Author Topic: Falcon Heavy Demo Mission Payload Speculation  (Read 214550 times)

Offline Space Ghost 1962

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Re: Falcon Heavy Demo Mission Payload Speculation
« Reply #200 on: 11/08/2017 07:13 pm »
<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.

FWIW, there is a interesting article in the just out Physics Today called "The relentless pursuit of hypersonic flight", by Ivett A. Leyva. I'm looking at it in front of me right now.

Recommended reading for those interested in understanding the challenges faced in handling a US about 5 minutes past EI, approaching max Q.
« Last Edit: 11/08/2017 10:39 pm by Space Ghost 1962 »

Offline john smith 19

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Re: Falcon Heavy Demo Mission Payload Speculation
« Reply #201 on: 11/08/2017 09:28 pm »
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.
I think you're missing a 2nd 180deg flip in that sequence if you want the MVac pointing in the direction of travel after it's locked onto its protective heat shield.
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Offline Kaputnik

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Re: Falcon Heavy Demo Mission Payload Speculation
« Reply #202 on: 11/08/2017 09:38 pm »
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.
I think you're missing a 2nd 180deg flip in that sequence if you want the MVac pointing in the direction of travel after it's locked onto its protective heat shield.

I think he's also missing the need to develop autonomous docking between two spacecraft, implying independent three axis control of each element with RCS and GNC, and a suitable docking interface. All for a tech demo on a vehicle that is supposed to be retired within five years when BFR comes along.
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Offline john smith 19

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Re: Falcon Heavy Demo Mission Payload Speculation
« Reply #203 on: 11/08/2017 09:48 pm »
FWIW, there is a interesting article in the just out Physics Today called "The relentless pursuit of hypersonic flight", by Ivett A. Leyva. I'm looking at it in front of me right now.

Recommended reading for those interested in understanding the challenges faced in handling a US about 5 minutes past EI, approaching max Q.
Excellent article.

In principle the simpler shape of a stage should make the modelling easier, but it's doubtful how much by.  :(

The big issues it mentions are the vast difference in heat transfer to the vehicle between areas with laminar flow and turbulent flow over them. But worse yet is how sensitive the point where this occurs is sensitive to surface roughness on the mm scale.

Then they are saying that the atmosphere it's flying through could be changing on the same scale and that could trigger a laminar to turbulent transition as well.  :o .
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline mikelepage

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Re: Falcon Heavy Demo Mission Payload Speculation
« Reply #204 on: 11/09/2017 02:00 am »
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?

You must be fun at parties.  Let's not forget that trying to recover the second stage is a crazy idea to start with, so no, I'm not particularly serious, but I am spitballing and was hoping to learn something...

The crux of the problem of returning the second stage is that you need a heat shield to return from orbital velocities, except the MVac is the heaviest part of the stage and it's in the way.  Essentially, you need the engine to *not be there* for some of the entry profile, hence the notion of temporarily covering it up.

Is your biggest objection the attempt to try and dock with your heat shield *after* you've performed the deorbit burn, or something else?


Offline mikelepage

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Re: Falcon Heavy Demo Mission Payload Speculation
« Reply #205 on: 11/09/2017 02:32 am »
I think he's also missing the need to develop autonomous docking between two spacecraft, implying independent three axis control of each element with RCS and GNC, and a suitable docking interface. All for a tech demo on a vehicle that is supposed to be retired within five years when BFR comes along.

I was going to leave the problem of precisely docking with one "dumb" (heat shield) element as accepted risk - isn't it a similar (or easier) control problem to a BFR booster precisely putting itself back in a "dumb" launch cradle? 

My follow up question was if the process of stage separation leaves the second stage "docking interface" in a permanently changed state? As in, if the second stage could place itself accurately enough inside the heat shield/interstage, would there be something for the interstage to latch onto?

Offline Semmel

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Re: Falcon Heavy Demo Mission Payload Speculation
« Reply #206 on: 11/09/2017 06:51 am »
Is your biggest objection the attempt to try and dock with your heat shield *after* you've performed the deorbit burn, or something else?

