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SpaceX Vehicles and Missions => SpaceX Reusable Rockets Section => Topic started by: corrodedNut on 05/21/2014 04:11 PM

Title: SpaceX DragonFly Discussion Thread
Post by: corrodedNut on 05/21/2014 04:11 PM
Updated first post with our article on this via Chris Gebhardt:
http://www.nasaspaceflight.com/2014/05/faa-moves-closer-spacex-permit-dragonfly-testing/

Thanks to TomNTex for finding the FAA Draft Environmental Assessment:

http://forum.nasaspaceflight.com/index.php?topic=32202.msg1201687#msg1201687

See:

http://www.faa.gov/about/office_org/headquarters_offices/ast/media/20140513_DragonFly_DraftEA(Public).pdf

http://www.faa.gov/about/office_org/headquarters_offices/ast/environmental/review/permits/

Title: Re: SpaceX DragonFly Discussion Thread
Post by: Garrett on 05/21/2014 04:27 PM
Sweet!

From the document:
Quote
SpaceX's purpose of requesting an experimental permit from the FAA is for SpaceX to test the capability of the DragonFly RLV to execute precision landings on land. SpaceX's need for the experimental permit is to conduct tests to further develop the capability for the Dragon capsule to land, so that it can be reused. One of SpaceX's goals is to reduce the cost of access to space. Being able to resuse Dragon capsule would help meet this goal by eliminating the costs associated with building another capsule
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars_J on 05/21/2014 04:29 PM
A nice find! Here is what I gleaned from a quick skimming of the PDF (from another thread)


Hmm, interesting information about the "DragonFly RLV" in that PDF:

 - up to four steel landing legs
 - weighs 14000 lbs unfueled
 - maximum proplellant load is 400 gallons

Four kinds of test flights expected:
 - propulsive assist landing (dropped from helicopter with chutes)
 - fully propulsive landing (dropped from helicopter)
 - propulsive assist hop (self launched, parachute deploys)
 - fully propulsive hop (like Grasshopper)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sublimemarsupial on 05/21/2014 04:29 PM
Some pretty awesome details in there. They anticipate the program taking two years (2014-2015), and there are four different flight profiles they will be testing.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: moralec on 05/21/2014 04:30 PM
A copy of the table included in the document. Seems the hops will be the most common.

Edit: Great post sublimemarsupial!  ;)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Jarnis on 05/21/2014 04:33 PM
Freefall, 5 sec burn at the last moment, soft touchdown.

Whoever will ultimately ride aboard that kind of flight profile (obviously not during these tests) is a brave man :)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: king1999 on 05/21/2014 04:36 PM
I am wondering who came up with those cool and apt names like Grasshopper and DragonFly ...  8)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: simonbp on 05/21/2014 04:38 PM
I believe the technical name for that is a brown pants landing...
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Jarnis on 05/21/2014 04:40 PM
I believe the technical name for that is a brown pants landing...

Capsule might be re-usable, but the pants will be another story...
Title: Re: SpaceX DragonFly Discussion Thread
Post by: JBF on 05/21/2014 04:42 PM
Freefall, 5 sec burn at the last moment, soft touchdown.

Whoever will ultimately ride aboard that kind of flight profile (obviously not during these tests) is a brave man :)

Can anyone model the G-Force curve on that?  It sounds like a rough ride.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars_J on 05/21/2014 04:49 PM
Freefall, 5 sec burn at the last moment, soft touchdown.

Whoever will ultimately ride aboard that kind of flight profile (obviously not during these tests) is a brave man :)

Can anyone model the G-Force curve on that?  It sounds like a rough ride.

If anyone can guess the terminal velocity of the capsule, it should be easy to calculate. If the G-load is evenly spread over 5 seconds, it might not be too bad.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 05/21/2014 04:50 PM
Freefall, 5 sec burn at the last moment, soft touchdown.

Whoever will ultimately ride aboard that kind of flight profile (obviously not during these tests) is a brave man :)
Slim will do it!

Title: Re: SpaceX DragonFly Discussion Thread
Post by: A12 on 05/21/2014 04:54 PM
I believe the technical name for that is a brown pants landing...

Capsule might be re-usable, but the pants will be another story...

Unless they install some kind of space-grade toiled embedded into the seat...
Title: Re: SpaceX DragonFly Discussion Thread
Post by: corrodedNut on 05/21/2014 04:54 PM
Sounds like they will use the Grasshopper pad unless they decide they will need a dedicated pad, which will be a 40' square pad near the SuperDraco facility. The report describes this as the "DragonRider test area".
Title: Re: SpaceX DragonFly Discussion Thread
Post by: randomly on 05/21/2014 04:54 PM
At 3G's that's dV of 65 mph/sec (sorry for the english units)
seems in the ballpark.

Apollo capsule terminal velocity was roughly 210 miles/hr  at 25,000 ft
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meadows.st on 05/21/2014 04:56 PM
Thanks to TomNTex for finding the FAA Draft Environmental Assessment:

http://forum.nasaspaceflight.com/index.php?topic=32202.msg1201687#msg1201687

See:

http://www.faa.gov/about/office_org/headquarters_offices/ast/media/20140513_DragonFly_DraftEA(Public).pdf

http://www.faa.gov/about/office_org/headquarters_offices/ast/environmental/review/permits/

My thanks to TomNTex as well but I think my head just exploded! ;)  (I think there is going to have to be a Dragonfly party thread created.)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: corrodedNut on 05/21/2014 04:56 PM
"The DragonFly RLV is the Dragon capsule with an integrated trunk (which may or may not be attached during a DragonFly operation) and up to four steel landing legs. The Dragon capsule primary structure consists of a welded aluminum pressure vessel, primary heat shield support structure, back shell thermal protection system support structure, and a nosecone. This structure supports secondary structures including eight SuperDraco engines (two in each of the four modules [quadrants]), propellant tanks, pressurant tanks, parachute system, and necessary avionics. The propulsion system includes four self‐contained quadrants with independent sets of propellant tanks for system redundancy. The SuperDraco engine uses a fuel‐centered injector to provide appropriate performance for the application. It is also designed to seal off both fuel and oxidizer from the combustion chamber, enabling operation with fast shut‐off and limited propellant “dribble” volumes.
The DragonFly RLV weighs approximately 14,000 pounds (lbs) un‐fueled, with a height of 17 ft and a base width of 13 ft. Each pair of SuperDraco engines (eight total engines) are mounted to a monolithic aluminum bracket. This bracket is connected to the pressure vessel with three mounts."
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars_J on 05/21/2014 04:57 PM
Sounds like they will use the Grasshopper pad unless they decide they will need a dedicated pad, which will be a 40' square pad near the SuperDraco facility. The report describes this as the "DragonRider test area".

No, the report indicates that it will be a separate pad:
Quote
"The proposed launch pad would be 40 ft by 40 ft located approximately 0.32 mile north of the Grasshopper launch pad."
Title: Re: SpaceX DragonFly Discussion Thread
Post by: VulcanCafe on 05/21/2014 04:58 PM
This might be obvious, but it sure sounds like the DragonFly = Dragon v2 testbed and closely matches the Dragon v2 size. It also seems to echo rumors about the Dragon v2 with the trunk attached, etc.

Please correct me if I'm wrong :)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars_J on 05/21/2014 04:59 PM
Yes, it is a Dragon 2 test bed.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 05/21/2014 05:00 PM
This was expected, and actually looooong overdue, but hell yeah  :)

Title: Re: SpaceX DragonFly Discussion Thread
Post by: corrodedNut on 05/21/2014 05:01 PM
Sounds like they will use the Grasshopper pad unless they decide they will need a dedicated pad, which will be a 40' square pad near the SuperDraco facility. The report describes this as the "DragonRider test area".

No, the report indicates that it will be a separate pad:
Quote
"The proposed launch pad would be 40 ft by 40 ft located approximately 0.32 mile north of the Grasshopper launch pad."

"SpaceX is currently considering two locations for the DragonFly RLV launch operations within the McGregor test site: the existing Grasshopper launch pad and the DragonRider test area. If operations would occur at the DragonRider test area, construction of a 40 ft by 40 ft launch pad would be necessary...."
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sublimemarsupial on 05/21/2014 05:01 PM
Freefall, 5 sec burn at the last moment, soft touchdown.

Whoever will ultimately ride aboard that kind of flight profile (obviously not during these tests) is a brave man :)

Can anyone model the G-Force curve on that?  It sounds like a rough ride.

If anyone can guess the terminal velocity of the capsule, it should be easy to calculate. If the G-load is evenly spread over 5 seconds, it might not be too bad.

For a very first order estimate I get a terminal velocity of ~150 m/s given a total mass of 17,000 lbs (dry mass plus 3000 lbs of fuel) and a drag coefficient of 0.8.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 05/21/2014 05:03 PM
This is not your standard LAS... all control elements here for reusable (Mars or Moon) landing vehicle,  For ascent, vehicle will obviously need more propulsion and more than 25(+residuals) seconds of fuel.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: corrodedNut on 05/21/2014 05:04 PM
"Propulsive Assist

For the propulsive assist test, a helicopter (an Erickson E‐model or equivalent) would arrive at the McGregor test site from Waco Regional Airport. The DragonFly RLV would then be tethered to the helicopter using a cable. A maximum of 300 gallons of propellant would be loaded into the DragonFly RLV for this test. The helicopter would take off with the DragonFly RLV attached and reach an altitude up to 10,000 ft. Once at that altitude, the DragonFly RLV would be released from the tether and three main parachutes would be deployed. The engines would not fire until the vehicle descends to approximately 98 ft above ground level (AGL). The engines would fire for approximately 5 seconds, and the RLV would make a powered landing. This type of operation would last approximately 30 minutes from helicopter take‐off to DragonFly RLV landing.
The test would be designed so that almost all fuel on board is used prior to landing. All fuel valves would shut automatically and retain any residual fuel in the capsule."
Title: Re: SpaceX DragonFly Discussion Thread
Post by: corrodedNut on 05/21/2014 05:06 PM
"Full Propulsive Landing

For the full propulsive landing test, a helicopter (an Erickson E‐model or equivalent) would arrive at the McGregor test site from Waco Regional Airport. The DragonFly RLV would then be tethered to the helicopter. A maximum of 300 gallons of propellant would be loaded into the DragonFly RLV for this test. The helicopter would take off with the DragonFly RLV attached and reach an altitude up to 10,000 ft. Once at that altitude, the DragonFly RLV would be released from the tether. There would be a period of free fall and then the engines would fire for approximately 5 seconds and the RLV would make a powered landing. This type of operation would last approximately 30 minutes from helicopter take‐off to DragonFly RLV landing."
Title: Re: SpaceX DragonFly Discussion Thread
Post by: corrodedNut on 05/21/2014 05:08 PM
"Propulsive Assist Hopping

Approximately 400 gallons of propellant would be loaded into the DragonFly RLV for this test. During a propulsive assisted hop test, the DragonFly RLV would launch from a launch pad and ascend to approximately 7,000 ft AGL (firing engines for 12.5 seconds). Two parachutes would be deployed for the descent, the engines would fire for 12.5 seconds, and the RLV would make a powered landing on the launch pad. This operation would last approximately 60 seconds."
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars_J on 05/21/2014 05:08 PM
Freefall, 5 sec burn at the last moment, soft touchdown.

Whoever will ultimately ride aboard that kind of flight profile (obviously not during these tests) is a brave man :)

Can anyone model the G-Force curve on that?  It sounds like a rough ride.

If anyone can guess the terminal velocity of the capsule, it should be easy to calculate. If the G-load is evenly spread over 5 seconds, it might not be too bad.

For a very first order estimate I get a terminal velocity of ~150 m/s given a total mass of 17,000 lbs (dry mass plus 3000 lbs of fuel) and a drag coefficient of 0.8.

A 5 second burn to brake from 150 m/s would result in an average of ~3Gs of deceleration.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: corrodedNut on 05/21/2014 05:09 PM
"Full Propulsive Hopping

Approximately 400 gallons of propellant would be loaded into the DragonFly RLV for this test. During a full propulsive hop test, the DragonFly RLV would launch from a launch pad and ascend to approximately 7,000 ft AGL (firing engines for approximately 12.5 seconds). The engines would then throttle down in order to descend (firing engines for an additional approximate 12. 5 seconds), and the RLV would make a powered landing on the launch pad. This operation would last approximately 60 seconds."
Title: Re: SpaceX DragonFly Discussion Thread
Post by: GalacticIntruder on 05/21/2014 05:10 PM
All these 31 flavors of Dragon, are giving me a brain freeze.

How does this craft, DragonFly RLV, compare with the May 29 Dragon mk2 reveal, and CCdev?  Does NASA even know what craft  they would get if they awarded SpaceX the win.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars_J on 05/21/2014 05:13 PM
All these 31 flavors of Dragon, are giving me a brain freeze.

How does this craft, DragonFly RLV, compare with the May 29 Dragon mk2 reveal, and CCdev?  Does NASA even know what craft  they would get if they awarded SpaceX the win.

Huh? Why wouldn't they know?

How do you translate the idea of multiple test articles of varying fidelity to the idea of "31 flavors of Dragon"?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: randomly on 05/21/2014 05:16 PM
Spacex will need to address the problems of dealing with Hydrazine/NTO in case of accidents.
keep the cows upwind or something.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: notsorandom on 05/21/2014 05:28 PM
Freefall, 5 sec burn at the last moment, soft touchdown.

Whoever will ultimately ride aboard that kind of flight profile (obviously not during these tests) is a brave man :)

Can anyone model the G-Force curve on that?  It sounds like a rough ride.

If anyone can guess the terminal velocity of the capsule, it should be easy to calculate. If the G-load is evenly spread over 5 seconds, it might not be too bad.

For a very first order estimate I get a terminal velocity of ~150 m/s given a total mass of 17,000 lbs (dry mass plus 3000 lbs of fuel) and a drag coefficient of 0.8.

A 5 second burn to brake from 150 m/s would result in an average of ~3Gs of deceleration.
Doing some more math on those assumed figures it looks like the start of the landing burn starts about 375 meters in altitude. That assumes a deceleration of about 3g's and initial velocity of 150 m/s. If something should go wrong at the start of the burn like a stuck valve is that enough time and altitude to pop a parachute out?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: corrodedNut on 05/21/2014 05:30 PM
Spacex will need to address the problems of dealing with Hydrazine/NTO in case of accidents.
keep the cows upwind or something.

That's what environmental assessments are for.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: abaddon on 05/21/2014 05:31 PM
This is great stuff!   :D.

One interesting thing is the descent profile on the hop tests is much more gentle (12.5s firing, throttled down) then on the drop tests.  Presumably this is because the capsule is not free-falling when it starts the descent burn.  But since the engine can throttle down (as is confirmed here), why wouldn't they start the drop test burn earlier, throttled down, and then throttle the engine up?  That seems like it would provide a less freaky landing, it would also allow you to start your burn a little earlier, possibly early enough that a late chute might deploy might do some good if something went wrong.  I know there will be redundant thrusters and these are pretty simple engines but it seems like having a backup if something goes wrong when the burn beings might be a good idea.  5s/~400m seems way too late for a chute to help...

I'm also not sure how the drop tests are going to use all of 300 gallons of fuel but the hop tests will only need 400 gallons, ISTM like that ascent burn should consume a lot of fuel, even if the descent burn doesn't need as much.

Anyway, it's great to finally see some details about this program.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Jim on 05/21/2014 05:31 PM
This is not your standard LAS... all control elements here for reusable (Mars or Moon) landing vehicle,  For ascent, vehicle will obviously need more propulsion and more than 25(+residuals) seconds of fuel.

Not so.  A lot more propellant is needed for landing on Mars and even more for the moon.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meadows.st on 05/21/2014 05:35 PM
Freefall, 5 sec burn at the last moment, soft touchdown.

Whoever will ultimately ride aboard that kind of flight profile (obviously not during these tests) is a brave man :)

Can anyone model the G-Force curve on that?  It sounds like a rough ride.

If anyone can guess the terminal velocity of the capsule, it should be easy to calculate. If the G-load is evenly spread over 5 seconds, it might not be too bad.

For a very first order estimate I get a terminal velocity of ~150 m/s given a total mass of 17,000 lbs (dry mass plus 3000 lbs of fuel) and a drag coefficient of 0.8.

A 5 second burn to brake from 150 m/s would result in an average of ~3Gs of deceleration.
Doing some more math on those assumed figures it looks like the start of the landing burn starts about 375 meters in altitude. That assumes a deceleration of about 3g's and initial velocity of 150 m/s. If something should go wrong at the start of the burn like a stuck valve is that enough time and altitude to pop a parachute out?

I think there is a misunderstanding somewhere.  The "Propulsive Assist" (includes parachutes) has the engines firing for ~5 seconds (starting at a AGL height of 98ft) while the full-propulsive hopping landings have the engines firing for 12.5 seconds.  So the 150 m/s terminal velocity is likely slowed over 12.5 seconds rather than just 5sec.  The terminal velocity under parachute should be much less than 150m/s shouldn't it?

EDIT: Is there a typo in "Full Propulsive Landing" (states 5 s engine burn) and "Propulsive Assist Hopping" which states 12.5 s engine burn?

EDIT2: added "hopping" (underlined)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: abaddon on 05/21/2014 05:37 PM
I think there is a misunderstanding somewhere.  The "Propulsive Assist" (includes parachutes) has the engines firing for ~5 seconds (starting at a AGL height of 98ft) while the full-propulsive landings have the engines firing for 12.5 seconds.  So the 150 m/s terminal velocity is likely slowed over 12.5 seconds rather than just 5sec.  The terminal velocity under parachute should be much less than 150m/s shouldn't it?
The quoted full propulsive landing in this thread states "There would be a period of free fall and then the engines would fire for approximately 5 seconds and the RLV would make a powered landing."  I agree this seems odd, perhaps it is a typo and the 5 second burn is indeed parachute-assisted.  That would make more sense.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meadows.st on 05/21/2014 05:40 PM
I think there is a misunderstanding somewhere.  The "Propulsive Assist" (includes parachutes) has the engines firing for ~5 seconds (starting at a AGL height of 98ft) while the full-propulsive hopping landings have the engines firing for 12.5 seconds.  So the 150 m/s terminal velocity is likely slowed over 12.5 seconds rather than just 5sec.  The terminal velocity under parachute should be much less than 150m/s shouldn't it?
The quoted full propulsive landing in this thread states "There would be a period of free fall and then the engines would fire for approximately 5 seconds and the RLV would make a powered landing."  I agree this seems odd, perhaps it is a typo and the 5 second burn is indeed parachute-assisted.  That would make more sense.

Correct, I added a correction to my typo in my comment that was commenting on a possible typo. :P
Title: Re: SpaceX DragonFly Discussion Thread
Post by: corrodedNut on 05/21/2014 05:47 PM
Timeframe:

"SpaceX anticipates that the DragonFly RLV program would require up to 2 years to complete (2014 – 2015). Therefore, the Proposed Action considers one new permit and one potential permit renewal."
Title: Re: SpaceX DragonFly Discussion Thread
Post by: RocketGoBoom on 05/21/2014 06:02 PM
How could they have a controlled pinpoint landing back at the pad if they are using parachutes and if there is any sort of wind? I would think that this poses significant drift potential from 10,000 ft. They could drift quite a distance off of center. Once the Dracos fire, I think the potential for needing way more than 5 seconds is significant.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: bubbagret on 05/21/2014 06:03 PM
This is great stuff!   :D.

I'm also not sure how the drop tests are going to use all of 300 gallons of fuel but the hop tests will only need 400 gallons, ISTM like that ascent burn should consume a lot of fuel, even if the descent burn doesn't need as much.

Anyway, it's great to finally see some details about this program.

Reread it, it states UP TO before listing Height, fuel quantity, etc...
Title: Re: SpaceX DragonFly Discussion Thread
Post by: rcoppola on 05/21/2014 06:15 PM
It's very possible that SpaceX is pushing for propulsive landings (assisted to start with) right out of the gate. Where earlier it was mentioned more as a Dragon 2.1 after initial crew services roll-out. The testing regimen and timeline seems to align with a possibly accelerated CC contract award.

They may have offered NASA a very cost effective proposal on the assumption they could re-use Dragon as both SNC and Boeing intended to do. And will bring this capability from the onset of the contracts. After all, they're doing 30 tests over 2 years or less. That's a test regimen of more then 1 a month for the next 2 years.

I'm intrigued with this integrated trunk as well. Theoretically they could have designed a new trunk that would accommodate legs and enough fuel to do a Moon or Mars decent / ascent. (ladder included)
 
Title: Re: SpaceX DragonFly Discussion Thread
Post by: abaddon on 05/21/2014 06:19 PM
Reread it, it states UP TO before listing Height, fuel quantity, etc...
Actually, it says "a maximum of" not "up to", but I get what you're saying.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Jarnis on 05/21/2014 06:30 PM
How could they have a controlled pinpoint landing back at the pad if they are using parachutes and if there is any sort of wind? I would think that this poses significant drift potential from 10,000 ft. They could drift quite a distance off of center. Once the Dracos fire, I think the potential for needing way more than 5 seconds is significant.

I see propulsive assist landing to be similar to Soyuz. Land landing with parachutes, with engines smoothing the touchdown (but with the landing survivable even if they do not fire).

Beats fishing out the crews and cargo from the ocean, even if you need a fairly large open area to aim for. Could totally see this happening in future orbital flights as an intermediate step towards propulsive-only landing.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 05/21/2014 06:33 PM
I'm intrigued with this integrated trunk as well. Theoretically they could have designed a new trunk that would accommodate legs and enough fuel to do a Moon or Mars decent / ascent. (ladder included)
I would be careful to interpret too much into it, but it does sound interesting, indeed. Maybe the new Dragon will not lose the trunk anymore?
Hmmm.
Either way, I cant wait to see test hops of this! This must be really cool to watch!
Title: Re: SpaceX DragonFly Discussion Thread
Post by: moralec on 05/21/2014 06:35 PM
I'm intrigued with this integrated trunk as well. Theoretically they could have designed a new trunk that would accommodate legs and enough fuel to do a Moon or Mars decent / ascent. (ladder included)
I would be careful to interpret too much into it, but it does sound interesting, indeed. Maybe the new Dragon will not lose the trunk anymore?
Hmmm.
Either way, I cant wait to see test hops of this! This must be really cool to watch!

But the heat shield is integrated in the capsule. This is intriguing...
Title: Re: SpaceX DragonFly Discussion Thread
Post by: kirghizstan on 05/21/2014 06:36 PM
I'm intrigued with this integrated trunk as well. Theoretically they could have designed a new trunk that would accommodate legs and enough fuel to do a Moon or Mars decent / ascent. (ladder included)
I would be careful to interpret too much into it, but it does sound interesting, indeed. Maybe the new Dragon will not lose the trunk anymore?
Hmmm.
Either way, I cant wait to see test hops of this! This must be really cool to watch!

Ground abort test?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: docmordrid on 05/21/2014 06:40 PM
Conference video showing propulsive assist landing

http://youtu.be/vW3K3TfQbSI
Title: Re: SpaceX DragonFly Discussion Thread
Post by: CraigLieb on 05/21/2014 06:47 PM
How could they have a controlled pinpoint landing back at the pad if they are using parachutes and if there is any sort of wind? I would think that this poses significant drift potential from 10,000 ft. They could drift quite a distance off of center. Once the Dracos fire, I think the potential for needing way more than 5 seconds is significant.

I see propulsive assist landing to be similar to Soyuz. Land landing with parachutes, with engines smoothing the touchdown (but with the landing survivable even if they do not fire).

Beats fishing out the crews and cargo from the ocean, even if you need a fairly large open area to aim for. Could totally see this happening in future orbital flights as an intermediate step towards propulsive-only landing.

Any concerns about the capsule being tilted ~30 degrees from vertical due to the parachute attach point being on the side?  See picture(s) captured from the Drop test video.


Firing off the Draco Engines on landing may expect a horizontal component to the resulting motion.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: JasonAW3 on 05/21/2014 06:52 PM
Freefall, 5 sec burn at the last moment, soft touchdown.

Whoever will ultimately ride aboard that kind of flight profile (obviously not during these tests) is a brave man :)

Can anyone model the G-Force curve on that?  It sounds like a rough ride.

If anyone can guess the terminal velocity of the capsule, it should be easy to calculate. If the G-load is evenly spread over 5 seconds, it might not be too bad.

For a very first order estimate I get a terminal velocity of ~150 m/s given a total mass of 17,000 lbs (dry mass plus 3000 lbs of fuel) and a drag coefficient of 0.8.

A 5 second burn to brake from 150 m/s would result in an average of ~3Gs of deceleration.

Assuming a throttle up from a cold start, it could range from 1.5G's initial and ramp up to about 5G's at about 3.5 to 4 seconds.

  But that's just a rough estimate.

  Otherwise a full thrust at 3G's initial, would be a real kick in the rear.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Comga on 05/21/2014 06:54 PM
Any concerns about the capsule being tilted ~30 degrees from vertical due to the parachute attach point being on the side?  See picture(s) captured from the Drop test video.

Firing off the Draco Engines on landing may expect a horizontal component to the resulting motion.

Surely a team that sends a ten story single engine rocket sliding 100m off to the side and back while ascending and descending, nulling velocity and rates at touchdown, can work out how to null rates and attitudes on a four engine-pair vehicle.  Is there any doubt?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Comga on 05/21/2014 06:58 PM
One thing that is not in the plan is propulsive landing with only drogue chutes.
It would be an interesting intermediate case, but obviously not interesting enough to get in the way of SpaceX's ultimate goal: "Landing on a pillar of fire like God and Heinlein intended."
Title: Re: SpaceX DragonFly Discussion Thread
Post by: JasonAW3 on 05/21/2014 06:58 PM
Any concerns about the capsule being tilted ~30 degrees from vertical due to the parachute attach point being on the side?  See picture(s) captured from the Drop test video.

Firing off the Draco Engines on landing may expect a horizontal component to the resulting motion.

Surely a team that sends a ten story single engine rocket sliding 100m off to the side and back while ascending and descending, nulling velocity and rates at touchdown, can work out how to null rates and attitudes on a four engine-pair vehicle.  Is there any doubt?

Well, they didn't crash a couple of REALLY top heavy test articles, landing a thruster based capsule shouldn't be too hard for them.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: savuporo on 05/21/2014 07:01 PM
Surely a team that sends a ten story single engine rocket sliding 100m off to the side and back while ascending and descending, nulling velocity and rates at touchdown, can work out how to null rates and attitudes on a four engine-pair vehicle.  Is there any doubt?
Differential throttling is a tad harder because you have inherently less control bandwidth - engine throttling has a built in lag.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: simonbp on 05/21/2014 07:20 PM
And Grasshopper and F9R don't throttle their engines?

This isn't a purely experimental vehicle like Grasshopper, but a prototype like F9R-Dev1. It is a systems test to make sure everything works together in a relevant environment. In NASA-speak, it is getting from TRL 5 to TRL 6.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: savuporo on 05/21/2014 07:25 PM
And Grasshopper and F9R don't throttle their engines?

My point was balancing and attitude control of a differentially throttled multi engine vs a single engine gimbaled vehicle is marginally harder - because of control bandwidth. Not impossible and obviously achiveable. Thats all.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: JasonAW3 on 05/21/2014 07:28 PM
And Grasshopper and F9R don't throttle their engines?

This isn't a purely experimental vehicle like Grasshopper, but a prototype like F9R-Dev1. It is a systems test to make sure everything works together in a relevant environment. In NASA-speak, it is getting from TRL 5 to TRL 6.

So essentially, since we don't quite have the tech developed to do an SSTO craft like the DC-Y, SpaceX is doing a 3STO craft, that essentially can land like the DC-X. 

Couple of questions then;

How much mass do the Parachutes add to the Dragon capsule?

