit more polite to phrase that as, "Not unless you're an accredited journalist. Most people don't get that kind of access."

[The Roadie]

It might have been a bit more polite to phrase that as, "Not unless you're an accredited journalist. Most people don't get that kind of access."

At T-50 minutes on a weather-filled scrub delay day, I admit to letting stress overcome my normal politeness. Apologies for the snark. #nowbacktosweating

[cppetrie]

It will definitely be nice when the RSS is gone and we get a nearly unobstructed view of the rocket on the pad from the SFN camera feed.

[Welsh Dragon]

Poor booster knows the lack of legs and fins can only mean one thing, and it's not going anywhere!