Speculation about Dragon 3

[Roy_H]

I can't help thinking about all this "escaping from a Dragon" to where? You won't get me to open the hatch in space unless it is properly attached to a habitat of some sort. On the way up? Nope. After an abort and you are in the water, yes, but not in a panic then, just waiting for rescue.

[Robotbeat]

I can't help thinking about all this "escaping from a Dragon" to where? You won't get me to open the hatch in space unless it is properly attached to a habitat of some sort. On the way up? Nope. After an abort and you are in the water, yes, but not in a panic then, just waiting for rescue.

People are saying it because of Apollo 1. (Which I think can be addressed with the common-sense of not having 15psi of oxygen, not bolting the door shut, etc.)

[AncientU]

I think the capsule form is nearing its practical end.  3.6m, 5.2m, or 7-8m still have limitations that are sub-optimal. I would hope that a longer, narrower shape would be used with the heat shield on long axis -- maybe an ellipsoidal  or modified, flattened cylinder reentering like Shuttle or Dream Chaser, but without wings.  Control surfaces of some sort would be probably needed, maybe deployable.  The long aspect ratio would seem to be much more scalable to large volumes than the capsule form.  High speed electronic stability controls (of thrusters, engines, control surfaces, or some combination) can make a rock flyable as evidenced by the F117 Nighthawk.

[Rabidpanda]

I think the capsule form is nearing its practical end.  3.6m, 5.2m, or 7-8m still have limitations that are sub-optimal. I would hope that a longer, narrower shape would be used with the heat shield on long axis -- maybe an ellipsoidal  or modified, flattened cylinder reentering like Shuttle or Dream Chaser, but without wings.  Control surfaces of some sort would be probably needed, maybe deployable.  The long aspect ratio would seem to be much more scalable to large volumes than the capsule form.  High speed electronic stability controls (of thrusters, engines, control surfaces, or some combination) can make a rock flyable as evidenced by the F117 Nighthawk.

Perhaps something like the IXV.

[randomly]

If Orion is already exceeding it's parachute weight limits, is that a hard limitation for capsule weight? Above a certain weight do you need to use a winged vehicle or lifting body instead of parachutes?
Or are their other approaches to extend the weight limits with parachutes?

[A_M_Swallow]

Somewhere along the line it will be time for a 2001 style space plane.  With ~50 tonne LV payload we may be able to get ~25 people to orbit.

[Avron]

Somewhere along the line it will be time for a 2001 style space plane.  With ~50 tonne LV payload we may be able to get ~25 people to orbit.

Thinking more along the lines of a lifting body.. If I recall correctly, thats ok with Elon.. wings are a no go.

[Ben the Space Brit]

If Orion is already exceeding it's parachute weight limits, is that a hard limitation for capsule weight? Above a certain weight do you need to use a winged vehicle or lifting body instead of parachutes?
Or are their other approaches to extend the weight limits with parachutes?

I'm not sure but I think Orion has run into a combination of factors that's limiting its parachute weight. If I recall correctly, there isn't enough room in the nose bay for a fourth 'chute because of the steep sides of the vehicle imposed by using a scaled-up Apollo geometry. The Orion is almost too heavy to land safely in the event of the failure of one of the three 'chutes (which happened to Apollo 12, IIRC). So, the Orion design has come up to a hard limit of mass.

However, alternate capsule geometries wouldn't have this problem. A capsule with bigger 'chute bays should be able to get to higher weights.

[AncientU]

If Orion is already exceeding it's parachute weight limits, is that a hard limitation for capsule weight? Above a certain weight do you need to use a winged vehicle or lifting body instead of parachutes?
Or are their other approaches to extend the weight limits with parachutes?

I'm not sure but I think Orion has run into a combination of factors that's limiting its parachute weight. If I recall correctly, there isn't enough room in the nose bay for a fourth 'chute because of the steep sides of the vehicle imposed by using a scaled-up Apollo geometry. The Orion is almost too heavy to land safely in the event of the failure of one of the three 'chutes (which happened to Apollo 12, IIRC). So, the Orion design has come up to a hard limit of mass.

