SpaceX FH: STP-2 : LC-39A : June 25, 2019 - DISCUSSION

[ZachS09]

I have a question about the length of the webcast.

Obviously, they’ll show the early ascent culminating with SECO-1 and the center core touchdown, but what I’m wondering is if they’ll show the second and third burns before ending the webcast at the start of the 3-hour coast.

Is that a possible theory?

[Star One]

I wonder if the flight profile represents the way that the DoD conducts or wants to conduct its launches: launch in one direction, then after first stage separation change orbit/inclination multiple times and drop the sat(s) some time before the end of the whole second stage mission to make things harder for an observer.

I suspect what Space X are after is showing they can launch payloads like the KH-11 & Advanced Orion which probably represent big bucks.

[gongora]

I wonder if the flight profile represents the way that the DoD conducts or wants to conduct its launches: launch in one direction, then after first stage separation change orbit/inclination multiple times and drop the sat(s) some time before the end of the whole second stage mission to make things harder for an observer.

I don't think inclination changes like this will be a normal thing for DoD missions.  They had several payloads that needed rides, and they had a launch vehicle to test that supposedly was going to have a lot of performance, so they came up with this mission to see what it could do.

[Mandella]

I have a question about the length of the webcast.

Obviously, they’ll show the early ascent culminating with SECO-1 and the center core touchdown, but what I’m wondering is if they’ll show the second and third burns before ending the webcast at the start of the 3-hour coast.

Is that a possible theory?

I'm guessing they will do like they usually do and just pause and resume their live coverage as they have anything interesting to show.

[emerrill]

I have a question about the length of the webcast.

Obviously, they’ll show the early ascent culminating with SECO-1 and the center core touchdown, but what I’m wondering is if they’ll show the second and third burns before ending the webcast at the start of the 3-hour coast.

Is that a possible theory?

I'm guessing they will do like they usually do and just pause and resume their live coverage as they have anything interesting to show.

Yeah, I don't think any part of this mission is classified, so I would think we will get the normal webcast.

[LouScheffer]

[First orbit]         300 km x 860 km x 28.5 deg
[second orbit]     720 km x 720 km x 24 deg

I calculate 597.8 m/s from the first to second orbit [...]

http://www.sworld.com.au/steven/space/orbit.zip

Delta-V calculator by Steven S. Pietrobon. 22 Jun 2019.
Enter negative perigee height to exit program.
Enter negative height for geosynchronous altitude.

Enter initial perigee height (km): 300
Enter initial apogee height (km): 860
Enter required inclination change (deg): 4.5
Enter required perigee height (km): 720
Enter required apogee height (km): 720

[...]

Burn at   860.0 km: theta1 =  3.68 deg, dv1 =  484.3 m/s
Burn at   720.0 km: theta2 =  0.82 deg, dv2 =  113.5 m/s
dv =  597.8 m/s

Seems correct, but this is not the way SpaceX will do this, I think, since number of burns is a tighter limit than delta-V.   This can be done with one burn - as the 300 x 800 orbit crosses 720km, a single burn can re-direct into a 720x720 at any inclination.   The magnitude of this burn will require full 3D trig to figure out, though.  I suspect it's comparable.

Thinking about this further, it can be reduced to two 2D problems.  Use the reference frame tangent to a 720 km sphere where the original orbit crosses it, with the X axis aligned with the original orbit plane.  The two orbits cross at the origin in this frame.  Using the formula v=sqrt(gm * (2/r - 1/sma)), we find that

old_v = 7421.59  m/s (original orbit)
new_v= 7497.48 (new orbit)

Now the flight path angle, which is the angle of the rising orbit, can be found as cos^-1(sam/(r*v)), where sam = Specific Angular Momentum, a conserved quantity (equal to r*v at apogee or perigee) . In this case it is 0.0348994 radians, or  1.99959 degrees.  Now we have two 2-D problems in the tangent space:

x0 = old_v*cos(fpa);
y0 = 0;                  # because we picked the X axis to align with this frame.
z0 = old_v*sin(fpa);

With PC being the angle of the plane change,
x1 = new_v*cos(pc);
y1 = new_v*sin(pc);
z1 = 0;                  # because the new orbit, being circular, is tangent to the plane.

Now we take the difference between the two vectors to get
delta-V= 645.27 m/s

So a single burn can do the trick, but it's slightly less efficient than the two-burn solution calculated above.

