SpaceX Falcon Heavy Demo - Discussion and Speculation

[old_sellsword]

I'm just trying to ascertain what makes the difference between having to expend a centre core and being  able to recover it on the drone ship.

Center core reentry velocity becomes an issue way before ASDS capabilities. Sometimes Falcon 9 comes in too hot, and that’s without any assistance from side boosters.

[wannamoonbase]

Is there a practical limit in terms of how far away the ASDS can catch a returning centre core? Because if the side boosters impart the maximum possible assistance to the rocket, allowing the centre core to retain the maximum amount of fuel for use after side booster separation, I guess you want the centre core to keep thrusting for as long as possible before it separates from the second stage.

So if that means it is halfway over the Atlantic at that point, is there any reason why the drone ship cannot wait for it that far out? Or will such a distant landing never be required due to inherent limitations of the first stage performance?

I'm just trying to ascertain what makes the difference between having to expend a centre core and being  able to recover it on the drone ship. Because the greater the boost the side cores provide, my assumption is the further along the trajectory the centre core is able to travel before returning to earth.

Like with the F9, it will depend on the trajectory on how far downrange it is.  So what's the mission being accomplished?

They could be much further down range, so how long does that take to get back to port?   

I'd like to see a purpose built ASDS that is self propelled and maybe even lay the booster down and get it under protection for the ride home faster.

Edit: This first flight it will be interesting to see what they decide to do.  Do they go for easy and recoverable or do they stretch the capability and really push the envelop?  Exactly how many tons of cheese can FH send around the moon on a free return trajectory?

[Star One]

They dont expect any circumstance where the center core will ever be RTLS. Too far downrange to come back.

The last launch had a pretty lofted trajectory.  I would never say never.

I'd of thought the commercial manned lunar mission would preclude recovering the cores due to the requirements of the mission.

[hans_ober]

I'm just trying to ascertain what makes the difference between having to expend a centre core and being  able to recover it on the drone ship.

Center core reentry velocity becomes an issue way before ASDS capabilities. Sometimes Falcon 9 comes in too hot, and that’s without any assistance from side boosters.

I think a simulation once showed that they might be able to do a 1200km downrange landing on the core when the boosters RTLS. Booster fly a steepish trajectory, and core & S2 fly as flat as possible, which reduced gravity losses compared to a normal F9 flight. IIRC the core MECO velocity was 3 -3.5km/s.

[321_SNI]

Not to re-open a can of worms, but does anybody know WHEN they might announce what the demo "payload" is? Or will it remain "under wraps"  until after the flight like the cheese?

We had heard that the Planetary Society's Solar Sail was to go on the first Falcon Heavy, at least that was the talk a year ago or two.

[philw1776]

Sail on 2nd FH

[gongora]

Not to re-open a can of worms, but does anybody know WHEN they might announce what the demo "payload" is? Or will it remain "under wraps"  until after the flight like the cheese?

We had heard that the Planetary Society's Solar Sail was to go on the first Falcon Heavy, at least that was the talk a year ago or two.

That's on the STP-2 mission, which was never the first flight.

[envy887]

They dont expect any circumstance where the center core will ever be RTLS. Too far downrange to come back.

The last launch had a pretty lofted trajectory.  I would never say never.

I'd of thought the commercial manned lunar mission would preclude recovering the cores due to the requirements of the mission.

Not necessarily. They might be able to recover all three cores.

[MP99]

I'm just trying to ascertain what makes the difference between having to expend a centre core and being  able to recover it on the drone ship.

Center core reentry velocity becomes an issue way before ASDS capabilities. Sometimes Falcon 9 comes in too hot, and that’s without any assistance from side boosters.

I think a simulation once showed that they might be able to do a 1200km downrange landing on the core when the boosters RTLS. Booster fly a steepish trajectory, and core & S2 fly as flat as possible, which reduced gravity losses compared to a normal F9 flight. IIRC the core MECO velocity was 3 -3.5km/s.

Elon tweeted that FH core from Texas would fly past Florida. Not sure if that was with crossfeed.

Cheers, Martin

Sent from my Nexus 6 using Tapatalk

[Lars-J]

I'm just trying to ascertain what makes the difference between having to expend a centre core and being  able to recover it on the drone ship.

Center core reentry velocity becomes an issue way before ASDS capabilities. Sometimes Falcon 9 comes in too hot, and that’s without any assistance from side boosters.

I think a simulation once showed that they might be able to do a 1200km downrange landing on the core when the boosters RTLS. Booster fly a steepish trajectory, and core & S2 fly as flat as possible, which reduced gravity losses compared to a normal F9 flight. IIRC the core MECO velocity was 3 -3.5km/s.

Elon tweeted that FH core from Texas would fly past Florida. Not sure if that was with crossfeed.

That would be its ballistic trajectory... With a boost-back (or boost-sideways or boost-forward), the core has quite a bit of flexibility in targeting a landing spot. It all depends on the margin of propellant.

[Star One]

They dont expect any circumstance where the center core will ever be RTLS. Too far downrange to come back.

The last launch had a pretty lofted trajectory.  I would never say never.

I'd of thought the commercial manned lunar mission would preclude recovering the cores due to the requirements of the mission.

Not necessarily. They might be able to recover all three cores.

But surely it's an extremely high energy mission plus you want plenty of margin in performance when you're trying to maximise the safety and chances success for your passengers.

