Falcon Heavy Demo Mission Payload Speculation

[Space Ghost 1962]

AIUI the assumption has been that heavy modification of the US would invalidate the demo flight as a certification flight.

Doesn't affect the US other than letting the avionics take over the lower thruster ring after mission separation.

You'd have to reconcile the loads through the payload adapter as same.

[Ictogan]

Just out of curiosity, do we know  - or have a reasonable good guesstimate - what Falcon Heavy payload performance would be for GTO 1800 m/s with RTLS (not DRL) of all 3 stages?

(Whether that setup is practicable is another question)

- Cala

My guess would be the 8.0 tonnes listed on http://www.spacex.com/about/capabilities as available for $90m. At least that's the most obvious possible reason I could imagine for them making a pricing tier "up to 8mT to GTO".

[Oersted]

Would be the fourth electric car in space (the first three are still on the moon).

There are more than three on the moon, and four on Mars.

"Most definitions of car say they run primarily on roads, seat one to eight people, have four tires, and mainly transport people rather than goods" (Wikipedia)

I think it is fair to say that it would be the fourth electric car in space. The Moon and Mars rovers were robots, never intended for human transportation.

Anyway, this is not important by any standard.

[OneSpeed]

SX will risk if there's the point of gain. The gain can be as little as proving that an option cannot be made to work.

Agreed.

How to do this - integrated Dragon 2 propulsion system with appropriately sized tankage into payload adapter, lower interface/thrust structure accepting / transmitting loads two way to engine up (high CG) F9US on recovery, upper interface to dummy payload that is jettisoned with dummy payload, revealing one-off larger diameter Dragon derived heat shield. Propulsion/flight controls consist of upper (near MerlinVac) ring and lower ring (payload adapter) thrusters in addition to Dragon 2 derived SuperDraco's. Significant thrust structure between upper/lower payload adapter interfaces to handle asymmetric torques. Significant avionics/software challenge to merge/manage flight controls to handle stability from EI down to MaxQ, down to transonic, down to terminal braking (principle risk and benefit of this effort).

This is interesting, but I'm having trouble visualising the positioning of the dummy payload and the Dragon derived heatshield. Could you provide a sketch?

[john smith 19]

Back to F9US "hail mary" recovery attempt.

SX will risk if there's the point of gain. The gain can be as little as proving that an option cannot be made to work.

Not insignificant.  Demonstrates CFD modelling is optimistic, which is always better to know before risking more valuable assets. 

Significant avionics/software challenge to merge/manage flight controls to handle stability from EI down to MaxQ, down to transonic, down to terminal braking (principle risk and benefit of this effort).

Very definitely.

Profile - post boost phase standard ascent and orbital injection, high decay rate for mass simulator/upper adapter. Post separation US aligns for retro as if disposal burn, but guidance for terminal offshore target (as with Dragon recovery resources/assets, or other). Post retro burn enter recovery "high gate" to avoid tumble, and work down to maximum drag/loads density altitude. SuperDraco burns then expand drag plume to allow US with minimal SPAM to survive through thermal and transonic transition. Free fall at terminal velocity with cold gas roll/pitch/yaw stabilization to near sea level. Braking burn to hoverslam, engine shutdown / tankage vent / "fireball".

I'm having trouble picturing this.
You do a stage flip and have Merlin(s) do a retro burn at full orbital velocity first?
Then flip again to use a heat shield you brought up under the payload adaptor (which I presume is basically a hollow cone with the payload on top) for most of the reentry?
Dracos are replacing the grid fins for main control authority?
Then somehow you go from engine rear (as opposed to engine forward in the booster flight profile at this point) to engine vertical pointing down in time for the hoverslam when air density has become quite high (high enough for grid fins to work in the booster stage).

Control authority of such an approach concerns me. What doesn't concern me is parasitic payload loss, because that could be worked down if the "hail mary" came close.

Comments?

Control authority does look a definite problem. Also is the stage really going to be face on to the airstream? All the things I've on capsule reentry come in a few degrees below horizontal, while winged vehicles came in maybe 40deg above horizontal in a "belly flop" approach. the capsule entries put a huge heat load on a relatively small part of the "lip" between spherical front face and conical back shell.

I also doubt you'll have much unbalanced mass to shift the lift vector, like Apollo or Gemini had.
Coming in more like Shuttle puts significant side loads on the tanks.

I think the final nail in the dream of US reusability for VTOL rockets was the acceptance of wings on the BFS. 