If low enough mass, could they be added to either or both stages og the Falcon 9 as a back up/additional decellerator system?

Would it be worth the effort to do so?

Title: Re: SpaceX DragonFly Discussion Thread
Post by: Alpha Control on 05/21/2014 07:28 PM
"Propulsive Assist Hopping

Approximately 400 gallons of propellant would be loaded into the DragonFly RLV for this test. During a propulsive assisted hop test, the DragonFly RLV would launch from a launch pad and ascend to approximately 7,000 ft AGL (firing engines for 12.5 seconds). Two parachutes would be deployed for the descent, the engines would fire for 12.5 seconds, and the RLV would make a powered landing on the launch pad. This operation would last approximately 60 seconds."

For the Propulsive Assist Hopping, are the SDs firing twice? once for 12.5 seconds to reach altitude, then turn off, then fire a 2nd time for 12.5 seconds for the powered landing? I wasn't completely sure I interpreted the description correctly. Thanks!
Title: Re: SpaceX DragonFly Discussion Thread
Post by: JasonAW3 on 05/21/2014 07:29 PM
And Grasshopper and F9R don't throttle their engines?

My point was balancing and attitude control of a differentially throttled multi engine vs a single engine gimbaled vehicle is marginally harder - because of control bandwidth. Not impossible and obviously achiveable. Thats all.

I'm not sure that it would be much harder than flying a quadracopter drone.  Just got to have the right software, and you're good.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: JasonAW3 on 05/21/2014 07:31 PM
"Propulsive Assist Hopping

Approximately 400 gallons of propellant would be loaded into the DragonFly RLV for this test. During a propulsive assisted hop test, the DragonFly RLV would launch from a launch pad and ascend to approximately 7,000 ft AGL (firing engines for 12.5 seconds). Two parachutes would be deployed for the descent, the engines would fire for 12.5 seconds, and the RLV would make a powered landing on the launch pad. This operation would last approximately 60 seconds."

For the Propulsive Assist Hopping, are the SDs firing twice? once for 12.5 seconds to reach altitude, then turn off, then fire a 2nd time for 12.5 seconds for the powered landing? I wasn't completely sure I interpreted the description correctly. Thanks!

With the operation lasting 60 seconds, it looks like they're going for 35 seconds of zero thrust.  (12.5 x2 equals 25 seconds).
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sghill on 05/21/2014 07:32 PM
Freefall, 5 sec burn at the last moment, soft touchdown.

Whoever will ultimately ride aboard that kind of flight profile (obviously not during these tests) is a brave man :)

Can anyone model the G-Force curve on that?  It sounds like a rough ride.

If anyone can guess the terminal velocity of the capsule, it should be easy to calculate. If the G-load is evenly spread over 5 seconds, it might not be too bad.

For a very first order estimate I get a terminal velocity of ~150 m/s given a total mass of 17,000 lbs (dry mass plus 3000 lbs of fuel) and a drag coefficient of 0.8.

A 5 second burn to brake from 150 m/s would result in an average of ~3Gs of deceleration.
Doing some more math on those assumed figures it looks like the start of the landing burn starts about 375 meters in altitude. That assumes a deceleration of about 3g's and initial velocity of 150 m/s. If something should go wrong at the start of the burn like a stuck valve is that enough time and altitude to pop a parachute out?

Better up that return mass to 9,100 kg to account for the contents (people and gear).  BTW, pounds are weight, so the capsule will weigh zero in free fall. Kilograms are mass. Let's not crash into mars again over of this.  :)

Of course, you're going to burn off the fuel on those last couple of seconds during the landing which will soften your decent profile considerably at the end.

Also, my airplane had a ballistic parachute.  It's essentially useless for its purpose (reliable deployment) below 150 meters (500 ft)., so I suspect you are right that the landing burn will start around 400 meters, and then pull more than 3-Gs below 150 meters ft. to soft land--- or pop the emergency chute if there's a problem when the burn starts.

It'd be a monstrously terrifying landing if the burn is a short one.  I wonder if DreamChaser will get a leg up in the manned competition because of what the Astronaut Office thinks about this type of landing when it becomes clear just how close to a horrible death the astronauts have to come before the landing engines ignite each time.

Seriously.  My hands got clammy just thinking about that kind of plummet to the ground!
Title: Re: SpaceX DragonFly Discussion Thread
Post by: wannamoonbase on 05/21/2014 07:34 PM
Surely a team that sends a ten story single engine rocket sliding 100m off to the side and back while ascending and descending, nulling velocity and rates at touchdown, can work out how to null rates and attitudes on a four engine-pair vehicle.  Is there any doubt?
Differential throttling is a tad harder because you have inherently less control bandwidth - engine throttling has a built in lag.


I'd expect that they do some tethered tests with simulated inputs first.  Verifying strategy and collecting performance data at a safe elevation (a few inches or feet). 

But those probably don't need to be in the plan.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: savuporo on 05/21/2014 07:39 PM
I'm not sure that it would be much harder than flying a quadracopter drone.  Just got to have the right software, and you're good.
Quadcopters propellers respond to control signals in milliseconds. Throttling a rocket engine does not work that fast.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: TrevorMonty on 05/21/2014 07:44 PM
With pad abort test due in next few months, they will have to starting testing soon.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 05/21/2014 07:45 PM
Surely a team that sends a ten story single engine rocket sliding 100m off to the side and back while ascending and descending, nulling velocity and rates at touchdown, can work out how to null rates and attitudes on a four engine-pair vehicle.  Is there any doubt?
Differential throttling is a tad harder because you have inherently less control bandwidth - engine throttling has a built in lag.


I'd expect that they do some tethered tests with simulated inputs first.  Verifying strategy and collecting performance data at a safe elevation (a few inches or feet). 

But those probably don't need to be in the plan.

Seems to me this would be a striking change of MO for SpaceX.  Most tests to date have been aggressive and multi-faceted (e.g., the first flight of v1.1) -- the opposite of risk averse.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars_J on 05/21/2014 07:47 PM
It'd be a monstrously terrifying landing if the burn is a short one.  I wonder if DreamChaser will get a leg up in the manned competition because of what the Astronaut Office thinks about this type of landing when it becomes clear just how close to a horrible death the astronauts have to come before the landing engines ignite each time.

Seriously.  My hands got clammy just thinking about that kind of plummet to the ground!

I think what they are selling to NASA as the initial capability is the propulsion assisted landing, which should be a much more gentle experience.

I wouldn't expect to see a fully propulsive landing with crew for a while.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: docmordrid on 05/21/2014 08:03 PM
I'm not sure that it would be much harder than flying a quadracopter drone.  Just got to have the right software, and you're good.
Quadcopters propellers respond to control signals in milliseconds. Throttling a rocket engine does not work that fast.

According to NASA in 2012 SD went from 0% to 100% thrust in ~100ms.

http://www.nasaspaceflight.com/2012/02/spacex-dragon-advancing-launch-abort-system-new-heights/

Quote
>
SpaceX’s SuperDraco produced full thrust within approximately 100 milliseconds of the ignition command. It also fired for five seconds, which is the same amount of time the engines would burn during an emergency abort.
>
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars_J on 05/21/2014 08:06 PM
Yep, being pressure fed does reduce the "throttle-lag" significantly.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: savuporo on 05/21/2014 08:10 PM
According to NASA in 2012 SD went from 0% to 100% thrust in ~100ms.
Yeah, that about 20x slower than variable pitch quadcopter for example, and 0-100% step response is not the key metric in evaluating available control bandwidth.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 05/21/2014 08:10 PM
It'd be a monstrously terrifying landing if the burn is a short one.  I wonder if DreamChaser will get a leg up in the manned competition because of what the Astronaut Office thinks about this type of landing when it becomes clear just how close to a horrible death the astronauts have to come before the landing engines ignite each time.

Seriously.  My hands got clammy just thinking about that kind of plummet to the ground!

I think what they are selling to NASA as the initial capability is the propulsion assisted landing, which should be a much more gentle experience.

I wouldn't expect to see a fully propulsive landing with crew for a while.
Yes, this leads back to the discussion a while back about using this on Dragon 2 cargo version and getting experience with full propulsion landings before crewed landings.  Haven't heard any indication that this is SpaceX development path, but it seems to make sense.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: mme on 05/21/2014 08:24 PM

It'd be a monstrously terrifying landing if the burn is a short one.  I wonder if DreamChaser will get a leg up in the manned competition because of what the Astronaut Office thinks about this type of landing when it becomes clear just how close to a horrible death the astronauts have to come before the landing engines ignite each time.

Seriously.  My hands got clammy just thinking about that kind of plummet to the ground!
Maybe it will become a selling point when returning from Bigelow.  I can see it now. On departure you're asked, "Would you prefer mild, or wild?"  DreamChaser could become the "Chicken Exit" of space stations. ;)

NOTE: I don't have any issue with DreamChaser and I'm glad multiple avenues are being pursued.  I wish I could get a ride in both, but sadly I'm too old and too middle class. But a man can dream (no pun intended.)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: kttopdad on 05/21/2014 08:30 PM
According to NASA in 2012 SD went from 0% to 100% thrust in ~100ms.
Yeah, that about 20x slower than variable pitch quadcopter for example, and 0-100% step response is not the key metric in evaluating available control bandwidth.

Comparing response times between a rocket engine and a quad copter is meaningless.  The only metric that matters is the response time of the Super Dracos compared to the time it takes the Dragon capsule to roll out of the desired orientation.  I'm sure a 100ms response time is adequate for the intended purpose.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: corrodedNut on 05/21/2014 08:54 PM
According to NASA in 2012 SD went from 0% to 100% thrust in ~100ms.
Yeah, that about 20x slower than variable pitch quadcopter for example, and 0-100% step response is not the key metric in evaluating available control bandwidth.

Comparing response times between a rocket engine and a quad copter is meaningless.  The only metric that matters is the response time of the Super Dracos compared to the time it takes the Dragon capsule to roll out of the desired orientation.  I'm sure a 100ms response time is adequate for the intended purpose.

Related to this discussion is this description from section 2.2.1:

"The SuperDraco engine uses a fuel‐centered injector to provide appropriate performance for the application. It is also designed to seal off both fuel and oxidizer from the combustion chamber, enabling operation with fast shut‐off and limited propellant “dribble” volumes."

It doesn't say how they will keep the passengers from "dribbling", however.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Joffan on 05/21/2014 08:56 PM

Any concerns about the capsule being tilted ~30 degrees from vertical due to the parachute attach point being on the side?  See picture(s) captured from the Drop test video.

Firing off the Draco Engines on landing may expect a horizontal component to the resulting motion.


Perhaps the Draco thrusters (attitude control) could level the vehicle before the SuperDracos lit up. But in any case, the vehicle has to be able to cope with SuperDracos firing from an off-vertical position for the abort uses, although of course that case is not aiming for a landing pad.

Anyway a good question that we may see the answer to when the tests begin!
Title: Re: SpaceX DragonFly Discussion Thread
Post by: kttopdad on 05/21/2014 09:13 PM
I'm not sure the concerns about a high-G, brown-pants landing are warranted.  The landing profile for an operational DragonRider mission is unlikely to resemble the flight profiles for the DragonFly test program.  The DragonFly's 5-G short blast in the last few seconds before landing may be designed to test worst-case scenarios, or may just reflect the low-altitude reality of the testing conditions.  The DragonRider's operational landing profile may indeed be high-G, last second mega-blast, but I don't think it's safe to draw too direct of a line between the DragonFly flight profile and the DragonRider landing profile.  My $0.02.

Dean
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 05/21/2014 09:14 PM

Any concerns about the capsule being tilted ~30 degrees from vertical due to the parachute attach point being on the side?  See picture(s) captured from the Drop test video.

Firing off the Draco Engines on landing may expect a horizontal component to the resulting motion.


Perhaps the Draco thrusters (attitude control) could level the vehicle before the SuperDracos lit up. But in any case, the vehicle has to be able to cope with SuperDracos firing from an off-vertical position for the abort uses, although of course that case is not aiming for a landing pad.

Anyway a good question that we may see the answer to when the tests begin!
The simulation shown before and linked below has a depiction of this transient at about 2:40:
http://forum.nasaspaceflight.com/index.php?topic=34800.msg1201817#msg1201817
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 05/21/2014 09:32 PM
New article on DragonFly:
http://www.nbcnews.com/science/space/elon-musks-spacex-plans-dragonfly-landing-tests-n111386
Quote
Billionaire Elon Musk's high-flying space venture, SpaceX, has provided fresh details about its plan to test a Dragon capsule that can use retro rockets to make a soft landing on Earth — and perhaps eventually on Mars.
Quote
The DragonFly prototype's landing technology would eventually be incorporated into a future version of the seven-person DragonRider capsule. It also could be used on interplanetary trips, including a Mars mission code-named "Red Dragon" or Icebreaker. Last weekend, the 42-year-old Musk reported that he was making progress on a plan to send colonists to Mars during his lifetime.

(Video was old landing simulation)

Edit: changed link
Title: Re: SpaceX DragonFly Discussion Thread
Post by: JBF on 05/21/2014 09:34 PM
New article on DragonFly:
http://forum.nasaspaceflight.com/index.php?topic=34800.msg1201817#msg1201817
Quote
Billionaire Elon Musk's high-flying space venture, SpaceX, has provided fresh details about its plan to test a Dragon capsule that can use retro rockets to make a soft landing on Earth — and perhaps eventually on Mars.
Quote
The DragonFly prototype's landing technology would eventually be incorporated into a future version of the seven-person DragonRider capsule. It also could be used on interplanetary trips, including a Mars mission code-named "Red Dragon" or Icebreaker. Last weekend, the 42-year-old Musk reported that he was making progress on a plan to send colonists to Mars during his lifetime.

There is also a video simulation...

That video is watermarked 2012. Even the F9 is wrong.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 05/21/2014 09:37 PM
Yup. Noticed that after posting. Not much in article that hasn't been discussed here, either.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Comga on 05/21/2014 09:56 PM

Any concerns about the capsule being tilted ~30 degrees from vertical due to the parachute attach point being on the side?  See picture(s) captured from the Drop test video.

Firing off the Draco Engines on landing may expect a horizontal component to the resulting motion.

Perhaps the Draco thrusters (attitude control) could level the vehicle before the SuperDracos lit up. But in any case, the vehicle has to be able to cope with SuperDracos firing from an off-vertical position for the abort uses, although of course that case is not aiming for a landing pad.

Anyway a good question that we may see the answer to when the tests begin
The simulation shown before and linked below has a depiction of this transient at about 2:40:
http://forum.nasaspaceflight.com/index.php?topic=34800.msg1201817#msg1201817 (http://forum.nasaspaceflight.com/index.php?topic=34800.msg1201817#msg1201817)
Besides being old, landing under parachutes is not the issue.
What people find disturbing is coming in at terminal velocity down to 400 meters before turning on the SuperDracos and stopping in five seconds.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: douglas100 on 05/21/2014 10:01 PM
The thing that strikes me is how flexible the concept is, handling abort, parachute only landing, powered landing only and various  possibilities in between.

There should be enough redundancy to make a power only landing pretty safe even though it seems pretty scary.

Also,  the prop tanks and lines would have to be robust enough to take the shock of a parachute only landing without leaking or rupturing. The thought of hypergols coming in contact with each other due to a hard landing doesn't bear thinking about.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 05/21/2014 10:31 PM

Any concerns about the capsule being tilted ~30 degrees from vertical due to the parachute attach point being on the side?  See picture(s) captured from the Drop test video.

Firing off the Draco Engines on landing may expect a horizontal component to the resulting motion.

Perhaps the Draco thrusters (attitude control) could level the vehicle before the SuperDracos lit up. But in any case, the vehicle has to be able to cope with SuperDracos firing from an off-vertical position for the abort uses, although of course that case is not aiming for a landing pad.

Anyway a good question that we may see the answer to when the tests begin
The simulation shown before and linked below has a depiction of this transient at about 2:40:
http://forum.nasaspaceflight.com/index.php?topic=34800.msg1201817#msg1201817 (http://forum.nasaspaceflight.com/index.php?topic=34800.msg1201817#msg1201817)
Besides being old, landing under parachutes is not the issue.
What people find disturbing is coming in at terminal velocity down to 400 meters before turning on the SuperDracos and stopping in five seconds.
Of course that landing scenario is much more 'interesting' -- I was just providing comment on the quoted posts which were expressing concern about the 30 degree hang from parachutes when superdracos ignited.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lobo on 05/21/2014 11:22 PM
It'd be a monstrously terrifying landing if the burn is a short one.  I wonder if DreamChaser will get a leg up in the manned competition because of what the Astronaut Office thinks about this type of landing when it becomes clear just how close to a horrible death the astronauts have to come before the landing engines ignite each time.

Seriously.  My hands got clammy just thinking about that kind of plummet to the ground!

I think what they are selling to NASA as the initial capability is the propulsion assisted landing, which should be a much more gentle experience.

I wouldn't expect to see a fully propulsive landing with crew for a while.

Yes.  How will it be any different than how our astronauts land in Soyuz now?  It uses propuslive assist landing with parachutes.   Seems to have worked pretty good.

I would guess the CRS missions will really be the test beds for fully propulsive landing, unless there is some sort of downmass component that's of significant value and must be landed in tact.  Otherwise, I'd guess they'd practice with that before a crew would ever land that way.  Could even be that NASA wouldn't let them land fully propulsively for commercial crew, and all crewed landings must be propulsive assist only.  In which case it would be until there was some sort of commerical space station or commercial tourism orbit service before we see people landing fully propulsively.

Title: Re: SpaceX DragonFly Discussion Thread
Post by: butters on 05/21/2014 11:40 PM
I think that the parachute-assisted propulsive landing is just for the test flights. I suspect they won't even use the same chutes as they'll be using for aborts on the operational Dragon 2. Soyuz isn't a good example. The SuperDraco burn time is substantially longer than the Soyuz landing motors, and Soyuz is usually tipped over onto its side by its chute, which is unacceptable for a reusable spacecraft.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Spacenerd on 05/22/2014 12:11 AM
I'm intrigued with this integrated trunk as well. Theoretically they could have designed a new trunk that would accommodate legs and enough fuel to do a Moon or Mars decent / ascent. (ladder included)
I would be careful to interpret too much into it, but it does sound interesting, indeed. Maybe the new Dragon will not lose the trunk anymore?
Hmmm.
Either way, I cant wait to see test hops of this! This must be really cool to watch!
Ground abort test?

No.  It's a landing test, but not for landing on Earth.  :-)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: MP99 on 05/22/2014 12:35 AM
At 3G's that's dV of 65 mph/sec (sorry for the english units)
seems in the ballpark.

Apollo capsule terminal velocity was roughly 210 miles/hr  at 25,000 ft

3G of deceleration will appear as 4G to the crew.

Re aero loads, my first thought was:-

Note that when the final burn starts, the capsule will include the mass of all the landing prop, but will have the benefit of 1G of aerodynamic resistance.

As speed drops, the aero assist will decrease, but so will the prop load.


However, it occurs to me that the SD exhaust could cause a low pressure area under the capsule, meaning it would need greater thrust to overcome what's basically a negative lift from pressure above the capsule.

Thoughts?

Cheers, Martin
Title: Re: SpaceX DragonFly Discussion Thread
Post by: MP99 on 05/22/2014 12:41 AM

Any concerns about the capsule being tilted ~30 degrees from vertical due to the parachute attach point being on the side?  See picture(s) captured from the Drop test video.

Firing off the Draco Engines on landing may expect a horizontal component to the resulting motion.

Perhaps the Draco thrusters (attitude control) could level the vehicle before the SuperDracos lit up. But in any case, the vehicle has to be able to cope with SuperDracos firing from an off-vertical position for the abort uses, although of course that case is not aiming for a landing pad.

Anyway a good question that we may see the answer to when the tests begin
The simulation shown before and linked below has a depiction of this transient at about 2:40:
http://forum.nasaspaceflight.com/index.php?topic=34800.msg1201817#msg1201817 (http://forum.nasaspaceflight.com/index.php?topic=34800.msg1201817#msg1201817)
Besides being old, landing under parachutes is not the issue.
What people find disturbing is coming in at terminal velocity down to 400 meters before turning on the SuperDracos and stopping in five seconds.

Note that unlike M1D on the first stage RTLS, the SDs could clear their throats or otherwise perform test burns as the capsule approaches "last chance" for a safe parachute landing.

But still, you're right.

Cheers, Martin
Title: Re: SpaceX DragonFly Discussion Thread
Post by: aero on 05/22/2014 12:47 AM
Aren't the Super Dracos throttleable? I would think that they are so they would be ran at a thrust point where they could be throttled up incase of a problem with 1 (hence 2) of them. And they would have more than 5 seconds of fuel when throttled down.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: rcoppola on 05/22/2014 01:00 AM
At 3G's that's dV of 65 mph/sec (sorry for the english units)
seems in the ballpark.

Apollo capsule terminal velocity was roughly 210 miles/hr  at 25,000 ft

3G of deceleration will appear as 4G to the crew.

Re aero loads, my first thought was:-

Note that when the final burn starts, the capsule will include the mass of all the landing prop, but will have the benefit of 1G of aerodynamic resistance.

As speed drops, the aero assist will decrease, but so will the prop load.


However, it occurs to me that the SD exhaust could cause a low pressure area under the capsule, meaning it would need greater thrust to overcome what's basically a negative lift from pressure above the capsule.

Thoughts?

Cheers, Martin
Ok, honestly a bit over my head but...sine the SDs are not equally spaced around the capsule, could the low pressure form be canceled out or minimized?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: su27k on 05/22/2014 02:49 AM
I wonder if they'll reuse the Dragon from the two abort tests as the DragonFly test vehicle, could give us some idea of the timeline.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Alpha Control on 05/22/2014 03:41 AM
"Propulsive Assist Hopping

Approximately 400 gallons of propellant would be loaded into the DragonFly RLV for this test. During a propulsive assisted hop test, the DragonFly RLV would launch from a launch pad and ascend to approximately 7,000 ft AGL (firing engines for 12.5 seconds). Two parachutes would be deployed for the descent, the engines would fire for 12.5 seconds, and the RLV would make a powered landing on the launch pad. This operation would last approximately 60 seconds."

For the Propulsive Assist Hopping, are the SDs firing twice? once for 12.5 seconds to reach altitude, then turn off, then fire a 2nd time for 12.5 seconds for the powered landing? I wasn't completely sure I interpreted the description correctly. Thanks!

With the operation lasting 60 seconds, it looks like they're going for 35 seconds of zero thrust.  (12.5 x2 equals 25 seconds).

Thanks Jason.  I think I was missing the word "again", as in "the engines would fire for 12.5 seconds again", to more clearly denote the two separate engine firing events. Your calculations of the overall timing of the test help clarify that.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: QuantumG on 05/22/2014 05:03 AM
I'm just glad there's a name. The last thing SpaceX needs is another program/vehicle they refer to as "those flights we've been doing."

Title: Re: SpaceX DragonFly Discussion Thread
Post by: BrianNH on 05/22/2014 05:34 AM
Items I found interesting are (page 1-4) there will be (up to)10 F9R launches and that Dragonfly will not fly until the F9R testing is complete.  It also says that Dragonfly testing will be this year and next year, which implies that F9R testing will be completed this year (at McGregor).
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Garrett on 05/22/2014 07:45 AM
I wonder if they'll reuse the Dragon from the two abort tests as the DragonFly test vehicle, could give us some idea of the timeline.
That's what I was wondering too. My guess is they will use the Dragon article from the abort tests and I would further guess that DragonFly test flights could start around mid 2015, assuming the abort tests are on-time and successful and the EIS comes back positive.

Also, some more musings on what the different types of operations are aimed at:
Propulsive assist: testing a nominal landing for crew; variation to their CCtCap proposal which I believe involves a water splashdown*
Full propulsive landing: testing an off-nominal (failed primary and back-up chutes) crew landing or a nominal cargo landing (no chutes required possibly).
Propulsive assist hopping: preliminary tests before full propulsive hopping (i.e. SpaceX's version of a tethered flight)
Propulsive hopping: testing a nominal landing for crew/cargo as per their ultimate ambitions as shown in their promo vids, i.e. "helicopter pad" accurate landings for Dragon.

*I would presume however, that SpaceX have included the option to switch from splashdowns to landings in their proposal, and that the propulsive assist tests could be a compulsory milestone for such a switch?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: LouScheffer on 05/22/2014 11:26 AM
Freefall, 5 sec burn at the last moment, soft touchdown.

Whoever will ultimately ride aboard that kind of flight profile (obviously not during these tests) is a brave man :)


Note that amusement parks do exactly this, *for fun* - freefall from an otherwise fatal height, decelerate at several Gs, stop at ground level. So if you have confidence in the machine, it should be fun, not scary!
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Nomadd on 05/22/2014 11:47 AM
Freefall, 5 sec burn at the last moment, soft touchdown.

Whoever will ultimately ride aboard that kind of flight profile (obviously not during these tests) is a brave man :)


Note that amusement parks do exactly this, *for fun* - freefall from an otherwise fatal height, decelerate at several Gs, stop at ground level. So if you have confidence in the machine, it should be fun, not scary!
The difference between fun and scary is trust.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Ben the Space Brit on 05/22/2014 11:54 AM
Freefall, 5 sec burn at the last moment, soft touchdown.

Whoever will ultimately ride aboard that kind of flight profile (obviously not during these tests) is a brave man :)


Note that amusement parks do exactly this, *for fun* - freefall from an otherwise fatal height, decelerate at several Gs, stop at ground level. So if you have confidence in the machine, it should be fun, not scary!

There is probably a slight qualitative difference to mechanical brakes with multiple redundant safety fall-backs and sitting in the middle of eight pressure-fed rocket engines far too low for a parachute to be of any assistance.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: J-V on 05/22/2014 11:58 AM
There is probably a slight qualitative difference to mechanical brakes with multiple redundant safety fall-backs and sitting in the middle of eight pressure-fed rocket engines far too low for a parachute to be of any assistance.

Has there been any analysis what would happen if Dragon(Fly) would lose a number of SDs? In other words, how many SDs does it take to keep the crew alive or without serious injuries if parachutes are not used?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: corrodedNut on 05/22/2014 12:06 PM
There is probably a slight qualitative difference to mechanical brakes with multiple redundant safety fall-backs and sitting in the middle of eight pressure-fed rocket engines far too low for a parachute to be of any assistance.

Has there been any analysis what would happen if Dragon(Fly) would lose a number of SDs? In other words, how many SDs does it take to keep the crew alive or without serious injuries if parachutes are not used?

That what flight tests are for.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: J-V on 05/22/2014 12:08 PM
Has there been any analysis what would happen if Dragon(Fly) would lose a number of SDs? In other words, how many SDs does it take to keep the crew alive or without serious injuries if parachutes are not used?

That what flight tests are for.

Why I doubt they will test this with flight tests. It would, with very high probability, mean the loss of the test vehicle.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: docmordrid on 05/22/2014 12:12 PM
SpaceX has said they expected to crater some Grasshoppers. I doubt their expectations have changed for DragonFly.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: J-V on 05/22/2014 12:15 PM
SpaceX has said they expected to crater some Grasshoppers. I doubt their expectations have changed for DragonFly.

Expect to, or try to? I assume the first option.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: docmordrid on 05/22/2014 12:22 PM
Test flights often push the envelope to the breaking point. Just look at the Grasshopper 'divert' test, which had a distinct crater possibility. I doubt DragonFly will be any different.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: banjo on 05/22/2014 12:22 PM
i doubt whether spacex ever anticipate a crewed dragon being at terminal velocity 400m or so from the ground.  and even then,  a queasy looking crew would be expected to walk away in one piece.  we're seeing the multiple redundancy being tested.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: docmordrid on 05/22/2014 12:27 PM
I've doubted the 'slam on the brakes' landing for a while. ISTM more logical to decelerate at a lower throttle starting higher up then increase thrust for the last 100m or so.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: hrissan on 05/22/2014 01:39 PM
I've doubted the 'slam on the brakes' landing for a while. ISTM more logical to decelerate at a lower throttle starting higher up then increase thrust for the last 100m or so.
Losing single SuperDraco will probably lead to throttling of opposite pair to ~50% by control system, then losing one of those is also not a problem, the remaining one will throttle back to 100%.