The problem with this sequence is:
* it requires a ton of special development of hardware
* the interstage is not made for docking, it's clearance with MVac is way too small
* the heat shield is an expensive piece of hardware to throw away, not well suited for a first flight of a rocket
* the docking has to happen in less than a quarter orbit, say 15 minutes which is way too short to do it right
* second stage and  heat shield need independent guidance and flight control, which is expensive and takes a ton of work hours to develop, thrusters, nitrogen tanks, etc.

The problem I have with ideas like this is that it takes very little thinking to see why it wouldn't work. The fact that you still put it here means you didn't do the thinking. What you essentialy do is you outsource the thinking part to other people because you can't be bothered with it. I am sure this is not a popular view on a party, but is this a party?

Offline Kaputnik

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Re: Falcon Heavy Demo Mission Payload Speculation
« Reply #207 on: 11/09/2017 07:14 am »
I think he's also missing the need to develop autonomous docking between two spacecraft, implying independent three axis control of each element with RCS and GNC, and a suitable docking interface. All for a tech demo on a vehicle that is supposed to be retired within five years when BFR comes along.

I was going to leave the problem of precisely docking with one "dumb" (heat shield) element as accepted risk - isn't it a similar (or easier) control problem to a BFR booster precisely putting itself back in a "dumb" launch cradle? 

My follow up question was if the process of stage separation leaves the second stage "docking interface" in a permanently changed state? As in, if the second stage could place itself accurately enough inside the heat shield/interstage, would there be something for the interstage to latch onto?

The heatshield has a little less inertia than a landing cradle, which, you know, is attached to a big lump of rock.
If it doesn't have its own RCS etc, this is going to end up like watching a labrador chasing a beach ball around a swimming pool.
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Offline mikelepage

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Re: Falcon Heavy Demo Mission Payload Speculation
« Reply #208 on: 11/09/2017 08:26 am »
Is your biggest objection the attempt to try and dock with your heat shield *after* you've performed the deorbit burn, or something else?

The problem with this sequence is:
* it requires a ton of special development of hardware
* the interstage is not made for docking, it's clearance with MVac is way too small
* the heat shield is an expensive piece of hardware to throw away, not well suited for a first flight of a rocket
* the docking has to happen in less than a quarter orbit, say 15 minutes which is way too short to do it right
* second stage and  heat shield need independent guidance and flight control, which is expensive and takes a ton of work hours to develop, thrusters, nitrogen tanks, etc.

The problem I have with ideas like this is that it takes very little thinking to see why it wouldn't work. The fact that you still put it here means you didn't do the thinking. What you essentialy do is you outsource the thinking part to other people because you can't be bothered with it. I am sure this is not a popular view on a party, but is this a party?

Not a lack of thinking, just an absence of specific knowledge, one of the main reasons I come here.  When it comes to my expertise (Immunology and molecular biology more generally) I would say it takes little thinking to see why when it comes to the effects of microgravity exposure over the long term (>2 years), nothing short of implementing spin gravity is going to cut it, yet you still get a surprising number of engineers insisting that existing drug and exercise regimes will solve the problem.

When people don't appreciate the size of the problems they are handwaving away, because a solution to <something seemingly similar> exists, you get ideas like this.  I thought it was somewhat obvious that I was putting it up because I thought it was within in the ballpark of existing capability of existing components, and would qualify as a "hail mary" set of steps.  Thanks for your answers.


Offline Herb Schaltegger

Re: Falcon Heavy Demo Mission Payload Speculation
« Reply #209 on: 11/09/2017 12:08 pm »
Can we steer the topic back towards a realistic demo mission payload and away from Goldberg-esque second stage recovery schemes? Thanks.

On that note, has anyone lately dug through FCC permit applications and grand looking for clues? We’re in the relevant timeframe around now.
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Offline Nate_Trost

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Re: Falcon Heavy Demo Mission Payload Speculation
« Reply #210 on: 11/09/2017 03:51 pm »
I'm still holding firm on my prediction of: mass simulator built by interns that apes a typical jumbo comsat targeted for FH (but nothing outlandishly heavy). With some unknown bonus surprise addition that amuses Elon.

