Author Topic: SpaceX FH: STP-2 : LC-39A : June 25, 2019 - DISCUSSION (Read 446834 times)

PM3 · « **Reply #320 on:** 04/15/2019 10:56 pm »

Quote from: Lars-J on 04/15/2019 10:21 pm

Based on the Arabsat FH center core being lost (toppled over in rough seas), I'm guessing the decision makers for this mission feel pretty good that they insisted on a new-build FH center core.

Source for "the decision makers insisted", which implies that someone at SpaceX did not want to build a new center core?

Lars-J · « **Reply #321 on:** 04/15/2019 11:04 pm »

Quote from: PM3 on 04/15/2019 10:56 pm

Quote from: Lars-J on 04/15/2019 10:21 pm
Based on the Arabsat FH center core being lost (toppled over in rough seas), I'm guessing the decision makers for this mission feel pretty good that they insisted on a new-build FH center core.

Source for "the decision makers insisted", which implies that someone at SpaceX did not want to build a new center core?

What I mean is the prime customer - USAF. I can't seem to find the source for it at the moment, I could be mistaken. I will edit the post if I find it.

crandles57 · « **Reply #322 on:** 04/15/2019 11:36 pm »

Perhaps
https://www.nasaspaceflight.com/2019/03/falcon-heavy-starlink-headline-spacexs-manifest/

Quote

However, it is important to note that despite reports that all three cores from Arabsat 6A would be reused for STP-2, NASASpaceflight.com understands that the mission will in fact use a brand new center core.
...
STP-2 will then feature the second flights of B1052 and B1053 along with B1057 – a brand new center core.

The existence of a second center core makes sense, as B1055’s landing during Arabsat 6A will likely be one of SpaceX’s most challenging to date. Due to Falcon Heavy’s flight profile, the booster will reach a higher than usual velocity. Consequently, the booster will make a hot reentry and land on OCISLY nearly 1,000 kilometers downrange – making it by far the farthest recovery attempt in SpaceX’s history.

Therefore, by having a second center core for STP-2, SpaceX will eliminate the risk of a significant delay if B1055 were to be lost or require substantial refurbishment.

That isn't clear whether it was SpaceX's decision or the customer, USAF.

Alexphysics · « **Reply #323 on:** 04/16/2019 07:20 pm »

SpaceX has put an exclusive page on their website just for this mission with descriptions of the payloads and a launch animation

www.spacex.com/stp-2

gongora · « **Reply #324 on:** 04/16/2019 08:11 pm »

The video shows the deployments being:

Oculus, cubesats : 300 x 860km at 28.5 deg?

Prox-1, NPSat, OTB, GPIM, COSMIC-2 : 720 x 720km at 24 deg?

DSX : 6000 x 12000km at 43 deg?

"Propulsive passivation" I guess means they'll move it away from DSX, passivate and leave in MEO.

Draggendrop · « **Reply #325 on:** 04/17/2019 09:58 pm »

https://twitter.com/SurreySat/status/1118500672360648704

Chris Bergin · « **Reply #326 on:** 04/19/2019 11:19 am »

Quote from: Alexphysics on 04/16/2019 07:20 pm

SpaceX has put an exclusive page on their website just for this mission with descriptions of the payloads and a launch animation

www.spacex.com/stp-2

Looks like they changed the link:

Comga · « **Reply #327 on:** 04/19/2019 04:54 pm »

Questions on the video:
It ends with a "three hour coast" followed by a "propulsive passivation".
Do we know why they plan to coast that long before passivation?
They were careful to show the passivation emitting cold gas, not igniting and heating up the engine bell.
Do we know why this is labeled "propulsive"?
Can blowing down the cold propellants change the orbit appreciably?
(I ask if we know why because guessing is OK, but sourced knowledge is what I'm after.)

gongora · « **Reply #328 on:** 04/19/2019 05:49 pm »

They specifically say 4 upper stage engine burns, and the original contract (which has been modified many times since it was signed) called for a relight after the coast. Can they do all of the satellite deployments with the first 3 burns? This was probably intended to be the first long coast demo flight, but with the STP-2 delays they've already done it a few times on other flights. More practice doesn't hurt.

Comga · « **Reply #329 on:** 04/19/2019 06:46 pm »

Quote from: gongora on 04/19/2019 05:49 pm

They specifically say 4 upper stage engine burns, and the original contract (which has been modified many times since it was signed) called for a relight after the coast. Can they do all of the satellite deployments with the first 3 burns? This was probably intended to be the first long coast demo flight, but with the STP-2 delays they've already done it a few times on other flights. More practice doesn't hurt.

But they clearly show the passivation as not igniting the engine.
It looks very intentional, as they have the stage lighting three times earlier in the video.
They could have glossed over the orbital insertion.
Do we know if its a continuous burn to the initial 300 x 860 km orbit, or if they do a coast and burn?
Scattered around we do have enough data to calculate how long a burn it would take to drop the perigee of the 6,000 by 12,000 km final orbit to ~200 km, for quick decay, but it shouldn't be much. There must be a good reason for not doing that.