So I'd calculate the stopping profile with 6/8 of total thrust, losing single SuperDraco (or opposing two) would lead to immediate throttle of remaining to 100% and trouble-free landing (in case of no more failures).

But if at that time the height still allows for mortar chute deployment, I'd do it immediately (in case of cascade of failures). Once under chute we can throttle remaining SDs to minimal or switch them off and then start them again just before touchdown to cushion the impact, again using less than 100% thrust initially, so that in case of failure the remaining will throttle up to 100%.

If at the moment of first failure the height is so low that it is futile to deploy chute, then we just count on our luck that no more SDs fail, and if they do, we use remaining working to brake as much as possible. Low height == low speed, so even 2 working SDs may be survivable.

Overall looks like very robust system with dissimilar redundancy, much better than capsule with chute-only doomed in case of chute failure.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 05/22/2014 01:58 PM
8 SuperDraco will provide ~10g for escape when used as a LAS.  So four can provide 5g, plenty more than needed. Didn't that FAA Draft Environmental Assessment have a paragraph saying they are divided into two completely independent sets? That would make it extremely unlikely that both fail unless there is something wrong with the fuel.

Even two might have enough thrust, provided the Dracos could do attitude control, which they may not under these conditions.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Mike_1179 on 05/22/2014 01:58 PM
I've doubted the 'slam on the brakes' landing for a while. ISTM more logical to decelerate at a lower throttle starting higher up then increase thrust for the last 100m or so.

That uses more fuel than a "brown pants" landing.  It's a trade.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: J-V on 05/22/2014 02:04 PM
8 SuperDraco will provide ~10g for escape when used as a LAS.  So four can provide 5g, plenty more than needed. Didn't that FAA Draft Environmental Assessment have a paragraph saying they are divided into two completely independent sets? That would make it extremely unlikely that both fail unless there is something wrong with the fuel.

Even two might have enough thrust, provided the Dracos could do attitude control, which they may not under these conditions.

Thank you for the estimate! Looks like they won't run out of thrust or SDs too easily.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sghill on 05/22/2014 02:57 PM

Any concerns about the capsule being tilted ~30 degrees from vertical due to the parachute attach point being on the side?  See picture(s) captured from the Drop test video.

Firing off the Draco Engines on landing may expect a horizontal component to the resulting motion.



The Mk2 capsule may not have offset parachutes.

Also, any sort of parachute assisted landing precludes precision targeted landings.  They'll have to land out in the desert if they want to come down on land.  Even if the final approach uses motors, they can't just release the chutes over populated areas.

Of course with re-light landing capability, they can always apologize to the people sitting in the living room they came down in, and then sheepishly fly back to the intended landing pad.  :)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: HMXHMX on 05/22/2014 03:04 PM
Freefall, 5 sec burn at the last moment, soft touchdown.

Whoever will ultimately ride aboard that kind of flight profile (obviously not during these tests) is a brave man :)


Note that amusement parks do exactly this, *for fun* - freefall from an otherwise fatal height, decelerate at several Gs, stop at ground level. So if you have confidence in the machine, it should be fun, not scary!
The difference between fun and scary is trust.

No, it's steel.  ;)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: bilbo on 05/22/2014 03:34 PM
I wonder what other witty names SpaceX will come up with, they already have Dragonflys and grasshoppers, so this leads the Question, What will the next vehicle be called? Ladybug? hornet? Fruitfly? Mosquito? Cricket?
Im guessing there might even be a Bullfrog somewhere within the nameing mix. :)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars_J on 05/22/2014 03:58 PM
Finally, I guess one of the abort test articles could be used for these MK2 landing tests, but the other one is just a big welded steel pressure vessel.  That also got me thinking that DragonRider can't look too different from Dragon v1 because the pressure vessels look nearly the same as v1.

The pressure vessel will be very close to the existing Dragon, but the SDs and fairings for them might make the exterior look a bit different.

This is one possibility of how it will look - but it could also be a home-made fake. This mysterious image is discussed here: http://forum.nasaspaceflight.com/index.php?topic=33598.msg1196921#msg1196921

Title: Re: SpaceX DragonFly Discussion Thread
Post by: llanitedave on 05/22/2014 05:46 PM
Those fairings look reminiscent of the legs on the first stage.  I wonder if fold-out legs can act as fairings until the speed is low enough for them to deploy.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: ChefPat on 05/22/2014 05:49 PM
Is there any indication of when testing will begin with Dragonfly?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: corrodedNut on 05/22/2014 05:51 PM
Is there any indication of when testing will begin with Dragonfly?

Just this:

http://forum.nasaspaceflight.com/index.php?topic=34800.msg1201781#msg1201781
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars_J on 05/22/2014 05:52 PM
Those fairings look reminiscent of the legs on the first stage.  I wonder if fold-out legs can act as fairings until the speed is low enough for them to deploy.

No, I really don't think they are legs - while on the surface the fairings do look similar to stage 1 legs, they would serve a very different purpose here. Besides, such legs would be waaaay too large and heavy for a capsule this size.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: kirghizstan on 05/22/2014 05:56 PM
Those fairings look reminiscent of the legs on the first stage.  I wonder if fold-out legs can act as fairings until the speed is low enough for them to deploy.

No, I really don't think they are legs - while on the surface the fairings do look similar to stage 1 legs, they would serve a very different purpose here. Besides, such legs would be waaaay too large and heavy for a capsule this size.

I initially questioned this when the image first surfaced, but when i thought more about it, having the legs directly in line with the Super Dracos doesn't seem like the best idea.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: JasonAW3 on 05/22/2014 05:56 PM
Those fairings look reminiscent of the legs on the first stage.  I wonder if fold-out legs can act as fairings until the speed is low enough for them to deploy.

That actually makes a lot of sense.  As they would deploy, apparently, hydraulically, they could also be used, as large as they are, to act as both a steering and decellerator system.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: llanitedave on 05/22/2014 06:04 PM
Those fairings look reminiscent of the legs on the first stage.  I wonder if fold-out legs can act as fairings until the speed is low enough for them to deploy.

No, I really don't think they are legs - while on the surface the fairings do look similar to stage 1 legs, they would serve a very different purpose here. Besides, such legs would be waaaay too large and heavy for a capsule this size.

They're large, but they don't really need to be very heavy -- mostly just skin.  And if they deploy outward, there remains a good-sized opening for the super dracos to fire through.

On the other hand, I guess there's too many of them; there only need to be three short pods for landing on a concrete pad.  So it's an interesting idea, but I think you're right that they aren't legs.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: HMXHMX on 05/22/2014 06:16 PM
I wonder what other witty names SpaceX will come up with, they already have Dragonflys and grasshoppers, so this leads the Question, What will the next vehicle be called? Ladybug? hornet? Fruitfly? Mosquito? Cricket?
Im guessing there might even be a Bullfrog somewhere within the nameing mix. :)

At the risk of using up my quip quota for the day, it is also obvious what name a competitor should give to the spacecraft that competes with Dragon:  Dragonslayer.

The launch vehicle could be St. George.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: simonbp on 05/22/2014 06:19 PM
Freefall, 5 sec burn at the last moment, soft touchdown.

Whoever will ultimately ride aboard that kind of flight profile (obviously not during these tests) is a brave man :)


Note that amusement parks do exactly this, *for fun* - freefall from an otherwise fatal height, decelerate at several Gs, stop at ground level. So if you have confidence in the machine, it should be fun, not scary!
The difference between fun and scary is trust.

Trust in thrust!

This sounds rather mild compared to some of the landings Apollo and Soyuz have had. And compared to the Soyuz landing rocket system (triggered by a radioactive source and a geiger counter!) that only triggers only a few meters above the ground, I think SpaceX will be fine.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: yg1968 on 05/22/2014 06:50 PM
Some pretty awesome details in there. They anticipate the program taking two years (2014-2015), and there are four different flight profiles they will be testing.

The document indicates that none of the tests will be crewed. But I am guessing that option two (full propulsive landing) is merely an intermediary test and will never be attempted for any crewed flight. The fact that most of the tests are going to be full propulsive hop tests suggests that this is the end result which they are trying to achieve.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: neoforce on 05/22/2014 06:53 PM
There is a thread called "Falcon 9R and Dragon Mk II Suborbital Tourism?" started by RyanC which includes this:

...

Basically use only a F9R first stage to loft a Dragon Mark II into a suborbital arc (ala Mercury-Redstone); then fly back the F9R while Dragon Mk II either lands at sea or on land

...

Any speculation about suborbital tourism should stay in that thread...  But for the DragonFly...  Does anyone think the configuration proposed by RyanC is likely for testing over at Spaceport America?  Of course landing on land, not sea.

SpaceX appears to prefer rigorous test programs, so to me it seems reasonable that the proposed testing at McGregor could be followed by expanding the envelope in New Mexico.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 05/22/2014 06:58 PM
The document indicates that none of the tests will be crewed. But I am guessing that option two (full propulsive landing) is merely an intermediary test and will never be attempted for any crewed flight. The fact that most of the tests focus on full propulsive hop suggests that this is the end result which they are trying to achieve.
And what would that be useful for? They have stated that their ultimate goal is purely propulsive landing. The hops just seem to be a way to test that and more complex maneuvers without needing a helicopter for dropping the capsule.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: yg1968 on 05/22/2014 07:18 PM
The document indicates that none of the tests will be crewed. But I am guessing that option two (full propulsive landing) is merely an intermediary test and will never be attempted for any crewed flight. The fact that most of the tests focus on full propulsive hop suggests that this is the end result which they are trying to achieve.
And what would that be useful for? They have stated that their ultimate goal is purely propulsive landing. The hops just seem to be a way to test that and more complex maneuvers without needing a helicopter for dropping the capsule.

You have to look at the chart to understand my comment. What they call full propulsive landing (option 2) in the chart isn't actually full propulsive landing. The capsule is dropped from a helicopter, the SD are only fired for 5 seconds and no parachutes are used. There is only 2 tests like that. It's obviously just an intermediary step. For option 4, no parachutes are used either but the SD are fired for 12.5 seconds on descent. I am simply saying that the engines are likely to be fired for 12.5 seconds on crewed flights (not 5 seconds). The majority of the tests are done in this configuration. 
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 05/22/2014 07:21 PM
You have to look at the chart to understand my comment. What they call full propulsive landing (option 2) in the chart isn't actually full propulsive landing. The capsule is dropped from a helicopter, the SD are only fired for 5 seconds and no parachutes are used. There is only 2 tests like that. It's obviously just an intermediary step. For option 4, no parachutes are used either but the SD are fired for 25 seconds. I am simply saying that the engines are likely to be fired for 25 seconds on crewed flights (not 5 seconds). The majority of the tests are done in this configuation.
But those 25 seconds are for take off and landing...
The drop from a helicopter would be just landing, like well a landing...
Title: Re: SpaceX DragonFly Discussion Thread
Post by: yg1968 on 05/22/2014 07:24 PM
You have to look at the chart to understand my comment. What they call full propulsive landing (option 2) in the chart isn't actually full propulsive landing. The capsule is dropped from a helicopter, the SD are only fired for 5 seconds and no parachutes are used. There is only 2 tests like that. It's obviously just an intermediary step. For option 4, no parachutes are used either but the SD are fired for 25 seconds. I am simply saying that the engines are likely to be fired for 25 seconds on crewed flights (not 5 seconds). The majority of the tests are done in this configuation.
But those 25 seconds are for take off and landing...
The drop from a helicopter would be just landing, like well a landing...

Sorry, I fixed it in my comment. It's actually 12.5 seconds on descent (and 12.5 seconds on ascent). It's still more than 5 seconds.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 05/22/2014 07:30 PM
I have to admit, I find the emphasis on tests that test taking off with superdracos quite peculiar. I guess it is somehow related to testing launch abort scenarios. Maybe they are planning a scenario where the Dragon does a propulsive landing after a launch abort? But would it have that much fuel?
Really strange.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars_J on 05/22/2014 07:32 PM
I have to admit, I find the emphasis on tests that test taking off with superdracos quite peculiar. I guess it is somehow related to testing launch abort scenarios. Maybe they are planning a scenario where the Dragon does a propulsive landing after a launch abort? But would it have that much fuel?
Really strange.

Once you have the capability to take off under your own thrust, landing tests becomes significantly cheaper, since you don't need to contract for a special helicopter for every test.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: corrodedNut on 05/22/2014 07:39 PM
I don't think that the tests listed in the document are necessarily in the same order that they will be conducted. I suspect that the first tests will be short hops as was with Grasshopper.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 05/22/2014 08:12 PM
Once you have the capability to take off under your own thrust, landing tests becomes significantly cheaper, since you don't need to contract for a special helicopter for every test.
That's what I thought (and wrote earlier), but I did not really understand how the 8 tests with powered take off and parachute landing would fit into that. I can only think of abort tests or something like that.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: MP99 on 05/22/2014 08:24 PM
I have to admit, I find the emphasis on tests that test taking off with superdracos quite peculiar. I guess it is somehow related to testing launch abort scenarios. Maybe they are planning a scenario where the Dragon does a propulsive landing after a launch abort? But would it have that much fuel?
Really strange.

Once you have the capability to take off under your own thrust, landing tests becomes significantly cheaper, since you don't need to contract for a special helicopter for every test.

This makes sense. Need only the DF to perform tests. Much more convenient.

Also puts more seconds on the engines, and so on.

Cheers, Martin
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 05/22/2014 09:12 PM
I have to admit, I find the emphasis on tests that test taking off with superdracos quite peculiar. I guess it is somehow related to testing launch abort scenarios. Maybe they are planning a scenario where the Dragon does a propulsive landing after a launch abort? But would it have that much fuel?
Really strange.
Think of non-LAS applications... Mars, Moon (x-prize) whatever.  The LAS 'feature' will rarely, if ever, be used.  This is a rocket-powered lander (prototype or software development platform) that will fill the requirement for a LAS for a few minutes each trip.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 05/23/2014 12:03 AM
Think of non-LAS applications... Mars, Moon (x-prize) whatever.  The LAS 'feature' will rarely, if ever, be used.  This is a rocket-powered lander (prototype or software development platform) that will fill the requirement for a LAS for a few minutes each trip.
The lander aspect makes sense, I guess. But it seems quite far down the road compared to the powered landing application on earth. I am also quite sure they still want to test the LAS aspect quite thoroughly. If they can test it several times until the CCDev decision, it might give them an edge over their competitors (could be argued to be safer since tested more often).
Title: Re: SpaceX DragonFly Discussion Thread
Post by: go4mars on 05/23/2014 12:36 AM
I was recently up in a Hughes 500 helicopter and the pilot mentioned that the long legs were a crumple-zone.  Should be survivable in low-flying ops up to 100 feet. 

For places with no atmosphere, like the moon; a "Silver Dragon" mission; I wonder how much payload mass might be usefully landed (one way only presumably) using the trunk as a crumpler stage as opposed to a crasher stage.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: oiorionsbelt on 05/23/2014 12:40 AM
"Silver Dragon"
Is that an original? :)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: metaphor on 05/23/2014 02:22 AM
I don't think that the tests listed in the document are necessarily in the same order that they will be conducted. I suspect that the first tests will be short hops as was with Grasshopper.

In my opinion, the number of flights suggests that they would be sequential:

Option 1 -2 flights (helicopter, parachutes and 5 seconds propulsive landing)
Option 2 -2 flights  (helicopter, no parachutes and 5 seconds propulsive landing)
Option 3 -8 flights (parachutes, 12.5 seconds propulsive landing and same for ascent)
Option 4 -18 flights (no parachutes, 12.5 seconds propulsive landing and same for ascent)

In my opinion, the fact that 26 out of the 30 tests have 12.5 seconds engines firing on descent suggests that they intend to fire them for 12.5 seconds (and not only 5 seconds).

Is it possible the hop tests would be 20 seconds of ascent followed by 5 seconds of landing?  It makes sense to have a longer ascent, since the aerodynamic drag is working against the engines on ascent and working with the engines on landing.  And maybe they want to test the Dragon coming down at near terminal velocity, which would mean an ascent long enough to put it higher up.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Comga on 05/23/2014 04:17 AM
Thinking about the "brown shorts" landing.
Did a quick "back-of-the envelope" calculation in a spreadsheet. 
It assumes the terminal velocity is 150 m/sec and that the SuperDracos throttle without losing any Isp, and that the fuel burned is a small fraction of the mass of the vehicle.

The first a is "subjective" acceleration in g's.
The second a is the acceleration in the fixed reference frame of the ground
t is the time from (instantaneous) ignition to "hoverslam" (which includes neither hover or slam) of zero velocity at zero altitude.
h is the altitude of the (instantaneous) ignition.
mdot*t is the fuel burn rate times the burn time, a measure of fuel consumed  (times some constant)
The last line compares mdot*t to the "nominal" five second (Tower of Doom with no tower) burn.

A subjective 2.2 g's takes ~12.5 seconds, a duration mentioned in the EIS, and consumes 36% more fuel.  The burn starts at over 900 m AGL, which would be slightly less terrifying.  (Over 6 seconds to impact vs just over 2.)
A "vigorous" 5 g's only saves 6% on the fuel, and ignition is less than 2 sec before impact.
A "relaxed" 3 g's only costs ~13% more fuel.
It seems to make sense to "start slow" with low thrust landings, perhaps at the limit of SuperDracos throttling.

Have I made any gross errors in these calculations?  (It's been known to happen...)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: go4mars on 05/23/2014 04:54 AM
"Silver Dragon"
Is that an original? :)
As far as I know.   ;)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: savuporo on 05/23/2014 05:00 AM
A subjective 2.2 g's takes ~12.5 seconds, a duration mentioned in the EIS, and consumes 36% more fuel.  The burn starts at over 900 m AGL, which would be slightly less terrifying.  (Over 6 seconds to impact vs just over 2.)
Not sure if the plan is to carry a BRS-type emergency parachute or no, but you'd probably want to light all engines above the hard deck. 5-6 seconds sounds about right.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: HMXHMX on 05/23/2014 05:41 AM
A subjective 2.2 g's takes ~12.5 seconds, a duration mentioned in the EIS, and consumes 36% more fuel.  The burn starts at over 900 m AGL, which would be slightly less terrifying.  (Over 6 seconds to impact vs just over 2.)
Not sure if the plan is to carry a BRS-type emergency parachute or no, but you'd probably want to light all engines above the hard deck. 5-6 seconds sounds about right.

It's a good idea (the parachute, that is).  :)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: beancounter on 05/23/2014 06:20 AM
Another step on the road to Mars.  ;)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Garrett on 05/23/2014 10:07 AM
I have to admit, I find the emphasis on tests that test taking off with superdracos quite peculiar.
I thought it was simply to avoid hiring a helicopter for every propulsive landing test?

But maybe it can also double as a sort of hot-fire - maybe they can hold down the DragonFly for a fraction of a second or ramp up thrust so that the mission can abort early if anomolies are detected?

Or maybe guidance software for take-off and landing are very similar, so each launch returns two test results?

Or gives the components more flight time, allowing for end-of-life analysis?

But yeah, an interesting approach and fun to muse about :)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Chris Bergin on 05/23/2014 10:33 AM
This thread is the sort of thing we like here.

Alos, Chris G is going to write an article about Dragonfly.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: ChefPat on 05/23/2014 12:55 PM
Are the Hop Tests simulating a Pad Abort with a Powered Landing?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sghill on 05/23/2014 01:02 PM
A subjective 2.2 g's takes ~12.5 seconds, a duration mentioned in the EIS, and consumes 36% more fuel.  The burn starts at over 900 m AGL, which would be slightly less terrifying.  (Over 6 seconds to impact vs just over 2.)
A "vigorous" 5 g's only saves 6% on the fuel, and ignition is less than 2 sec before impact.
A "relaxed" 3 g's only costs ~13% more fuel.
It seems to make sense to "start slow" with low thrust landings, perhaps at the limit of SuperDracos throttling.

Have I made any gross errors in these calculations?  (It's been known to happen...)

I couldn't tell if you were smoothing out the landing because of the decreased mass of the capsule as it burns through 3000 kg of fuel.  That'd be an integral (integer?) function.  The rate of decent would get progressively slower at the same throttle setting as the fuel burns off over a couple of seconds and decreases the capsule mass.  That's make for a smoother landing and longer burn time right at the end.

How about this question instead:  Let's say a ballistic parachute(s) has to deploy above 500m to be effective for a mass this large (I'm just throwing out a number, ballistic parachutes for 2000kg planes are effective at 100ft!).  That means the burn has to successfully start just above 500m, otherwise the chute pops.  How long are the burn times (and is there enough fuel) for the g-rates you've got above if the burn starts at 500m?

Note: 500m is still below the "Brown Pants Line" (BPL) in this pilot's opinion.  I'd want to know the motors are running up around 1000m, even if they are turning on a few at a time to provide some emotional comfort and stability at low altitude.

Also, we hadn't discussed cross-range landings for full engine assisted landings.  Cross winds are going to necessitate corrective burns higher up to keep on course for spot landings even if it's not a manned return.  That means we have less fuel to work with and/or more fuel to compensate for.





Title: Re: SpaceX DragonFly Discussion Thread
Post by: sheltonjr on 05/23/2014 01:36 PM
Could the table have a typo?

5 second burn for parachute assist.
12.5 second for unassisted makes more sense to me.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: ChefPat on 05/23/2014 02:47 PM
WacoTrib article with a little fresh info;

Grasshopper to DragonFly: SpaceX seeks approval for new McGregor testing  (http://www.wacotrib.com/blogs/joe_science/grasshopper-to-dragonfly-spacex-seeks-approval-for-new-mcgregor-testing/article_11d0c40a-e1f6-11e3-a868-001a4bcf887a.html)

[snip]
According to the FAA report, however, a trunk will be attached to the DragonFly for some of its tests — suggesting that a land landing will allow future flights to bring items back in the trunk as well as the Dragon proper (the trunk would have to be equipped with its own heat shield to survive re-entry, if that were the case).
[snip]
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cuddihy on 05/23/2014 02:53 PM
That makes no sense to me. Why double the heatshield , avionics, and RCS systems? Why wouldn't you just make a bigger Dragon capsule that contained a cargo bay?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: yg1968 on 05/23/2014 02:59 PM
That makes no sense to me. Why double the heatshield , avionics, and RCS systems? Why wouldn't you just make a bigger Dragon capsule that contained a cargo bay?

That might be what they have in mind. One heatshield at the bottom of the trunk but none at the bottom of the capsule. 
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 05/23/2014 03:00 PM
Or maybe the bottom of the capsule does not have a heat shield at all and it is only meant to detach from the trunk in case of a launch abort situation. Otherwise it would reenter and land with the trunk attached?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Rocket Science on 05/23/2014 03:02 PM
That makes no sense to me. Why double the heatshield , avionics, and RCS systems? Why wouldn't you just make a bigger Dragon capsule that contained a cargo bay?
Sounds like you're scaling it up into the "Big G" proposal, less the cargo bay.:)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: yg1968 on 05/23/2014 03:03 PM
Or maybe the bottom of the capsule does not have a heat shield at all and it is only meant to detach from the trunk in case of a launch abort situation. Otherwise it would reenter and land with the trunk attached?

That would make more sense. That's not what the Waco Tribune says. But it sounds like they are speculating.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: mlindner on 05/23/2014 03:33 PM
There is probably a slight qualitative difference to mechanical brakes with multiple redundant safety fall-backs and sitting in the middle of eight pressure-fed rocket engines far too low for a parachute to be of any assistance.

Has there been any analysis what would happen if Dragon(Fly) would lose a number of SDs? In other words, how many SDs does it take to keep the crew alive or without serious injuries if parachutes are not used?

I believe they can lose up to 4 of the 8 engines (if lost in the correct locations) and maintain full control. It was also mentioned that each engine in each pair is fed from different tanks so the loss of a tank would also not cause a failure. It sounds like they need two independent failures (in worst possible locations) to cause mission failure.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: eriblo on 05/23/2014 03:35 PM
Well, they are referring to the FAA-report, which most of us have probably read. I think that the only mention of the trunk is:

Quote from: FAA
The DragonFly RLV is the Dragon capsule with an integrated trunk (which may or may not be attached during a DragonFly operation)...

My guess is that the Waco Tribune simply extrapolated "may be attached during a DragonFly operation" to meaning the whole operation including landing instead of launching with it and then detaching. The report does not differentiate between these scenarios...
Title: Re: SpaceX DragonFly Discussion Thread
Post by: starsilk on 05/23/2014 03:42 PM
A subjective 2.2 g's takes ~12.5 seconds, a duration mentioned in the EIS, and consumes 36% more fuel.  The burn starts at over 900 m AGL, which would be slightly less terrifying.  (Over 6 seconds to impact vs just over 2.)
A "vigorous" 5 g's only saves 6% on the fuel, and ignition is less than 2 sec before impact.
A "relaxed" 3 g's only costs ~13% more fuel.
It seems to make sense to "start slow" with low thrust landings, perhaps at the limit of SuperDracos throttling.

Have I made any gross errors in these calculations?  (It's been known to happen...)

Note: 500m is still below the "Brown Pants Line" (BPL) in this pilot's opinion.  I'd want to know the motors are running up around 1000m, even if they are turning on a few at a time to provide some emotional comfort and stability at low altitude.

your new acronym should definitely be added to the human rating standards. with a suitable safety factor, of course...
Title: Re: SpaceX DragonFly Discussion Thread
Post by: billh on 05/23/2014 04:13 PM
BPL - Brown Pants Line. On descent, the altitude at which you will sh** in your pants if you are still in free fall.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: SaxtonHale on 05/23/2014 04:53 PM
I gotta remember to read the SpaceX threads after lunch...

(No need to reiterate the gross details and kill the joke)

I just hope the first passengers have good seats and a mouthguard.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AJA on 05/23/2014 05:27 PM
OK, I haven't been through all 11 pages on this thread, so someone forgive me if this has already been mentioned.

Where in the report does it say the engine firing will be continuous? They can fire for 10 x 0.5 seconds for a total of 5 seconds. Since the acceleration will not be sustained for a long period of time, they can get away with higher-G's too... possibly making the development of the SuperDracos easier..?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Joffan on 05/23/2014 05:33 PM
Well, they are referring to the FAA-report, which most of us have probably read. I think that the only mention of the trunk is:

Quote from: FAA
The DragonFly RLV is the Dragon capsule with an integrated trunk (which may or may not be attached during a DragonFly operation)...

My guess is that the Waco Tribune simply extrapolated "may be attached during a DragonFly operation" to meaning the whole operation including landing instead of launching with it and then detaching. The report does not differentiate between these scenarios...

This seems most likely to me. However the launched-then-detached trunk option makes me wonder if it would be straightforward (or even possible) to fit a small recovery chute in the trunk - for these Dragonfly tests only, of course, not for operational Dragon landings.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Llian Rhydderch on 05/23/2014 05:54 PM
OK, I haven't been through all 11 pages on this thread, so someone forgive me if this has already been mentioned.

Where in the report does it say the engine firing will be continuous? They can fire for 10 x 0.5 seconds for a total of 5 seconds. Since the acceleration will not be sustained for a long period of time, they can get away with higher-G's too... possibly making the development of the SuperDracos easier..?

