SpaceX FH : Falcon Heavy Demo : Feb 6, 2018 : Discussion Thread 2

[Jim]

On the press-kit there is a reference to a third stage. Is this an error? They are talking about a third burn of the second stage? Or ir there really a small third (kick) stage?

Outboard boosters + core = stage 1
Core only = stage 2
Upper stage = stage 3

I believe that D-IVH uses similar terminology.

No, it is:

Outboard boosters = stage 0
Core only = stage 1
Upper stage = stage 2


The press kit means to say third "stage two" burn

[JimO]

Can anybody compute the ground regions the stage-2 will be over for the three burns? Depending on launch time, of course, those regions in twilight [dark surface, sunlit space overhead] might offer residents a spectacular plume in the sky. A Falcon launch to ISS a year ago made a deorbit burn and fuel dump that was widely visible around the Persian Gulf. These burns will be longer and so more spectacular -- with lucky timing. 

[Kabloona]

Can anybody compute the ground regions the stage-2 will be over for the three burns? Depending on launch time, of course, those regions in twilight [dark surface, sunlit space overhead] might offer residents a spectacular plume in the sky. A Falcon launch to ISS a year ago made a deorbit burn and fuel dump that was widely visible around the Persian Gulf. These burns will be longer and so more spectacular -- with lucky timing.

Jonathan McDowell says 3rd burn over Ecuador.

https://mobile.twitter.com/planet4589/status/960754969170280448

[vanoord]

No, it is:

Outboard boosters = stage 0
Core only = stage 1
Upper stage = stage 2

Makes more sense as the upper stage is still called Stage 2, regardless of whether it's attached to an F9 or an FH.

[LouScheffer]

He haven't seen the press kit yet at that time. Here is his updated analysis:

What makes more sense is a 6hr period orbit, with an apogee around 20000 km. That would allow a 3rd burn at perigee after 6 hr, and only 1.5 km/s required to get an aphelion near Mars. Still tweaking things to get the timings right.

Very good. So the consensus seems to be a 6 hr orbit with apogee around 20,000 km and 3rd burn at perigee.

For launch at the beginning of the window, this makes sense.   Launch at 1:30 local, reach equator at 2:00, come back at 8:00, which is 7:00 local off the coast of Equador, the right time for a Mars injection burn.

But what if the launch is not at the opening of the window?  Then SpaceX has a choice.  If they want an optimum injection, to get as far as possible from Earth, they would choose a shorter intermediate orbit (shorter by about the amount of the delay).   This would demonstrate interplanetary flights with long launch windows.  However, I suspect they would keep the 6 hour intermediate orbit, since demonstrating the 6 hour coast is more important than an optimum injection.  They may have enough margin to do it anyway, and the exact obtained orbit is not at all critical.  So I think a 6 hour intermediate orbit no matter when the launch.

[Ben the Space Brit]

What is the battery life on the Falcon extended upper stage? That will probably be the primary constraint on the timing of the TOI2 burn.

[speedevil]

What is the battery life on the Falcon extended upper stage? That will probably be the primary constraint on the timing of the TOI2 burn.

Nobody knows.
The power use of the stage is going to be minimal in coast, other than heaters.
Everything can power down if it needs to.
Heaters to avoid kerosene freezing in awkward places might need quite high power indeed.
But, even if it needs 10kW constantly, for one day that is 'only' one ton or so of batteries.

[Jim]

What is the battery life on the Falcon extended upper stage? That will probably be the primary constraint on the timing of the TOI2 burn.

Nobody knows.
The power use of the stage is going to be minimal in coast, other than heaters.
Everything can power down if it needs to.
Heaters to avoid kerosene freezing in awkward places might need quite high power indeed.
But, even if it needs 10kW constantly, for one day that is 'only' one ton or so of batteries.

It will be nothing close to that.  Just battery or two more than a standard mission.

