SpaceX test parachute system for Commercial Crew Dragon

[Chris Bergin]

http://www.nasaspaceflight.com/2014/01/spacex-test-parachute-system-commercial-crew-dragon/

Used the materials added below and expanded on LAS and other things. The ascent abort is going to be very interesting, including visually, but I didn't want to run that out of L2 until SpaceX respond, so that'll be another article.

NASA Release and photos.
http://www.nasa.gov/content/nasa-commercial-crew-partner-spacex-tests-dragon-parachute-system/

NASA Video:

[Joffan]

Nice article.

My understanding of these additional parachute tests,  added in August last year for $20 million, is that the drogues are effectively fired out of the capsule, not merely "released". Probably in order to be effective even in the tumbling case set up here.

[rcoppola]

Nice article.

My understanding of these additional parachute tests,  added in August last year for $20 million, is that the drogues are effectively fired out of the capsule, not merely "released". Probably in order to be effective even in the tumbling case set up here.

That's my understanding as well. Do we know the mechanism of this "firing"? We know they don't like pyro.

[joek]

Thanks again Chris (that was fast!), and congrats to SpaceX.  In the article you state:

The pad abort test article Dragon is already being processed at SpaceX’s Californian base, ahead of its short flight in the latter half of this year.

So we shouldn't expect to see the pad abort test before July?

p.s. Also glad to see SpaceX is back to the expected 15 milestones, instead of the 17 shown in the last NASA CCP progress report.

[joek]

My understanding of these additional parachute tests,  added in August last year for $20 million, is that the drogues are effectively fired out of the capsule, not merely "released". Probably in order to be effective even in the tumbling case set up here.

That's my understanding as well. Do we know the mechanism of this "firing"? We know they don't like pyro.

Presumably there is an active mechanism, as the milestone mentions "mortar firing" tests, including a "flight-intent gas generator" (two preceding this drop test).

[rcoppola]

My understanding of these additional parachute tests,  added in August last year for $20 million, is that the drogues are effectively fired out of the capsule, not merely "released". Probably in order to be effective even in the tumbling case set up here.

That's my understanding as well. Do we know the mechanism of this "firing"? We know they don't like pyro.

Presumably there is an active mechanism, as the milestone mentions "mortar firing" tests, including a "flight-intent gas generator" (two preceding this drop test).

So a type of pressurized gas canister? (Meaning not a chemical destructive charge)

[Chris Bergin]

Thanks again Chris (that was fast!), and congrats to SpaceX.  In the article you state:

The pad abort test article Dragon is already being processed at SpaceX’s Californian base, ahead of its short flight in the latter half of this year.

So we shouldn't expect to see the pad abort test before July?

p.s. Also glad to see SpaceX is back to the expected 15 milestones, instead of the 17 shown in the last NASA CCP progress report.

Thanks! (Would have been faster, but had 50 things to do at the same time )

Pad abort is Q3/Q4 I was told. Will ask to update (per the second article I'll be doing).

[Thorny]

Just wondering about the article... what is the subject of the third photograph? It looks like a mountain or boulder.

[manboy]

Just wondering about the article... what is the subject of the third photograph? It looks like a mountain or boulder.

Dragon test article being carried by a helicopter.

[dragon44]

The Dragon drogue chutes have always been mortar deployed.

http://www.airborne-sys.com/pages/view/spacex-dragon-capsule and
http://www.airborne-sys.com/pages/view/airborne-systems-technology-brings-space-x-spacecraft-to-saf

I think the SpaceX preference against pyro doesn't mean 100% exclusion of pyro devices.

For instance, read the description of this SpaceX YouTube video:

[darkenfast]

Just wondering about the article... what is the subject of the third photograph? It looks like a mountain or boulder.

Morro Rock. It is the landmark for which Morro Bay is famous for in tourist brochures, calendars and photo-shoots of space capsule tests!

[meekGee]

A question for the veterans on this thread - has anyone seen a parachute test with induced tumble like this before?