Well the FAA report mentions engine throttling on several occasions.  My question to the rocket engine folks here is:  with respect to throttling on rocket engines, does throttling always refer to reduced thrust on a continuously-firing engine?  or can throttling also be accomplished with a less-than-100% duty cycle on engine firing?  (I'm asking about normal usage in the chemical rocket engine literature, as well as speculation about what might be expected here with SuperDracos.)

It seems to me that, for hypergolic RCS engines, the reaction force needed is often obtained from multiple-short firings of any specific thruster.  For something 100x as large in thrust, as the SuperDraco is over the Draco, might a sort of Pulse Width Modulation (PWM) be used to obtain a much more granular throttling, just like PWM is often used in varying the effective voltage in torsion motor drive electrical circuits like those used in some electric vehicles?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 05/23/2014 05:54 PM
Well, they are referring to the FAA-report, which most of us have probably read. I think that the only mention of the trunk is:

Quote from: FAA
The DragonFly RLV is the Dragon capsule with an integrated trunk (which may or may not be attached during a DragonFly operation)...

My guess is that the Waco Tribune simply extrapolated "may be attached during a DragonFly operation" to meaning the whole operation including landing instead of launching with it and then detaching. The report does not differentiate between these scenarios...

This seems most likely to me. However the launched-then-detached trunk option makes me wonder if it would be straightforward (or even possible) to fit a small recovery chute in the trunk - for these Dragonfly tests only, of course, not for operational Dragon landings.
Of course it could also mean that the trunk stays on the ground (in case of a simulated pad abort situation of sorts).
Title: Re: SpaceX DragonFly Discussion Thread
Post by: clongton on 05/23/2014 06:11 PM
Has there been any analysis what would happen if Dragon(Fly) would lose a number of SDs?

It's hard to loose even 1 hypergolic engine, let alone "a number" of them. No moving parts in the power stream, just a couple of valves to open or close the 2 propellant streams, which are pressure fed. Open the valves, propellant flows and the engine self-ignites. Close the valves and the engine shuts off. Simple. That's a big reason why Apollo CSM/LM went with hypergols. Practically foolproof.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AJA on 05/23/2014 06:23 PM
It's hard to loose even 1 hypergolic engine, let alone "a number" of them.

It's already happened. On orbit. To Dragon. (albeit to Draco, and not SuperDraco) Requirements for redundant systems aren't defined by probability of failure alone, but by the product of severity of failure x probability of failure.

In this case, if there's no parachute, or they're below minimum safe altitude for a parachuted landing, the severity is loss of/serious injury to crew. There's no way they're simply going to go ahead with "Yeah, hypergolics don't fail".

Also, engine control can be lost due to software glitches too.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sghill on 05/23/2014 06:26 PM
Has there been any analysis what would happen if Dragon(Fly) would lose a number of SDs?

It's hard to loose even 1 hypergolic engine, let alone "a number" of them. No moving parts in the power stream, just a couple of valves to open or close the 2 propellant streams, which are pressure fed. Open the valves, propellant flows and the engine self-ignites. Close the valves and the engine shuts off. Simple. That's a big reason why Apollo CSM/LM went with hypergols. Practically foolproof.

Except for that whole Gemini 8 thingy....

http://www.youtube.com/watch?v=Y1rp1BRL4qY
Title: Re: SpaceX DragonFly Discussion Thread
Post by: savuporo on 05/23/2014 06:45 PM
Note: 500m is still below the "Brown Pants Line" (BPL) in this pilot's opinion.  I'd want to know the motors are running up around 1000m, even if they are turning on a few at a time to provide some emotional comfort and stability at low altitude.
Having pulled the reserve twice so far, both above the  established hard deck, i would say that BPL is a mischaracterization, as your sphincter ani externus actually tends to rapidly contract.
AAD common firing altitudes are at 750 feet AGL by the way, which is of course determined by nominal terminal velocity and typical reserve canopy deployment sequence. I think BRS has performed saves as low as 200 feet AGL.

EDIT: well , actually much lower, but obviously very few of this saves were performed in vertical terminal descent
http://www.sky-walker.aero/pdfs/sonstiges/Lives-Saved.pdf
http://www.brs-vertrieb.de/en/news/
Title: Re: SpaceX DragonFly Discussion Thread
Post by: clongton on 05/23/2014 06:50 PM
BPL - Brown Pants Line. On descent, the altitude at which you will sh** deficate in your pants if you are still in free fall.

Fixed that for ya. Now it's legal and Chris can add it to the list. :)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 05/23/2014 06:59 PM
In this case, if there's no parachute, or they're below minimum safe altitude for a parachuted landing, the severity is loss of/serious injury to crew. There's no way they're simply going to go ahead with "Yeah, hypergolics don't fail".
Also, engine control can be lost due to software glitches too.
A few thoughts on that.
1. I think that a catastrophic software failure on ANY US manned spacecraft since Apollo would have probably resulted in a loss of crew. The timely deployment of parachutes and/or airbags will require software too.
The Shuttle and the Dream Chaser probably wont fly well without software to control them.
So this is not any different for any of the competing space craft.

2. If anything the powered landing adds another level of redundancy to the whole system. I am sure that SpaceX will test various emergency scenarios for the whole system. That will most likely include any combination of hardware, software, valve, engine and other failures.

3. If the normal method for landing a Dragon2 will indeed be with the trunk attached (and this is only one possible interpretation of the FAA permit), I presume that the trunk could act as an additional crush/crumble zone, that could improve the survivability even with severely reduced engine power and very late parachute deployment. Modern cars have quite good survivability in head on collisions, even at high speeds. Of course a capsule like Dragon has added risk because of fuel leaks and other things...
Title: Re: SpaceX DragonFly Discussion Thread
Post by: savuporo on 05/23/2014 07:03 PM
The timely deployment of parachutes and/or airbags will require software too.
In a piloted flight, not necessarily. Light aircraft rely on a pilot pulled handle, and in skydiving manual reserve deployments are far more common than AAD firing. I'd be suprised if they didnt have a handle in there for deployment.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: dlapine on 05/23/2014 07:12 PM

3. If the normal method for landing a Dragon2 will indeed be with the trunk attached (and this is only one possible interpretation of the FAA permit), I presume that the trunk could act as an additional crush/crumble zone, that could improve the survivability even with severely reduced engine power and very late parachute deployment. Modern cars have quite good survivability in head on collisions, even at high speeds. Of course a capsule like Dragon has added risk because of fuel leaks and other things...

Um, wouldn't that assume that no hypergolic propellent is stored in trunk? I don't believe that is and that the stores in the capsule are probably shock isolated to a reasonable extent, but wasn't there some talk of storing additional supplies in the trunk earlier in this thread.

Hypergolic Tanks + crumple zone = Hollywood movie car crash. :)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 05/23/2014 07:26 PM
Um, wouldn't that assume that no hypergolic propellent is stored in trunk? I don't believe that is and that the stores in the capsule are probably shock isolated to a reasonable extent, but wasn't there some talk of storing additional supplies in the trunk earlier in this thread.
Hypergolic Tanks + crumple zone = Hollywood movie car crash. :)
I am quite convinced that even if (and that is a big if), the trunk is indeed meant to stay attached during normal operation (and landing) of the Dragon, I am very sure that there is no propellant stored on the trunk.
If anything, I would assume that some of(!) the battery packs that presumably will replace the solar panels ( think Musk said that) for crewed flight, will be in the trunk. That could match a (speculative!) flexible architecture, where trunks with different outfits are attached to the Dragon capsule, depending on the mission.
I think there once was a mention of a bigger trunk with more space for unpressurized payloads. In addition to that, I could see trunks with solar panels, trunks with bigger heat shields, trunks with bigger batteries and so on (yes very speculative).
Either way, I am skeptical of the idea of having something as integral as the hypergolic fuel tanks in the trunk, but then I might be completely wrong here. All this is a lot of speculation anyway. I cant wait for the reveal in a few days, when we will finally know for sure what the thing will look like.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AJA on 05/23/2014 07:44 PM
...
The Shuttle and the Dream Chaser probably wont fly well without software to control them.
So this is not any different for any of the competing space craft.

Sorry, but this had to be done (http://www.anyclip.com/movies/space-cowboys/perfect-landing/#!quotes/)

I concur that they'll add redundancy. However, I don't think the trunk can be counted on as one such redudancy. After all, it'll presumably be packed with a lot of downmass. Then again, if all that downmass is squishy human waste etc. - then I guess it still works.

Having pulled the reserve twice so far, both above the  established hard deck, i would say that BPL is a mischaracterization, as your sphincter ani externus actually tends to rapidly contract.

It's different for different people, and different stimuli (http://www.slate.com/articles/news_and_politics/explainer_extra/2011/10/peeing_your_pants_why_do_people_urinate_when_they_re_scared_.html). (And possibly also dependent on whether your bowels are currently full, or empty). There are different forcing agents, but adrenaline apparently leads to a relaxation of the external sphincter. (http://www.bbc.co.uk/dna/place-lancashire/plain/A641206)

Even if having the "shit scared out of you" doesn't literally happen... there's still a good chance that there would be a BPL. You'd very likely still soil your pants once you're down and safe, and the physiological tension of the fight or flight response gives way to.. "HOLY LIVING SH%#!". Don't forget that the occupants would have fluid-loaded, and that they would have a downward fluid shift, increasing pressure on the bowels. (Even IF they hadn't had >1g accelerations in the past few seconds, this would probably make them want to poop).

Or, in a less desirable situation, post-mortem sphincter distension would also leave their pants soiled (if the impact forces didn't also lead to RUD of the body). Not to mention the trunk squishing I've mentioned above.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lar on 05/23/2014 07:49 PM
Thanks for the biology lessons but I think we're probably done with it on this thread, right?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Space OurSoul on 05/23/2014 08:25 PM
Re: trunk attach. I wonder if the LAS process, were it to occur, would disconnect both the trunk from the second stage and the trunk from the dragon simultaneously. Since it's an emergency situation, who knows if either of those separation points will actually succeed. So you have to plan for the case when the trunk separates from the stage but not from the dragon, and then land with the two still connected. It would kinda suck if the software didn't take this possibility into account and then they broke the crew in a real abort just because the extra weight threw off the landing algorithm.


Title: Re: SpaceX DragonFly Discussion Thread
Post by: andreto on 05/23/2014 09:03 PM
Another step on the road to Mars.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 05/23/2014 11:13 PM
An interesting feature of all this is that SpaceX will be flying the capsule all the way from orbit to within a km or two of the landing pad... That will be a ride!

Edit: Not actually DragonFly, but the real version.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: 411rocket on 05/23/2014 11:40 PM
An interesting feature of all this is that SpaceX will be flying the capsule all the way from orbit to within a km or two of the landing pad... That will be a ride!

Edit: Not actually DragonFly, but the real version.

I would think, they would like to nail the landing pad. But did you mean, the launch pad???
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 05/24/2014 12:00 AM
An interesting feature of all this is that SpaceX will be flying the capsule all the way from orbit to within a km or two of the landing pad... That will be a ride!

Edit: Not actually DragonFly, but the real version.

I would think, they would like to nail the landing pad. But did you mean, the launch pad???
Landing.  Might be on left coast, at least at first.  My point was reentry all the way to within a km or so of the ground without drogues, mains, nothing... and flying/maneuvering the capsule until the last tens of seconds before landing when the burn starts... what an entry to watch! Or ride!!!
Title: Re: SpaceX DragonFly Discussion Thread
Post by: llanitedave on 05/24/2014 12:47 AM
Um, wouldn't that assume that no hypergolic propellent is stored in trunk? I don't believe that is and that the stores in the capsule are probably shock isolated to a reasonable extent, but wasn't there some talk of storing additional supplies in the trunk earlier in this thread.
Hypergolic Tanks + crumple zone = Hollywood movie car crash. :)
I am quite convinced that even if (and that is a big if), the trunk is indeed meant to stay attached during normal operation (and landing) of the Dragon, I am very sure that there is no propellant stored on the trunk.
If anything, I would assume that some of(!) the battery packs that presumably will replace the solar panels ( think Musk said that) for crewed flight, will be in the trunk. That could match a (speculative!) flexible architecture, where trunks with different outfits are attached to the Dragon capsule, depending on the mission.
I think there once was a mention of a bigger trunk with more space for unpressurized payloads. In addition to that, I could see trunks with solar panels, trunks with bigger heat shields, trunks with bigger batteries and so on (yes very speculative).
Either way, I am skeptical of the idea of having something as integral as the hypergolic fuel tanks in the trunk, but then I might be completely wrong here. All this is a lot of speculation anyway. I cant wait for the reveal in a few days, when we will finally know for sure what the thing will look like.

IF you have an integrated truck with heat shield coming back with the Dragon, then I don't see how it could be anything like the current Dragon's trunk.  It would have to continue the same aerodynamic lines as the current dragon, or very close to it, which would mean a base pretty similar  to the current fairing diameter of 5m.  That would have the appearance of a very large single capsule.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: pogo661 on 05/24/2014 04:08 AM
If each SD has an independent fuel source, losing 1 would mean losing 25% of your fuel, counting the fuel of the opposing pair.  2 could mean 50% fuel loss.   What does that do to the necessary deceleration profile with engine out?  Also, does that suggest that under normal conditions lots of fuel will be left after landing?
   
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Hauerg on 05/24/2014 05:30 AM
Maybe i missed it (haven't read the whole thread) but if you land the whole thing including the trunk, you would need two sets of landing gear, just in case you haave to seperate the trunk for any reason.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Geron on 05/24/2014 05:48 AM
The trunk is not integrated with capsule, the solar panels are integrated with the trunk.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: dglow on 05/24/2014 11:53 AM
DragonRider
The trunk is not integrated with capsule, the solar panels are integrated with the trunk.

Yes, but not for the crewed Dragon. Word is that it flies sans solar panels.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: MP99 on 05/24/2014 01:58 PM
If each SD has an independent fuel source, losing 1 would mean losing 25% of your fuel, counting the fuel of the opposing pair.  2 could mean 50% fuel loss.   What does that do to the necessary deceleration profile with engine out?  Also, does that suggest that under normal conditions lots of fuel will be left after landing?

That would need eight separate fuel sources. ISTM more likely each source will feed two engines.

SDs do far more Gs when operating as LAS, so they should be operating well below 100% during landing. When one engine fails, it's adjacent pair (same pod) can throttle up.

If each tank feeds an opposing pair (ome engine each in opposite pods), then the opposite pair can do complementary throttling. Instead of each tank 50% feeding two engines @ 50%, each can 100% feed one engine @ 100%. They'll still drain at the same rate (for balance) and with balanced thrust side-to-side.

There are similar options if a tank feeds SDs in pods 90 degrees apart.

Cheers, Martin
Title: Re: SpaceX DragonFly Discussion Thread
Post by: modemeagle on 05/25/2014 12:44 AM
I modified my simulator for a drop test.  Here is a table of what I found.  This includes drag calculated into the drop.  I ran it at 1/10th second until 1,000 meters and then 1/100th second until touchdown.  Maximum velocity was reach at 16.5 seconds and velocity at impact was 55.81 m/s.  This also assumes zero cosine loses.  I left it this way since it is unknown at this time.

EDIT: Removed chart, will re-post after I fix it.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 05/25/2014 01:28 AM
I modified my simulator for a drop test.  Here is a table of what I found.  This includes drag calculated into the drop.  I ran it at 1/10th second until 1,000 meters and then 1/100th second until touchdown.  Maximum velocity was reach at 16.5 seconds and velocity at impact was 55.81 m/s.  This also assumes zero cosine loses.  I left it this way since it is unknown at this time.
Very cool! Thanks for sharing! Even the 7Gs don't sound quite so bad in an emergency situation of sorts.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 05/25/2014 01:36 AM
If terminal velocity near sea level is only 70m/s (250kph/160mph), the low power stopping would be very mild.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Comga on 05/25/2014 02:04 AM
I modified my simulator for a drop test.  Here is a table of what I found.  This includes drag calculated into the drop.  I ran it at 1/10th second until 1,000 meters and then 1/100th second until touchdown.  Maximum velocity was reach at 16.5 seconds and velocity at impact was 55.81 m/s.  This also assumes zero cosine loses.  I left it this way since it is unknown at this time.

Nice
Your table has terminal velocity of just over 70 m/s.
I could put that into my simple spreadsheet, however much less they are than your simulations.
My point was that the testing could start with high ignition and low thrust and build to a last second burst, the BPL.
Your table just has "high" at around 200 m and not much more than 3 seconds to impact. The 5 g scenario has ignition at 0.56 seconds before impact.  That's hairy, even with no one on board.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: modemeagle on 05/25/2014 01:20 PM
My table had the maximum velocity reached during the fall while my post lists speed at impact without assistance.  My simulator also estimated a 4 meter deep crater but that is probably not realistic.

Edit: Added Graph Attachment
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meadows.st on 05/25/2014 05:32 PM
I modified my simulator for a drop test.  Here is a table of what I found.  This includes drag calculated into the drop.  I ran it at 1/10th second until 1,000 meters and then 1/100th second until touchdown.  Maximum velocity was reach at 16.5 seconds and velocity at impact was 55.81 m/s.  This also assumes zero cosine loses.  I left it this way since it is unknown at this time.

Nice
Your table has terminal velocity of just over 70 m/s.
I could put that into my simple spreadsheet, however much less they are than your simulations.
My point was that the testing could start with high ignition and low thrust and build to a last second burst, the BPL.
Your table just has "high" at around 200 m and not much more than 3 seconds to impact. The 5 g scenario has ignition at 0.56 seconds before impact.  That's hairy, even with no one on board.

ME, your Sim results look reasonable and certainly bound the solution space.  I agree with Comga that the BPL and max thrust doesn't make sense since in such a scenario, there would not be any room for reacting to an engine out scenario, however, 7 g's is survivable as a worst case scenario.

On the other hand, it looks like the altitude at engine on would be quite low <200m (I know this is only a10,000 ft drop) if thrust is only 20% so if something goes wrong, there is very little time for the software to react. Therefore I am left with the working hypothesis that the craft will use pulsed, short,  high thrust bursts to result in an average thrust as suggested up thread. This approach would also allow much higher altitude lighting of the SDs (and fewer Brown Pants for all involved).
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 05/25/2014 06:33 PM
What if the trunk remains attached for these landings? Weight maybe as much as doubled, terminal velocity higher, burn times longer due to both extra mass and higher initial velocities.  This might get us up toward those 5 second burns in the FAA doc.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: go4mars on 05/25/2014 06:48 PM
[quote autho 7 g's is survivable as a worst case scenario.

On the other hand, it looks like the altitude at engine on would be quite low <200m (I know this is only a10,000 ft drop) if thrust is only 20% so if something goes wrong, there is very little time for the software to react. Therefore I am left with the working hypothesis that the craft will use pulsed, short,  high thrust bursts to result in an average thrust as suggested up thread. This approach would also allow much higher altitude lighting of the SDs (and fewer Brown Pants for all involved).
People pay $ to experience a transient 7 g's. 

Pulsing from higher up would be much less efficient (more gravity losses). 

Baseline for Red Dragon is 7 g's.

The BPL should be as low as reasonably possible from an efficiency standpoint.

Trunk might be crumple zone for off-nominal events.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: hrissan on 05/25/2014 07:22 PM
My table had the maximum velocity reached during the fall while my post lists speed at impact without assistance.  My simulator also estimated a 4 meter deep crater but that is probably not realistic.

Edit: Added Graph Attachment
What is interesting - how much propellant required for 50%, 75% and 100% thrust landing? Some difference due to different gravity losses, some to worse ISP.

Nominal 75% thrust allows losing pair of SDs anytime, 50% thrust allows losing two pairs of SDs anytime!

If we know required propellant difference, we can guess the SpaceX decision.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Kaputnik on 05/25/2014 11:13 PM
Would anyone like to hazard a guess at how Dragon will transition from lifting entry, using roll to control lift, to a non rotational final approach?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: modemeagle on 05/26/2014 12:53 AM
I am going to do my chart again as I did more work on the equations, which is going to effect the results. 

Here is a possible nominal profile with ignition at ~ 1,000 meters at 10% thrust with an increase to 20% for the final stop.  This should allow plenty of time to check operation of the Super Draco engines and shutdown any that are not up to par.  I think this also shows that very low thrust is needed for the final brake and touchdown.  Starting the 10% thrust later and 20% sooner will use less propellant due to gravity loses.

I suspect the excess delta-v remaining will be used up while dropping the horizontal velocity.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Comga on 05/26/2014 01:08 AM
I am going to do my chart again as I did more work on the equations, which is going to effect the results. 

Here is a possible nominal profile with ignition at ~ 1,000 meters at 10% thrust with an increase to 20% for the final stop.  This should allow plenty of time to check operation of the Super Draco engines and shutdown any that are not up to par.  I think this also shows that very low thrust is needed for the final brake and touchdown.  Starting the 10% thrust later and 20% sooner will use less propellant due to gravity loses.

I suspect the excess delta-v remaining will be used up while dropping the horizontal velocity.

Very very good.

And as my simple calculations showed, the higher gravity losses from the higher altitude, lower force ignition, only result in a slight increase in fuel over the BPL ignition with less than two seconds to impact.

"Early" ignition, at 1000 m or more altitude, might also be necessary, including the gravity losses, to allow for low force, minimum fuel, steering to the designated landing pad.

PS Your initial post on this had both maximum velocity of something like 65 m/sec and "Terminal Velocity" of 70.45 m/sec.  I assumed that was the velocity at impact if the engines never fired, the case producing "568 g's". :P

PPS: Could your simulation include a divert maneuver to cover, say, a kilometer of lateral distance?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lar on 05/26/2014 01:34 AM
Awesome sim, Modemeagle!  While we're tossing requests at you can you revisit the "zero cosine losses" assumption? I think that one's a bit suspect. The thrusters are going to be angled at least 10 degrees if not more, we all think... That's not a LOT of loss but it should change the answers a bit.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meadows.st on 05/26/2014 01:37 AM
[quote autho 7 g's is survivable as a worst case scenario.

On the other hand, it looks like the altitude at engine on would be quite low <200m (I know this is only a10,000 ft drop) if thrust is only 20% so if something goes wrong, there is very little time for the software to react. Therefore I am left with the working hypothesis that the craft will use pulsed, short,  high thrust bursts to result in an average thrust as suggested up thread. This approach would also allow much higher altitude lighting of the SDs (and fewer Brown Pants for all involved).
People pay $ to experience a transient 7 g's. 

Pulsing from higher up would be much less efficient (more gravity losses). 

Baseline for Red Dragon is 7 g's.

The BPL should be as low as reasonably possible from an efficiency standpoint.

Trunk might be crumple zone for off-nominal events.

re: Red Dragon, 7 g's sounds high but survivable.  Can you provide a link for those specs please? 

I understand the efficiency issue in terms of using as much "free" drag delta-v as possible but what I don't know is what would the effect (on ISP) be of short (80% to 100% thrust) bursts?  I suspect there will be a trade-off of efficiency and safety.

A planned 7 g's of extended deceleration might be OK for a healthy adult that hasn't been in zero g for an extended period of time but what about one that has had an extended duration stay on the ISS or time on Mars followed by a return trip?  Is there anyone on this thread in the medical field that can comment on high g's after extended periods in low (Mars) and micro-gravity?  Is there any data from MIR on this? I am only basing my comments on what I have observed with the astronauts/cosmonauts being removed from Soyuz and treated very gingerly upon removal and what I have read about muscle/bone mass loss while in micro-gravity.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Comga on 05/26/2014 03:58 AM
[snip]
I understand the efficiency issue in terms of using as much "free" drag delta-v as possible but...
[snip]
The real efficiency issue is not getting as much "free drag delta-v as possible", but in avoiding gravity losses.

Reduction to the absurd:  If the capsule hits zero velocity at some elevated altitude, then it has to do an additional burn to stop after it starts falling again.  That's a gravity loss.

Every additional second the capsule spends off the ground is one second times one g of acceleration needed from the engines.   So the most fuel efficient burn is the shortest, which translates to high acceleration, low altitude.  It's just not the most comfortable, reassuring, or most flexible if something goes wrong.  The goal is to get all of those things without greatly increasing the amount of fuel needed.

Quote
but what I don't know is what would the effect (on ISP) be of short (80% to 100% thrust) bursts?

As for short bursts, it was seen that the Dragon departs from the ISS using series (something like seven and twelve) short bursts from pairs of Dracos.  It would be interesting to know why that's preferable.  Perhaps for very small delta V maneuvers any potential loss of efficiency is not important, if one occurs.  But pulses are preferred under some circumstances.

I just wouldn't want to pulse-width-modulate a 10g system to get less by pulsing on and off. :P
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meadows.st on 05/26/2014 05:07 AM
[snip]
I understand the efficiency issue in terms of using as much "free" drag delta-v as possible but...
[snip]
The real efficiency issue is not getting as much "free drag delta-v as possible", but in avoiding gravity losses.

Reduction to the absurd:  If the capsule hits zero velocity at some elevated altitude, then it has to do an additional burn to stop after it starts falling again.  That's a gravity loss.

Every additional second the capsule spends off the ground is one second times one g of acceleration needed from the engines.   So the most fuel efficient burn is the shortest, which translates to high acceleration, low altitude.  It's just not the most comfortable, reassuring, or most flexible if something goes wrong.  The goal is to get all of those things without greatly increasing the amount of fuel needed.
<snip>

Fair enough.

I understand the gravity loss; what I was talking about was the net (downwards) acceleration (gravity - drag) that must be counteracted by the SDs (only the drag is free).  If the craft slows down too early, the net deceleration required will be larger (more inefficient) - the most efficient method, as you say is not the safest (I think that is true for most/all low/zero margin activities) the trick is going to be finding an acceptable risk/efficiency ratio.  (IANARS and I don't know how reliable the systems) The pulse-width modulation approach was just a question related to efficiency:risk ratio vs., say 25% or 50% (can the SDs throttle this low?) started early (for safety) but I guess that is the question that everyone is trying to answer.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 05/26/2014 05:32 AM
This is my uneducated guess:

Do a test fire at an altitude where it is still safe to deploy parachutes if the engines fail. Probably two short bursts of the two largely independend sets of four engines. Decide if it is ok to go for powered landing if one of the two sets does not perform or both sets have to work for redundancy at that point. If necessary go for (thrust assisted) parachute landing.

If the engines are ok at that point it is very very likely they will fire successfully again a few seconds later for the landing burn. If the available fuel allows it go for a 3g landing. 3g for a few seconds should not be too harsh even for sick or injured persons.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: TrevorMonty on 05/26/2014 09:10 AM
This is my uneducated guess:

Do a test fire at an altitude where it is still safe to deploy parachutes if the engines fail. Probably two short bursts of the two largely independend sets of four engines. Decide if it is ok to go for powered landing if one of the two sets does not perform or both sets have to work for redundancy at that point. If necessary go for (thrust assisted) parachute landing.

If the engines are ok at that point it is very very likely they will fire successfully again a few seconds later for the landing burn.

My thoughts exactly.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: mikes on 05/26/2014 09:39 AM
Your table has terminal velocity of just over 70 m/s.

To put that into context, the STS orbiters (before they flared for landing) had a descent rate of 10,000fpm which is 50m/s

http://www.century-of-flight.net/Aviation%20history/space/Space%20Shuttle%20history.htm
Title: Re: SpaceX DragonFly Discussion Thread
Post by: douglas100 on 05/26/2014 10:37 AM
What if the trunk remains attached for these landings? Weight maybe as much as doubled, terminal velocity higher, burn times longer due to both extra mass and higher initial velocities.  This might get us up toward those 5 second burns in the FAA doc.