It was implied the problem was the Isp of Kerolox, but the fact that even with Methalox it's impossible without wings suggests the physics is just too tough (something only SX have had the actual persistence to find out, when other companies have assured governments "Oh yes it's doable, if you pay us enough").

 I'm quite sure SX would have tried everything they could imagine before accepting that fact , since it ends the dream of a single vehicle that can land on any body in the solar system without penalty.  A Titan lander will not be just a BFS with a lot of refueling. 

[MATTBLAK]

[gorgon69]

Lol, after 40 sec it looks like a sci-fi movie from the 90s
When it comes to rockets, they like them a lot. As a child I dreamed my daddy bought a crate with a rocket set. Now I'm grown up, my dreams are not fulfilled. The only thing I buy is crates for the rocket league, now it's rocket league trade is my favorite job. They've had their childhoods probably never come back - they can buy rocket league items and rocket league crates, comfortably here https://odealo.com/games/rocket-league I recommend

[MATTBLAK]

I thought parts of the animation were very well done and I had just discovered it by chance of YouTube; so I thought I'd show it to folks.

[nacnud]

Like how it launches from SLC-41 then is immediately over '39 

[Bob Shaw]

The Lunakhods were part of the Soviet manned Lunar landing effort, and were designed to carry a cosmonaut from his LK to a backup vehicle if required. So, they didn’t carry any humans, but were intended to and thus are cars, two of the five on the Moon.

[Kaputnik]

I'll be pleasantly surprised if the US recovery attempt is anything other than just flying the stage engine-first at low throttle during re-entry, using the exhaust plume to create a bow-shock.

[Space Ghost 1962]

I'll be pleasantly surprised if the US recovery attempt is anything other than just flying the stage engine-first at low throttle during re-entry, using the exhaust plume to create a bow-shock.

Reminds of Wile E. Coyote's little umbrella he'd unfold, just before getting demolished by a boulder.

In theory you might ride down EI this way. But then all the control authority is in the MerlinVac gimbal moving rapidly enough to hold the CP above the CG on axis. Also, the avionics are in the top of the US, first to get cooked if the plume does not encompass the stage. And, since the engine is centered in the plume it will not widen the plume that much (one can continuously "swivel" the plume to create an astable vortex to flatten the plume, assuming that does not destabilize the vehicle  during buffeting). And use the cold gas thrusters to desaturate the gimbal occasionally.

To have enough propellant to do any good, you'd need to have a short ascent burn, which might need to be explained on the mission profile ("see, we can use the core stage to obviate the need for US consumption").

[Lar]

P2P transport being wingless is way way way off topic. SOME of us know better.

Update:  What part of this were you guys having trouble with? Chris posted that some offtopic trimming occurred and warned not to continue.  Then. I warned. Then two posts continued even after the warning. Aetherized.

Seriously. What the... ?

[john smith 19]

In theory you might ride down EI this way. But then all the control authority is in the MerlinVac gimbal moving rapidly enough to hold the CP above the CG on axis. Also, the avionics are in the top of the US, first to get cooked if the plume does not encompass the stage. And, since the engine is centered in the plume it will not widen the plume that much (one can continuously "swivel" the plume to create an astable vortex to flatten the plume, assuming that does not destabilize the vehicle  during buffeting). And use the cold gas thrusters to desaturate the gimbal occasionally.

If they are talking about a slightly engine down direction doesn't that put most of the top end behind most of the engines and tankage? I thought your approach was to have it come in nose first with heat shield? That would still have the control package subjected to most of the heat.

[Mike_1179]

In theory you might ride down EI this way. But then all the control authority is in the MerlinVac gimbal moving rapidly enough to hold the CP above the CG on axis. Also, the avionics are in the top of the US, first to get cooked if the plume does not encompass the stage. And, since the engine is centered in the plume it will not widen the plume that much (one can continuously "swivel" the plume to create an astable vortex to flatten the plume, assuming that does not destabilize the vehicle  during buffeting). And use the cold gas thrusters to desaturate the gimbal occasionally.

If they are talking about a slightly engine down direction doesn't that put most of the top end behind most of the engines and tankage? I thought your approach was to have it come in nose first with heat shield? That would still have the control package subjected to most of the heat.

Hypersonic retro-propulsion does wacky things depending on when you fire the engines and what the body entering looks like.

A big flat shape like the bottom end of a capsule makes a wide bow shock that is offset from the surface of the capsule. This means it does a good job of slowing the capsule down and pushes the super hot shockwave away from the surface. A pointed surface (nose first of a streamlined shape) wouldn't create as large a bow shock and that shockwave might impinge on the surface directly.