[docmordrid]

Emulating an asymmetrical SuperDraco firing?

[mlindner]

A few interesting screenshots from the video.

First image shows the fiery red from just after the drogue mortar fires, so they're apparently using pyros rather than compressed gas. Second shows just after parachute ejection and that the mortars and drogues were above the line where the nosecap meets the spacecraft.

Also, was there any new information in the NSF article that wasn't in the NASA press release?

[cambrianera]

Does anyone have any guesses as to what the protuberances are?

They could be fairings for high speed cameras, to follow the deployment of lines and early deployment of parachutes (maybe unzip of protection).
Close up on one of mlinder screenshots above seems to show some hole for the lenses.

[douglas100]

Emulating an asymmetrical SuperDraco firing?

Or maybe emulating the tumbling you would get after an abort?

[cambrianera]

Another view of the bottom protuberance (green oval) and one for the drogue chute (red oval).
Likely high speed cameras.

[mrmandias]

Great article.

[Roy_H]

8000ft, How high does the pad abort take the Dragon? I would think it would be a lot less than 8000ft, so I don't understand the validity of this test.

[Ben the Space Brit]

I think that image of Dragon descending under its parachutes must have brought back a lot of good memories to the Apollo guys.

[Jcc]

8000ft, How high does the pad abort take the Dragon? I would think it would be a lot less than 8000ft, so I don't understand the validity of this test.

They can see how quickly he chutes deploy and reach safe velocity for landing. As long as that occurs within a vertical range less than the pad abort altitude, it passes the test.

[veblen]

I think that image of Dragon descending under its parachutes must have brought back a lot of good memories to the Apollo guys.

Actually, not so much compared to this:

www.youtube.com/JLdP-L7D58g‎

The Orion mock-up was propelled over 3800 ft up and almost 7000 ft downrange.

[AJW]

That link was broken.  Here's another:

[Robotbeat]

Orion pad abort 1 had an apogee of 6000ft, and Apollo's pad abort had an apogee of over 9000ft, I believe. So 8000ft isn't that different.

[veblen]

Thnks for posting the video and the correct apogee. Looking forward to SpaceX pad abort later this year.

[clongton]

The LAS seemed to come awfully close to the descending Orion at 1:59 in the video. Any idea how close it came to hitting the capsule?

[AJW]

At 5:40 there is a second camera angle and the whole system goes nearly horizontal just before release.  The LAS continues to fire after release and this may be designed to create the maximum separation from the capsule.  The falling LAS is not visible in the second angle, but this footage may end before that point.

[Avron]

Is this a Spacex LAS test.. if not please move  or paint a Spacex logo on the new"Dragon"

[corrodedNut]

The Dragon drogue chutes have always been mortar deployed.

I agree. Whether it's pyro or pressurized gas we may never know, to me the real differences are the location of the mortar tubes, the parachute riser troughs, and the main parachute compartment, see attached photo:

By moving the mortar tubes closer to the attach point of the main risers, the drogue risers no longer have to rip through x-amount of backshell TPS to deploy properly (one less failure mode).

Moving the main parachute attach point to the hatch side of the vehicle, the crew come down "back first" rather than "feet first" in the event of a splashdown.

This puts the hatch in the way of the main 'chute riser trough that extends down to the main 'chute compartment, which explains why they bifurcated it around the hatch.

There's no need for a grapple fixture on a spacecraft that docks, presumably any other equipment from the "sensor bay" will be moved elsewhere. That leaves a lot of space for additional Draco and SuperDraco propellant storage.

[Eyetam]

Great analysis corrodedNut!

I wonder if there is any changes on Dragon2 related to the nosecone...I have the impression the drogue mortars are located in what used to be the nosecone?

[Comga]

Another view of the bottom protuberance (green oval) and one for the drogue chute (red oval).
Likely high speed cameras.

This image says to me that the protuberances are guides for the helicopter lifting cables.
I highly doubt that they are camera housings.  They are bigger than one would really need, and not a good shape for that.