I don't think that's going to happen if the DragonFly tests are designed to support Dragon 2. They may launch with a trunk attached to test behaviour of the combined vehicle for an abort scenario but it would separate before landing. I think the speculation about the trunk remaining attached throughout the flight is a misinterpretation. A vehicle with an integrated trunk (it would really be a payload bay) would be essentially a brand new vehicle and I think such a thing would be further down the line. I now await The Big Reveal to see if I'm wrong!  :)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Jcc on 05/26/2014 10:52 AM
A permanently attached trunk would defeat the purpose of having a trunk, in that it would need to be closed off in the back with a heat shield, then you would not be able to use it for external cargo. Besides, the aerodynamics for EDL would be all wrong, and furthermore, there would be a need for an adapter to attach it to the second stage, as the trunk fulfills that purpose now, being an open cylinder.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: clongton on 05/26/2014 11:02 AM
I agree that a permanently attached trunk is unlikely but for a different reason. Dragon is passively stable during re-entry, meaning that its CG is located low enough in the structure that it will always passively present its heatshield first at the first sign of atmosphere resistance. That dynamic completely flips if a now-empty trunk is still attached at re-entry. With the CG now substantially higher in the structure, Dragon will passively flip around and re-enter nose first, providing a bad day for everyone aboard.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 05/26/2014 12:24 PM
I agree that a permanently attached trunk is unlikely but for a different reason. Dragon is passively stable during re-entry, meaning that its CG is located low enough in the structure that it will always passively present its heatshield first at the first sign of atmosphere resistance. That dynamic completely flips if a now-empty trunk is still attached at re-entry. With the CG now substantially higher in the structure, Dragon will passively flip around and re-enter nose first, providing a bad day for everyone aboard.
Good point. Pretty much kills the idea.
Thanks.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: fatjohn1408 on 05/26/2014 01:22 PM
Freefall, 5 sec burn at the last moment, soft touchdown.

Whoever will ultimately ride aboard that kind of flight profile (obviously not during these tests) is a brave man :)

Can anyone model the G-Force curve on that?  It sounds like a rough ride.

If anyone can guess the terminal velocity of the capsule, it should be easy to calculate. If the G-load is evenly spread over 5 seconds, it might not be too bad.

For a very first order estimate I get a terminal velocity of ~150 m/s given a total mass of 17,000 lbs (dry mass plus 3000 lbs of fuel) and a drag coefficient of 0.8.

A 5 second burn to brake from 150 m/s would result in an average of ~3Gs of deceleration.

But assuming you try to decelerate while traveling toward the ground (I know crazy assumption huh) you need another G to counteract gravity. So astronaut Brown Pants will experience 4G.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: go4mars on 05/26/2014 02:19 PM
I agree that a permanently attached trunk is unlikely but for a different reason. Dragon is passively stable during re-entry, meaning that its CG is located low enough in the structure that it will always passively present its heatshield first at the first sign of atmosphere resistance. That dynamic completely flips if a now-empty trunk is still attached at re-entry. With the CG now substantially higher in the structure, Dragon will passively flip around and re-enter nose first, providing a bad day for everyone aboard.
Good point. Pretty much kills the idea.
Thanks.
I'm not sure it's been fully dismissed.

1) CG issue is only what it is designed to be.  Why assume the trunk would be empty? Perhaps the more dense cargo would preferentially be stowed there (potentially removes center of grav issue).
2) Redundancy.  Potential to re-enter dragon & trunk either attached or unattached if designed to (ideally some emergency way to move from one to the other if need arises -(anyone remember that scene from "Fortress 2"?)
3) Redundancy.  If both pieces have superdracos and tanks, and they enter together, a random engine out becomes less relevant, and the trunk can become the crumple zone if underperformance is too significant.
4) Staging.  Trunk could be used as an extra stage in certain circumstances (either reusably or not). 

Obviously I'm not talking about a slight modification of current trunk.  This would be a new phenotype.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: douglas100 on 05/26/2014 02:45 PM

....Obviously I'm not talking about a slight modification of current trunk.  This would be a new phenotype.

Indeed. This is complete speculation with little evidence connecting it to what we know at the moment about the DragonFly tests.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Coastal Ron on 05/26/2014 02:55 PM
I agree that a permanently attached trunk is unlikely but for a different reason. Dragon is passively stable during re-entry, meaning that its CG is located low enough in the structure that it will always passively present its heatshield first at the first sign of atmosphere resistance. That dynamic completely flips if a now-empty trunk is still attached at re-entry. With the CG now substantially higher in the structure, Dragon will passively flip around and re-enter nose first, providing a bad day for everyone aboard.
Good point. Pretty much kills the idea.
Thanks.
I'm not sure it's been fully dismissed.

1) CG issue is only what it is designed to be.  Why assume the trunk would be empty? Perhaps the more dense cargo would preferentially be stowed there (potentially removes center of grav issue).

I'm not an engineer, but keeping the trunk attached while the Dragon is returning to Earth does not look like a good idea.

With the attached trunk, I would imagine the aerodynamics of the whole assembly change.  Whereas the capsule by itself would naturally orient it's heatshield to the direction of travel, if the trunk is attached it will have wind resistance and a different CG, and want to flip around and point the capsule into the wind like an arrow - which is wrong for many reasons.

Unless it separates and has it's own re-entry system, I would imagine the trunk is disposable.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 05/26/2014 04:00 PM

....Obviously I'm not talking about a slight modification of current trunk.  This would be a new phenotype.

Indeed. This is complete speculation with little evidence connecting it to what we know at the moment about the DragonFly tests.

Not complete...  The FAA license application(impact statement) talked about landing with trunk -- that's what got me thinking along this path. A new phenotype would be to have 'trunk' on crew Dragon/DragonFly be shortened to maybe half of original trunk length and be fitted out with battery, larger fuel tanks, and any other liquid cargo like water or fuel for ISS.  Adding the heat shield to its bottom along with landing legs will move c/g significantly lower. Pressure volume with astros will be fairly fluffy, so still might work.  How low does the c/g need to go to reestablish passive stability on reentry?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Geron on 05/26/2014 04:05 PM
It still has solar panels they just r not deployed. They wrap around trunk
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Joffan on 05/26/2014 05:13 PM
The FAA license application(impact statement) talked about landing with trunk -- that's what got me thinking along this path.

It doesn't actually talk about landing with the trunk. Here's what the draft EA actually said about the trunk:
Quote
The DragonFly RLV is the Dragon capsule with an integrated trunk (which may or may not be attached during a DragonFly operation) and up to four steel landing legs.
There is also a picture of the Dragon + Trunk in processing which also uses the term "integrated".

The text in brackets means that the trunk is detachable. So speculation about a composite vehicle that extends the Dragon to include the trunk seems unfounded.

"Attached during an operation" doesn't necessarily mean that it stays attached for the entire duration of the flight, either.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: modemeagle on 05/26/2014 08:57 PM
I ran the simulation again and made a new chart.  This attachment includes graphs and data for 0% and 20-100% thrust profiles.  I am not running a cosine loss for 10 degrees since it would only be a 1.5% difference which is less than my current error rate.

If I can locate my dragon reentry simulation then I will try to run a more realistic simulation with horizontal velocity to cancel out.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Jcc on 05/26/2014 09:10 PM
I agree that a permanently attached trunk is unlikely but for a different reason. Dragon is passively stable during re-entry, meaning that its CG is located low enough in the structure that it will always passively present its heatshield first at the first sign of atmosphere resistance. That dynamic completely flips if a now-empty trunk is still attached at re-entry. With the CG now substantially higher in the structure, Dragon will passively flip around and re-enter nose first, providing a bad day for everyone aboard.

I recall a similar thing happened to a Soyuz, when the service module failed to detach. It reentered nose first until whatever was holding the SM on scorched and burned off, then the capsule could reorientate, it landed normally and the crew survived.
http://www.spacesafetymagazine.com/2011/10/29/soyuz-5-multiply-reentry-failures-endanger-cosmonaut/
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Joffan on 05/26/2014 09:11 PM
I ran the simulation again and made a new chart.  This attachment includes graphs and data for 0% and 20-100% thrust profiles.  I am not running a cosine loss for 10 degrees since it would only be a 1.5% difference which is less than my current error rate.

If I can locate my dragon reentry simulation then I will try to run a more realistic simulation with horizontal velocity to cancel out.

Haha... I suppose 8g for just under a second (the 100% profile)  is still better than crashing, but hopefully it's not nominal. Interesting that even the gentle 20% 2.5g solution has ignition below 200m.

And hopefully the touchdown g-force would be eliminated with an active control loop, at least on the lower throttle options.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 05/27/2014 06:49 AM
The amount of fuel on board will be determined by abort needs. Subtract from that what is needed for on orbit maneuvers then you get what you have for landing. As you will want to burn most of that fuel before touchdown to reduce hypergolic fuel load the spare fuel will determine, how soft you can land.

Title: Re: SpaceX DragonFly Discussion Thread
Post by: Chris Bergin on 05/27/2014 01:14 PM
Converted and edited the first post to make this a DragonFly discussion thread (remember to keep it on DragonFly)

Here's our article on this via Chris Gebhardt. Yes, we know we used some regular Dragon propulsive landing images, as that's all there is out there, but Chris did a great job with the documentation and overview.

http://www.nasaspaceflight.com/2014/05/faa-moves-closer-spacex-permit-dragonfly-testing/

This will be our own launch pad for approaching SpaceX for more.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: yg1968 on 05/27/2014 01:51 PM
Converted and edited the first post to make this a DragonFly discussion thread (remember to keep it on DragonFly)

Here's our article on this via Chris Gebhardt. Yes, we know we used some regular Dragon propulsive landing images, as that's all there is out there, but Chris did a great job with the documentation and overview.

http://www.nasaspaceflight.com/2014/05/faa-moves-closer-spacex-permit-dragonfly-testing/

This will be our own launch pad for approaching SpaceX for more.

I like the article. Very comprehensive.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lar on 05/27/2014 03:21 PM
Converted and edited the first post to make this a DragonFly discussion thread (remember to keep it on DragonFly)

Here's our article on this via Chris Gebhardt. Yes, we know we used some regular Dragon propulsive landing images, as that's all there is out there, but Chris did a great job with the documentation and overview.

http://www.nasaspaceflight.com/2014/05/faa-moves-closer-spacex-permit-dragonfly-testing/

This will be our own launch pad for approaching SpaceX for more.

I like the article. Very comprehensive.

^this

Remember peeps... share share share! Read the article, then post about it on your social media feeds... every share increases space literacy which is good for everyone.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Comga on 05/27/2014 04:09 PM
I ran the simulation again and made a new chart.  This attachment includes graphs and data for 0% and 20-100% thrust profiles.  I am not running a cosine loss for 10 degrees since it would only be a 1.5% difference which is less than my current error rate.

If I can locate my dragon reentry simulation then I will try to run a more realistic simulation with horizontal velocity to cancel out.

Better and better!

Can we take it that "Impact G", which varies randomly between cases, is just the imprecision of the simulation with some assumed stopping distance into the dirt?   That would make Joffan's question moot, as with higher precision, and the thrust controlled like Grasshopper or F9-Dev1, it's always zero altitude, zero velocity, one g.
 
If the "Final G" is multiplied by the "Total Burn (s)"  and gravitational acceleration (9.8 m/s^2) is added to the "Reserve Delta V (m/s)" one gets close to a constant 398 m/s pre-ignition fuel load.
 
Why doesn't averaging with the "Initial G" help?  Does your simulation settle down to the "Final G" quickly rather than building to it linearly?
 
That said, using 20% thrust rather than 100% thrust almost doubles the fuel used but only goes from using 16% of the fuel to 28%.  That seems to be a small price to pay for the additional 3 seconds and 160 m standoff from impact. :D
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 05/27/2014 04:57 PM
My understanding of the changing g-load:

The thrust remains the same but with deceleration the g-load component from drag is reduced so the resulting g-load experienced by the passengers decreases.

Is that understanding correct or am I wrong and the changing g-load has another source?

Title: Re: SpaceX DragonFly Discussion Thread
Post by: Joffan on 05/27/2014 05:12 PM

Can we take it that "Impact G", which varies randomly between cases, is just the imprecision of the simulation with some assumed stopping distance into the dirt?   That would make Joffan's question moot, as with higher precision, and the thrust controlled like Grasshopper or F9-Dev1, it's always zero altitude, zero velocity, one g.

Yeah, that's what I meant by "active control", which might be needed also for wind shear (although one advantage of BPL is that there isn't much time for the wind to have large effects :) )

My understanding of the changing g-load:

The thrust remains the same but with deceleration the g-load component from drag is reduced so the resulting g-load experienced by the passengers decreases.

Is that understanding correct or am I wrong and the changing g-load has another source?

looks right; the reduction is always about 1g, which corresponds to the terminal velocity drag.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: modemeagle on 05/27/2014 11:02 PM
The drop in g-force is completely due to the drop in drag as the vehicle slows down.  I am not sure how the plume will effect the drag on the shied, but I assume zero unless I get information of the contrary.  The engines shut down when one of two things occur; the vehicle reaches zero altitude or vertical velocity equals zero.  I adjust the ignition time to minimize the final g-force and it either shoots for shutdown just above the ground, less than 1 meter, or with minimal velocity hitting the ground.  The final g could be adjusted with throttling and shock absorbers.  Currently it throttles down once velocity is below 9.8 m/s but it is automatic and not to adjust the final touchdown.  This is actually part of the changes I made for the impact.  I simulate impact with the ground by changing the atmospheric density to 1470 (density of soft Earth) and removing the gravity pull from acceleration (otherwise it continues to sink since I don't simulate increasing density as the ground would be compacted)

The simulation was written for orbital insertion and needed changes for powered descent.  I spent over a year developing my guidance algorithm for orbital insertion and I could probably do the same for the descent throttling if I could find the time. 

I think the 10%/20% simulation is the closest to real world since it has an early start to verify thruster operation and fine tune horizontal velocity before the final acceleration for touchdown.

I will see if I can run a deorbit burn and simulate a powered landing.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: go4mars on 05/28/2014 04:57 AM
Baseline for Red Dragon is 7 g's.
re: Red Dragon, 7 g's... Can you provide a link for those specs please?
I'm sure I read it in an official looking presentation/document somewhere but can't seem to quickly find it.  adrianwyard in Post #768 on the first Red Dragon thread refers to a video presentation (presentation links seem to be posted in #766 - same thread). 
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Micahgtb on 05/28/2014 05:10 AM
https://www.youtube.com/watch?v=lIGVi_rMFGw

Is this throttling, or is it just a consequence of the firing? It looks like throttling to me. Thoughts?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Joffan on 05/28/2014 06:16 AM

Is this throttling, or is it just a consequence of the firing? It looks like throttling to me. Thoughts?

I agree - it looks like a test for range of throttling followed by speed of throttling. And that throttling rate looked good enough, very solid, for a control system to come in to land with.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: docmordrid on 05/28/2014 06:22 AM
And the email that linked to that video conforms it's 3D printed using Inconel. 16,000 lbf.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Llian Rhydderch on 05/28/2014 01:02 PM
And the email that linked to that video conforms it's 3D printed using Inconel. 16,000 lbf.

Yeah, this is being discussed on the SuperDraco engine thread. 

This appears to be new news, to me at least:

Quote
The SuperDraco engine chamber is manufactured using state-of-the-art direct metal laser sintering (DMLS), otherwise known as 3D printing.

I was aware that they had test printed a combustion chamber in inconel using 3D printing last year, but that was long after the first video had been released of a full-duration-burn SuperDraco engine firing.

I was not aware that the 3D printed combustion chamber would be the standard part for the standard SuperDraco engine in production.  Cool.  8)

So now we can see some serious 3D-printing metal manufacturing equipment being sent to Mars on the early MCTs.   :o

Had SpaceX previously revealed that the 3D-printing technique for the engine combustion chambers would be their standard manufacturing technique, rather than a one-off test of a novel new additive manufacturing technology for metal parts?

Looks like DragonFly testing will also get some considerable additional operational time on these engines, helping to further prove them out before DragonRider missions.

Title: Re: SpaceX DragonFly Discussion Thread
Post by: Comga on 05/30/2014 03:24 AM
From over in the LIVE: Dragon V2 Revealed thread:
26 second braking burn, with all eight engines firing.  Either they are throttling to below 10% or there is some other detail missing or inaccurately portrayed.  This is discussed in the Reusable Rockets thread.
...
But man! Is that cool or what?
I will go back and try to calculate the throttle level for 26 seconds, assuming constant thrust, but it's pretty low.  Of course, modemeagle will do a better job.  Then we can form opinions on whether this is accurate or "artistic license".
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cscott on 05/30/2014 04:22 AM
I will go back and try to calculate the throttle level for 26 seconds, assuming constant thrust, but it's pretty low.  Of course, modemeagle will do a better job.  Then we can form opinions on whether this is accurate or "artistic license".

One consideration is probably that they need to test the superdracos at an altitude sufficient for deploying the parachute, and they probably don't want to turn them off once they've tested that they work.  That's going to make for a long burn.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: aero on 05/30/2014 04:50 AM
I will go back and try to calculate the throttle level for 26 seconds, assuming constant thrust, but it's pretty low.  Of course, modemeagle will do a better job.  Then we can form opinions on whether this is accurate or "artistic license".

One consideration is probably that they need to test the superdracos at an altitude sufficient for deploying the parachute, and they probably don't want to turn them off once they've tested that they work.  That's going to make for a long burn.

Well - What? Its 120,000 lbs for 5 seconds full throttle isn't it? So cut the fuel flow by 5 and increase the time by 5. That gives 25 seconds burn at 20%, or 24,000 lbs. thrust on average. When they light off, aero drag is still strong so they could be throttled down below 20% initially, then throttled up above 20% before touchdown since drag isn't very helpful at soft landing speed and they really, really do want to stop the descent before, or at the surface.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: dglow on 05/30/2014 04:51 AM
From over in the LIVE: Dragon V2 Revealed thread:
26 second braking burn, with all eight engines firing.  Either they are throttling to below 10% or there is some other detail missing or inaccurately portrayed.  This is discussed in the Reusable Rockets thread.
...
But man! Is that cool or what?
I will go back and try to calculate the throttle level for 26 seconds, assuming constant thrust, but it's pretty low.  Of course, modemeagle will do a better job.  Then we can form opinions on whether this is accurate or "artistic license".

26 seconds of video time, or real time? They aren't the same animal.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: mme on 05/30/2014 04:57 AM
26 second braking burn, with all eight engines firing.  ...
...
I will go back and try to calculate the throttle level for 26 seconds, assuming constant thrust, but it's pretty low.  Of course, modemeagle will do a better job.  Then we can form opinions on whether this is accurate or "artistic license".

26 seconds of video time, or real time? They aren't the same animal.
Yeah, might as well run the numbers but I wouldn't put too much stock in the animation for those sorts of details.  It could just as easily be that the video looks too scary without the engines on. :)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Comga on 05/30/2014 04:59 AM
So modemeagle posted this discussion with his simulation of a 10% to 20% thrust profile

I am going to do my chart again as I did more work on the equations, which is going to effect the results. 

Here is a possible nominal profile with ignition at ~ 1,000 meters at 10% thrust with an increase to 20% for the final stop.  This should allow plenty of time to check operation of the Super Draco engines and shutdown any that are not up to par.  I think this also shows that very low thrust is needed for the final brake and touchdown.  Starting the 10% thrust later and 20% sooner will use less propellant due to gravity loses.

I suspect the excess delta-v remaining will be used up while dropping the horizontal velocity.

The duration is ~17.6 sec.
As modemeagle found the velocity never hits zero at 10% the remainder of the 26 seconds shown in tonight's video must be more 10% thrusting, pre-testing the engines with time to deploy the chutes, targeting for landing on the pad "like a copter" and generally reducing the BPL factor.


Or it could be "artistic license" in the video, like dglow and mme said.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cscott on 05/30/2014 05:26 AM
Here is a possible nominal profile with ignition at ~ 1,000 meters at 10% thrust with an increase to 20% for

FWIW, Elon said, "When Dragon reaches a particular altitude, a few miles before landing, it will test and verify all the engines are working and then proceed to a propulsive landing." (See Chris' article for the quote.)  So a "few miles" is a "few" times higher than 1,000 meters.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: aero on 05/30/2014 05:42 AM
Here is a possible nominal profile with ignition at ~ 1,000 meters at 10% thrust with an increase to 20% for

FWIW, Elon said, "When Dragon reaches a particular altitude, a few miles before landing, it will test and verify all the engines are working and then proceed to a propulsive landing." (See Chris' article for the quote.)  So a "few miles" is a "few" times higher than 1,000 meters.

For the sake of discussion let's say that the Dragon is dropping at 300 m/s at a "few miles" altitude. With uniform deceleration it would average 150 m/s from a "few miles" altitude to ground zero. Now, 25 seconds at 150 m/s is 3750 meters, equals 2.3 miles. So my guess is that a "few miles" = 2.3 miles. It's more than a couple and less than several.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: wolfpack on 05/30/2014 01:47 PM
OK, a couple of things that I just can't believe. Real spacecraft designers please opine if you will!

1. No switchguards around those center console buttons?

2. A handle on the outside of the hatch?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sghill on 05/30/2014 01:52 PM
Regarding the landing burn height,  if we use the video for clues (yes, I know it's not scientific), the burn begins at about 20 miles, not two miles.

Here's a Google Earth comparison from 18 miles with the video when KSC comes into view. The engines are already firing before KSC comes into the frame, so the burn begins around 20 miles.

Well above the BPL.  I'm pleased!

That could all be artistic license on the part of the animators, but it's the only solid thing we have to go on.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Crispy on 05/30/2014 02:19 PM
Here's a Google Earth comparison from 18 miles with the video when KSC comes into view. The engines are already firing before KSC comes into the frame, so the burn begins around 20 miles.

Without knowing the field of view for either camera, that comparison is effectively meaningless, unfortunately.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 05/30/2014 02:26 PM
OK, a couple of things that I just can't believe. Real spacecraft designers please opine if you will!
1. No switchguards around those center console buttons?
I would assume that these buttons are only used in certain situations. There might be some other mechanism that is required to make the active.
Also, I am not concerned about the touch screen. You can program the interface in such a way, that buttons on the screen can not be accidentally pushed (e.g. require a sliding motion followed by a push, or some combination like that).
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars_J on 05/30/2014 04:32 PM
Here's a Google Earth comparison from 18 miles with the video when KSC comes into view. The engines are already firing before KSC comes into the frame, so the burn begins around 20 miles.

Without knowing the field of view for either camera, that comparison is effectively meaningless, unfortunately.

How do you figure?  The land mass would look stretched or shrunken if the field of view differed greatly between the two and it doesn't so the field of view has to be roughly similar.  And since the land looks pretty close to the same in both images, the altitude must also be the same. 

In other words, KSC isn't going to look like that from 2 miles up (versus 20 miles) even with a fisheye lens.

It's a CG rendering. And not a very high fidelity one either. And as someone who does photography, trust me, you cannot make that determination.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Sohl on 05/30/2014 04:38 PM
Or it could be "artistic license" in the video, like dglow and mme said.

I'm firmly in the "lots of artistic license" camp.  Dragon2 will not have enough fuel to burn continuously from the depicted height. 
Title: Re: SpaceX DragonFly Discussion Thread
Post by: RanulfC on 05/30/2014 05:47 PM
Anyone else have the feeling when the "Dragon-2/Trunk" was shown in the video that it would make a really neat sub-orbital hopper?

Randy
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars_J on 05/30/2014 05:49 PM
Why would the trunk be a part of it? It is expendable. I would think a trunk-less Dragon 2 would be a much neater suborbital hopper, even though its range would be just a few miles at best. ;)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: notsorandom on 05/30/2014 05:58 PM
They might also want to stretch out the landing burn so they can fly out any aiming errors they have. Before the engines come on they only way to change the course is to orient the capsule. Which is something that might not give much control compared to having the super dracos on low thrust for a mile or so before they are needed to slow the capsule down.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: RanulfC on 05/30/2014 06:18 PM
Why would the trunk be a part of it? It is expendable. I would think a trunk-less Dragon 2 would be a much neater suborbital hopper, even though its range would be just a few miles at best. ;)

Think= "non-expendable" Trunk with extra propellant etc to provide more performance. Yes I know all the arguments against that for an Orbital vehicle but we'd be talking a "de-rated" D-V2 (possibly a "retired" orbital model??) for short-hop suborbial runs. Trunk-less would be very neat of course but is only a few miles altitude "worth" the trouble?
(Really. To ever hit "gas-and-go" EM/SpaceX is going to have to get away from the current propellant mix. Hmmm, wonder if EM has thought about applying for Federal "Flex-Fuel" incentives on the D-V2? :) )

(To use an older "scale" a friend and I worked out it would be a Class-1 Sub-Orbital, straight-up/straight-down mission mode)

That's why I noted when it "first" showed. Fins, capsule, etc, heck I immediatly thought "That's a Spaceship!" :)

Randy
Title: Re: SpaceX DragonFly Discussion Thread
Post by: RanulfC on 05/30/2014 06:19 PM
They might also want to stretch out the landing burn so they can fly out any aiming errors they have. Before the engines come on they only way to change the course is to orient the capsule. Which is something that might not give much control compared to having the super dracos on low thrust for a mile or so before they are needed to slow the capsule down.

Well there are some other options as well. CG shift for example.
"Everyone lean as far as you can to the left!" :)

Randy
Title: Re: SpaceX DragonFly Discussion Thread
Post by: StephenB on 05/30/2014 07:12 PM
Why would the trunk be a part of it? It is expendable. I would think a trunk-less Dragon 2 would be a much neater suborbital hopper, even though its range would be just a few miles at best. ;)

Think= "non-expendable" Trunk with extra propellant etc to provide more performance. Yes I know all the arguments against that for an Orbital vehicle

Is this an obstacle?: If the fuel is below the nozzles, how does it get from a tank in the trunk against both gravity and the acceleration from the super dracos?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: RanulfC on 05/30/2014 07:37 PM
Is this an obstacle?: If the fuel is below the nozzles, how does it get from a tank in the trunk against both gravity and the acceleration from the super dracos?

The propellants are delivered by high pressure. The point was made that a high-pressure, "seperable" connection system would be problimatical due to the "weak-link" point of the seperation mechanism. This holds "true" with the suggested aplication as well unless there are significant changes to the D-V2/Trunk. But then again that's pretty much what I'm suggesting anyway :)

First of all the (suborbital) D-V2 and trunk don't normally seperate at all during operation, the vehicle being a "Single-Stage-To-Sub-Orbital" vehicle.

Further thought though suggests it might just be "simpler" all around to mount a "standard" D-V2 to a specifically designed and built "trunk-stage" and retain serperate operations capability.

Randy
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Llian Rhydderch on 05/30/2014 08:22 PM
Could we maybe get this thread back to the more narrow scope of the DragonFly test vehicle, flying 30-odd test flights in Texas?   :)

Maybe leave all the Dragon V2 design, CG, animation, altitude of burns on orbital descents, etc. to the threads where those topics are already being discussed.   ::)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: modemeagle on 05/30/2014 10:23 PM
So modemeagle posted this discussion with his simulation of a 10% to 20% thrust profile

I am going to do my chart again as I did more work on the equations, which is going to effect the results. 

Here is a possible nominal profile with ignition at ~ 1,000 meters at 10% thrust with an increase to 20% for the final stop.  This should allow plenty of time to check operation of the Super Draco engines and shutdown any that are not up to par.  I think this also shows that very low thrust is needed for the final brake and touchdown.  Starting the 10% thrust later and 20% sooner will use less propellant due to gravity loses.

I suspect the excess delta-v remaining will be used up while dropping the horizontal velocity.

The duration is ~17.6 sec.
As modemeagle found the velocity never hits zero at 10% the remainder of the 26 seconds shown in tonight's video must be more 10% thrusting, pre-testing the engines with time to deploy the chutes, targeting for landing on the pad "like a copter" and generally reducing the BPL factor.


Or it could be "artistic license" in the video, like dglow and mme said.