Firing an engine retrograde can make the bow shock wider (simulating the effect of the wide body entry) or it can make the bow shock more pointed which would actually reduce the deceleration on the vehicle (it would be going faster than if you didn't fire the engine - I know, totally counter-intuitive). If you watch the re-entry burn from stage 1 landings, the stage accelerates right up until the burn starts. Then the burn slows the stage down AND gets it to a lower part of the atmosphere so that after the burn is complete, the stage is not accelerating anymore - the thickening atmosphere slows it down from there but not so much that heat loading on the bottom end is too much.

So...you can't just wave a magic wand and say burn the engines so the second stage can re-enter. You have to consider heat loading on the second stage before re-entry burn, the shape of the plume / bow shock during hypersonic retropropulsion, aero forces and heat loading on the stage after re-entry shutdown. No matter which way you spin it, you are dissipating a massive amount of energy as heat to get the second stage to 0/0.

[john smith 19]

So...you can't just wave a magic wand and say burn the engines so the second stage can re-enter. You have to consider heat loading on the second stage before re-entry burn, the shape of the plume / bow shock during hypersonic retropropulsion, aero forces and heat loading on the stage after re-entry shutdown. No matter which way you spin it, you are dissipating a massive amount of energy as heat to get the second stage to 0/0.

As you do for every human made object that has conducted a planned, controlled reentry.

All of which have started by a rocket burn to bring the velocity of the vehicle (whatever it is) below full orbital velocity. AFAIK all other others where not actually at full orbital velocity to begin with.

[deruch]

<snip>
If you watch the re-entry burn from stage 1 landings, the stage accelerates right up until the burn starts. Then the burn slows the stage down AND gets it to a lower part of the atmosphere so that after the burn is complete, the stage is not accelerating anymore - the thickening atmosphere slows it down from there but not so much that heat loading on the bottom end is too much.
<snip>

In actuality, the stage accelerates again after the entry burn as well for about 10-12 seconds.  But it doesn't gain all that much before the aerodynamic effects fully overcome gravity.  On the order of +100 m/s.  This is visible in the analyses of the webcast telemetry data, e.g.: http://forum.nasaspaceflight.com/index.php?topic=40328.msg1673183#msg1673183 

In the above linked post from Welsh Dragon, it is most visible in the middle graph (Speed vs. time) immediately following the re-entry burn (green section).

None of which invalidates the point you were making in your comment.  Just correctly a slight mis-impression.   

[ugordan]

<snip>
If you watch the re-entry burn from stage 1 landings, the stage accelerates right up until the burn starts. Then the burn slows the stage down AND gets it to a lower part of the atmosphere so that after the burn is complete, the stage is not accelerating anymore - the thickening atmosphere slows it down from there but not so much that heat loading on the bottom end is too much.
<snip>

In actuality, the stage accelerates again after the entry burn as well for about 10-12 seconds.  But it doesn't gain all that much before the aerodynamic effects fully overcome gravity.  On the order of +100 m/s.  This is visible in the analyses of the webcast telemetry data, e.g.: http://forum.nasaspaceflight.com/index.php?topic=40328.msg1673183#msg1673183 

Not all flights were like that, though. Check out the Echostar 105 / SES-11 webcast. It gained less than 10 km/h before starting to decelerate again.

[mikelepage]

What if you had a FH secondary payload that was essentially an Falcon family interstage adaptor with a Dragon heat shield attached? (underneath the fairing this payload would launch heat shield facing up).

The second stage would:
1) arrive in orbit.
2) deploy primary payload
3) perform deorbit burn
4) deploy interstage adaptor with heat shield
5) stage flips 180 degrees and docks with interstage/heat shield (this would cover the MVac for reentry).
6) Entry interface through transonic, performs guidance with CGS - hopefully enough control authority since stage is smaller.
7) Ejects heat shield after Max-Q (maybe use parachutes to recover interstage/heat shield).
8/ Uses MVac for landing burn.

[Semmel]

What if you had a FH secondary payload that was essentially an Falcon family interstage adaptor with a Dragon heat shield attached? (underneath the fairing this payload would launch heat shield facing up).

The second stage would:
1) arrive in orbit.
2) deploy primary payload
3) perform deorbit burn
4) deploy interstage adaptor with heat shield
5) stage flips 180 degrees and docks with interstage/heat shield (this would cover the MVac for reentry).
6) Entry interface through transonic, performs guidance with CGS - hopefully enough control authority since stage is smaller.
7) Ejects heat shield after Max-Q (maybe use parachutes to recover interstage/heat shield).
8/ Uses MVac for landing burn.

Are you serious?