SpaceX Dragon 2 Updates and Discussion - Thread 3

[Joffan]

Questions about possible uses of superdracos and hypergolic fuel in orbit:

Crew Dragon carries into orbit superdracos, dracos, and extra hypergolic fuel (needed for superdraco aborts). What uses could those assets have in once Crew Dragon is in orbit?

Fuel load: is the fuel load more or less equal to Dragon V1's fuel load plus fuel for aborts, or is there just enough fuel for aborts, which also serves for normal draco activity on orbit?

Station reboost: Could Crew Dragon provide ISS reboost with its extra fuel? Could the IDA take the strain? If it can, and superdracos are too powerful, could normal dracos provide milder acceleration while still using the excess fuel?

As I understand it, the hypergolic fuel is common to Dracos and Superdracos and is still sufficient in principle for a Superdraco landing. So, given that powered landing is currently off the table, I would think that station reboost using a long burn of Dracos would be feasible. The impulse of Superdracos  might be too high for the strength of the docking port (or perhaps some other equipment or experiments). Since the US docking process comes in to the "front" of the ISS, the station would need to flip to support this.

Personally I have been puzzled for a long time why ion thrusters are not in use on the ISS, cancelling drag and thus improving the microgravity environment.

[whitelancer64]

Questions about possible uses of superdracos and hypergolic fuel in orbit:

Crew Dragon carries into orbit superdracos, dracos, and extra hypergolic fuel (needed for superdraco aborts). What uses could those assets have in once Crew Dragon is in orbit?

Fuel load: is the fuel load more or less equal to Dragon V1's fuel load plus fuel for aborts, or is there just enough fuel for aborts, which also serves for normal draco activity on orbit?

Station reboost: Could Crew Dragon provide ISS reboost with its extra fuel? Could the IDA take the strain? If it can, and superdracos are too powerful, could normal dracos provide milder acceleration while still using the excess fuel?

As I understand it, the hypergolic fuel is common to Dracos and Superdracos and is still sufficient in principle for a Superdraco landing. So, given that powered landing is currently off the table, I would think that station reboost using a long burn of Dracos would be feasible. The impulse of Superdracos  might be too high for the strength of the docking port (or perhaps some other equipment or experiments). Since the US docking process comes in to the "front" of the ISS, the station would need to flip to support this.

Personally I have been puzzled for a long time why ion thrusters are not in use on the ISS, cancelling drag and thus improving the microgravity environment.

Mostly power requirements.

Remember VASIMR was going to be used for station reboost, but would have had to have been battery powered and only fire for 15 minutes at a time because the solar arrays don't produce enough power for both the ISS and for them to fire constantly.

[Lars-J]

Fuel load: is the fuel load more or less equal to Dragon V1's fuel load plus fuel for aborts, or is there just enough fuel for aborts, which also serves for normal draco activity on orbit?

The propellant load for Crew Dragon appears to be more than Dragon 1. Dragon 1 (picture one) uses spherical tanks, but Dragon 2 (picture two) has stretched tanks with a cylindrical middle section.

[WmThomas]

Fuel load: is the fuel load more or less equal to Dragon V1's fuel load plus fuel for aborts, or is there just enough fuel for aborts, which also serves for normal draco activity on orbit?

The propellant load for Crew Dragon appears to be more than Dragon 1. Dragon 1 (picture one) uses spherical tanks, but Dragon 2 (picture two) has stretched tanks with a cylindrical middle section.

Thanks for the pix. But now two people now have misunderstood what I wrote. Let me be more clear. My question (about fuel) is:

1) Is the total hypergolic fuel load of Crew Dragon equal to:
a) Dragon V1 draco fuel load PLUS all the fuel needed for the superdracos to abort from the pad or max-Q?
OR
b) Just the fuel needed to aborts at the pad or Max-Q, because on orbit this fuel is more than enough for the ordinary dracos to use in orbital maneuvering?

It's obvious that Crew Dragon has more fuel than Dragon V1 (its abort system requires it), the question is, how much more?

I asked because I'm curious how much unused fuel Crew Dragon will tend to carry into orbit and not end up using at all. This fuel could then be used to a) boost station, b) perform emergency maneuvers such as landing without parachutes or engaging in hypersonic retro propulsion if need be.