Comga,
The actual burn was 32.56 seconds as the 10% burn started at 997 meters and 35.01 seconds from drop.  Shut down was at 67.57 seconds from drop.

I would expect the "test" burn to be higher and sooner, probably higher than 5 km so there is sufficient time for parachutes.  This is only a guess on my part and I have no indications it is correct.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: eriblo on 05/31/2014 12:48 AM
More than 5 km sounds very careful considering that the drop test was at less than half that (8000 feet) :)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: rpapo on 05/31/2014 10:19 AM
More than 5 km sounds very careful considering that the drop test was at less than half that (8000 feet) :)
But the drop test didn't start at terminal velocity either.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: eriblo on 05/31/2014 10:44 AM
More than 5 km sounds very careful considering that the drop test was at less than half that (8000 feet) :)
But the drop test didn't start at terminal velocity either.
True that :) But it did start with a tumbling capsule that fell for at least 5 seconds before being stabilized and slowed by the drogues, so think the difference is less than say 1 km. If they are tumbling out of control at 3.5 km (or 5 km) they have my permission to deploy the drogues ;)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: adrianwyard on 05/31/2014 09:19 PM
While powered landing tests with DragonFly will certainly grab the headlines, based on discussions over in the Dragon V2 Reveal thread it seems to me that parachute land-landing tests will be important too in order to gain confidence in the whole system.

While parachutes are a backup available in case the powered landing is not possible, they present their own challenges, these include:

+ A completely unpowered land landing will be very hard. With hypergolics onboard you do not want those tanks to breach, so verifying the survivability of a hard landing would be a worthwhile test. Note: if some residual Draco/SuperDraco functionality is available this could be used to cushion the touchdown (a la Soyuz).

+ It appears as though Dragon V2 will hang at an angle under the chutes (as did V1) which is best for water impact after a launch abort. But this will mean that during a parachute land landing just one, or possibly two landing struts will need to take the brunt of the impact force. (And again, if some SD power is available it could bring the Dragon to level flight before impact.)

+ Under parachutes the horizontal velocity at landing could be quite high due to crosswinds. While a powered landing can take any crosswinds out, an unpowered parachute landing Dragon will need to be able to skid to a halt. If you're unlucky, the Dragon will already by 'tipped over' in the direction of crosswind travel under the chutes, and so be in danger of tumbling once it hits the ground.

For the prior discussion see here: http://forum.nasaspaceflight.com/index.php?topic=34828.msg1207214#msg1207214

Title: Re: SpaceX DragonFly Discussion Thread
Post by: adrianwyard on 05/31/2014 09:50 PM
I should say that I doubt if any of these concerns will prove to be showstoppers, especially if your goal is simply to survive a crash landing. But ISTM hard landings and/or toppling over are more of a concern for Dragon V2 than other spacecraft because it could have have a substantial amount of hypergolic propellant onboard.

I suppose it may be possible to burn off unneeded propellant when under the chutes, but I doubt if dumping it overboard would be considered...
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Prober on 06/02/2014 10:18 AM
WacoTrib article with a little fresh info;

Grasshopper to DragonFly: SpaceX seeks approval for new McGregor testing  (http://www.wacotrib.com/blogs/joe_science/grasshopper-to-dragonfly-spacex-seeks-approval-for-new-mcgregor-testing/article_11d0c40a-e1f6-11e3-a868-001a4bcf887a.html)

[snip]
According to the FAA report, however, a trunk will be attached to the DragonFly for some of its tests — suggesting that a land landing will allow future flights to bring items back in the trunk as well as the Dragon proper (the trunk would have to be equipped with its own heat shield to survive re-entry, if that were the case).
[snip]

the trunk will be added to test 2nd stage return concepts.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: douglas100 on 06/02/2014 11:15 AM
WacoTrib article with a little fresh info;

Grasshopper to DragonFly: SpaceX seeks approval for new McGregor testing  (http://www.wacotrib.com/blogs/joe_science/grasshopper-to-dragonfly-spacex-seeks-approval-for-new-mcgregor-testing/article_11d0c40a-e1f6-11e3-a868-001a4bcf887a.html)

[snip]
According to the FAA report, however, a trunk will be attached to the DragonFly for some of its tests — suggesting that a land landing will allow future flights to bring items back in the trunk as well as the Dragon proper (the trunk would have to be equipped with its own heat shield to survive re-entry, if that were the case).
[snip]

the trunk will be added to test 2nd stage return concepts.

I don't think so. I think the tests with the trunk will be to simulate abort scenarios. The trunk and its fins are needed for aerodynamic stability at low altitudes.

I think we're reading to much into the mention of the trunk. And I don't think those tests are anything to do with second stage recovery. That's a separate effort.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: InfraNut2 on 06/03/2014 01:41 PM
While powered landing tests with DragonFly will certainly grab the headlines, based on discussions over in the Dragon V2 Reveal thread it seems to me that parachute land-landing tests will be important too in order to gain confidence in the whole system.

While parachutes are a backup available in case the powered landing is not possible, they present their own challenges, these include:

+ A completely unpowered land landing will be very hard. With hypergolics onboard you do not want those tanks to breach, so verifying the survivability of a hard landing would be a worthwhile test. Note: if some residual Draco/SuperDraco functionality is available this could be used to cushion the touchdown (a la Soyuz).

+ It appears as though Dragon V2 will hang at an angle under the chutes (as did V1) which is best for water impact after a launch abort. But this will mean that during a parachute land landing just one, or possibly two landing struts will need to take the brunt of the impact force. (And again, if some SD power is available it could bring the Dragon to level flight before impact.)

+ Under parachutes the horizontal velocity at landing could be quite high due to crosswinds. While a powered landing can take any crosswinds out, an unpowered parachute landing Dragon will need to be able to skid to a halt. If you're unlucky, the Dragon will already by 'tipped over' in the direction of crosswind travel under the chutes, and so be in danger of tumbling once it hits the ground.

For the prior discussion see here: http://forum.nasaspaceflight.com/index.php?topic=34828.msg1207214#msg1207214

Agree, but will add a few points:

I think SpaceX will do similarly to what you suggest and switch to a soft propulsive landing for the last seconds (like some of the DragonFly tests) if/when the error triggering use of parachutes does not introduce significant extra risk for soft landing vs parachutes only. For example a single SD malfunction would only reduce redundancy, not eliminate it.

IIRC the Dragon has a lower terminal velocity under parachutes than Soyuz so that reduces the impact somewhat when thrusters are not used.

The rear legs of the Dragon V2 are placed closer together so that the initial load will almost always be shared between 2 legs. The shock absorption in the legs presumably replace the function of the shock absorbers under the Soyuz Kazbekh seats, since I saw no seat shock absorbers in DV2.

However, I am not sure that the mentioned DV2 features are effective enough to match the effect of the soyuz retro-rockets too, when doing a parachute-only landing. Maybe they will also add some seat shock absorbers under the DV2 seats later, so that combined with the leg shock absorbers, an emergency parachute-only land landing will be no worse than a Soyuz landing.

So, yes, the parachutes-only landings will probably be quite rough if/when they happen on land. But they should presumably be very rare based on the ample redundancy of thrusters etc.

Additionally. it would also be possible to direct most parachute-only landings to land in the sea if the landing site placement and landing trajectories are designed with that in mind.

edits: many, but all before next message
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cscott on 06/03/2014 03:05 PM
IIRC the Dragon has a lower terminal velocity under parachutes than Soyuz so that reduces the impact somewhat when thrusters are not used.

The rear legs of the Dragon V2 are placed closer together so that the initial load will almost always be shared between 2 legs. The shock absorption in the legs presumably replace the function of the shock absorbers under the Soyuz Kazbekh seats, since I saw no seat shock absorbers in DV2.

However, I am not sure that the mentioned DV2 features are effective enough to match the effect of the soyuz retro-rockets too, when doing a parachute-only landing. Maybe they will also add some seat shock absorbers under the DV2 seats later, so that combined with the leg shock absorbers, an emergency parachute-only land landing will be no worse than a Soyuz landing.

Having just watched a video of the Soyuz landing as well as listening to Musk talk about Dragon V2, it seems that another big difference is that Soyuz trims its parachutes so that it is level when it hits the ground.  This presumably is related to how its unthrottled retro-rockets work, etc.

On the other hand, from the video we've seen of the Dragon v2 parachute test, plus the comment Musk made about the pair of legs close together so that they impact first and take the load...  I suspect that dragon will contact the ground at an angle, which has the potential to spread out the deceleration over a long time period.  Instead of hitting the ground flat all at once, you'll have one side hit, compress legs, then the other side hit and compress legs.  That should roughly double the time of the deceleration event, which will cut the acceleration in half. (For a given velocity at touch down, v ~= at.)

It also looks to me like the legs have a longer travel distance than the Soyuz seat shock absorbers (the Soyuz is so cramped inside!).  Doubling the travel distance also cuts the acceleration in half (d ~= vt, so doubling the distance doubles the time available to decelerate, which halves the acceleration required).

And then there's the fact that dragon is said to have a lower terminal velocity under parachutes than soyuz.  (It has three parachutes, presumably only needing two to land safely, compared to soyuz' one parachute, plus an additional reserve which is only deployed if there are problems with the main.)

So, even without firing the retrorockets or accounting for parachute differences it seems plausible to me that dragon will have roughly 4x less ground impact acceleration than soyuz.

Also remember that humans have something like a 45G tolerance in the chest-to-back axis (see http://ftp.rta.nato.int/public/PubFullText/RTO/EN/RTO-EN-HFM-113/EN-HFM-113-06.pdf).  So there's a big spread between "comfortable" and "survivable", which gives you lots of margin to play with for off-nominal landings.

EDIT: Here's the Soyuz landing video, thanks to gommtu: http://youtu.be/-l7MM9yoxII?t=15m12s
Title: Re: SpaceX DragonFly Discussion Thread
Post by: adrianwyard on 06/03/2014 04:25 PM
Thanks for that Soyuz video. It was interesting that they noted propellant is vented at altitude specifically to prevent explosion of hypergolics on landing. SpaceX will have had to make a difficult trafeoff with Dragon V2 for chute land landings: either vent all the propellant before landing a la Soyuz and rely on the struts to make a hard landing tolerable, or retain a little propellant for a softened landing and assume you will successfully land softly (in which case having residual hypergolics onboard won't cause problems).

My guess is SpaceX will test chute land landings without SDs at some point to verify that loads are tolerable by crew. And only if they're not will they retain some fuel. Actually, rather than potentially wrecking a DragonFly it would make more sense to instrument a mass simulator with landing struts, and perhaps representative seats. Perhaps they could reuse the Dragon from the V2 chute tests.

I agree that landing first on the two-strut side would help soften the impact, but then you have the crosswind topple case to worry about. Boeing had to test for this with CST-100, but they have the advantage of landing flat to the ground and skidding to a halt on airbags; Dragon's struts could dig in.

It's guaranteed that all of these issues were worked through years ago, so hopefully Chris and company can use this thread to ask some good questions of SpaceX at some point.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: MP99 on 06/03/2014 10:00 PM
I had wondered about the landing under parachutes.

As I understand it, the capsule could be facing in any direction when it lands?

If it happens to be facing backwards, how close would it be to tip onto its side?

Would the dracos be able to keep the capsule facing in the direction of travel under parachutes?

Cheers, Martin
Title: Re: SpaceX DragonFly Discussion Thread
Post by: adrianwyard on 06/03/2014 10:15 PM
Good question. The roll Dracos will give you about 90 lb force. I'm not sure that is enough to reorientate the Dragon and/or the chutes...

But the question before this one is: do you want to keep any hypergolics onboard what is already an off-nominal landing.

And as far as toppling goes, you can just accept that as a possibility you plan for. A parachute/hard landing might render the Dragon non-reusable anyway, so denting it wouldn't matter...
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars_J on 06/04/2014 01:24 AM
The concern about hypergolics on board is overblown. The propulsive landing (either fully propulsive or parachute assisted) will always have some hypergolics remaining. That's a necessity of the landing mode. You just need to establish proper procedures before stepping out.

If you are coming in for a non-standard landing, you have bigger issues to deal with already.

I had wondered about the landing under parachutes.

As I understand it, the capsule could be facing in any direction when it lands?

If it happens to be facing backwards, how close would it be to tip onto its side?

The parachute attachment point is located just above the hatch, so if under a parachute landing, it will always impact with the rear edge first. (although there might be a bit of a spin) Elon indicated in a follow-up interview that the two rear legs are closer together to help deal with the increased loads for those legs during a parachute landing.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: QuantumG on 06/04/2014 01:28 AM
Unfortunately, I've never heard SpaceX say anything about moving away from hypergolics. It's a shame, really. It'd make reuse operations easier.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: TrevorMonty on 06/04/2014 03:15 AM
There are some space tests of greener propellants coming up, I think NASA is doing the tests.

The one I read about was denser and had lower freezing point so they do have some major pluses. At present there is no flight history and require the development of new engines, not a cheap exercise.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: savuporo on 06/04/2014 03:35 AM
There are some space tests of greener propellants coming up, I think NASA is doing the tests.

The one I read about was denser and had lower freezing point so they do have some major pluses. At present there is no flight history and require the development of new engines, not a cheap exercise.


Yeah we have a lot of threads on these, they are still hypergolics. Also, there is flight history with at least one of these.

NASA Selects Green Propellant Technology Demonstration Mission (http://forum.nasaspaceflight.com/index.php?topic=29719.0;all)

Joint Industry/Government Demo Mission: Green Propellant Infusion Mission (GPIM)  (http://forum.nasaspaceflight.com/index.php?topic=31821.0;all)

New "Green" Monopropellants as potential first stage propellants  (http://forum.nasaspaceflight.com/index.php?topic=32444.0;all)

Aerojet’s confidence in Next Generation Engine and green propellants  (http://forum.nasaspaceflight.com/index.php?topic=27967.0;all)

EDIT: Latest deck, http://www.nasa.gov/sites/default/files/files/GreenPropellantInfusionMissionProject_v2.pdf

Guess what, looks like it's scheduled to be flown on Falcon Heavy on AF STP-2 launch (http://forum.nasaspaceflight.com/index.php?topic=30544.0)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Prober on 06/04/2014 11:05 AM
Thanks for that Soyuz video. It was interesting that they noted propellant is vented at altitude specifically to prevent explosion of hypergolics on landing.

small point Soyuz uses H2O2
Title: Re: SpaceX DragonFly Discussion Thread
Post by: MP99 on 06/04/2014 01:26 PM
The concern about hypergolics on board is overblown. The propulsive landing (either fully propulsive or parachute assisted) will always have some hypergolics remaining. That's a necessity of the landing mode. You just need to establish proper procedures before stepping out.

If you are coming in for a non-standard landing, you have bigger issues to deal with already.

I had wondered about the landing under parachutes.

As I understand it, the capsule could be facing in any direction when it lands?

If it happens to be facing backwards, how close would it be to tip onto its side?

The parachute attachment point is located just above the hatch, so if under a parachute landing, it will always impact with the rear edge first. (although there might be a bit of a spin) Elon indicated in a follow-up interview that the two rear legs are closer together to help deal with the increased loads for those legs during a parachute landing.

You seem to be assuming that the hatch will be facing in whatever direction that the wind is blowing the parachutes laterally.

Unless the draco thrusters have enough authority to control capsule orientation, I don't see why that can be assumed.


If the hatch happens to be facing exactly backwards relative to direction of travel, the wind will pull the parachutes in a direction towards toppling the capsule onto it's back.


Obviously, the capsule will hang so it's CoM is under the parachute attach point. ISTM to be a question of how large the offset is of the foot contact point from a point directly under the parachute attach point.

I believe this will determine to safety criterion for allowable winds at the landing site.

cheers, Martin
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cscott on 06/04/2014 04:48 PM
Unfortunately, I've never heard SpaceX say anything about moving away from hypergolics. It's a shame, really. It'd make reuse operations easier.

At the same time people complain that SpaceX is doing "too many new things" with its rocket designs. ;)

For something as safety-critical as the launch-escape engines, using a conservative hypergolic thruster makes a lot of sense.  If you consider draco as part of the development roadmap for superdraco, then using hypergolics there also makes sense.  Sure, I wouldn't be unhappy (or surprised) if Dragon v3 or v4 eventually switches to a green hypergolic fuel (probably for draco first), but I don't blame them for moving this out of their critical path.  After all, as folks have noted, the exhaust products of their thrusters are safe, and the handling hypergolics is a well-understood routine.  (And similarly, crash-protection of the tanks is also well understood.)

The bigger question for me is about MCT plans.  Elon confirmed that MCT will not use helium pressurization.  Draco and Superdraco both use helium pressurization.  So it seems that "something new" is required for MCT RCS -- perhaps QuantumG will get his wish.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Joffan on 06/04/2014 04:59 PM
The bigger question for me is about MCT plans.  Elon confirmed that MCT will not use helium pressurization.  Draco and Superdraco both use helium pressurization.  So it seems that "something new" is required for MCT RCS -- perhaps QuantumG will get his wish.

I don't see any significant issues switching to nitrogen for the hypergolic pressurization, for a vehicle where helium isn't used elsewhere. It was only really the cryogenics that posed the risk of condensing/dissolving a nitrogen pressurant.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 06/04/2014 05:02 PM
The bigger question for me is about MCT plans.  Elon confirmed that MCT will not use helium pressurization.  Draco and Superdraco both use helium pressurization.  So it seems that "something new" is required for MCT RCS -- perhaps QuantumG will get his wish.

I don't see any significant issues switching to nitrogen for the hypergolic pressurization, for a vehicle where helium isn't used elsewhere. It was only really the cryogenics that posed the risk of condensing/dissolving a nitrogen pressurant.

I am positive there will be no hypergolics on MCT. They will use methane thrusters just like on Morpheus.

Title: Re: SpaceX DragonFly Discussion Thread
Post by: sublimemarsupial on 06/04/2014 05:04 PM
The bigger question for me is about MCT plans.  Elon confirmed that MCT will not use helium pressurization.  Draco and Superdraco both use helium pressurization.  So it seems that "something new" is required for MCT RCS -- perhaps QuantumG will get his wish.

I don't see any significant issues switching to nitrogen for the hypergolic pressurization, for a vehicle where helium isn't used elsewhere. It was only really the cryogenics that posed the risk of condensing/dissolving a nitrogen pressurant.

I am positive there will be no hypergolics on MCT. They will use methane thrusters just like on Morpheus.

Agreed. I would take it a step further and say MCT won't use any consumables that can't be replenished on Mars. But this is getting OT for DragonFly...
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cscott on 06/04/2014 05:09 PM
The bigger question for me is about MCT plans.  Elon confirmed that MCT will not use helium pressurization.  Draco and Superdraco both use helium pressurization.  So it seems that "something new" is required for MCT RCS -- perhaps QuantumG will get his wish.

I don't see any significant issues switching to nitrogen for the hypergolic pressurization, for a vehicle where helium isn't used elsewhere. It was only really the cryogenics that posed the risk of condensing/dissolving a nitrogen pressurant.

I am positive there will be no hypergolics on MCT. They will use methane thrusters just like on Morpheus.

Agreed. I would take it a step further and say MCT won't use any consumables that can't be replenished on Mars. But this is getting OT for DragonFly...

Bringing it back on topic: presumably another incidental accomplishment of the dragonfly program will be gaining a lot of experience with ground-handling and refueling of hypergolics.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: deruch on 06/10/2014 04:48 PM
I think the thread was unfortunately misdirected quite early by what has to be a mistake in the FAA filing.  On consideration, I don't see how they can have landings, both under canopy and fully propulsive, that fire the engines for the same amount of time.  Just how good is the throttling supposed to be?  I can't imagine that it gets low enough to take 12.5 seconds of thrust to land under chutes while it also takes 12.5 seconds when landing "fully propulsive".  The five second landing burns will only take place under canopy.  i.e. No brown pants landings!  (I vote to still keep BPL as valid terminology cause it's hilarious.)  The FAA filing has to be mistaken.  It does however make sense to have 5 second burns to ensure a soft landing under canopy (whether the flight is helo-drop or hop) and 12.5 second burns for full propulsive landings (helo or hop).  That would mean that the burns started high enough AGL to insure time for chute deployment in the event of engine failure.  I think @sheltonjr might have come to the same conclusion. 

As to the discussion of Dragonfly flights with an attached trunk, I think @douglas100 gets that one right.  It only really makes sense to me to have any tests with the trunk at McGregor, which has a 10,000ft ceiling, to observe flight characteristics in an abort scenario.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars_J on 06/10/2014 04:52 PM
A 5 second burn is much longer than what would be needed "under canopy". Check your gut reaction to the numbers again.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: deruch on 06/10/2014 06:01 PM
A 5 second burn is much longer than what would be needed "under canopy". Check your gut reaction to the numbers again.

I agree.  But then how much worse is the 12.5 second burn under canopy, which the FAA document also calls for.  Something's rotten in Denmark.  The landings (especially the ones with the parachutes), as described, don't make any sense to me.  My logic: per the FAA doc, there are 2 "burn profiles", 5 second and 12.5 second, currently matched to 2 "flight profiles", helo drop and propulsive hop, respectively.  Those matches don't make sense.  Can't be the same duration burns from free fall as under parachutes, regardless of what the length of those burns are or any believable throttling.  Ergo something in the document is wrong.  What if the matching was supposed to be to "descent profile", i.e. parachute or propulsive, instead of to "flight profile".  That seems a better fit.  The assumption being that the person who wrote up the document either goofed, misunderstood, or was confused. 

edit:  Maybe the numbers are just placeholders and not meant to be too exact?  I don't know if that would be acceptable in a document of this type?  Unlikely, I feel.  But if so, the discussion/speculation earlier is still off base.

@Lars_J, or anyone else, if you see some obvious point that I haven't understood, please let me know.  Thanx.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cscott on 06/10/2014 06:28 PM
I think the thread was unfortunately misdirected quite early by what has to be a mistake in the FAA filing.

I doubt it.  I suggest that reader misinterpretation of the point and purpose of the filing is more likely.  Presumably the numbers are conservative maximums, hand-waving over the fact that there are multiple dracos and superdracos on board.  It may be that the durations are from "first firing" to "last firing" of any engine (superdraco or draco),  or they may be cumulative firing durations summed across all engines.  The durations are there to allow emissions and noise limits to be checked, not to provide two significant digits of accuracy for NSF modelers.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sghill on 06/10/2014 07:42 PM
Read the report closer! Get off of the chart on Page 2-1, and go to Page 2-5 and 2-6.  They've described 4 scenarios in detail.  Quoting from the document (emphasis mine) They are:

1) Propulsive Assist
For the  propulsive  assist test,  a  helicopter (an  Erickson  E‐model  or  equivalent) would  arrive  at the McGregor test site from Waco Regional Airport.  The DragonFly RLV would then be tethered to the helicopter using a cable. A maximum of 300 gallons of propellant would be loaded into the DragonFly RLV for this test. The helicopter would take off with the DragonFly RLV attached and reach an altitude up to 10,000 ft. Once at that altitude, the DragonFly RLV would be released from the tether and three main parachutes would  be  deployed.  The  engines  would  not  fire  until  the  vehicle  descends  to approximately 98 ft above ground level (AGL). The engines would fire for approximately 5 seconds, and the RLV would make a powered landing. This type of operation would last approximately 30 minutes from helicopter takeoff to DragonFly RLV landing.  The test would be designed so that almost all fuel on board is used prior to landing. All fuel valves would shut automatically and retain any residual fuel in the capsule.

2) Full Propulsive Landing
For the full propulsive landing test, a helicopter (an Erickson E‐model or equivalent) would arrive at the McGregor test site from Waco Regional Airport.  The DragonFly RLV would then be tethered to the helicopter. A maximum of 300 gallons of propellant would be loaded into the DragonFly RLV for this test. The helicopter would take off with the DragonFly RLV attached and reach an altitude up to 10,000 ft. Once at that altitude, the DragonFly RLV would be released from the tether. There would be a period of free fall and then the engines would fire for approximately 5 seconds and the RLV would make a powered landing. This type of operation would last approximately 30 minutes from helicopter take‐off to DragonFly RLV landing. 

{ed. note: This would definitely be the BPL landing scenario.}

3) Propulsive Assist Hopping
Approximately 400 gallons of propellant would be loaded into the DragonFly RLV for this test. During a propulsive  assisted  hop  test,  the  DragonFly  RLV  would  launch  from  a  launch  pad  and  ascend  to
approximately 7,000 ft AGL (firing engines for 12.5 seconds). Two parachutes [not three] would be deployed for the descent, the engines would fire for 12.5 seconds, and the RLV would make a powered landing on the launch pad. This operation would last approximately 60 seconds.

{ed. note: I find this scenario interesting because they're still talking about landing on the landing pad- even under parachute assisted conditions.  This looks like a release of the deployed parachutes with powered recovery scenario.}

4) Full Propulsive Hopping
Approximately 400 gallons of propellant would be loaded into the DragonFly RLV for this test.  During a full propulsive hop test, the DragonFly RLV would launch from a launch pad and ascend to approx. 7,000 ft AGL (firing engines for approximately 12.5 seconds).  The engines would then throttle down in order to descend (firing for an additional approximate 12.5 seconds), and the RLV would make a powered landing on the launch pad.  This operation would last approximately 60 seconds.

I'd also like to point out the blurb about the trunk "which may or may not be attached during DragonFly operations" being used in these tests.  IMHO, they may be testing scenarios where the trunk doesn't separate in an abort situation (intentionally or otherwise), and/or they may be looking at the trunk as a potential "launch pad" for the DragonFly in the propulsive hops.

Also, from Page 1-4, the F9R program has a permit for 10 launches.  They've done 2 so far (perhaps more if the FAA is including the ground testing burns), and the DragonFly permit won't kick in (if approved) until after those ten launches.

Title: Re: SpaceX DragonFly Discussion Thread
Post by: deruch on 06/10/2014 08:38 PM
I did read those.  In fact, it wasn't until I read those that the scenarios seemed wrong.

3) Propulsive Assist Hopping
Approximately 400 gallons of propellant would be loaded into the DragonFly RLV for this test. During a propulsive  assisted  hop  test,  the  DragonFly  RLV  would  launch  from  a  launch  pad  and  ascend  to
approximately 7,000 ft AGL (firing engines for 12.5 seconds). Two parachutes [not three] would be deployed for the descent, the engines would fire for 12.5 seconds, and the RLV would make a powered landing on the launch pad. This operation would last approximately 60 seconds.

{ed. note: I find this scenario interesting because they're still talking about landing on the landing pad- even under parachute assisted conditions.  This looks like a release of the deployed parachutes with powered recovery scenario.}


12.5 seconds of engine firing while the craft is already under parachutes????  That's the bit that doesn't make sense to me.  Just how low do you think these engines can be throttled?

edit: Oops, just noticed your note.  That's interesting and it could explain my perceived discrepancy.  Thanks.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: inventodoc on 06/10/2014 09:35 PM
Perhaps the thrusters continue firing at a lower level after landing in order to consume all the propellant????
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Joffan on 06/10/2014 11:07 PM
Yeah, I assumed that 12.5s of ascent burn + 12.5s of landing burn was a misinterpretation of a 20s ascent burn, engine out, fall, then a 5s landing burn.  Numbers may need tweaking between the two phases, but something like that.

And the assisted landing burn has just conservatively been given the same duration (for planning purposes) as the unassisted.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: ncb1397 on 06/10/2014 11:52 PM
I did read those.  In fact, it wasn't until I read those that the scenarios seemed wrong.

3) Propulsive Assist Hopping
Approximately 400 gallons of propellant would be loaded into the DragonFly RLV for this test. During a propulsive  assisted  hop  test,  the  DragonFly  RLV  would  launch  from  a  launch  pad  and  ascend  to
approximately 7,000 ft AGL (firing engines for 12.5 seconds). Two parachutes [not three] would be deployed for the descent, the engines would fire for 12.5 seconds, and the RLV would make a powered landing on the launch pad. This operation would last approximately 60 seconds.

