Speculation into what future versions of Dragon will involve

[simonbp]

And something that they are already dealing with for Grasshopper flights.

[gin455res]

Payload shrouds are often wider than the rockets that carry them. Is there any history of second stages being wider than the first stages that carry them?

What is the widest modified second stage that could be sensibly carried by falcon 9, and would a much squatter second stage; a)  re-enter the atmosphere more benignly - due to it being much fluffier, and having a larger base/mass ratio; and b) have a better mass fraction as it would be stubbier and have more efficient tanks that more closely resemble spheres not cylinders?

[Jim]

Payload shrouds are often wider than the rockets that carry them. Is there any history of second stages being wider than the first stages that carry them?

See Titan IV Centaur and Delta III

[ciscosdad]

I believe they can go to ~1.5 x the main stage diameter before they get unreasonable structural or aerodynamic stability probelems. I think I recall it being called a "hammerhead" configuration.
Not sure what sacrifices would need to be made to enable larger diameter ratios, or even if it is practically possible.

[solartear]

Could a used Falcon upper stage be used to de-orbit Dragon 2?  either its own (dormant for weeks/months) or later mission.

If there's a lot of margin leftover on upper stage, maybe Dragon could save more of it's own propellent for landing instead of de-orbit burn. Could it help or would too much propellant be used up just reconnecting to an upper stage?

Could be very useful for DragonLab to stay connected from launch until de-orbit burn completed.

[Lars_J]

Payload shrouds are often wider than the rockets that carry them. Is there any history of second stages being wider than the first stages that carry them?

Several... And one example of an upcoming launcher that will do it is the Angara family, where all but the smallest version (Angara-1.1) will have upper stages of greater diameter than the boosters/1st stage. (see image below)

What is the widest modified second stage that could be sensibly carried by falcon 9, and would a much squatter second stage; a)  re-enter the atmosphere more benignly - due to it being much fluffier, and having a larger base/mass ratio; and b) have a better mass fraction as it would be stubbier and have more efficient tanks that more closely resemble spheres not cylinders?

Since a ~5m diameter payload fairing is planned, it they should be able to go to 5m at least.

[Jim]

Could a used Falcon upper stage be used to de-orbit Dragon 2?  either its own (dormant for weeks/months) or later mission.

If there's a lot of margin leftover on upper stage, maybe Dragon could save more of it's own propellent for landing instead of de-orbit burn. Could it help or would too much propellant be used up just reconnecting to an upper stage?

Could be very useful for DragonLab to stay connected from launch until de-orbit burn completed.

The LO2 would have boiled away in days, the batteries would be dead in hours and there is limited control gas for attitude control

[Robotbeat]

I believe they can go to ~1.5 x the main stage diameter before they get unreasonable structural or aerodynamic stability probelems. I think I recall it being called a "hammerhead" configuration.
Not sure what sacrifices would need to be made to enable larger diameter ratios, or even if it is practically possible.

That isn't the limit at all. Atlas V has an available configuration for a 7.2m diameter fairing (for a 3.8m diameter rocket, giving a ratio of 1.9x), and that's not necessarily the upper limit:

Should a customer have a unique requirement to accommodate a larger payload, longer and wider payload fairings can be developed. Payload fairings as large as 7.2m (283 in.) in diameter and up to 32.3m (106 ft) in length have been considered. These larger fairings require moderate vehicle changes and modifications to the launch pad, which are limited mostly to secondary vertical processing facility structure. Please contact ULA for additional information on larger fairings.

http://www.ulalaunch.com/site/docs/product_cards/guides/AtlasVUsersGuide2010.pdf

So that's what's possible for a fairing. Probably wouldn't want such a huge upper stage, but if you have a special payload that needs a 7m diameter fairing, there's nothing in principle that says it /can't/ be launched on a Falcon 9.

[go4mars]

the batteries would be dead in hours

Maybe the trunk power system could keep these topped up?

The LO2 would have boiled away in days

Has there ever been reasonably serious plans for gas-bladders/balloons to vent into in space?
Rube Goldbergy.  I know. 

there is limited control gas for attitude control

Maybe some from the vent gas bladders?

Follow-on question:  Does gaseous combustion in a chamber work in vacuum?  Better?  Worse?  Not at all?  Does the thrust transient from F1 flight 3 suggest it's fine?  Was that gaseous combustion?  Or liquid combustion?   

