Author Topic: F9 - S2 reusable modification as evolution steps to BFS(ITS)  (Read 89601 times)

Offline guckyfan

  • Senior Member
  • *****
  • Posts: 7438
  • Germany
  • Liked: 2332
  • Likes Given: 2891
No problem with nose first reentry or only a small angle of attack. Then gradually switch to side entry when the speed is already reduced.

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 39270
  • Minnesota
  • Liked: 25240
  • Likes Given: 12115
I'm pretty sure they'd do side entry like Shuttle or Delta Clipper.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline spacenut

  • Senior Member
  • *****
  • Posts: 5181
  • East Alabama
  • Liked: 2587
  • Likes Given: 2895
Side entry would give them information on ITS or ITSY.  Top entry doesn't.  If it could flip after side entry and land engine down with Superdracos, that would be cool. 

Offline mikelepage

  • Full Member
  • ****
  • Posts: 1218
  • ExodusSpaceSystems.com
  • Perth, Australia
  • Liked: 855
  • Likes Given: 1358
Question: do we know if grid fins can turn to an angle 90+ degrees from launch orientation?  Should be easy enough to do, right?

What I'm currently imagining for the "hail mary" attempt of the FH S2 is a second stage with side mounted heat shield/resistant coating(?), plus four grid fins: two grid fins are mounted either side of the heat shield at the top/front, and then two more grid fins mounted on the sides below these, next to the MVac, below/behind center of gravity.  No landing legs.  No super dracos.

Pacific ASDS hosts some kind of experimental cradle based on interstage connector.  S2 performs deorbit burn, then uses cold gas thrusters to orient stage side on to reentry.  Lower pair of grid fins deploy, turning right angles to stowed orientation - upper pair are (I think) counter productive at early stage when you want to use the side mounted heat shield and CoG is already so far towards the rear.

Flip to vertical landing orientation should be achievable without engine relighting if you have upper and lower pairs of grid fins, so well after peak heating (but before max Q I think), upper grid fin pair deploy and start flip motion.  Engine relight happens for landing burn, hopefully into the cradle mounted on ASDS. 

I believe the grid fins are only on the order of 50kg each, so not the biggest mass penalty.  The question in my mind is how heavy a side mounted heat shield is?

Offline alang

  • Full Member
  • ****
  • Posts: 406
  • Liked: 213
  • Likes Given: 8
Dumb question: does an inflatable heat shield have to cover the engine bell? Could it be done as a torus around the second stage engine?
Intuitively the answer is it wouldn't work because of the fragility of the second stage engine bell and the hypersonic re-entry, but having read the comments about the non-intuitive nature of aerodynamics and given the ubiquity of cheap computing power I wonder if anyone has actually modelled some of the more outlandish scenarios.
« Last Edit: 08/06/2017 10:49 am by alang »

Offline tdperk

  • Full Member
  • ***
  • Posts: 369
  • Liked: 152
  • Likes Given: 95
It would be like if a competitor to Six Flags opened up a theme park 3 states over in the middle of nowhere and expected you to go there because it's cheaper instead of the Six Flags that is down the road.

How much cheaper?  Also, three of the big Western states or going to West CT From Attleboro, MA?

Offline First Mate Rummey

  • Member
  • Posts: 94
  • Liked: 104
  • Likes Given: 37
Sorry for asking, but what do you mean with ITSY?
Thanks.

Sorry for asking, but what do you mean with ITSY?
Thanks.

ITSy is the nickname we've given to the subscale ITS. It's not official at all.

Offline Lar

  • Fan boy at large
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 13463
  • Saw Gemini live on TV
  • A large LEGO storage facility ... in Michigan
  • Liked: 11864
  • Likes Given: 11086
Sorry for asking, but what do you mean with ITSY?
Thanks.

ITSy is the nickname we've given to the subscale ITS. It's not official at all.

Keep using it and maybe it'll catch on!!!
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline oldAtlas_Eguy

  • Senior Member
  • *****
  • Posts: 5304
  • Florida
  • Liked: 5005
  • Likes Given: 1444
As a version of and speculation if S2 is heavily modified then it may likely also see the use of carbon composite tanks. This would increase the capability to reduce the impacts made by additional reuse hardware on the payload capability of the US. Then if such major changes are made then also is a possibility of changing the stage out to use methalox with autogenous pressurization. That would also likely change the stage to also be a 5m diameter but the same length reducing impacts on towers and other items placement in the GSE in support of the US and payloads on top.