[TomH]

Just wondering about the article... what is the subject of the third photograph? It looks like a mountain or boulder.

Morro Rock. It is the landmark for which Morro Bay is famous for in tourist brochures, calendars and photo-shoots of space capsule tests!

Yup, Morrow Bay is a cool little resort village, less than 10 miles from Cal Poly where my daughter is an engineering major.

[cambrianera]

Another view of the bottom protuberance (green oval) and one for the drogue chute (red oval).
Likely high speed cameras.

This image says to me that the protuberances are guides for the helicopter lifting cables.
I highly doubt that they are camera housings.  They are bigger than one would really need, and not a good shape for that.

It seems to me that the on board sequence of deployment of drogue was taken likely from the upper protuberance POV.

[Lars_J]

It looks like the KSC commercial crew gallery section has been updated with more images from the parachute drop test: http://mediaarchive.ksc.nasa.gov/search.cfm?cat=240 (two pages of pictures)

Here are two of them:

[sublimemarsupial]

Another view of the bottom protuberance (green oval) and one for the drogue chute (red oval).
Likely high speed cameras.

This image says to me that the protuberances are guides for the helicopter lifting cables.
I highly doubt that they are camera housings.  They are bigger than one would really need, and not a good shape for that.

Looking at one of the images from the KSC media gallery, it definitely appears like those protrusions are for cameras. It actually looks like a GoPro to me.

[Robotbeat]

Nice catch!

[Comga]

Another view of the bottom protuberance (green oval) and one for the drogue chute (red oval).
Likely high speed cameras.

This image says to me that the protuberances are guides for the helicopter lifting cables.
I highly doubt that they are camera housings.  They are bigger than one would really need, and not a good shape for that.

Looking at one of the images from the KSC media gallery, it definitely appears like those protrusions are for cameras. It actually looks like a GoPro to me.

Ha!  Nice one. You have convinced me. Good spotting.
A GoPro. Clever. I see them all the time on the ski slopes.   Simple, rugged, high def, waterproof, shock resistant. Perfect.

[LEGO_Man]

Looks like a reversed Arlon logo in that last KSC image. Here's their silicates, thermal, and electronics materials sites, respectively.  I wonder which of their products SpaceX is using? My bet is on some type of high-temp adhesive.

[Comga]

In the NASA press release (#14-018 2014-01-17) and web posting they said:

During a normal spacecraft landing, the parachutes will be aided by the Dragon’s SuperDraco thrusters to provide a soft controlled landing. This redundancy on both the parachutes and thrusters is designed to ensure safe landings for crews.

[emphasis added]
This does not line up exactly with what SpaceX has been saying.  Sounds like a Soyuz landing.
Could this be what SpaceX has agreed to for NASA manned missions or just a garbled description?
As Emily Shanklin of Spacex was listed on the release, one would think that it would be accurate.

[Robotbeat]

That isn't a surprise. We saw a similar Dragon parachute+Superdraco landing video at least a year ago, I believe.

[guckyfan]

In the NASA press release (#14-018 2014-01-17) and web posting they said:

During a normal spacecraft landing, the parachutes will be aided by the Dragon’s SuperDraco thrusters to provide a soft controlled landing. This redundancy on both the parachutes and thrusters is designed to ensure safe landings for crews.

[emphasis added]
This does not line up exactly with what SpaceX has been saying.  Sounds like a Soyuz landing.
Could this be what SpaceX has agreed to for NASA manned missions or just a garbled description?
As Emily Shanklin of Spacex was listed on the release, one would think that it would be accurate.

I see it as an intermediate step. It can be used until NASA (and SpaceX) has more confidence in the reliability of SuperDraco landing.

[Avron]

Redundancy , critical for human spaceflight.. If the parachutes don't work then its 100% SuperDraco landing.

[guckyfan]

Redundancy , critical for human spaceflight.. If the parachutes don't work then its 100% SuperDraco landing.

They will want 100% SuperDraco landings as standard for pinpoint landing on a landing pad of helipad size.