{ed. note: I find this scenario interesting because they're still talking about landing on the landing pad- even under parachute assisted conditions.  This looks like a release of the deployed parachutes with powered recovery scenario.}


12.5 seconds of engine firing while the craft is already under parachutes????  That's the bit that doesn't make sense to me.  Just how low do you think these engines can be throttled?

edit: Oops, just noticed your note.  That's interesting and it could explain my perceived discrepancy.  Thanks.

As far as throttle range, the similar hypergolic engine on the Apollo DPS acheived throttle down to ~10% which means 2 engines in each pod can maybe throttle to 5% by turning one off. Assuming at minimum 4 engines firing, 10% thrust would be 1,640 lbf X 4 or 6560 lbf. If the craft can throttle this low, thrust to weight of 1 is easily acheivable and so hover, slow descent or slow ascent is limited by the available fuel supply.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cscott on 06/11/2014 03:20 AM
Perhaps the thrusters continue firing at a lower level after landing in order to consume all the propellant????

Why are we assuming that the "thrusters" mean only the superdracos?  If you read the numbers as the total time the dracos *or* superdracos are firing, they make much more sense.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Kenm on 06/11/2014 04:21 AM
I did read those.  In fact, it wasn't until I read those that the scenarios seemed wrong.

3) Propulsive Assist Hopping
Approximately 400 gallons of propellant would be loaded into the DragonFly RLV for this test. During a propulsive  assisted  hop  test,  the  DragonFly  RLV  would  launch  from  a  launch  pad  and  ascend  to
approximately 7,000 ft AGL (firing engines for 12.5 seconds). Two parachutes [not three] would be deployed for the descent, the engines would fire for 12.5 seconds, and the RLV would make a powered landing on the launch pad. This operation would last approximately 60 seconds.

{ed. note: I find this scenario interesting because they're still talking about landing on the landing pad- even under parachute assisted conditions.  This looks like a release of the deployed parachutes with powered recovery scenario.}


12.5 seconds of engine firing while the craft is already under parachutes????  That's the bit that doesn't make sense to me.  Just how low do you think these engines can be throttled?

edit: Oops, just noticed your note.  That's interesting and it could explain my perceived discrepancy.  Thanks.

As far as throttle range, the similar hypergolic engine on the Apollo DPS acheived throttle down to ~10% which means 2 engines in each pod can maybe throttle to 5% by turning one off. Assuming at minimum 4 engines firing, 10% thrust would be 1,640 lbf X 4 or 6560 lbf. If the craft can throttle this low, thrust to weight of 1 is easily acheivable and so hover, slow descent or slow ascent is limited by the available fuel supply.

Note that it says two parachutes so I think that this might be the drogue parachutes.
This would have several features you would get far less drift with the drogues, it would be a test for failure of the main chutes to deploy and if you need to deploy the main chutes the droques are ready to pull them out.

edit
One other thing if you look at the picture of the drop test at
http://www.spacex.com/files/assets/img/20100820_34dragon.jpg

Note how the Dragon hangs on a tilt under the drogue chutes. Now if the picture was taken level you can see that the tilt is causing the Dragon to fly off to the left (look at the angle between the vertical and a line from the attachment point to the center of the two drogue chutes).
This glide angle can be used to steer to the landing area by rotating the capsule just like they do during reentery.

Title: Re: SpaceX DragonFly Discussion Thread
Post by: Prober on 06/15/2014 04:48 PM
So when are the first of these tests?

Title: Re: SpaceX DragonFly Discussion Thread
Post by: docmordrid on 06/15/2014 06:33 PM
AIUI, FAA has to issue the final EIS and permit. There is a 30 day comment period after the EIS before things can actually move on the permit.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Prober on 06/16/2014 01:30 AM
AIUI, FAA has to issue the final EIS and permit. There is a 30 day comment period after the EIS before things can actually move on the permit.

ahhh the red tape  :o
Title: Re: SpaceX DragonFly Discussion Thread
Post by: neoforce on 06/16/2014 03:21 AM
AIUI, FAA has to issue the final EIS and permit. There is a 30 day comment period after the EIS before things can actually move on the permit.

ahhh the red tape  :o

Besides the red tape, I'm sure they aren't' ready.   SpaceX knew about the red tape, so they applied before they were close to testing DragonFly.  And there is still work on the F9R at McGregor which probably has to finish up (with test of that vehicle moved to Spaceport America) before DragonFly tests start at McGregor.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: docmordrid on 06/16/2014 04:07 AM
The F9R permit at McGregor expires Feb. 26, 2015, though they probably won't run it out. The Grasshopper's permit expires Oct. 17, 2014 and they were done months before.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: king1999 on 06/16/2014 06:05 AM

Besides the red tape, I'm sure they aren't' ready.   SpaceX knew about the red tape, so they applied before they were close to testing DragonFly.  And there is still work on the F9R at McGregor which probably has to finish up (with test of that vehicle moved to Spaceport America) before DragonFly tests start at McGregor.

Spaceport America will have a different F9R (dev2). Most likely dev 1 will stay with DF.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: CameronD on 07/14/2014 06:26 AM
I notice the only current FAA/AST permit mentioning Dragon of any kind is for the Pad Abort Test Vehicle and is restricted to (a) one flight from Cape Canaveral Air Force Station, Florida, and (b) a suborbital trajectory to a water landing.

Nothing on Dragonfly yet?
 
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Roy_H on 08/04/2014 03:13 PM
Read the report closer! Get off of the chart on Page 2-1, and go to Page 2-5 and 2-6.  They've described 4 scenarios in detail.  Quoting from the document (emphasis mine) They are:
...
Also, from Page 1-4, the F9R program has a permit for 10 launches.  They've done 2 so far (perhaps more if the FAA is including the ground testing burns), and the DragonFly permit won't kick in (if approved) until after those ten launches.

Are you sure about that? Why would all of the F9R Dev flights have to be completed before any DragonFly flights? And given the few F9R Dev flights so far, the DragonFly flights  could be a long way into the future. As I speculated before, ISTM that SpaceX would like to have at least some (if not all) DragonFly flights before doing the Abort Tests.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Jet Black on 08/04/2014 03:46 PM
Read the report closer! Get off of the chart on Page 2-1, and go to Page 2-5 and 2-6.  They've described 4 scenarios in detail.  Quoting from the document (emphasis mine) They are:
...
Also, from Page 1-4, the F9R program has a permit for 10 launches.  They've done 2 so far (perhaps more if the FAA is including the ground testing burns), and the DragonFly permit won't kick in (if approved) until after those ten launches.

Are you sure about that? Why would all of the F9R Dev flights have to be completed before any DragonFly flights? And given the few F9R Dev flights so far, the DragonFly flights  could be a long way into the future. As I speculated before, ISTM that SpaceX would like to have at least some (if not all) DragonFly flights before doing the Abort Tests.

As docmordrid said, the F9R permit runs out on the 26th Feb 2015, so DragonFly can start after that.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: rpapo on 08/04/2014 03:49 PM
As docmordrid said, the F9R permit runs out on the 26th Feb 2015, so DragonFly can start after that.
Why wait?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Doesitfloat on 08/04/2014 04:06 PM
As docmordrid said, the F9R permit runs out on the 26th Feb 2015, so DragonFly can start after that.
Why wait?

They don't have to wait.(to paraphrase)  In various places in the EIS the impact of doing nothing is business will continue as usual with Merlin-D tests and Falcon 9 tests.
This permit is for additional capability. Flying rocket with Hypergolic propellants.
Does not effect current operations.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Llian Rhydderch on 08/05/2014 04:51 AM
Read the report closer! Get off of the chart on Page 2-1, and go to Page 2-5 and 2-6.  They've described 4 scenarios in detail.  Quoting from the document (emphasis mine) They are:
...
Also, from Page 1-4, the F9R program has a permit for 10 launches.  They've done 2 so far (perhaps more if the FAA is including the ground testing burns), and the DragonFly permit won't kick in (if approved) until after those ten launches.

Are you sure about that? Why would all of the F9R Dev flights have to be completed before any DragonFly flights? And given the few F9R Dev flights so far, the DragonFly flights  could be a long way into the future. As I speculated before, ISTM that SpaceX would like to have at least some (if not all) DragonFly flights before doing the Abort Tests.

I think we should clarify a point.  A permit from a government regulatory body to make ten flights does not equal a firm plan by SpaceX management and the F9R-Dev project manager to definitely make ten flights.

For one, flight tests always reveal new info in each test.  Progress on test objectives may very well cut the number of tests on that test vehicle down.

Moreover, it is often wise project planning strategy to apply for regulatory permits for more of an activity (in this case, test flights) rather than too few.  So if you think you need 6 test flights, but best case could beat that, and worst case would need, say, ten; then you apply for ten.

So we should not read that FAA permit as number of F9R Dev1 flights that must occur prior to the commencement of DragonFly testing.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 08/06/2014 02:32 PM
After all, the DragonFly testing at McGregor is not about abort, it's about return-flight & landing control. But they could potentially wait until the Pad abort before beginning the DragonFly testing program.
What is the difference between a pad abort and some of the tests they had proposed in their FAA license request? In some of these tests it does a powered take off and lands with parachutes. Sounds like a pad abort to me.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: rcoppola on 08/06/2014 05:04 PM
After all, the DragonFly testing at McGregor is not about abort, it's about return-flight & landing control. But they could potentially wait until the Pad abort before beginning the DragonFly testing program.
What is the difference between a pad abort and some of the tests they had proposed in their FAA license request? In some of these tests it does a powered take off and lands with parachutes. Sounds like a pad abort to me.
Yes, your referring to the Propulsive Assist Hopping. The DragonFly testing program is very similar to the F9R in that they will validate as many hardware / software elements for as many profiles as they can without exceeding the limitations of McGregor. An actual Pad Abort can not be done at McGregor. But they can and will test important sub-profiles of everything the SDs will be tasked to do.

I can't remember where I read / heard this but the real pad abort will actually see the Dragon sit atop a platform that approximates the height it would be if sitting on an actual F9 launch vehicle. Also, a full-up pad abort would require most if not all SD fuel be consumed, necessitating a water landing. (Dragon is not meant to do a land landing under parachutes alone) I have never heard any reports that they would or even could do a propulsive landing post any abort scenario, pad, max-Q or otherwise.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 08/06/2014 05:20 PM
An actual Pad Abort can not be done at McGregor.
Why? IIRC, Blue Origin did their pad abort test at their facility in Texas.

. Also, a full-up pad abort would require most if not all SD fuel be consumed, necessitating a water landing. (Dragon is not meant to do a land landing under parachutes alone)
Do you have a source for any of this, because this does not match the impression, I have had. IIRC, parachutes are claimed to be a backup for the propulsive landing in case something goes wrong with starting up the super dracos. Anyone got an exact quote for this?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars_J on 08/06/2014 05:22 PM
. Also, a full-up pad abort would require most if not all SD fuel be consumed, necessitating a water landing. (Dragon is not meant to do a land landing under parachutes alone)
Do you have a source for any of this, because this does not match the impression, I have had.

Indeed. The impression I get is that it will simply be launched from a trunk-like launch adapter, located near the ground level.

Being at 0 or 200 ft altitude at the start doesn't matter significantly for the test. (other than making sure that the test Dragon doesn't impact the lightning protection towers or wires)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: rcoppola on 08/06/2014 05:47 PM
An actual Pad Abort can not be done at McGregor.
Why? IIRC, Blue Origin did their pad abort test at their facility in Texas.

. Also, a full-up pad abort would require most if not all SD fuel be consumed, necessitating a water landing. (Dragon is not meant to do a land landing under parachutes alone)
Do you have a source for any of this, because this does not match the impression, I have had. IIRC, parachutes are claimed to be a backup for the propulsive landing in case something goes wrong with starting up the super dracos. Anyone got an exact quote for this?
You're conflating two different scenarios. During an abort, there is not enough SD fuel left to do a propulsive landing, parachute assist or otherwise.  Dragon will land in the water.

Upon normal operational reentry, Dragon will check to make sure the SD's are good before committing to a propulsive landing which is the operational landing of first choice. If it detects an issue with the SDs, it will parachute into the water. There is also a parachute assisted propulsive landing scenario that has been discussed and will be tested. Not sure which way they will go at the beginning of Dragon V2 services ie. full propulsive landing or parachute assist. They will be testing both at McGregor.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 08/06/2014 06:00 PM
An actual Pad Abort can not be done at McGregor.
Why? IIRC, Blue Origin did their pad abort test at their facility in Texas.

. Also, a full-up pad abort would require most if not all SD fuel be consumed, necessitating a water landing. (Dragon is not meant to do a land landing under parachutes alone)
Do you have a source for any of this, because this does not match the impression, I have had. IIRC, parachutes are claimed to be a backup for the propulsive landing in case something goes wrong with starting up the super dracos. Anyone got an exact quote for this?
You're conflating two different scenarios. During an abort, there is not enough SD fuel left to do a propulsive landing, parachute assist or otherwise.  Dragon will land in the water.

Upon normal operational reentry, Dragon will check to make sure the SD's are good before committing to a propulsive landing which is the operational landing of first choice. If it detects an issue with the SDs, it will parachute into the water. There is also a parachute assisted propulsive landing scenario that has been discussed and will be tested. Not sure which way they will go at the beginning of Dragon V2 services ie. full propulsive landing or parachute assist. They are testing both at McGregor.
No, I am not conflating two different scenarios. I want to see a source that says that Dragon can not do a parachute landing on land. All information that I have seen makes me think otherwise. I am not even sure that there is not enough fuel left for propulsive landing after an abort. It is likely (and I would have assumed as much as well), but I have not seen an actual source for that either.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: neoforce on 08/06/2014 06:11 PM

<snip>
I can't remember where I read / heard this but the real pad abort will actually see the Dragon sit atop a platform that approximates the height it would be if sitting on an actual F9 launch vehicle.
<snip>

Here is the source for the "atop a platform"  From Elon at http://shitelonsays.com/transcript/spacex-dragon-2-unveil-qa-2014-05-29

Quote
We're planning to do a Dragon v2 abort test where Dragon v2 will take off from, essentially launch vehicle height, so it simulates something going wrong on the launch pad. The astronauts are just about to take off, it's maybe a few seconds before liftoff, and there's a fire on the launchpad, you need to make sure that the spacecraft can fire the SuperDracos, get to a safe altitude, and then take the astronauts to safety. That test is due to occur later this year, then next year we expect to do what's called the high altitude abort test. That's where we launch the rocket, it's at a very high altitude, very quickly, at something called Max-Q which is the maximum dynamic air pressure, and then we want to initiate an abort. This is considered the hardest time to do an abort. Obviously, these are tests, so they could go wrong. That high altitude abort test is due to occur next year. Conceivably we could do the first flight to orbit, and we'd initially do it without people, at the end of next year, and then the first flight with people, in 2016 we think is very achievable
Title: Re: SpaceX DragonFly Discussion Thread
Post by: rcoppola on 08/06/2014 06:18 PM
. Also, a full-up pad abort would require most if not all SD fuel be consumed, necessitating a water landing. (Dragon is not meant to do a land landing under parachutes alone)
Do you have a source for any of this, because this does not match the impression, I have had.

Indeed. The impression I get is that it will simply be launched from a trunk-like launch adapter, located near the ground level.

Being at 0 or 200 ft altitude at the start doesn't matter significantly for the test. (other than making sure that the test Dragon doesn't impact the lightning protection towers or wires)
Thanks neoforce. There's another mention from Shotwell out there somewhere as well.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: rcoppola on 08/06/2014 06:39 PM
An actual Pad Abort can not be done at McGregor.
Why? IIRC, Blue Origin did their pad abort test at their facility in Texas.

. Also, a full-up pad abort would require most if not all SD fuel be consumed, necessitating a water landing. (Dragon is not meant to do a land landing under parachutes alone)
Do you have a source for any of this, because this does not match the impression, I have had. IIRC, parachutes are claimed to be a backup for the propulsive landing in case something goes wrong with starting up the super dracos. Anyone got an exact quote for this?
You're conflating two different scenarios. During an abort, there is not enough SD fuel left to do a propulsive landing, parachute assist or otherwise.  Dragon will land in the water.

Upon normal operational reentry, Dragon will check to make sure the SD's are good before committing to a propulsive landing which is the operational landing of first choice. If it detects an issue with the SDs, it will parachute into the water. There is also a parachute assisted propulsive landing scenario that has been discussed and will be tested. Not sure which way they will go at the beginning of Dragon V2 services ie. full propulsive landing or parachute assist. They are testing both at McGregor.
No, I am not conflating two different scenarios. I want to see a source that says that Dragon can not do a parachute landing on land. All information that I have seen makes me think otherwise. I am not even sure that there is not enough fuel left for propulsive landing after an abort. It is likely (and I would have assumed as much as well), but I have not seen an actual source for that either.
If you want to see a source, then go find one. Show me one video, one picture or one mention that Dragon V2 can land on land without a propulsive assist. They have only ever showed full propulsive landing or parachute assisted propulsive landing. Never only parachutes except for a splashdown.

-For the Pad Abort, they will splashdown
-For the Max-Q abort, they will splashdown

Look at the tests they will do for DragonFly. Every one of them is either full propulsive landing or parachute assisted propulsive landing. Where has there ever been mention of parachute only land landing?

Now, with regard to there being enough SD fuel post certain abort scenarios allowing to do a parachute assisted propulsive land landing... Let's play that through. If it's a real Pad abort, you're going to abort out over the ocean as fast and as far as you can. Would you have the fuel or is it even technically possible to make it back to a slightly downrange landing pad with enough margin for a pinpoint propulsive landing? Why even risk it? Same goes for an in-flight abort.

I'm not saying it's not possible, although IMO it isn't or at the very least doesn't provide benefits beyond the potential risks.
But on top of that, every abort scenario I have seen mentioned, ends with a splashdown. And every non-abort landing scenario I have ever seen ends with  A) Parachutes combined with SDs or B) SDs only. Never parachutes only, except for a splashdown.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: JasonAW3 on 08/06/2014 06:55 PM

Also, my airplane had a ballistic parachute.  It's essentially useless for its purpose (reliable deployment) below 150 meters (500 ft)., so I suspect you are right that the landing burn will start around 400 meters, and then pull more than 3-Gs below 150 meters ft. to soft land--- or pop the emergency chute if there's a problem when the burn starts.


I though they had a motar system that was supposed to be able to deploy the parachute as low as 75 meters?

I know ejection seats can pop chutes under 100 meters.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Scylla on 08/06/2014 06:59 PM
From a Jan 2013 article....
http://www.spacenews.com/article/civil-space/33240spacex-plans-dragon-pad-abort-test-in-december

Quote
The pad abort test, slated for December, will be staged from the company’s launch complex at Cape Canaveral Air Force Station adjacent to the Kennedy Space Center. For the test, a flight-like, full-scale Dragon capsule will ignite its SuperDraco thrusters, fly itself out over the Atlantic Ocean and parachute into the water.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: JasonAW3 on 08/06/2014 07:25 PM
Crazy idea here.

If they could rig it, wouldn't be interesting if SpaceX were to attempt to land both first and second stages of the Falcon 9 used in the Inflight Abort test?

    Just need 2 barges and landing gear on the upper stage.  (yeah and a whole avionics upgrade, etc and so forth).

   As neither of the stages is planned to go into orbit, it would be a whole lot more economical, (and one heck of a PR stunt for SpaceX to do that, then film the two barges with both stages on landing gear deployed, standing upright on the barges as they come into port?  If they are fully or mostly fueled, they might actually be able to do it.

  The upper stage would be a stunt, as I don't think SpaceX has quite figured out how to handle reentry for that stage.

   Suggestion?  Plug Nozzle.  Gives optimal performance during all phases of flight.  Yeah, I doubt that they've developed one in house, but they have the systems that they would need, just have to develope the actual plug nozzle itself.  Most of the hard work was done in the 1960's and should make developement quite a bit easier.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: JasonAW3 on 08/06/2014 07:30 PM
An actual Pad Abort can not be done at McGregor.
Why? IIRC, Blue Origin did their pad abort test at their facility in Texas.

. Also, a full-up pad abort would require most if not all SD fuel be consumed, necessitating a water landing. (Dragon is not meant to do a land landing under parachutes alone)
Do you have a source for any of this, because this does not match the impression, I have had. IIRC, parachutes are claimed to be a backup for the propulsive landing in case something goes wrong with starting up the super dracos. Anyone got an exact quote for this?

When the heck did this happen and why didn't I hear about it?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: kirghizstan on 08/06/2014 07:38 PM
Crazy idea here.

If they could rig it, wouldn't be interesting if SpaceX were to attempt to land both first and second stages of the Falcon 9 used in the Inflight Abort test?

    Just need 2 barges and landing gear on the upper stage.  (yeah and a whole avionics upgrade, etc and so forth).

   As neither of the stages is planned to go into orbit, it would be a whole lot more economical, (and one heck of a PR stunt for SpaceX to do that, then film the two barges with both stages on landing gear deployed, standing upright on the barges as they come into port?  If they are fully or mostly fueled, they might actually be able to do it.

  The upper stage would be a stunt, as I don't think SpaceX has quite figured out how to handle reentry for that stage.

   Suggestion?  Plug Nozzle.  Gives optimal performance during all phases of flight.  Yeah, I doubt that they've developed one in house, but they have the systems that they would need, just have to develope the actual plug nozzle itself.  Most of the hard work was done in the 1960's and should make developement quite a bit easier.

i believe it will be flying with a dummy 2nd stage.

please correct me if i'm wrong on that
Title: Re: SpaceX DragonFly Discussion Thread
Post by: rcoppola on 08/06/2014 07:42 PM
Crazy idea here.

If they could rig it, wouldn't be interesting if SpaceX were to attempt to land both first and second stages of the Falcon 9 used in the Inflight Abort test?

    Just need 2 barges and landing gear on the upper stage.  (yeah and a whole avionics upgrade, etc and so forth).

   As neither of the stages is planned to go into orbit, it would be a whole lot more economical, (and one heck of a PR stunt for SpaceX to do that, then film the two barges with both stages on landing gear deployed, standing upright on the barges as they come into port?  If they are fully or mostly fueled, they might actually be able to do it.

  The upper stage would be a stunt, as I don't think SpaceX has quite figured out how to handle reentry for that stage.

   Suggestion?  Plug Nozzle.  Gives optimal performance during all phases of flight.  Yeah, I doubt that they've developed one in house, but they have the systems that they would need, just have to develope the actual plug nozzle itself.  Most of the hard work was done in the 1960's and should make developement quite a bit easier.

i believe it will be flying with a dummy 2nd stage.

please correct me if i'm wrong on that
That's my impression as well. Although they do intend to recover the core stage post abort. Unless they changed their mind but I haven't heard they have. So should still make for quite an interesting event.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: rcoppola on 08/06/2014 07:44 PM
An actual Pad Abort can not be done at McGregor.
Why? IIRC, Blue Origin did their pad abort test at their facility in Texas.

. Also, a full-up pad abort would require most if not all SD fuel be consumed, necessitating a water landing. (Dragon is not meant to do a land landing under parachutes alone)
Do you have a source for any of this, because this does not match the impression, I have had. IIRC, parachutes are claimed to be a backup for the propulsive landing in case something goes wrong with starting up the super dracos. Anyone got an exact quote for this?

When the heck did this happen and why didn't I hear about it?
When did what happen?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Comga on 08/06/2014 07:49 PM
Crazy idea here.

If they could rig it, wouldn't be interesting if SpaceX were to attempt to land both first and second stages of the Falcon 9 used in the Inflight Abort test?

    Just need 2 barges and landing gear on the upper stage.  (yeah and a whole avionics upgrade, etc and so forth).

   As neither of the stages is planned to go into orbit, it would be a whole lot more economical, (and one heck of a PR stunt for SpaceX to do that, then film the two barges with both stages on landing gear deployed, standing upright on the barges as they come into port?  If they are fully or mostly fueled, they might actually be able to do it.

  The upper stage would be a stunt, as I don't think SpaceX has quite figured out how to handle reentry for that stage.

   Suggestion?  Plug Nozzle.  Gives optimal performance during all phases of flight.  Yeah, I doubt that they've developed one in house, but they have the systems that they would need, just have to develope the actual plug nozzle itself.  Most of the hard work was done in the 1960's and should make developement quite a bit easier.

The inflight abort test is a "Max Q" abort test.  The capsule will leave the blunt-ended booster in a supersonic airflow.  The booster most likely won't survive intact.  We know that the early Falcons broke up during uncontrolled reentries.  SpaceX won't do anything to moderate the forces that isn't on the flight stages.  They wouldn't, for instance, pre-deploy the grid fins for stability because that wouldn't simulate an emergency abort. 
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 08/06/2014 08:02 PM
An actual Pad Abort can not be done at McGregor.
Why? IIRC, Blue Origin did their pad abort test at their facility in Texas.

. Also, a full-up pad abort would require most if not all SD fuel be consumed, necessitating a water landing. (Dragon is not meant to do a land landing under parachutes alone)
Do you have a source for any of this, because this does not match the impression, I have had. IIRC, parachutes are claimed to be a backup for the propulsive landing in case something goes wrong with starting up the super dracos. Anyone got an exact quote for this?

When the heck did this happen and why didn't I hear about it?
At the Dragon v2 unveil, Elon Musk mentioned that (about 7:30 into the video):
https://www.youtube.com/watch?v=yEQrmDoIRO8
Title: Re: SpaceX DragonFly Discussion Thread
Post by: rcoppola on 08/06/2014 08:26 PM
The fact that the parachutes will act as a backup in case something goes wrong with the SDs is not in dispute, never has been.

What is in dispute is your contention that after such an occurrence and the resulting parachutes deploy, that Dragon V2 will land on land and not in the water. Elon said that Dragon V2 can still safely land if no SDs are available. He didn't say where it would safely land in that sentence. Judging by everything seen and heard with regards to propulsive vs. non-propulsive landing, they will do non-propulsive landings in the Atlantic.

For the sake of you and I filling this thread up, let's try to have this answered definitively. I'm always open to being incorrect...or not.

Edit: This article has it the way I believe it will work. But it's just one source and I don't think taken from an attributable quote.

"If the engines detect any problems, the landing thrusters wont fire; parachutes will deploy and the spacecraft will default to a splashdown landing instead."

http://motherboard.vice.com/read/spacex-unveiled-its-reusable-dragon-v2-spacecraft-but-questions-still-abound
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars_J on 08/06/2014 08:49 PM
Edit: This article has it the way I believe it will work. But it's just one source and I don't think taken from an attributable quote.

"If the engines detect any problems, the landing thrusters wont fire; parachutes will deploy and the spacecraft will default to a splashdown landing instead."

http://motherboard.vice.com/read/spacex-unveiled-its-reusable-dragon-v2-spacecraft-but-questions-still-abound

I don't see that really working well, unless the landing pad is *right* on the beach. There won't be enough propellant for a significant divert maneuver.

Dragon v2 could likely handle a parachute landing on land without landing thruster assist, but it would likely be very rouch and cause damage to the capsule.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: symbios on 08/06/2014 08:56 PM
This statement is taken out of context. This statement is in regards to decent not pad abort.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: oiorionsbelt on 08/06/2014 09:06 PM
I have always assumed abort to splash down under parachute but now I'm wondering how much the Dragon legs will aid in a parachute, land landing. Are they enough, in an emergency to soften the impact enough for survivability? Sort of like a crumple zone.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: rcoppola on 08/06/2014 09:13 PM
This statement is taken out of context. This statement is in regards to decent not pad abort.
It's not out of context at all. Regardless of abort or non-abort mission decent profiles, both of which we have been discussing, my contention is that any non-propulsive decent whether because of an abort scenario or because of SDs not working on a regular mission decent profile, the Dragon V2 will land in the water not on land.