Offline Arb

  • Full Member
  • ****
  • Posts: 553
  • London
  • Liked: 514
  • Likes Given: 433
That would also likely change the stage to also be a 5m diameter but the same length reducing impacts on towers and other items placement in the GSE in support of the US and payloads on top.
That'd require reworking of the transporter erector to accommodate the increased diameter; how would that even work/look-like?

|
\
 |
 |
 |
 |
 ---
(transporter/erector not to scale)

It'd also be a pain when horizontal; with the first stage having to be somewhat higher off the ground than at present.
   ________|
__/


Interesting trade...

Edit: spelling.
« Last Edit: 08/11/2017 07:41 pm by Arb »

Offline GWH

  • Full Member
  • ****
  • Posts: 1742
  • Canada
  • Liked: 1929
  • Likes Given: 1277
I feel like this topic has been brought up lots before, but....

It looks to me like there could be space, however the cradle arms would need to move to the outside rather than fully under.

Two different angles shown in the photo below, the bottom one rotated in orientation to fit better.  Looks like 5m clear would fit the whole length if the arms weren't in place, and then note the shipping splice in the TEL that is located 1/3 of the way up the interstage.

Theoretically this upper section could simply be replaced, theoretically because I have no idea of the inner details.

There may have been a very recent image floating around where the TEL was erected and the upper section was removed, but I can't find where I saw that.
« Last Edit: 08/11/2017 12:09 am by GWH »

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 10350
  • Everyplaceelse
  • Liked: 2430
  • Likes Given: 13605
I'm pretty sure they'd do side entry like Shuttle or Delta Clipper.
Only if you make the structure a) Winged or b) Lower aspect ratio.  :(

"Upper stage reuse" has been known to be possible since the first Shuttle reflight if you're prepared to design a vehicle to do it.

What has made it difficult is if you insist on doing it with a high aspect ratio US, which is what a conventional US is.

You are aware that the Shuttle reentry angle (when it lost most of its velocity) was rather nearer to 70degrees to the horizontal than horizontal?

Or the DC-X slightly nose down concept was inspired by the USAF's experience with warhead reentry?

This idea has a couple of inescapable facts connected with it.

1) Every unit of mass you put on the US comes off the payload. On boosters it's more like 13:1.  So you can add a (comparatively) huge amount of hardware to do recovery while sacrificing a (comparatively) small amount of payload.

2) You can make VTO LV's very light because they are very optimized to be strong in exactly 1 axis, just like a soda can  :( I've stacked 10 fully filled (but unpressurized, which is important as pressurization really helps) vertically. Try stacking with the 9 fully loaded cans on the side of a closed can and see what happens. Make sure you do it in a bowl. It's going to get messy. :(

We know that a layer of paint is enough to insulate a LOX tank through 1st stage recovery engine on, but I don't think that's going to hack it for a side entry (let along not exploding due to flash boiling), do you?

So (assuming you've beefed up the whole tank structure to handle substantial side loads) how will you handle the heat, given you have to retain propellant for landing?

Obvious options I can see are
a)Minimal mass by putting TPS on the "windward" side of the tank.
b)Even layer of TPS on the sides of the whole stage
c)Thinner layer of TPS on whole stage and slow spin the stage on landing ("Rotisserie" mode as they called it for Apollo and Saturn EDS).

All of these offer exciting opportunities to advance the science of control systems quite a lot, with the possible exception of b), Which is the simplest (and heaviest) option.  :)

Fortunately the US Army has done quite a lot of work on the guidance issues associated with pairs of spinning tanks in tandem during their development of binary nerve gas shells (and some on bombs), as the consequences of a stray shell were quite serious.
Obviously the tanks are rather smaller (and faster spinning) but AFAIK the mathematics still applies wheather it be 50Kg or 5000Kg of fluid and 1 or 1000RPM. Simply insert appropriate operating conditions and fluid properties.

But remember
a)All require the interior structure and/or the tank pressures to be increased, since this is completely unnecessary for current expendable US practice
and
b) the "exchange rate" for US is 1:1.
Every lb/Kg/banana of mass you add comes off the payload reserve (which is no longer the payload reserve, and you'd be misleading people if you called it that) or off the available payload to orbit.