[Elmar Moelzer]

Which is another reason why I expect them to use a slightly modified Dragon2 for cargo as well. It would give them a chance to practice powered landings without parachutes to get more experience with it.

[Lars_J]

Which is another reason why I expect them to use a slightly modified Dragon2 for cargo as well. It would give them a chance to practice powered landings without parachutes to get more experience with it.

Except based on what we are seeing, on Dragon 2 the parachute compartment now takes up the space under the hatch where the ISS arm attachment point is. The star trackers and approach sensors to used to be placed there also have presumably been moved up to around the docking port - next to the new drogue canisters.

This changes things. And will make it difficult to use the Dragon 2 with station capture and berthing.

[Jason1701]

Which is another reason why I expect them to use a slightly modified Dragon2 for cargo as well. It would give them a chance to practice powered landings without parachutes to get more experience with it.

Except based on what we are seeing, on Dragon 2 the parachute compartment now takes up the space under the hatch where the ISS arm attachment point is. The star trackers and approach sensors to used to be placed there also have presumably been moved up to around the docking port - next to the new drogue canisters.

This changes things. And will make it difficult to use the Dragon 2 with station capture and berthing.

Berthing will be impossible for other reasons with Dragon 2 - mostly because of various subsystems filling the space on the forward bulkhead that was previously taken up by the CBM.

[Elmar Moelzer]

That's why I said "modified". Obviously, the cargo dragon will have to be able to berth with the station.

[Lurker Steve]

That's why I said "modified". Obviously, the cargo dragon will have to be able to berth with the station.

Only if you meant modified to revert those items back to the original Dragon 1 design.

[Ben the Space Brit]

That's why I said "modified". Obviously, the cargo dragon will have to be able to berth with the station.

Only if you meant modified to revert those items back to the original Dragon 1 design.

So, basically, what we're seeing here is the point where the Cargo and Crew Dragons diverge in commonality? There is a common OML and pressure module but they are almost totally different in outfitting.

[Elmar Moelzer]

So, basically, what we're seeing here is the point where the Cargo and Crew Dragons diverge in commonality? There is a common OML and pressure module but they are almost totally different in outfitting.

And I don't think that this is what will happen. I am pretty sure that they will try to keep as much commonality between the two versions as possible. We don't even know for sure yet what Dragon 2 will look like. It is likely going to look like some of the mockups we have seen and the shape of the pressure vessel seems to be pretty certain at this point. But otherwise, we cant be sure. Maybe there is a certain amount of modularity that allows turning a crew Dragon into a cargo Dragon and vice versa. It seems quite against SpaceX MO to have two so specialized versions. I certainly cant wait for the Dragon 2 reveal, which will hopefully give us a better idea about all this. It is overdue already anyway. Wonder what the holdup is.

[Lar]

I certainly cant wait for the Dragon 2 reveal, which will hopefully give us a better idea about all this. It is overdue already anyway. Wonder what the holdup is.

Today is the day that many proposals are due for CCDev/CCiCAP ... . See http://forum.nasaspaceflight.com/index.php?topic=28699.msg1151708#msg1151708 for example.

After those proposals are submitted we may see more.

[manboy]

That isn't a surprise. We saw a similar Dragon parachute+Superdraco landing video at least a year ago, I believe.

The was from late July 2012. The is from early August 2012.

Which is another reason why I expect them to use a slightly modified Dragon2 for cargo as well. It would give them a chance to practice powered landings without parachutes to get more experience with it.

Except based on what we are seeing, on Dragon 2 the parachute compartment now takes up the space under the hatch where the ISS arm attachment point is. The star trackers and approach sensors to used to be placed there also have presumably been moved up to around the docking port - next to the new drogue canisters.

That doesn't mean the grapple fixture can't be moved elsewhere.

Which is another reason why I expect them to use a slightly modified Dragon2 for cargo as well. It would give them a chance to practice powered landings without parachutes to get more experience with it.