Lars-J · « **Reply #330 on:** 04/19/2019 09:07 pm »

Quote from: Comga on 04/19/2019 06:46 pm

Quote from: gongora on 04/19/2019 05:49 pm
They specifically say 4 upper stage engine burns, and the original contract (which has been modified many times since it was signed) called for a relight after the coast. Can they do all of the satellite deployments with the first 3 burns? This was probably intended to be the first long coast demo flight, but with the STP-2 delays they've already done it a few times on other flights. More practice doesn't hurt.
But they clearly show the passivation as not igniting the engine.
It looks very intentional, as they have the stage lighting three times earlier in the video.
They could have glossed over the orbital insertion.

Don't treat the video as gospel. There very little to go on there, and what is there is not detailed enough.

aviators99 · « **Reply #331 on:** 04/20/2019 03:28 pm »

One of the Facebook groups has an "event time" of 2300. Is this the current plan? With all of the deployments, I imagine the window is very, very small, right?

ChrisGebhardt · « **Reply #332 on:** 04/20/2019 03:47 pm »

Quote from: aviators99 on 04/20/2019 03:28 pm

One of the Facebook groups has an "event time" of 2300. Is this the current plan? With all of the deployments, I imagine the window is very, very small, right?

No daily launch windows have been announced, nor are any pending approval right now on the Eastern Range for STP-2.

Random Facebook event aside, basic rule here on NSF is that as soon as a date and time are known, we let folks know because of the immense interest and planning that people need to do to attend the launches.

Alexphysics · « **Reply #333 on:** 04/20/2019 03:48 pm »

If it is the SpaceX facebook group, all the times there are just placeholders because Facebook requires some time for an event to be posted on the group, the launch time is currently not publicly known

GWR64 · « **Reply #334 on:** 04/20/2019 05:28 pm »

How comes the upper stage with the last burn from the LEO to the MEO? COSMIC-2 -> DSX

Something is wrong in the animation.

PM3 · « **Reply #335 on:** 04/24/2019 01:52 pm »

Satellite data; some FCC filings missing

soltasto · « **Reply #336 on:** 04/24/2019 02:05 pm »

Quote from: PM3 on 04/24/2019 01:52 pm

Satellite data; some FCC filings missing

GPIM is from NASA so they shouldn't need any FCC permit.

The Formosat 7 satellites are from NSPO but it also is a collaboration with NOAA so maybe the NOAA side will sort it out by themselves.

I'm not quite sure about the BRICSat 2 and the PSat 2 cubesats as they should be operated by the US Naval Academy Satellite Lab that has strong ties with the government, but I have no idea about their licensing.

GWR64 · « **Reply #337 on:** 04/24/2019 08:42 pm »

Quote from: PM3 on 04/24/2019 01:52 pm

Satellite data; some FCC filings missing

Thanks,
I still think, from 720 km cirkular to 6000 x 12000 km with the last ignition,
it does not work. Something does not fit with the animation.

gongora · « **Reply #338 on:** 04/24/2019 09:00 pm »

Quote from: GWR64 on 04/24/2019 08:42 pm

Quote from: PM3 on 04/24/2019 01:52 pm
Satellite data; some FCC filings missing

Thanks,
I still think, from 720 km cirkular to 6000 x 12000 km with the last ignition,
it does not work. Something does not fit with the animation.

They say they're doing four burns of the second stage. It's not clear now if they still have to relight the engine after coast, or if that would be counted as one of the four burns. They may be able to use two burns to reach one of the deployment orbits.

soltasto · « **Reply #339 on:** 04/24/2019 10:05 pm »

It can be like this:

First burn (Insertion Burn): 300kmx860kmx28.5°
First payload deploy.
Second Burn -> fire the engine at the descending node while climbing to 720 km altitude, also make a slight inclination change there (not fully prograde, but also a bit radial in and normal): 720kmx720kmx24°
Second payload deploy
Now, two options:
Option 1 (More efficient, requires more time)
Third burn -> Make a burn at the Ascending node, rise the apogee to 12000km: 720kmx12000kmx24°
Fourth burn -> Make a burn at the Descending node (Also the Apogee), rise the Perigee and change the inclination (not fully prograde, also a bit anti-normal): 6000kmx12000kmx43°
DSX deploy

Option 2 (Less efficient, requires less time)
Third burn -> Make a burn at the Ascending node, rise the apogee to 6000km: 720kmx6000kmx24°
Fourth burn -> Make a burn at the Descending node (Also the Apogee), rise the Apogee and change the inclination (not fully prograde, also a bit anti-normal): 6000kmx12000kmx43°
DSX deploy