[ZachS09]

I have a question about the length of the webcast.

Obviously, they’ll show the early ascent culminating with SECO-1 and the center core touchdown, but what I’m wondering is if they’ll show the second and third burns before ending the webcast at the start of the 3-hour coast.

Is that a possible theory?

I'm guessing they will do like they usually do and just pause and resume their live coverage as they have anything interesting to show.

Yeah, I don't think any part of this mission is classified, so I would think we will get the normal webcast.

So basically, they'll take a three-hour break before coming back with the end of mission?

I didn't mean by the webcast ending because of classification. I was judging it based off of how long the viewers would want to sit and watch.

[lonestriker]

I have a question about the length of the webcast.

Obviously, they’ll show the early ascent culminating with SECO-1 and the center core touchdown, but what I’m wondering is if they’ll show the second and third burns before ending the webcast at the start of the 3-hour coast.

Is that a possible theory?

I'm guessing they will do like they usually do and just pause and resume their live coverage as they have anything interesting to show.

Yeah, I don't think any part of this mission is classified, so I would think we will get the normal webcast.

So basically, they'll take a three-hour break before coming back with the end of mission?

I didn't mean by the webcast ending because of classification. I was judging it based off of how long the viewers would want to sit and watch.

IIRC when SpaceX has had a very long delay, they've just closed the webcast and told people to follow them on social media for deployment and updates.  I doubt they'll play hold music for 3 hours and wait, especially given the launch is 30 minutes before midnight Eastern Daylight Time.

[Rondaz]

Falcon Heavy L-2 Weather Forecast: 70% Chance Favorable

Sarah Loff Posted on June 22, 2019

Meteorologists with the U.S. Air Force 45th Space Wing predict a 70% chance of favorable weather for liftoff of a SpaceX Falcon Heavy rocket Monday, June 24, from Launch Complex 39A at NASA’s Kennedy Space Center in Florida. The launch window opens at 11:30 p.m. EDT.

The Falcon Heavy will launch two dozen satellites to space for the U.S. Department of Defense Space Test Program-2 mission.

Aboard are two NASA technology demonstrations to improve how spacecraft propel and navigate, as well as two NASA science missions to help us better understand the nature of space and how it impacts technology on spacecraft and the ground.

Forecast Details
An upper-level ridge remains over the Southeast U.S., reducing the coverage of the shower and thunderstorm activity over Central Florida. The surface ridge axis will remain south of the Space Coast however, keeping the east coast sea breeze pinned close to shore with only isolated afternoon showers. This southwesterly flow will also bring high temperatures in the 90s over the Spaceport. This pattern will begin to change Sunday into Monday, as a storm system digs into the Gulf Coast States, destabilizing the atmosphere and increasing shower and thunderstorm activity across Central Florida. The primary weather concerns for a launch attempt overnight Monday into early Tuesday morning are lingering anvil and thick layer clouds from afternoon convection.

On Tuesday, the upper-level ridge will continue moving east, allowing the storm system to drop into Northern Florida. Consequently, the coverage and intensity of showers and storms are expected to increase.

Prelaunch Technology Show: June 23
A prelaunch NASA technology show is scheduled for Sunday, June 23 at noon from Kennedy. NASA will stream the briefing live at https://www.nasa.gov/live.

Launch Coverage: June 24
Live NASA Television coverage of the Falcon Heavy launch will begin 30 minutes before liftoff.

While each has a unique set of objectives, the NASA missions on this launch have a common goal: improve future spacecraft design and performance, no matter the destination. For additional information about the NASA technologies aboard the launch, visit: www.nasa.gov/spacex

https://blogs.nasa.gov/spacex/2019/06/22/falcon-heavy-l-2-weather-forecast-70-chance-favorable/

[ZachS09]

I have a question about the length of the webcast.

Obviously, they’ll show the early ascent culminating with SECO-1 and the center core touchdown, but what I’m wondering is if they’ll show the second and third burns before ending the webcast at the start of the 3-hour coast.

Is that a possible theory?

I'm guessing they will do like they usually do and just pause and resume their live coverage as they have anything interesting to show.

Yeah, I don't think any part of this mission is classified, so I would think we will get the normal webcast.

So basically, they'll take a three-hour break before coming back with the end of mission?

I didn't mean by the webcast ending because of classification. I was judging it based off of how long the viewers would want to sit and watch.