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Re: Falcon Heavy Demo Mission Payload Speculation
« Reply #211 on: 11/09/2017 04:32 pm »
I mused that the payload inside the PLF might be extra tanks for 2nd stage to allow for a de-orbit, entry, and landing burn (in the sea)?
It would give FH demo something to lift. It wouldn't violate the fairing qualification(?) and it might validate some hypothetical questions - like: given enough fuel, how well/badly would the 2nd stage perform on re-entry.

However then I thought that too many mods would be required to the 2nd stage pluming and the payload adapter. Would I be right?
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Offline Wolfram66

Re: Falcon Heavy Demo Mission Payload Speculation
« Reply #212 on: 11/09/2017 04:59 pm »
I'm still holding firm on my prediction of: mass simulator built by interns that apes a typical jumbo comsat targeted for FH (but nothing outlandishly heavy). With some unknown bonus surprise addition that amuses Elon.

I like that suggestion. But a Dummy Mass simulator floating around GTO might not be good. Maybe a Mass Simulator that can maneuver and possibly deorbit itself [passive or active] or serve as DARPA satellite servicing / refueling target

Offline Lar

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Re: Falcon Heavy Demo Mission Payload Speculation
« Reply #213 on: 11/09/2017 05:08 pm »
(fan) My vote is a spherical cow[1].

(mod) No, this isn't a party thread. But it is a bit looser and less serious than some other threads without actually being all the way to a party thread. There is no need to jump down the throat of someone for posting a suggestion that you know  might not work because you know more about rockets or docking or on-orbit ops than the poster does. Yes, there's a gradation there too... we discourage crackpots with "look at the perpetual motion machine I invented" threads, but it's OK to learn by being corrected.

1 -  It's basic physics after all..
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Offline Semmel

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Re: Falcon Heavy Demo Mission Payload Speculation
« Reply #214 on: 11/09/2017 07:02 pm »
mikelepage and Lar,

My apologies for the snarkiness. I was out of line there, even for a less loose thread like this one.

wrt. the thread topic, I think the payload will be something very mundane, cheap and funny. Something that cant get wrong and doesnt have any advanced features.

Offline john smith 19

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Re: Falcon Heavy Demo Mission Payload Speculation
« Reply #215 on: 11/10/2017 08:32 am »
I'm still holding firm on my prediction of: mass simulator built by interns that apes a typical jumbo comsat targeted for FH (but nothing outlandishly heavy). With some unknown bonus surprise addition that amuses Elon.
This is a sensible and pragmatic use of limited resources to advance SX's future business plans. A perfectly reasonable option with a high likelihood of success.

And yet....

It lacks a certain vision  :(

Remember when the mass simulator for a Dragon capsule was basically a Dragon capsule?
I mused that the payload inside the PLF might be extra tanks for 2nd stage to allow for a de-orbit, entry, and landing burn (in the sea)?
It would give FH demo something to lift. It wouldn't violate the fairing qualification(?) and it might validate some hypothetical questions - like: given enough fuel, how well/badly would the 2nd stage perform on re-entry.

However then I thought that too many mods would be required to the 2nd stage pluming and the payload adapter. Would I be right?
The eternal question.

When does a little change become a significant one?

You're right about the plumbing. Specifically how do you get the relevant propellant into the bottom main tank? The simplest fix is to run 2 pipes down the outside of the stage into the engine area, but even fairly narrow external pipes and fairings have been known to shift the aerodynamic of LV's, despite their diameters being quite tiny next to the stage diameter.

But preserving external flow means adding internal piping to the top of the top tank and then running a pipe through it into the bottom.

You could do that, and leave it as a permanent design feature. Then you'd know know what you'd tested was the same as what is flying on future missions. Hey Presto! Significant design change becomes new baseline. Problem solved.  :)

The trouble is outside of this test mission I can't think of any other use for the plumbing, and that represents a dead weight that's carried to orbit, every Kg of which comes straight off the FH's margins.