[dragon44]

Could a used Falcon upper stage be used to de-orbit Dragon 2?  either its own (dormant for weeks/months) or later mission.

If there's a lot of margin leftover on upper stage, maybe Dragon could save more of it's own propellent for landing instead of de-orbit burn. Could it help or would too much propellant be used up just reconnecting to an upper stage?

Could be very useful for DragonLab to stay connected from launch until de-orbit burn completed.

The LO2 would have boiled away in days, the batteries would be dead in hours and there is limited control gas for attitude control

What Jim said.

A different possibility is MMH and NTO tanks in the trunk. The trunk interconnect (claw) has electrical and fluid connections. The trunk MMH/NTO tanks could refill the Dragon tanks. It wouldn't take large pipes, just 'trickle charge' them.

[RanulfC]

I don't think we can read too much into Elon's 'flying saucer' comment. He probably means 'UFO' and there are lots of alleged shapes for UFOs.

I believe the quote was that it will look "like something from the future."

Unless there's another interview I'm not aware of, Elon never said flying saucer.

Well, bummer... there went MY "speculative-idea" on the matter
http://www.nianet.org/rascal/forum2005/presentations/georgia_paper.pdf

Randy

[go4mars]

there went MY "speculative-idea" on the matter
http://www.nianet.org/rascal/forum2005/presentations/georgia_paper.pdf

Randy

Nice find!  From a volume perspective, it seems crappier than a dragon shape.  From cross-range and larger cross-sectional area perspective, it's great (especially with the window-cover/aerosurface flaps/tabs).  Needs some superdracos and legs in there somewhere.  Looks like it's squat enough to fit beneath underpasses.  From a landed mass at Mars perspective, with those flaps, this pancake should outperform the current "red dragon" numbers by a lot.  It also allows for an easier egress of rovers and equipment.            Interesting direction.  Perhaps some of these ideas will make their way into dragon 2.  Maybe the craft would have the superdracos and legs on the window side, flip when subsonic using control surfaces, and come in fast for the "brown pants" landing. 

I'd love to hear some initial comments from the big guns here.

[Jim]

Nice find!  From a volume perspective, it seems crappier than a dragon shape.  From cross-range and larger cross-sectional area perspective, it's great (especially with the window-cover/aerosurface flaps/tabs).  Needs some superdracos and legs in there somewhere.  Looks like it's squat enough to fit beneath underpasses.  From a landed mass at Mars perspective, with those flaps, this pancake should outperform the current "red dragon" numbers by a lot.  It also allows for an easier egress of rovers and equipment.         

Useless for Mars and a bad shape for cargo

[go4mars]

a bad shape for cargo

Agreed.

Useless for Mars

Curious.  I would have expected some of the ideas would benefit atmospheric drag, cross-range, and downmass (with use of superdracos).

[Jim]

a bad shape for cargo

Agreed.

Useless for Mars

Curious.  I would have expected some of the ideas would benefit atmospheric drag, cross-range, and downmass.

Atmosphere is too thin

[go4mars]

Atmosphere is too thin

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110015739_2011016739.pdf

Trim tab seems relevant.  These would be bigger. 

[Okie_Steve]

Just ran across this article about crew dragon testing.

http://venturebeat.com/2013/01/09/spacex-ccdev-updates/

[ciscosdad]

Nice Find!
Look at the image of the Dragon. Looks like a forward pointing conical section has been added to the base. I wonder how different this would be aerodynamically to the current flat based version?

[go4mars]

Just ran across this article about crew dragon testing.

http://venturebeat.com/2013/01/09/spacex-ccdev-updates/

Cool. 

The picture with the wire-escape from the tower shows a high-bay and a low-bay hangar.  Any ideas why?  And whether the part we've seen construction pictures of is the high or low?

[Jason1701]

Nice Find!
Look at the image of the Dragon. Looks like a forward pointing conical section has been added to the base. I wonder how different this would be aerodynamically to the current flat based version?

What do you mean? The pressure vessel looks the same as this:
http://digitalvideo.8m.net/SpaceX/DragonRider/DragonPressureHull.jpg

Just ran across this article about crew dragon testing.

http://venturebeat.com/2013/01/09/spacex-ccdev-updates/

Cool. 

The picture with the wire-escape from the tower shows a high-bay and a low-bay hangar.  Any ideas why?  And whether the part we've seen construction pictures of is the high or low?

They recently finished constructing a high bay extension to the rear of the hangar.