Except based on what we are seeing, on Dragon 2 the parachute compartment now takes up the space under the hatch where the ISS arm attachment point is. The star trackers and approach sensors to used to be placed there also have presumably been moved up to around the docking port - next to the new drogue canisters.

This changes things. And will make it difficult to use the Dragon 2 with station capture and berthing.

Berthing will be impossible for other reasons with Dragon 2 - mostly because of various subsystems filling the space on the forward bulkhead that was previously taken up by the CBM.

It might be possible to fit both the CBM and drogues.

[Lars_J]

Berthing will be impossible for other reasons with Dragon 2 - mostly because of various subsystems filling the space on the forward bulkhead that was previously taken up by the CBM.

It might be possible to fit both the CBM and drogues.

Take another look at how little space there is around the CBM.

[Elmar Moelzer]

Berthing will be impossible for other reasons with Dragon 2 - mostly because of various subsystems filling the space on the forward bulkhead that was previously taken up by the CBM.

It might be possible to fit both the CBM and drogues.

Take another look at how little space there is around the CBM.

Who says the arrangement wont be different on the Dragon2?

[Lars_J]

Berthing will be impossible for other reasons with Dragon 2 - mostly because of various subsystems filling the space on the forward bulkhead that was previously taken up by the CBM.

It might be possible to fit both the CBM and drogues.

Take another look at how little space there is around the CBM.

Who says the arrangement wont be different on the Dragon2?

Different how? Do you not see the size of the CBM ring? I think you are grasping at straws here.

It's becoming clearer and clearer that "Dragon 2" won't have room for a CBM hatch. I.e. = No cargo version of Dragon 2.

[manboy]

Berthing will be impossible for other reasons with Dragon 2 - mostly because of various subsystems filling the space on the forward bulkhead that was previously taken up by the CBM.

It might be possible to fit both the CBM and drogues.

Take another look at how little space there is around the CBM.

How deep are the drogues?

[Lars_J]

Berthing will be impossible for other reasons with Dragon 2 - mostly because of various subsystems filling the space on the forward bulkhead that was previously taken up by the CBM.

It might be possible to fit both the CBM and drogues.

Take another look at how little space there is around the CBM.

How deep are the drogues?

Hard to tell, but I would assume they are ~1.5-2.5ft deep. See this diagram, the current drogue canister is the blue cylinder near the top.

[Elmar Moelzer]

It's becoming clearer and clearer that "Dragon 2" won't have room for a CBM hatch. I.e. = No cargo version of Dragon 2.

I still don't get where you are making those deductions from. I doubt that Dragon2 will look like the parachute test article, which seems to look more like Dragon1.

[Lars_J]

It's becoming clearer and clearer that "Dragon 2" won't have room for a CBM hatch. I.e. = No cargo version of Dragon 2.

I still don't get where you are making those deductions from. I doubt that Dragon2 will look like the parachute test article, which seems to look more like Dragon1.

I sure hope that they tested the final drogue/parachute layout, otherwise what is the point?  And that drogue location would be make hard or impossible to fit a CBM hatch in there. You can doubt all you want, but that sounds more like wishful thinking on your part to fit data to your theory rather than evaluation of the data we have.

[Lurker Steve]

It's becoming clearer and clearer that "Dragon 2" won't have room for a CBM hatch. I.e. = No cargo version of Dragon 2.

I still don't get where you are making those deductions from. I doubt that Dragon2 will look like the parachute test article, which seems to look more like Dragon1.

I sure hope that they tested the final drogue/parachute layout, otherwise what is the point?  And that drogue location would be make hard or impossible to fit a CBM hatch in there. You can doubt all you want, but that sounds more like wishful thinking on your part to fit data to your theory rather than evaluation of the data we have.

It doesn't have to be the "FINAL" layout, but it is certainly the current reference location in their design documents. After all, the test is to test the chute deployment in the new configuration. The rest of the craft doesn't have to look like the Dragon 2. It just needs to have more or less the same center of gravity. I'm sure they just modified the old test article instead of creating a new test article from scratch for this test.