However, alternate capsule geometries wouldn't have this problem. A capsule with bigger 'chute bays should be able to get to higher weights.

Chutes are an anachronism... as are 60s era LASs that are jettisoned (after wasting lots of fuel).

[AncientU]

I think the capsule form is nearing its practical end.  3.6m, 5.2m, or 7-8m still have limitations that are sub-optimal. I would hope that a longer, narrower shape would be used with the heat shield on long axis -- maybe an ellipsoidal  or modified, flattened cylinder reentering like Shuttle or Dream Chaser, but without wings.  Control surfaces of some sort would be probably needed, maybe deployable.  The long aspect ratio would seem to be much more scalable to large volumes than the capsule form.  High speed electronic stability controls (of thrusters, engines, control surfaces, or some combination) can make a rock flyable as evidenced by the F117 Nighthawk.

Perhaps something like the IXV.

exactly

[AncientU]

If Orion is already exceeding it's parachute weight limits, is that a hard limitation for capsule weight? Above a certain weight do you need to use a winged vehicle or lifting body instead of parachutes?
Or are their other approaches to extend the weight limits with parachutes?

I'm not sure but I think Orion has run into a combination of factors that's limiting its parachute weight. If I recall correctly, there isn't enough room in the nose bay for a fourth 'chute because of the steep sides of the vehicle imposed by using a scaled-up Apollo geometry. The Orion is almost too heavy to land safely in the event of the failure of one of the three 'chutes (which happened to Apollo 12, IIRC). So, the Orion design has come up to a hard limit of mass.

However, alternate capsule geometries wouldn't have this problem. A capsule with bigger 'chute bays should be able to get to higher weights.

Chutes are an anachronism... as are 60s era LASs that are jettisoned (after wasting lots of fuel).

Remember, the clever engineers that developed the capsule, parachute, LAS approach drove Edsels to work and had sliderules and black rotary-dial phones on their desks. I think EM and crew can do better.

[kttopdad]

If Orion is already exceeding it's parachute weight limits, is that a hard limitation for capsule weight? Above a certain weight do you need to use a winged vehicle or lifting body instead of parachutes?
Or are their other approaches to extend the weight limits with parachutes?

IIRC, the current parachutes are a leftover from a previous iteration of the capsule design.  Heavier 'chute loads are possible, just not in the current Orion picture.

[RanulfC]

I think the capsule form is nearing its practical end.  3.6m, 5.2m, or 7-8m still have limitations that are sub-optimal. I would hope that a longer, narrower shape would be used with the heat shield on long axis -- maybe an ellipsoidal  or modified, flattened cylinder reentering like Shuttle or Dream Chaser, but without wings.  Control surfaces of some sort would be probably needed, maybe deployable.  The long aspect ratio would seem to be much more scalable to large volumes than the capsule form.  High speed electronic stability controls (of thrusters, engines, control surfaces, or some combination) can make a rock flyable as evidenced by the F117 Nighthawk.

SpaceX brand Flying Saucer's! YES!
http://en.wikipedia.org/wiki/Lenticular_Reentry_Vehicle

(Ok, sorry but I had to )

I suspect the "capsule" form will actually continue as it goes to "biconic" from the current design form once you go to a "side" entry. And following the "logic" of aiming everything towards going to Mars while "wings" don't work the higher surface area of a biconic, (or yes a LREV) would be appricated for aerobraking.

Randy

[RanulfC]

I'm not sure but I think Orion has run into a combination of factors that's limiting its parachute weight. If I recall correctly, there isn't enough room in the nose bay for a fourth 'chute because of the steep sides of the vehicle imposed by using a scaled-up Apollo geometry. The Orion is almost too heavy to land safely in the event of the failure of one of the three 'chutes (which happened to Apollo 12, IIRC). So, the Orion design has come up to a hard limit of mass.