IIRC when SpaceX has had a very long delay, they've just closed the webcast and told people to follow them on social media for deployment and updates.  I doubt they'll play hold music for 3 hours and wait, especially given the launch is 30 minutes before midnight Eastern Daylight Time.

Exactly. That was my point from the beginning. They did that during the early commercial missions for the v1.1 version. Examples include SES-8 and Thaicom 6.

[emerrill]

Note that at a briefing I just came from, the STP-2 mission manager said the second stage will just be disposed of in the DSX orbit.

[Alexphysics]

Note that at a briefing I just came from, the STP-2 mission manager said the second stage will just be disposed of in the DSX orbit.

No surprise on that, tbh. Considering they dropped the deorbit burn and now it's just passivation of the second stage.

[emerrill]

Note that at a briefing I just came from, the STP-2 mission manager said the second stage will just be disposed of in the DSX orbit.

No surprise on that, tbh. Considering they dropped the deorbit burn and now it's just passivation of the second stage.

Yeah, I just wanted to state it, basically from the horses mouth, since there has recently been talk in this thread about it, if they would be doing a burn or not, etc.

[ZachS09]

How many hours in advance will the press kit be released tomorrow?

[Scylla]

How many hours in advance will the press kit be released tomorrow?

Just posted it to the update thread.

[Skyrocket]

https://twitter.com/exploreplanets/status/1141493728495845376

Here's Our First Look at LightSail 2 Installed on SpaceX's Falcon Heavy Rocket

Is this really the Prox1 satellite, where Lightsat is hitching it's ride? It looks more like a dummy (e.g. no solar cells, no camera or sensor apertures) holding the PPod. This is, what Prox1 was supposed to look like (https://prox-1.gatech.edu/):

[OneSpeed]

How many hours in advance will the press kit be released tomorrow?

Just posted it to the update thread.

STP-2 Max-Q is at T+00:42, a full 27 seconds earlier than for Arabsat-6A at T+01:09. This is going to be interesting.

[emerrill]

https://twitter.com/exploreplanets/status/1141493728495845376

Here's Our First Look at LightSail 2 Installed on SpaceX's Falcon Heavy Rocket

Is this really the Prox1 satellite, where Lightsat is hitching it's ride? It looks more like a dummy (e.g. no solar cells, no camera or sensor apertures) holding the PPod. This is, what Prox1 was supposed to look like (https://prox-1.gatech.edu/):

I don't know, but I will say Oculus is missing all its solar cells in the integrated stack photo as well...

[cscott]

At the Lightsail mission briefing, Dave Spencer mentioned that Prox-2 had to be radically "descoped" to make its mission deadline after a last minute change to the hardware.  This entailed stripping out the cameras and many other components so that it was basically just a container for Lightsail 2.  It is still Georgia Tech's first satellite and will provide educational experience, just won't be able to do the full station-keeping mission originally envisioned.

(Apparently the original computer had trouble booting properly in a space environment during testing, and they had to switch to a different SBC with (I think) a different architecture, and that required extensive software changes at a time when the author of their original software had graduated/moved on; they couldn't spin up new software with all the original functionality in time to make the integration deadlines.)

[Rondaz]

Launch Day Arrives for Space Test Program-2 Mission

Danielle Sempsrott Posted on June 24, 2019

A SpaceX Falcon Heavy rocket stands at Kennedy Space Center’s Launch Complex 39A in Florida for tonight’s launch of the Department of Defense’s (DoD) Space Test Program-2 (STP-2) mission. Lift off is scheduled for 11:30 p.m. EDT, with a four-hour launch window. The mission, managed by the U.S. Air Force Space and Missile Systems Center, will deliver 24 satellites to space, including four NASA payloads.

Meteorologists with the U.S. Air Force 45th Space Wing predict an 80% chance of favorable weather for liftoff. Primary weather concerns are anvil cloud rule and thick cloud layer rule.

Tonight’s launch will be among one of the most challenging in SpaceX’s history with four separate upper-stage engine burns, three separate deployment orbits and a propulsive passivation maneuver, where the engine continues to run until it empties out the second stage of fuel. SpaceX also plans to recover the rocket’s three boosters after launch by landing the two side boosters at the Cape Canaveral landing site and the center core downrange on the drone ship “Of Course I Still Love You.”

https://blogs.nasa.gov/spacex/2019/06/24/launch-day-arrives-for-space-test-program-2-mission/