Of course, the test article that Boeing dropped for their chute tests didn't look too much like the final configuration of the CST-100 either. It was just something they had Bigelow throw together for the test.

[joek]

It doesn't have to be the "FINAL" layout, but it is certainly the current reference location in their design documents. After all, the test is to test the chute deployment in the new configuration.
...

Yes.  From the SpaceX SAA amendment 1, Dragon Parachute Tests (emphasis added):

Full-scale Dragon test unit prepared with all characteristics deemed appropriate by SpaceX (mass, moment of intertia, etc.) as close to those of the flight configuration following an on-pad abort as possible.

[Elmar Moelzer]

I am pretty sure that the test article we saw there is not what Dragon2 will look like. E.g., there is no room for the super dracos, which would also change the center of gravity.

[Lars_J]

I am pretty sure that the test article we saw there is not what Dragon2 will look like. E.g., there is no room for the super dracos, which would also change the center of gravity.

But Dragon 2 and Dragon 1 aren't that different, from what we have seen. Dragon 2 adds SD thrusters, and relocates parachutes/drogues. It might even have legs. Otherwise it will from an external point of view look pretty much the same.

[Rabidpanda]

I am pretty sure that the test article we saw there is not what Dragon2 will look like. E.g., there is no room for the super dracos, which would also change the center of gravity.

Of course the test article doesn't look exactly like Dragon 2. It just needs to have the parachutes in the correct location and have the same center of mass and moment of inertia, which shouldn't be too hard to adjust.

[a_langwich]

I am pretty sure that the test article we saw there is not what Dragon2 will look like. E.g., there is no room for the super dracos, which would also change the center of gravity.

Of course the test article doesn't look exactly like Dragon 2. It just needs to have the parachutes in the correct location and have the same center of mass and moment of inertia, which shouldn't be too hard to adjust.

Right, the standard solution is to use ballast as appropriate, which need not advertise itself for Internet observers.  I don't see any use for outer mold line fidelity.

[Joffan]

I am pretty sure that the test article we saw there is not what Dragon2 will look like. E.g., there is no room for the super dracos, which would also change the center of gravity.

But Dragon 2 and Dragon 1 aren't that different, from what we have seen. Dragon 2 adds SD thrusters, and relocates parachutes/drogues. It might even have legs. Otherwise it will from an external point of view look pretty much the same.

All right, but apart from the sanitation, medicine, education, wine, public order, irrigation, roads, the fresh water system and public health, what have the Romans ever done for us?

[joek]

I am pretty sure that the test article we saw there is not what Dragon2 will look like. E.g., there is no room for the super dracos, which would also change the center of gravity.

Undoubtedly crew Dragon will look significantly different than the test article.  However, the test article doesn't need to look like to act like--or at least act like sufficient to prove the new parachute arrangement and be "as close to those of the flight configuration following an on-pad abort as possible".  That means the parachute arrangement for crew Dragon will be as seen with the test article.

I'm sure SpaceX will try for as much commonality between crew and cargo Dragon as possible.  If you think that includes a common parachute configuration, some changes to cargo Dragon would be required.  As others have suggested, that would include at minimum:
1. Fitting a CBM given the placement and intrusion of the crew Dragon drogues.
2. Relocating the grappling fixture and sensor bay (e.g., LIDAR) compartment and hatch given that the crew Dragon mains will occupy that space.

edit: Also, crew Dragon will likely have forward-looking sensors up top (next to the offset docking ring), which would make it that much harder to fit a CBM in a common configuration.

[Roy_H]

I agree with those who say that re-locating the grapple fixture etc. should be possible. But, is it really required? Why can't the cargo Dragon dock like the crew version instead of having to be berthed by the CanadaArm?

[Elmar Moelzer]

There is a small possibility that Dragon2 will not jetison the cover for the docking adapter (or the CBM in case of the cargo version), but that it will open like a clamshell. Would it make sense to put the things currently in the sensor bay into/onto the cover (attached to either side of the cover)?
Anyway, we will see what Dragon2 will look like, hopefully soon. Then we will know.