However, alternate capsule geometries wouldn't have this problem. A capsule with bigger 'chute bays should be able to get to higher weights.

And at some point you can actually just "dump" the "capsule" for cylinder shape if you really "want" to. There are alternatives to "convetional" design. The Para-Shield is a good example:
http://www.techscience.com/doi/10.3970/fdmp.2012.008.453.pdf
http://spacecraft.ssl.umd.edu/publications/2010/SpaceOps2010ParaShieldx.pdf
http://www.planetaryprobe.org/SessionFiles/Session4/Papers/Rohrschneider_Inflat&Deploy-Paper.pdf

This also helps with your terminal velocity and parachute needs.
(Edit) Includes your terminal thrust needs as well
Randy

[butters]

The F9R upper stage reentry concept implies that SpaceX has a solution for reentering and propulsively landing cylindrical vehicles from earth orbit. If they can do that, then why not make "Dragon 3" a cylindrical pressure vessel with aft-mounted propulsion? Simple to manufacture, efficient lightweight structure, and relatively low ballistic coefficients at high angles of attack. It would be characteristic of SpaceX to integrate the upper stage and design its propellant system to also drive RCS thrusters.

Remember, Elon said that the exciting thing about Raptor isn't the engine, it's the spaceship it's attached to...

[Robotbeat]

The F9R upper stage reentry concept implies that SpaceX has a solution for reentering and propulsively landing cylindrical vehicles from earth orbit. If they can do that, then why not make "Dragon 3" a cylindrical pressure vessel with aft-mounted propulsion? Simple to manufacture, efficient lightweight structure, and relatively low ballistic coefficients at high angles of attack. It would be characteristic of SpaceX to integrate the upper stage and design its propellant system to also drive RCS thrusters.

Remember, Elon said that the exciting thing about Raptor isn't the engine, it's the spaceship it's attached to...

You're describing what I think MCT is. Which makes sense: I don't think there will be a Dragon 3, just MCT.

[cuddihy]

Ok, so can you describe it a little better? Would it fit a vacuum-exposed payload bay? Do you think cryo (methalox) oms/rcs is a necessity?
Would it functionally be a third stage that does mundane tasks like releasing satellites at GTO and then returning to earth or is it for human transport only?

[beancounter]

The F9R upper stage reentry concept implies that SpaceX has a solution for reentering and propulsively landing cylindrical vehicles from earth orbit. If they can do that, then why not make "Dragon 3" a cylindrical pressure vessel with aft-mounted propulsion? Simple to manufacture, efficient lightweight structure, and relatively low ballistic coefficients at high angles of attack. It would be characteristic of SpaceX to integrate the upper stage and design its propellant system to also drive RCS thrusters.

Remember, Elon said that the exciting thing about Raptor isn't the engine, it's the spaceship it's attached to...

Sounds a bit like the Bigelow concept.

[guckyfan]

Ok, so can you describe it a little better? Would it fit a vacuum-exposed payload bay? Do you think cryo (methalox) oms/rcs is a necessity?
Would it functionally be a third stage that does mundane tasks like releasing satellites at GTO and then returning to earth or is it for human transport only?

I think methalox RCS is very likely. NASA is doing it on their experimental moon lander.

I think it would functionally be a second stage. But there would be a payload version without all the MCT functions I believe.

It is an interesting question wether MCT will carry astronauts to orbit. There is the problem with the abort function. It may not have the thrust to fulfill that function. In that case and assuming more than 7 astronauts capacity they may need a bigger spacecraft than Dragon 2 to deliver them. Yes, I think it quite possible it will be of cylindrical form. Why not if they solve that problem for Falcon 9 upper stages?

[AncientU]

As to size of the vehicle, a possible configuration would be approximately the diameter and volume of the existing payload fairing (recall the figure of it enclosing a schoolbus -- see link below); launched from the FH, it would allow volume for BLEO missions, larger numbers of passengers, other features depending on mission(s).
http://www.spacex.com/falcon9