Either the mass hit would have to be very small or the data acquired very valuable to justify doing this.  :( In any case the stage itself may have enough propellant left to do this test anyway.
« Last Edit: 11/10/2017 08:36 am by john smith 19 »
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline mikelepage

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Re: Falcon Heavy Demo Mission Payload Speculation
« Reply #216 on: 11/10/2017 09:27 am »
I'm still holding firm on my prediction of: mass simulator built by interns that apes a typical jumbo comsat targeted for FH (but nothing outlandishly heavy). With some unknown bonus surprise addition that amuses Elon.

I like that suggestion. But a Dummy Mass simulator floating around GTO might not be good. Maybe a Mass Simulator that can maneuver and possibly deorbit itself [passive or active] or serve as DARPA satellite servicing / refueling target

Given aforementioned difficulties docking with a dumb (or dummy) payload, will it be a sufficient demonstration of FH for the second stage to put itself, plus a dummy mass simulator into GTO, and simply do everything but deploy the payload? Later on, the second stage would deorbit both itself and the (still attached) payload.

Offline wannamoonbase

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Re: Falcon Heavy Demo Mission Payload Speculation
« Reply #217 on: 11/10/2017 04:03 pm »
I'm still holding firm on my prediction of: mass simulator built by interns that apes a typical jumbo comsat targeted for FH (but nothing outlandishly heavy). With some unknown bonus surprise addition that amuses Elon.

I like that suggestion. But a Dummy Mass simulator floating around GTO might not be good. Maybe a Mass Simulator that can maneuver and possibly deorbit itself [passive or active] or serve as DARPA satellite servicing / refueling target

Given aforementioned difficulties docking with a dumb (or dummy) payload, will it be a sufficient demonstration of FH for the second stage to put itself, plus a dummy mass simulator into GTO, and simply do everything but deploy the payload? Later on, the second stage would deorbit both itself and the (still attached) payload.

I agree.  It's tempting to think of adventurous things to do with this demo launch.  However, that requires funds and resources and most importantly just getting the FH to fly successfully is a long over due monumental effort.
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Offline Space Ghost 1962

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Re: Falcon Heavy Demo Mission Payload Speculation
« Reply #218 on: 11/10/2017 05:15 pm »
No, you can't have drop tanks in the fairing to supplant props. For one thing no way to fill/drain them, as they are not a part of the LV, and we're back to Goldberg kludges. Just drop the idea.

Have already described barely feasible schemes up thread that already press credulity (fueling, control authority).

The easiest, most likely is a mass simulator as with other LV's initial tests. Not that exciting. Sprinkle it with cubesats (although then they'll likely be too long lived unless the orbit has a high decay).

The only reasons for discussing US recover is a) it touches upon the "reuse fly in the ointment", and b) Musk has hinted at wishing to do so.

Another item to bring up here is the desire to qualify FH in three flights of same. Keep in mind he has already surplus of potential side boosters, unlike Delta Heavy. Two more cores past the one flown in the initial launch.

So if we have a hidden flight test post mission on orbit, perhaps it might have two repeats?

So lets expand this payload speculation - what if its "three in a row" of the same post mission after different payload? Could this be a reasonable "development program"?

How would one advance FH/F9 futures?

Offline Patchouli

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Re: Falcon Heavy Demo Mission Payload Speculation
« Reply #219 on: 11/10/2017 05:49 pm »
I mused that the payload inside the PLF might be extra tanks for 2nd stage to allow for a de-orbit, entry, and landing burn (in the sea)?
It would give FH demo something to lift. It wouldn't violate the fairing qualification(?) and it might validate some hypothetical questions - like: given enough fuel, how well/badly would the 2nd stage perform on re-entry.

However then I thought that too many mods would be required to the 2nd stage pluming and the payload adapter. Would I be right?


Or an inflatable heat shield like HIAD.
Though I think sending a Dragon on a Lunar free return or better yet with with an upper stage and have it get into a lunar parking orbit would be a good stunt.
That or put a couple of Starlink sats in orbit around the moon.
« Last Edit: 11/10/2017 05:50 pm by Patchouli »

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