[Lars-J]

Fuel load: is the fuel load more or less equal to Dragon V1's fuel load plus fuel for aborts, or is there just enough fuel for aborts, which also serves for normal draco activity on orbit?

The propellant load for Crew Dragon appears to be more than Dragon 1. Dragon 1 (picture one) uses spherical tanks, but Dragon 2 (picture two) has stretched tanks with a cylindrical middle section.

Thanks for the pix. But now two people now have misunderstood what I wrote. Let me be more clear. My question (about fuel) is:

1) Is the total hypergolic fuel load of Crew Dragon equal to:
a) Dragon V1 draco fuel load PLUS all the fuel needed for the superdracos to abort from the pad or max-Q?
OR
b) Just the fuel needed to aborts at the pad or Max-Q, because on orbit this fuel is more than enough for the ordinary dracos to use in orbital maneuvering?

It's obvious that Crew Dragon has more fuel than Dragon V1 (its abort system requires it), the question is, how much more?

No, it's not obvious, since we don't know how much its abort system requires. (or do you know?)

Since the propellant is shared between abort and normal in space-ops, the answer is clearly not A, but B. Or a variant thereof, since we don't know if abort or normal space operations uses more propellant. The tanks are sized for the larger of the two needs. But Dragon 2 is also heavier than Dragon 1, which alone could explain the difference in tank size.

If you want a more detailed answer than that, you may not get it, since we don't know the exact numbers.

[Charlie Beran]

I have a question about Dragon 2 landing. How will the parachutes deploy? Are they under the cap and it needs to be opened or ejected?

The parachutes are not under the nose cap. The main chutes are stowed in a bay directly underneath the side-hatch. The drogue chutes are deployed from mortar bays that are located above the main hatch. Rip-out lines connect the drogues with the mains.

So, no need to open or eject the nose cap for parachute deployment.

After watching the pad abort test, it appears that the main chutes are stowed in the bay directly above the side-hatch.  Unless this has changed since the 2015 test.

[joek]

After watching the pad abort test, it appears that the main chutes are stowed in the bay directly above the side-hatch.  Unless this has changed since the 2015 test.

Main parachutes are stowed below the hatch; visible in the attached snip (mortar and mains attach points above the hatch).

[Lars-J]

I have a question about Dragon 2 landing. How will the parachutes deploy? Are they under the cap and it needs to be opened or ejected?

The parachutes are not under the nose cap. The main chutes are stowed in a bay directly underneath the side-hatch. The drogue chutes are deployed from mortar bays that are located above the main hatch. Rip-out lines connect the drogues with the mains.

So, no need to open or eject the nose cap for parachute deployment.

After watching the pad abort test, it appears that the main chutes are stowed in the bay directly above the side-hatch.  Unless this has changed since the 2015 test.

No, that is the drogues. (above the hatch). The mains are under the hatch. See this image from an early Dragon 2 parachute test. (simplified test capsule without SDs) It has not changed since then.

Here is an old image illustrating the placement compared to Dragon 1:

[Charlie Beran]

Thank you for the clarification.  It appeared to me in the video that the bay directly below the side-hatch remained covered.  That is what I get for only using one source of information!

[Riley1066]

The flip up nose cone should have a camera in it aimed down at the docking port from above ...

[Riley1066]

Will the Dragon have the ability to conduct fly-arounds of the station do to video and photographic surveys of the ISS?

[Lars-J]

Will the Dragon have the ability to conduct fly-arounds of the station do to video and photographic surveys of the ISS?

Sure, if manned, If one of the astronauts has a decent camera and shoots out of the window. (How it was done with Shuttle)

The built in cameras (as seen during approach) are not of high enough quality to do a decent inspection.

[ThomasGadd]

Will the Dragon have the ability to conduct fly-arounds of the station do to video and photographic surveys of the ISS?

Sure, if manned, If one of the astronauts has a decent camera and shoots out of the window. (How it was done with Shuttle)

The built in cameras (as seen during approach) are not of high enough quality to do a decent inspection.

There is  no reason Dragon couldn't be loaded with camera's and remotely controlled from ISS.