[Elmar Moelzer]

I agree with those who say that re-locating the grapple fixture etc. should be possible. But, is it really required? Why can't the cargo Dragon dock like the crew version instead of having to be berthed by the CanadaArm?

I think it has to do with the availability of docking ports, but I might be wrong.

[Jcc]

I agree with those who say that re-locating the grapple fixture etc. should be possible. But, is it really required? Why can't the cargo Dragon dock like the crew version instead of having to be berthed by the CanadaArm?

I think it has to do with the availability of docking ports, but I might be wrong.

also the docking ports have a smaller diameter, which makes unloading bulky cargo more difficult, besides, with less confidence in the control of the COTS spacecraft, they would prefer not to have them thrust into the port, but would rather grapple them.

[Prober]

I am pretty sure that the test article we saw there is not what Dragon2 will look like. E.g., there is no room for the super dracos, which would also change the center of gravity.

Agree with you.   Looks like two options are available.   Keeping the pressure hull size the same (given), and enlarging the panels surrounding it, or major compromises in the Dragon 1 design.

[joek]

I agree with those who say that re-locating the grapple fixture etc. should be possible. But, is it really required? Why can't the cargo Dragon dock like the crew version instead of having to be berthed by the CanadaArm?

I think it has to do with the availability of docking ports, but I might be wrong.

Good point.  There are currently only two USOS docking ports planned, and nominally one must be open in case there is a problem with the other.  One will be occupied by a crew vehicle for most of the time.  Beyond that, CBM (berthing) allows larger cargo/containers than NDS (docking) and is also the only way to get ISS standard racks in and out.  Not sure if the latter is still a significant consideration.

[manboy]

I agree with those who say that re-locating the grapple fixture etc. should be possible. But, is it really required? Why can't the cargo Dragon dock like the crew version instead of having to be berthed by the CanadaArm?

It could but it's not going to happen. Two berthing ports are shared between Dragon Cargo, Cygnus and HTV. Two docking ports are reserved for Commercial Crew, although only one will be used at a time (the other is meant as a backup). If Dragon Cargo starts to use a docking mechanism than it would mess up how ISS traffic management is currently planned.

Also docking mechanisms have smaller hatches, so you wouldn't be able to transport certain cargo.

[JBF]

I agree with those who say that re-locating the grapple fixture etc. should be possible. But, is it really required? Why can't the cargo Dragon dock like the crew version instead of having to be berthed by the CanadaArm?

It could but it's not going to happen. Two berthing ports are shared between Dragon Cargo, Cygnus and HTV. Two docking ports are reserved for Commercial Crew, although only one will be used at a time (the other is meant as a backup). If Dragon Cargo starts to use a docking mechanism than it would mess up how ISS traffic management is currently planned.

Also docking mechanisms have smaller hatches, so you wouldn't be able to transport certain cargo.

As the crew will double as life boats they will need to be able to undock quickly and independently. This is not possible with a berthing port.

[mheney]

I agree with those who say that re-locating the grapple fixture etc. should be possible. But, is it really required? Why can't the cargo Dragon dock like the crew version instead of having to be berthed by the CanadaArm?

It could but it's not going to happen. Two berthing ports are shared between Dragon Cargo, Cygnus and HTV. Two docking ports are reserved for Commercial Crew, although only one will be used at a time (the other is meant as a backup). If Dragon Cargo starts to use a docking mechanism than it would mess up how ISS traffic management is currently planned.

Also docking mechanisms have smaller hatches, so you wouldn't be able to transport certain cargo.

I think manboy's question is "is it possible to dock rather than berth using the CBM mechanisms?"  I don't see any reason myself why it makes any difference physically whether the approach and contact is done via arm-and-grapple vs thrusters - but I readily admit that I might be missing something.

[Go4TLI]

I think manboy's question is "is it possible to dock rather than berth using the CBM mechanisms?"  I don't see any reason myself why it makes any difference physically whether the approach and contact is done via arm-and-grapple vs thrusters - but I readily admit that I might be missing something.