[OneSpeed]

... They might be able to recover all three cores.

But surely it's an extremely high energy mission plus you want plenty of margin in performance when you're trying to maximise the safety and chances success for your passengers.

A lot of the energy will come from the moon itself.

[Star One]

... They might be able to recover all three cores.

But surely it's an extremely high energy mission plus you want plenty of margin in performance when you're trying to maximise the safety and chances success for your passengers.

A lot of the energy will come from the moon itself.

True as it's a free return mission. Isn't the distance from the Earth intended to be greater than any of the Apollo missions achieved, if it is why have they chosen that as won't the re-entry speed to the Earth also be consequently higher?

[OneSpeed]

A lot of the energy will come from the moon itself.

True as it's a free return mission. Isn't the distance from the Earth intended to be greater than any of the Apollo missions achieved, if it is why have they chosen that as won't the re-entry speed to the Earth also be consequently higher?

There are two classes of free return trajectories. Those that pass 'in front' of the moon to reduce velocity, and return immediately to Earth (e.g. Apollo), and those that pass 'behind' the moon's trajectory to obtain a gravity assist or 'kick', and continue beyond the moon's orbit. The tourist lunar flyby would top out at 480-650,000 kms, and so be in the second category. The return velocity from the former peaks at 10.8 km/s, from the latter at around 11.2 km/s. Higher, but not a huge difference. A good test though.

[Star One]

A lot of the energy will come from the moon itself.

True as it's a free return mission. Isn't the distance from the Earth intended to be greater than any of the Apollo missions achieved, if it is why have they chosen that as won't the re-entry speed to the Earth also be consequently higher?

There are two classes of free return trajectories. Those that pass 'in front' of the moon to reduce velocity, and return immediately to Earth (e.g. Apollo), and those that pass 'behind' the moon's trajectory to obtain a gravity assist or 'kick', and continue beyond the moon's orbit. The tourist lunar flyby would top out at 480-650,000 kms, and so be in the second category. The return velocity from the former peaks at 10.8 km/s, from the latter at around 11.2 km/s. Higher, but not a huge difference. A good test though.

Is it possible to calculate, I am assuming it is, what kind of temperatures the Dragon's re-entry shield is likely to be exposed to on the mission?

[envy887]

They dont expect any circumstance where the center core will ever be RTLS. Too far downrange to come back.

The last launch had a pretty lofted trajectory.  I would never say never.

I'd of thought the commercial manned lunar mission would preclude recovering the cores due to the requirements of the mission.

Not necessarily. They might be able to recover all three cores.

But surely it's an extremely high energy mission plus you want plenty of margin in performance when you're trying to maximise the safety and chances success for your passengers.

There aren't a lot of scenarios where expending the booster(s) increases useful margins. If there's a performance issue with a booster, FH can use landing fuel to make up the difference.

But once the upper stage and Dragon are in LEO, it's all up to the upper stage - a major performance shortfall from the MVac would likely result in Dragon returning early. Dragon 2 has a considerable amount of abort fuel that can be used to modify the trajectory for a quicker return post-TLI or in the event of an aborted or short injection.

[321_SNI]

Not to re-open a can of worms, but does anybody know WHEN they might announce what the demo "payload" is? Or will it remain "under wraps"  until after the flight like the cheese?

We had heard that the Planetary Society's Solar Sail was to go on the first Falcon Heavy, at least that was the talk a year ago or two.

That's on the STP-2 mission, which was never the first flight.

Thanks, Gongora (and phil1776)!  Great to hear your info.  This might be like a technicality.  But I really remember them saying that the awesome solar saill project of the Planetary Society was going on the maiden flight of FH, back then.  We thought that was so cool, so appropriate and fitting to have those two cutting edge organizations right together in making history (www.planetary.org and Spacex).  But I also cringed at it going on the FH debut when I heard that, with the possibility of a repeat of Planetary's launch from Russia!  Maybe this weekend I can track down some articles on whether they really had been thinking of going up, on the debut flight.  But thanks again, just love all your Spacex discussions -- and about FH especially, as the excitement draws nearer!! 

[cscott]

The lightsail is currently planned to be the third FH mission.  Another mission jumped the line to be #2. As I mentioned, I got tickets to watch that launch by supporting the lightsail Kickstarter.

[321_SNI]

The lightsail is currently planned to be the third FH mission.  Another mission jumped the line to be #2. As I mentioned, I got tickets to watch that launch by supporting the lightsail Kickstarter.

Glad to see your involvement, Cscott.   Lightsail is  a project which at one time seemed like a wild, far reach for just a grassroots group – kind of like a guy starting his own rocket company from scratch and going on to engineer the first reusable commercial rockets!  Did you join in the kickstarter a few years ago, and do you recall if there was talk of them going on the debut FH flight?  In any case, its cool to talk about this sci-fi sounding stuff, now going forward with visionary Spacex.  Btw, haven’t seen the schedule lately, but I recall that FH’s will be going strong after a successful debut.  #4 is for ’18, right?  Hope you have a good location with your tickets  (and have a great launch!).

[Lar]

Payload speculation belongs here

http://forum.nasaspaceflight.com/index.php?topic=42801

I just went through and moved some posts that seemed to me to be only about possible payloads. Some posts may have been moved incorrectly, PM me if you think so, with the URL of the post you think I goofed up.