With the exception of tank pressurization gas (which could in principle be vented, if you could retain the propellant) every unit of mass that goes to orbit on the stage (except the payload) has to come back, and be decelerated in the final landing.  :(
« Last Edit: 08/28/2017 03:45 pm 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 meekGee

  • Senior Member
  • *****
  • Posts: 14158
  • N. California
  • Liked: 14046
  • Likes Given: 1392
I'm pretty sure they'd do side entry like Shuttle or Delta Clipper.
Only if you make the structure a) Winged or b) Lower aspect ratio.  :(

"Upper stage reuse" has been known to be possible since the first Shuttle reflight if you're prepared to design a vehicle to do it.

What has made it difficult is if you insist on doing it with a high aspect ratio US, which is what a conventional US is.

You are aware that the Shuttle reentry angle (when it lost most of its velocity) was rather nearer to 70degrees to the horizontal than horizontal?

Or the DC-X slightly nose down concept was inspired by the USAF's experience with warhead reentry?

This idea has a couple of inescapable facts connected with it.

1) Every unit of mass you put on the US comes off the payload. On boosters it's more like 13:1.  So you can add a (comparatively) huge amount of hardware to do recovery while sacrificing a (comparatively) small amount of payload.

2) You can make VTO LV's very light because they are very optimized to be strong in exactly 1 axis, just like a soda can  :( I've stacked 10 fully filled (but unpressurized, which is important as pressurization really helps) vertically. Try stacking with the 9 fully loaded cans on the side of a closed can and see what happens. Make sure you do it in a bowl. It's going to get messy. :(

We know that a layer of paint is enough to insulate a LOX tank through 1st stage recovery engine on, but I don't think that's going to hack it for a side entry (let along not exploding due to flash boiling), do you?

So (assuming you've beefed up the whole tank structure to handle substantial side loads) how will you handle the heat, given you have to retain propellant for landing?

Obvious options I can see are
a)Minimal mass by putting TPS on the "windward" side of the tank.
b)Even layer of TPS on the sides of the whole stage
c)Thinner layer of TPS on whole stage and slow spin the stage on landing ("Rotisserie" mode as they called it for Apollo and Saturn EDS).

All of these offer exciting opportunities to advance the science of control systems quite a lot, with the possible exception of b), Which is the simplest (and heaviest) option.  :)

Fortunately the US Army has done quite a lot of work on the guidance issues associated with pairs of spinning tanks in tandem during their development of binary nerve gas shells (and some on bombs), as the consequences of a stray shell were quite serious.
Obviously the tanks are rather smaller (and faster spinning) but AFAIK the mathematics still applies wheather it be 50Kg or 5000Kg of fluid and 1 or 1000RPM. Simply insert appropriate operating conditions and fluid properties.

But remember
a)All require the interior structure and/or the tank pressures to be increased, since this is completely unnecessary for current expendable US practice
and
b) the "exchange rate" for US is 1:1.
Every lb/Kg/banana of mass you add comes off the payload reserve (which is no longer the payload reserve, and you'd be misleading people if you called it that) or off the available payload to orbit.

With the exception of tank pressurization gas (which could in principle be vented, if you could retain the propellant) every unit of mass that goes to orbit on the stage (except the payload) has to come back, and be decelerated in the final landing.  :(
The 1:1 payload penalty is a red herring.

For LEO missions, a 5 ton US places a payload that's in excess of 20 tons for F9b5, not to mention FH.

So even if US reusability doubles the empty mass of the stage, a 1:1 penalty only drops the payload mass to 15 tons - hardly a show stopper... Not to mention that the mass penalty estimates are more like 3 tons.


Further, many LEO missions are volume limited.

There is absolutely nothing that is preventing SpaceX from building a recoverable upper stage for LEO missions.

All zat is rekvired is the VILL to do so!
ABCD - Always Be Counting Down

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 39270
  • Minnesota
  • Liked: 25240
  • Likes Given: 12115
I'm pretty sure they'd do side entry like Shuttle or Delta Clipper.
Only if you make the structure a) Winged or b) Lower aspect ratio.  :(...
Why is your post full of frowny faces? They'll figure it out eventually. And in the meantime, we get explosions! Win, win! :D

Anyway, I'm sure the recovery-attempt upper stage will look all weird with funky aerosurfaces for Falcon Heavy's maiden launch. Like a bastardized ITS spaceship.

Turn that frown upside down! :D
« Last Edit: 08/29/2017 04:09 am by Robotbeat »
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 10350
  • Everyplaceelse
  • Liked: 2430
  • Likes Given: 13605
Further, many LEO missions are volume limited.