No. 

There are many reasons from thruster plume impingement to other areas of the station, tolerances for the CBMs to mate and lock, vibration dampening, etc. 

[manboy]

I agree with those who say that re-locating the grapple fixture etc. should be possible. But, is it really required? Why can't the cargo Dragon dock like the crew version instead of having to be berthed by the CanadaArm?

It could but it's not going to happen. Two berthing ports are shared between Dragon Cargo, Cygnus and HTV. Two docking ports are reserved for Commercial Crew, although only one will be used at a time (the other is meant as a backup). If Dragon Cargo starts to use a docking mechanism than it would mess up how ISS traffic management is currently planned.

Also docking mechanisms have smaller hatches, so you wouldn't be able to transport certain cargo.

I think manboy's question is "is it possible to dock rather than berth using the CBM mechanisms?"

I wasn't asking anything and there really isn't any reason why Dragon would dock with a CBM. The point I was trying to make is that I think it's highly unlikely that the Dragon Cargo will start using NDS.

[Sesquipedalian]

There is a small possibility that Dragon2 will not jetison the cover for the docking adapter (or the CBM in case of the cargo version), but that it will open like a clamshell. Would it make sense to put the things currently in the sensor bay into/onto the cover (attached to either side of the cover)?

That's a very insightful thought, but think of the Dragon berthed to the ISS using this arrangement.  Would there be enough clearance for the arm to grapple the PDGF?

[Joffan]

There is a small possibility that Dragon2 will not jetison the cover for the docking adapter (or the CBM in case of the cargo version), but that it will open like a clamshell. Would it make sense to put the things currently in the sensor bay into/onto the cover (attached to either side of the cover)?

That's a very insightful thought, but think of the Dragon berthed to the ISS using this arrangement.  Would there be enough clearance for the arm to grapple the PDGF?

If we're making up new configurations using the nosecone, it could be hinged at the top and at one side, allowing the split nosecone to lay along one wall of the Dragon capsule. Then if it latched to the side, it could provide an accessible location for the sensor bay equipment, comparable to the current location.

It's a relatively large change though, to a mission-critical piece of kit. Ideally any opening nosecone placement would be flown on a Dragon that has the current sensor bay configuration so that actuation and clearances can be easily tested. Since the closure (or worst-case, jettison) of the nosecone might be a critical task for successful re-entry, NASA would probably be a little anxious about downmass risks.

EDIT... but all this is cargo dragon speculation, off-topic here.

[jedsmd]

There is a small possibility that Dragon2 will not jetison the cover for the docking adapter (or the CBM in case of the cargo version), but that it will open like a clamshell. Would it make sense to put the things currently in the sensor bay into/onto the cover (attached to either side of the cover)?

That's a very insightful thought, but think of the Dragon berthed to the ISS using this arrangement.  Would there be enough clearance for the arm to grapple the PDGF?

If we're making up new configurations using the nosecone, it could be hinged at the top and at one side, allowing the split nosecone to lay along one wall of the Dragon capsule. Then if it latched to the side, it could provide an accessible location for the sensor bay equipment, comparable to the current location.

It's a relatively large change though, to a mission-critical piece of kit. Ideally any opening nosecone placement would be flown on a Dragon that has the current sensor bay configuration so that actuation and clearances can be easily tested. Since the closure (or worst-case, jettison) of the nosecone might be a critical task for successful re-entry, NASA would probably be a little anxious about downmass risks.

Cargo Dragon approaches the ISS grapple fixture (and Sensor Bay) first.  Manned Dragon should approach the station nose first?  Therefore makes some since to have the sensors under the nose cone to point toward the station during approach.

[Joffan]

Cargo Dragon approaches the ISS grapple fixture (and Sensor Bay) first.  Manned Dragon should approach the station nose first?  Therefore makes some since to have the sensors under the nose cone to point toward the station during approach.

I was thinking of cargo dragon, which is off-topic for this thread in fact, apologies.