[Johnnyhinbos]

Though fully hoping for the launch to be today, we all know full well there’s also a high likelihood of a scrub. There’s a lot riding on this launch, and I mean beyond SpaceX - a lot of folks have converged to watch this historic event and not everyone has the luxury of extending their stay to accommodate a scrub.

So... what’s the likelihood of this happening?

[abaddon]

Though fully hoping for the launch to be today, we all know full well there’s also a high likelihood of a scrub. There’s a lot riding on this launch, and I mean beyond SpaceX - a lot of folks have converged to watch this historic event and not everyone has the luxury of extending their stay to accommodate a scrub.

So... what’s the likelihood of this happening?

Somewhere between zero and one.

[SkipMorrow]

What's the significance/importance of being able to coast for six hours?

[rpapo]

What's the significance/importance of being able to coast for six hours?

Qualification for some Department of Defense payloads that want direct injection into GSO.

[IanThePineapple]

What's the significance/importance of being able to coast for six hours?

Direct GEO insertion for military and national security payloads

[PahTo]

So... what’s the likelihood of this happening?

Consider this:  I visited KSC to watch three shuttle launches.  In each case we front-loaded the visit (arrived the day before the nominal launch, stayed for a week).  In each case, there was a scrub, and in each case we witnessed the launches, to include upgrading viewing to causeway, and even Saturn V Center.
At that time, STS was well in to the 100s in terms of missions.  FH has never flown...

[BeamRider]

Terminology also goes back to Soyuz with its four side boosters, I believe.

[deruch]

What's the significance/importance of being able to coast for six hours?

Extended coasting allows the upper stage to circularize the orbit at apogee.  So, instead of delivering to a transfer orbit where the payload has to finish raising the orbit and circularizing, the upper stage does it all and injects the payload into a full direct GEO or direct MEO (Semi-Sychronous orbit).

The different EELV reference orbits can be found HERE

[SkipMorrow]

What's the significance/importance of being able to coast for six hours?

Extended coasting allows the upper stage to circularize the orbit at apogee.  So, instead of delivering to a transfer orbit where the payload has to finish raising the orbit and circularizing, the upper stage does it all and injects the payload into a full direct GEO or direct MEO (Semi-Sychronous orbit).

The different EELV reference orbits can be found HERE

That makes sense, thanks. So the six hours is kind of a placeholder where IF we were going to GEO, we would be using that time to move to the final position?

What would a failure look like in this (FH Demo) case? Let's say we get to orbit, no problem. Start the coast phase and then BAM? Something goes wrong while coasting? I guess I am saying this (coasting) sounds easy, but I know it isn't easy.

[dnavas]

What would a failure look like in this (FH Demo) case? Let's say we get to orbit, no problem. Start the coast phase and then BAM? Something goes wrong while coasting? I guess I am saying this (coasting) sounds easy, but I know it isn't easy.

Well, that's where the various statements didn't align in my mind.  The most likely failure case in my mind is not that we're stuck in LEO (strictly), but that we're stuck in some odd/elliptical pre-TMI orbit.  Falcon doesn't use hardened electronics, does it?

[speedevil]

What would a failure look like in this (FH Demo) case? Let's say we get to orbit, no problem. Start the coast phase and then BAM? Something goes wrong while coasting? I guess I am saying this (coasting) sounds easy, but I know it isn't easy.

If FH goes to sleep after the injection into 12 hour orbit, and never wakes up, it is in a ~150km*20000km or so orbit.
Over the next few weeks or months, the orbit gradually becomes more and more circular, as it's aerobraking a little at each perigee and eventually reenters.
What sets the timescale is the perigee.
Unless they want an extra complication - a burn at apogee - the perigee is set as the engine shuts off, so to avoid much drag affecting the mission, they don't want to be very low, so probably weeks-months to reenter, not days.
In the hours before reentry, the orbit is basically circular.

[FutureSpaceTourist]

In 1963 President Kennedy talked about doing the “hard” things.  @SpaceX is doing that.  Best of luck to @elonmusk and his team today.  T-4 hours and counting.

https://twitter.com/shuttlecdrkelly/status/960885168524361728