There is absolutely nothing that is preventing SpaceX from building a recoverable upper stage for LEO missions.
If you discount the fact landing gear on the first stage turned out considerably heavier than most early estimates expected (more like 7% of GTOW IIRC) and as I noted the interesting control systems problems of landing such a stage, especially if it comes in at anything more than a shallow angle to the horizontal IE 3-5 degrees, not 70+

Quote from: meekGee
All zat is rekvired is the VILL to do so!
Which was pretty much the claim made by stage mfg's and recovery advocates in the 1960's for first stage recovery.

All that was needed was the (government) money to demonstrate it.  :(

None of those concepts had grid fins at the top end of the stage because everyone thought they could do it with thrust vectoring the engines if any control was needed.

That tells me that every single one of those concepts was not worked out in sufficient detail to realize they were needed. 

IOW they were all fantasies:(

SX have set the bar for what it takes to do this IRL. No Powerpoints, no videos.  It took them 5 attempts to get a successful barge landing and right first time for a land landing, despite the Grasshopper test programme before they made any actual attempts. I'm quite sure data from the barge landings fed their first land attempt and made it successful.
Why is your post full of frowny faces? They'll figure it out eventually. And in the meantime, we get explosions! Win, win! :D
I've no doubt that if the problem can be solved at all the SX team is smart enough to do it.

As someone who's keen to see launch prices drop radically the fuller the reuse the better. In money terms I'm betting fairing reuse will have an earlier (positive) impact on their bottom line than US recovery but only US recovery gives the really big price drops.

Quote from: Robotbeat
Anyway, I'm sure the recovery-attempt upper stage will look all weird with funky aerosurfaces for Falcon Heavy's maiden launch. Like a bastardized ITS spaceship.

Turn that frown upside down! :D
I'll try to keep that in mind.

I prefer my development programmes explosion free. Great entertainment but they make potential customers very nervous.

It's not just the loud bangs.

Stage reuse is meant to improve reliability above the expendable level.

SG1962's idea that the actual FH US will be a stock FH US (which ideally will be just a stock F9 US, but may not be,  given how far the design of the FH core has diverged) and the recovery attempt will be tried by the payload makes a lot of sense to me.  It's a classic "Get the core tasks out of the way and see if we can make bonus features work" SX approach.

If it works, brilliant.  :) If it doesn't, FH has demonstrated flight readiness, possibly with full first stage core recovery (and at relatively low cost). A key task if they want to go after the bigger NSS payloads with higher orbits.
« Last Edit: 08/29/2017 08:01 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 meekGee

  • Senior Member
  • *****
  • Posts: 14158
  • N. California
  • Liked: 14046
  • Likes Given: 1392
7% GTOW - wouldn't that make the legs as heavy as the entire rocket?

Anyway, what legs?  Parachute, aim for near shore, mid-air recovery of an empty US. 

No need for landing engines or any of that.  Grid fins for control, and a heat shield.

That's why thinking a 5 tons penalty is excessive.

This here is the first time there's any real motivation to recover the upper stage.  (Because of LEO demand).

GEO recovery is just much harder, and the mass penalty becomes a showstopper.
ABCD - Always Be Counting Down

Offline envy887

  • Senior Member
  • *****
  • Posts: 8144
  • Liked: 6801
  • Likes Given: 2965
7% GTOW - wouldn't that make the legs as heavy as the entire rocket?
...

7% of LANDING weight, not takeoff weight. And mostly due to the large span required for stability. The upper stage is relatively short and fat.

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 10350
  • Everyplaceelse
  • Liked: 2430
  • Likes Given: 13605
7% GTOW - wouldn't that make the legs as heavy as the entire rocket?
...

7% of LANDING weight, not takeoff weight. And mostly due to the large span required for stability. The upper stage is relatively short and fat.
Thank you for reminding me. Note that the heuristic for HTO vehicles is 4% of landing weight, despite the fact the XB70 managed to do it for 2% as the Boeing page of XB70 shows.
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 meekGee

  • Senior Member
  • *****
  • Posts: 14158
  • N. California
  • Liked: 14046
  • Likes Given: 1392
7% GTOW - wouldn't that make the legs as heavy as the entire rocket?
...

7% of LANDING weight, not takeoff weight. And mostly due to the large span required for stability. The upper stage is relatively short and fat.
Thank you for reminding me. Note that the heuristic for HTO vehicles is 4% of landing weight, despite the fact the XB70 managed to do it for 2% as the Boeing page of XB70 shows.
This is not about HTO vs VTO, or heuristics vs. real.... 

This is about US reusability and the long posts above arguing that US recovery is so difficult because mass mass mass.
ABCD - Always Be Counting Down

Tags:
 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
1