[flyright]

Will the Dragon have the ability to conduct fly-arounds of the station do to video and photographic surveys of the ISS?

Sure, if manned, If one of the astronauts has a decent camera and shoots out of the window. (How it was done with Shuttle)

The built in cameras (as seen during approach) are not of high enough quality to do a decent inspection.

There is  no reason Dragon couldn't be loaded with camera's and remotely controlled from ISS.

I don't believe the ISS has the capability of controlling the Dragon other than to signal it to stop, or abort it's approach. However, it might be possible to program the Dragon to autonomously do the fly-around.
I haven't seen or read anything to indicate this is being considered though.

[DigitalMan]

Will the Dragon have the ability to conduct fly-arounds of the station do to video and photographic surveys of the ISS?

Sure, if manned, If one of the astronauts has a decent camera and shoots out of the window. (How it was done with Shuttle)

The built in cameras (as seen during approach) are not of high enough quality to do a decent inspection.

There is  no reason Dragon couldn't be loaded with camera's and remotely controlled from ISS.

Elon had said Dragon has a number of cameras (not an exact quote).  I don't think an explicit number and placement is known publicly. Hopefully we will get a better idea once it has returned to earth and they release footage.

[basedoesgames]

I've attempted to model Crew Dragons decent across North America to splashdown. I've attached the STK Ephemeris file if you want to check it out yourself.
This is the track I've generated


Here was my basic process to calculate the starting (technically modeled as the ending) altitude:
Deoribt burn may occur around 250 miles at ~7:30 AM EST
Takes around an hour and three minutes to arrive at entry interface

250-75.75= 174.24 mile difference (75.75 miles is 121 km)

174.24/63=2.77 mi/m (1h and 3m = 63m)
Dropping at 2.77 miles per minute

Starts crossing NA at 8:29 AM, 59 minutes after DoB

59*2.77 = 163.43
250-163.43= 86.57 miles
Altitude at ~86.6 miles once NA crossing begins

Splashdown occurs at ~8:45 AM EST

250 miles roughly calculated from typical Soyuz deobit distance from the space station (I'm aware dragon will be different (or maybe not?), so take my calculations and model with a grain of salt)

Splashdown location based off of this google map:https://www.google.com/maps/d/viewer?mid=17sTdDuaLN-EJeuALqkvhM2hULM5lvIKZ&hl=en&usp=sharing

Also included is Azimuth and Elevation viewing angles from locations in the picture. Start times may be somewhere around 6 minutes before the ISS.

[RoboGoofers]

Elon had said Dragon has a number of cameras (not an exact quote).  I don't think an explicit number and placement is known publicly. Hopefully we will get a better idea once it has returned to earth and they release footage.

there's at least:
one inside
two visible spectrum cameras for docking
two IR cameras for docking
any others?

[Joffan]

I wonder why there isn't a short lifting sling or two, stowed behind the parachute lines, ready to grab the free end out of the parachute bay and use for lifting the Dragon. Extra weight of course but quicker and more convenient than climbing a pitching capsule.

[woods170]

I wonder why there isn't a short lifting sling or two, stowed behind the parachute lines, ready to grab the free end out of the parachute bay and use for lifting the Dragon. Extra weight of course but quicker and more convenient than climbing a pitching capsule.

Not necessary. Climbing a pitching capsule has been well practised by SpaceX recovery crews on 17 open sea splash-downs of cargo Dragon so far (15 operational missions, as well as C1 and C2+ missions) as well as on dozens of recovery practice runs off the coast of Florida.

It is not a concern.

[Joffan]

I wonder why there isn't a short lifting sling or two, stowed behind the parachute lines, ready to grab the free end out of the parachute bay and use for lifting the Dragon. Extra weight of course but quicker and more convenient than climbing a pitching capsule.

Not necessary. Climbing a pitching capsule has been well practised by SpaceX recovery crews on 17 open sea splash-downs of cargo Dragon so far (15 operational missions, as well as C1 and C2+ missions) as well as on dozens of recovery practice runs off the coast of Florida.

It is not a concern.

Yes, I don't doubt the existing process works, but if there is a desire to get the astros onto the boat more quickly it would be an option to help that along.

And that goes double for direct orbital tourism customers of SpaceX I'd think.