That Dragon V2 has not been designed and will not attempt a land landing under ONLY parachutes. If parachutes are all it has for whatever reason, it will land in the water not on land. THAT is what we are trying to determine. Although I stated my thinking on it over 2 pages now. I can't be any clearer on it. (That doesn't mean I'm right but have seen nor heard anything that says I'm definitively wrong)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: yg1968 on 08/06/2014 09:18 PM
The fact that the parachutes will act as a backup in case something goes wrong with the SDs is not in dispute, never has been.

What is in dispute is your contention that after such an occurrence and the resulting parachutes deploy, that Dragon V2 will land on land and not in the water. Elon said that Dragon V2 can still safely land if no SDs are available. He didn't say where it would safely land in that sentence. Judging by everything seen and heard with regards to propulsive vs. non-propulsive landing, they will do non-propulsive landings in the Atlantic.

For the sake of you and I filling this thread up, let's try to have this answered definitively. I'm always open to being incorrect...or not.

Edit: This article has it the way I believe it will work. But it's just one source and I don't think taken from an attributable quote.

"If the engines detect any problems, the landing thrusters wont fire; parachutes will deploy and the spacecraft will default to a splashdown landing instead."

http://motherboard.vice.com/read/spacex-unveiled-its-reusable-dragon-v2-spacecraft-but-questions-still-abound

I think that the statement in the article is wrong. Here is what Elon Musk actually said:

Quote from: Elon Musk
Dragon version two still retains the parachutes of Dragon version one, so that - what it'll do when it reaches a particular altitude just a few miles before landing, it will test the engines, verify that all the engines are working, it will then proceed to a propulsive landing. If there's any anomaly detected with the engines or the propulsion system it will then deploy the parachutes to ensure a safe landing even in the event the propulsion system is not working. Even after starting the propulsion system, it can afford to lose up to two engines and still land safely. After the engines are started it deploys the landing legs for a soft landing.

http://shitelonsays.com/transcript/spacex-unveils-dragon-2-2014-05-29

Title: Re: SpaceX DragonFly Discussion Thread
Post by: symbios on 08/06/2014 09:23 PM
Edit: This article has it the way I believe it will work. But it's just one source and I don't think taken from an attributable quote.

"If the engines detect any problems, the landing thrusters wont fire; parachutes will deploy and the spacecraft will default to a splashdown landing instead."

http://motherboard.vice.com/read/spacex-unveiled-its-reusable-dragon-v2-spacecraft-but-questions-still-abound

I don't see that really working well, unless the landing pad is *right* on the beach. There won't be enough propellant for a significant divert maneuver.

Dragon v2 could likely handle a parachute landing on land without landing thruster assist, but it would likely be very rouch and cause damage to the capsule.

Sorry for the misunderstanding. To clarify the statement quoted here by rcoppola is taken out of context. This statement as yg1968 pointed to is regarding ascent and not pad abort. The rest I'm not arguing about.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: rcoppola on 08/06/2014 09:25 PM
The fact that the parachutes will act as a backup in case something goes wrong with the SDs is not in dispute, never has been.

What is in dispute is your contention that after such an occurrence and the resulting parachutes deploy, that Dragon V2 will land on land and not in the water. Elon said that Dragon V2 can still safely land if no SDs are available. He didn't say where it would safely land in that sentence. Judging by everything seen and heard with regards to propulsive vs. non-propulsive landing, they will do non-propulsive landings in the Atlantic.

For the sake of you and I filling this thread up, let's try to have this answered definitively. I'm always open to being incorrect...or not.

Edit: This article has it the way I believe it will work. But it's just one source and I don't think taken from an attributable quote.

"If the engines detect any problems, the landing thrusters wont fire; parachutes will deploy and the spacecraft will default to a splashdown landing instead."

http://motherboard.vice.com/read/spacex-unveiled-its-reusable-dragon-v2-spacecraft-but-questions-still-abound

I think that this sentence is wrong. Here is what Elon Musk actually said:

Quote from: Elon Musk
Dragon version two still retains the parachutes of Dragon version one, so that - what it'll do when it reaches a particular altitude just a few miles before landing, it will test the engines, verify that all the engines are working, it will then proceed to a propulsive landing. If there's any anomaly detected with the engines or the propulsion system it will then deploy the parachutes to ensure a safe landing even in the event the propulsion system is not working. Even after starting the propulsion system, it can afford to lose up to two engines and still land safely. After the engines are started it deploys the landing legs for a soft landing.

http://shitelonsays.com/transcript/spacex-unveils-dragon-2-2014-05-29
What I posted in that particular post, as I said, is not an attributable quote from Elon, it was what the author inferred. Elon never says "WHERE" that safe parachute landing would be. I submit it would be in the Atlantic, not back on land.

So I'm just looking for anything that definitively backs up my contention that Dragon V2 will never land on land if it doesn't have any SD propulsive control. It will never attempt a land landing under parachutes only.

As for the leg comment from orionsbelt:

 I don't think those legs are meant to handle that kind of force any more then the F9R legs could handle a really hard landing.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: oiorionsbelt on 08/06/2014 09:30 PM
Just to wander a bit from this tack, is there a scenario during ascent or descent, where abort can not bring Dragon down in the ocean? If not no need for land landing under chutes only, if there is such a scenario then there is a need for land landing under parachutes only. That doesn't mean the vehicle has to be reusable afterwards but it would need to be survivable.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: yg1968 on 08/06/2014 09:44 PM
Another quote from the same press conference suggests that Dragon version 2 will land on land except in emergency situations:

Quote from: Elon Musk
Yes, this [Dragon version 2] will land on land. In fact, much like the video you saw. We want to land this back at Cape Canaveral ideally. Initially, we may land it somewhere else, but it's a normal condition landing. Except for emergency landing, all landings will be on land.
http://shitelonsays.com/transcript/spacex-dragon-2-unveil-qa-2014-05-29

This quote on the reuse of the capsule is also interesting:

Quote from: Elon Musk
How many flights can Dragon v2 fly without any refurbishment? We're aiming for ten flights without any significant refurbishment and then the thing that would have to be refurbished is the main heat shield, but that remains to be seen. The heat shield material is called PICA-X version three, which is a phenolic impregnated carbon ablator. With each version we've been able to reduce the amount of recession that occurs in the heat shield. You can think of the heat shield like it's a giant brake pad, basically. The better that material technology gets, the more uses it can go through - just like a brake pad on a car, eventually it does need to be replaced, but I think we can eventually get up to, maybe, 100 flights or something like that.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cscott on 08/06/2014 09:51 PM
I don't see that really working well, unless the landing pad is *right* on the beach. There won't be enough propellant for a significant divert maneuver.

All the proposed launch and landing sites are *right* on the beach.  Not that this settles the issue one way or the other.  (With the exception of Vandenburg, but I don't believe crewed flights are planned for there.)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: yg1968 on 08/06/2014 09:52 PM
What I posted in that particular post, as I said, is not an attributable quote from Elon, it was what the author inferred. Elon never says "WHERE" that safe parachute landing would be. I submit it would be in the Atlantic, not back on land.

So I'm just looking for anything that definitively backs up my contention that Dragon V2 will never land on land if it doesn't have any SD propulsive control. It will never attempt a land landing under parachutes only.

As for the leg comment from orionsbelt:

 I don't think those legs are meant to handle that kind of force any more then the F9R legs could handle a really hard landing.

I think that you are right that landing on land is meant to be done with propulsion. If it's done without propulsion, it would make more sense to land in the water. But landing in the water will only be done in an emergency situation.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: rcoppola on 08/06/2014 10:07 PM
What I posted in that particular post, as I said, is not an attributable quote from Elon, it was what the author inferred. Elon never says "WHERE" that safe parachute landing would be. I submit it would be in the Atlantic, not back on land.

So I'm just looking for anything that definitively backs up my contention that Dragon V2 will never land on land if it doesn't have any SD propulsive control. It will never attempt a land landing under parachutes only.

As for the leg comment from orionsbelt:

 I don't think those legs are meant to handle that kind of force any more then the F9R legs could handle a really hard landing.

I think that you are right that landing on land is meant to be done with propulsion. If it's done without propulsion, it would make more sense to land in the water. But landing in the water will only be done in an emergency situation.
Yes. Exactly.

2 overall water landing scenarios:

1. Aborts
2. Detected issue with SDs upon systems check when returning from a regular operational mission.

All other nominal returns are propulsive land landings.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 08/06/2014 10:29 PM
I don't see that really working well, unless the landing pad is *right* on the beach. There won't be enough propellant for a significant divert maneuver.

Dragon v2 could likely handle a parachute landing on land without landing thruster assist, but it would likely be very rouch and cause damage to the capsule.
That's how I see it and understood it as well. They do have these piston legs that provide some extra cushioning as well.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: rcoppola on 08/06/2014 11:11 PM
I don't see that really working well, unless the landing pad is *right* on the beach. There won't be enough propellant for a significant divert maneuver.

Dragon v2 could likely handle a parachute landing on land without landing thruster assist, but it would likely be very rouch and cause damage to the capsule.
That's how I see it and understood it as well. They do have these piston legs that provide some extra cushioning as well.
Those legs are not intended to cushion that kind of force. Even if they were, that presupposes that Dragon is coming down on those chutes level. The capsule comes in at quite the nice angle with additional lateral forces from wind. Those legs would either rip off and/or cause the capsule to go on one hell of a tumble if they tried a land landing like that. No way you're landing Dragon on those legs with no propulsion.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Scylla on 08/06/2014 11:30 PM
In the argument back and forth on a sea or land landing after a pad abort, it seems to me the the KISS principle is being forgotten. Under KISS, you get the astronauts as far away, as fast as possible from the impending KABOOM and then get them down in the simplest way possible.

That would be a parachute sea landing.

Anything else adds complexity to an already extreme situation. Remember, the purpose is to save the lives of the astronauts. Not try to save the lives of the astronauts in a really cool way.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: oiorionsbelt on 08/07/2014 12:11 AM
Unless there is a chance that an abort does not make it to the ocean. Is there such a case?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cscott on 08/07/2014 12:45 AM
Unless there is a chance that an abort does not make it to the ocean. Is there such a case?
Again, look at the launch and landing sites.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Scylla on 08/07/2014 12:59 AM
If they can't reach the water from here, they have much bigger problems than where they land.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: MichaelRBrumm on 08/07/2014 02:14 AM
2 overall water landing scenarios:

1. Aborts
2. Detected issue with SDs upon systems check when returning from a regular operational mission.

All other nominal returns are propulsive land landings.

I could be wrong, but everything that I've read about the subject (including various quotes from SpaceX) indicates that this is correct. If someone has proof that this is wrong, please provide it. Otherwise, can we move on?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: 411rocket on 08/07/2014 02:45 AM
The fact that the parachutes will act as a backup in case something goes wrong with the SDs is not in dispute, never has been.

What is in dispute is your contention that after such an occurrence and the resulting parachutes deploy, that Dragon V2 will land on land and not in the water. Elon said that Dragon V2 can still safely land if no SDs are available. He didn't say where it would safely land in that sentence. Judging by everything seen and heard with regards to propulsive vs. non-propulsive landing, they will do non-propulsive landings in the Atlantic.

For the sake of you and I filling this thread up, let's try to have this answered definitively. I'm always open to being incorrect...or not.

Edit: This article has it the way I believe it will work. But it's just one source and I don't think taken from an attributable quote.

"If the engines detect any problems, the landing thrusters wont fire; parachutes will deploy and the spacecraft will default to a splashdown landing instead."

http://motherboard.vice.com/read/spacex-unveiled-its-reusable-dragon-v2-spacecraft-but-questions-still-abound

I think that this sentence is wrong. Here is what Elon Musk actually said:

Quote from: Elon Musk
Dragon version two still retains the parachutes of Dragon version one, so that - what it'll do when it reaches a particular altitude just a few miles before landing, it will test the engines, verify that all the engines are working, it will then proceed to a propulsive landing. If there's any anomaly detected with the engines or the propulsion system it will then deploy the parachutes to ensure a safe landing even in the event the propulsion system is not working. Even after starting the propulsion system, it can afford to lose up to two engines and still land safely. After the engines are started it deploys the landing legs for a soft landing.

http://shitelonsays.com/transcript/spacex-unveils-dragon-2-2014-05-29
What I posted in that particular post, as I said, is not an attributable quote from Elon, it was what the author inferred. Elon never says "WHERE" that safe parachute landing would be. I submit it would be in the Atlantic, not back on land.

So I'm just looking for anything that definitively backs up my contention that Dragon V2 will never land on land if it doesn't have any SD propulsive control. It will never attempt a land landing under parachutes only.

As for the leg comment from orionsbelt:

 I don't think those legs are meant to handle that kind of force any more then the F9R legs could handle a really hard landing.

Watch the Q&A after the Dragon V2 unveiling, at about 43:10, Elon starts on describing landing initially on the rear legs, & then front legs making contact, due to capsule angle from chute attachment. This was one of our members present that night, got a great recording, in addition to questions & autographs on F9 1.1 pictures.

It would not make sense, to deploy the legs for a water landing. But for testing purposes only, anything is possible (recent first stage landing tests).

https://www.youtube.com/watch?v=uBaLYDbk4fY&list=WL&index=5
Title: Re: SpaceX DragonFly Discussion Thread
Post by: MichaelRBrumm on 08/07/2014 03:08 AM
Elon starts on describing landing initially on the rear legs, & then front legs making contact, due to capsule angle from chute attachment.

That is the first somewhat convincing evidence of a possible parachute landing on land. However...

It would not make sense, to deploy the legs for a water landing.

Why not? The legs would absorb impact on water, and make the blunt body impact against a flat water surface less intense. These are emergency scenarios, so saltwater damage is not of high concern. Saving the passengers is paramount.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Coastal Ron on 08/07/2014 03:51 AM
Why not? The legs would absorb impact on water, and make the blunt body impact against a flat water surface less intense.

The legs don't have enough surface area to make much of a difference when they impact the water.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: darkenfast on 08/07/2014 04:03 AM
Okay, here's the issue then.  You have a known distance from the launch pad to the shore (which changes slightly with the tide).  You have a zone running from the beach out to a certain point past which it is much easier to retrieve people and a floating spacecraft.  Keep in mind that Dragon will need a certain depth to float and avoid slamming on the bottom in waves. You have wind coming from various directions which will affect both the drift of the spacecraft under chutes and it's behavior after splashdown.  We mere mortals don't really know how far Dragon can fly, yet.  My ignorant assumption is that Dragon will be safest either on the beach or out a certain distance where she can float safely until she can be brought under control.  Perhaps someone with more knowledge of the beach there can give us a guesstimate.  I'm sure Apollo had to work this all out too and plan for land, surf and water rescue!
Title: Re: SpaceX DragonFly Discussion Thread
Post by: MichaelRBrumm on 08/07/2014 04:35 AM
You have wind coming from various directions which will affect both the drift of the spacecraft under chutes and it's behavior after splashdown.

This would be one of the biggest issues I would have with an uncontrolled parachute landing on land: hitting the surface at a bad angle (or a structure) due to wind.

With water, you just aim reentry/abort to an appropriate distance offshore, and wind and drift becomes irrelevant.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 08/07/2014 01:48 PM
When the Dragon capsule returns from orbit, it might not land somewhere near water. As Musk said, they will check the function of the SuperDracos and then either do a powered or a parachute landing. In the latter case, they still have to be able to perform a safe landing. So to me that implies that the Dravon v2 can land on land with parachutes. It does not matter whether the capsule survives the landing as long as the passengers do. The legs would provide a nice cushion and if that is not enough, the heat shield would be a crush zone. The landing might be rough, but the only thing that matters is if it is survivable. IIRC Soyuz landing is not described as being all that pleasant either.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 08/07/2014 02:55 PM
Also, suppose that if one SD doesn't pass the test, they switch to parachutes.
A remaining set of 4 can still operate at 100% to give you a cushioning burn (Soyuz style, only softer).
At that point their functionality is not critical, so it's ok to operate w/o redundancy.


 
Title: Re: SpaceX DragonFly Discussion Thread
Post by: yg1968 on 08/07/2014 04:13 PM
When the Dragon capsule returns from orbit, it might not land somewhere near water. As Musk said, they will check the function of the SuperDracos and then either do a powered or a parachute landing. In the latter case, they still have to be able to perform a safe landing. So to me that implies that the Dravon v2 can land on land with parachutes. It does not matter whether the capsule survives the landing as long as the passengers do. The legs would provide a nice cushion and if that is not enough, the heat shield would be a crush zone. The landing might be rough, but the only thing that matters is if it is survivable. IIRC Soyuz landing is not described as being all that pleasant either.

I suspect that landing on land with parachutes is survivable but that it would only be done if no other option is available. In other words, if the SD malfunction, they would try to land in water if possible.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: yg1968 on 08/07/2014 04:20 PM
Watch the Q&A after the Dragon V2 unveiling, at about 43:10, Elon starts on describing landing initially on the rear legs, & then front legs making contact, due to capsule angle from chute attachment. This was one of our members present that night, got a great recording, in addition to questions & autographs on F9 1.1 pictures.

It would not make sense, to deploy the legs for a water landing. But for testing purposes only, anything is possible (recent first stage landing tests).

Here is the exact quote from Musk taken form that video:

Quote
Behind the dragon here is where the main chute is, and then the drogues are at the top and you can see those lines basically go from where the drogues are to the mains. Where it's held, where the parachute lines attach, is just above where the hatch is, and so it actually comes in at an angle. It'll be coming in through the wind with lateral velocity, and you want the load to be taken up by the legs. You don't want it to land on one leg, because then one leg is going to take too much load. By having two legs closer together actually helps that too. It sort of takes the initial impact on those two rear legs and then onto the front.

http://shitelonsays.com/transcript/spacex-dragon-2-unveil-qa-2014-05-29

Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 08/07/2014 06:14 PM

Here is the exact quote from Musk taken form that video:

Quote
Behind the dragon here is where the main chute is, and then the drogues are at the top and you can see those lines basically go from where the drogues are to the mains. Where it's held, where the parachute lines attach, is just above where the hatch is, and so it actually comes in at an angle. It'll be coming in through the wind with lateral velocity, and you want the load to be taken up by the legs. You don't want it to land on one leg, because then one leg is going to take too much load. By having two legs closer together actually helps that too. It sort of takes the initial impact on those two rear legs and then onto the front.

http://shitelonsays.com/transcript/spacex-dragon-2-unveil-qa-2014-05-29
And to me that means that Dragon v2 can land on land with chutes. I don't see a reason why that is so hard to believe for some people here. As I mentioned earlier, Blue Origin did the pad abort test on their Texas launch site as well and it landed safely on land with chutes.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Mongo62 on 08/07/2014 08:38 PM
And to me that means that Dragon v2 can land on land with chutes. I don't see a reason why that is so hard to believe for some people here. As I mentioned earlier, Blue Origin did the pad abort test on their Texas launch site as well and it landed safely on land with chutes.

How I see Dragon c2 landings:

Superdracos fully operational: propulsive-only landing on land

Superdracos partly operational: parachute-aided propulsive landing on land or water

Superdracos severely or entirely non-functional: parachute-only splashdown in water

I would expect that Dragon v2 descending on parachutes alone might impact the ground fairly hard and still have the passengers survive, but the spacecraft itself would be a write-off. This would be done only if there were no other options.

If the Superdracos are partly useable, then a parachute-aided propulsive landing would presumably be the better option (better control of location, ground speed and attitude, and lower rate of descent). A landing on either land or water would be possible, but water would be safer, if there is a choice. If the Superdracos are completely unuseable, then a parachute splashdown in water would be the obvious choice. Both of those options would allow for reuse of the Dragon, and would pose less risk of injury to the crew.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 08/07/2014 08:46 PM
I would expect that Dragon v2 descending on parachutes alone might impact the ground fairly hard and still have the passengers survive, but the spacecraft itself would be a write-off.
What is that based on? Also in case of a emergency crew escape, a harder landing is probably acceptable.
And again, BO did not seem to care about their launch escape test landing the capsule on terra firma. So if BO can do it, why can SpaceX?
Also, do we even know for sure that in case of a launch escape there wont be any propellant left for the superdracos to do a half second breaking burn right before the capsule hits the ground?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Robert Thompson on 08/07/2014 09:35 PM
BO has vertical descent. BO impact implies heat shield is a crush zone. Look at the dirt fly. So, BO implies survivability.
https://www.youtube.com/watch?v=S8NFLIJSMM4

EM's statements on rear legs certainly assure survivability during parachute landing on land. Those are some powerful shock absorbers, and some massive, or extremely engineered leg hard points, if EM's statements on rear legs are meant to imply that DragonFly can approach on its angle, not break anyone's neck, not damage the heat shield, skid to a stop, and preserve reuseability.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: 411rocket on 08/07/2014 09:58 PM
And to me that means that Dragon v2 can land on land with chutes. I don't see a reason why that is so hard to believe for some people here. As I mentioned earlier, Blue Origin did the pad abort test on their Texas launch site as well and it landed safely on land with chutes.

How I see Dragon c2 landings:

Superdracos fully operational: propulsive-only landing on land

Superdracos partly operational: parachute-aided propulsive landing on land or water

Superdracos severely or entirely non-functional: parachute-only splashdown in water

I would expect that Dragon v2 descending on parachutes alone might impact the ground fairly hard and still have the passengers survive, but the spacecraft itself would be a write-off. This would be done only if there were no other options.

If the Superdracos are partly useable, then a parachute-aided propulsive landing would presumably be the better option (better control of location, ground speed and attitude, and lower rate of descent). A landing on either land or water would be possible, but water would be safer, if there is a choice. If the Superdracos are completely unuseable, then a parachute splashdown in water would be the obvious choice. Both of those options would allow for reuse of the Dragon, and would pose less risk of injury to the crew.

This presumes a planned landing, at or near the launch site & not some other location. Such as NASA Houston for example, or Nevada. This is probably why the Dragonfly test program, is planned. Could also be a contingency plan, for a medical emergency to get someone to hospital ASAP, landing at an airport, with an ambulance waiting. A thruster landing, could be anywhere a helicopter can land, if testing supports this proposal. But in the interim, larger open areas are better.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Mongo62 on 08/07/2014 10:05 PM
I would expect that Dragon v2 descending on parachutes alone might impact the ground fairly hard and still have the passengers survive, but the spacecraft itself would be a write-off.
What is that based on? Also in case of a emergency crew escape, a harder landing is probably acceptable.
And again, BO did not seem to care about their launch escape test landing the capsule on terra firma. So if BO can do it, why can SpaceX?
Also, do we even know for sure that in case of a launch escape there wont be any propellant left for the superdracos to do a half second breaking burn right before the capsule hits the ground?

According to this Spaceflight101 article (http://www.spaceflight101.com/dragon-crs-1-mission-updates.html):

Quote
About 9 minutes before Splashdown, at an altitude of 13.7 Kilometers, Dragon opens its dual Drogue Chutes slowing the vehicle down. Full deployment of the Drogues triggers the Main Chute Opening Command. This occurs at an altitude of 3 Kilometers. Flying under the Main Chutes, Dragon is slowed to its landing speed of 17 to 20 Kilometers per Hour.

This is for Cargo Dragon, but I would expect that Dragon v2 under parachutes alone would have a similar vertical landing speed. This should be low enough that fatalities are unlikely, but the Dragon itself would be damaged.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 08/07/2014 10:42 PM
Quote
About 9 minutes before Splashdown, at an altitude of 13.7 Kilometers, Dragon opens its dual Drogue Chutes slowing the vehicle down. Full deployment of the Drogues triggers the Main Chute Opening Command. This occurs at an altitude of 3 Kilometers. Flying under the Main Chutes, Dragon is slowed to its landing speed of 17 to 20 Kilometers per Hour.
This is for Cargo Dragon, but I would expect that Dragon v2 under parachutes alone would have a similar vertical landing speed. This should be low enough that fatalities are unlikely, but the Dragon itself would be damaged.
I am not sure we can make that conclusion safely. First, the cargo dragon does not have legs. Second, it seems that Dragon v2 is going to have more horizontal momentum in some way. Third, it is not certain that a water landing is in any way safer for the crew or less damaging to the capsule.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Nilof on 08/07/2014 11:25 PM
20 km/h is fairly soft as far as capsule landings go. Apollo 15 splashed down at twice that speed (39.5 km/h, with one parachute failing). With all three parachutes working, the other Apollo capsules splashed down at ~35 km/h.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: TheWhiteZombie on 08/08/2014 06:15 AM
I'm reaching back a few pages in the thread, however I remember a question regarding whether or not there were two dragon v2s: one for each of the abort tests, and I just came across a video with Garrett Reisman stating the dragon from the pad abort test would be recycled for the in-flight abort test in January.

The 2014 AIAA conference on "Current Launch Vehicle Update" http://new.livestream.com/AIAAvideo/space2014/videos/58462185 (http://new.livestream.com/AIAAvideo/space2014/videos/58462185) it is interesting to watch what each company emphases.

almost exactly at the 30 minute mark. Sorry for digging this up if this question has already been answered.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: CuddlyRocket on 08/08/2014 08:00 AM
It does not matter whether the capsule survives the landing as long as the passengers do.

I wouldn't say it doesn't matter; those things are expensive! Obviously the capsule should be designed to maximise passenger survivability, but subject to that there's no harm in maximising capsule survivability as well!
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 08/08/2014 01:57 PM
It does not matter whether the capsule survives the landing as long as the passengers do.

I wouldn't say it doesn't matter; those things are expensive! Obviously the capsule should be designed to maximise passenger survivability, but subject to that there's no harm in maximising capsule survivability as well!
In case of a catastrophic launch vehicle failure that requires the use of the LAS, I think a little damage to the capsule from a slightly harder landing is the least of your worries. I am not even sure there is a lot of damage to be expected anyway.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 08/08/2014 02:00 PM
In case of a catastrophic launch vehicle failure that requires the use of the LAS, I think a little damage to the capsule from a slightly harder landing is the least of your worries. I am not even sure there is a lot of damage to be expected anyway.

We are not talking about launch abort. That will end in water for sure. We are talking about regular landings, scheduled for soft precision landing using the engines but ending as parachute landing because of engine trouble.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 08/08/2014 02:22 PM
We are not talking about launch abort. That will end in water for sure. We are talking about regular landings, scheduled for soft precision landing using the engines but ending as parachute landing because of engine trouble.
I am talking about launch abort as well as landing. It is very likely that it would end up in the water, but it is quite a way from the pad to the water and I find the requirement for a body of water to be nearby rather limiting.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 08/08/2014 04:43 PM
FWIW, if the legs have 50 cm travel, stopping from v=5 m/s at constant acceleration means a=2.5 g, over 0.2 seconds.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 08/08/2014 04:45 PM
We are not talking about launch abort. That will end in water for sure. We are talking about regular landings, scheduled for soft precision landing using the engines but ending as parachute landing because of engine trouble.
I am talking about launch abort as well as landing. It is very likely that it would end up in the water, but it is quite a way from the pad to the water and I find the requirement for a body of water to be nearby rather limiting.

So you are talking about first the need of an abort and then an abort gone badly wrong. Wow.

Title: Re: SpaceX DragonFly Discussion Thread
Post by: Burninate on 08/08/2014 06:02 PM
If something goes wrong and there is either a launch or a powered descent abort, the spacecraft becomes expendable, and the only priority becomes saving the passengers.  There's no need to speculate about the need for a water landing, because a hard parachute landing on tarmac that's survivable at the cost of breaking a few ribs and totalling the Dragon is perfectly acceptable.

I say this because you are suggesting redirect, which compromises the safety of the passengers for the safety of the crew capsule.  But that's not going to happen, because a crew loss would cost SpaceX considerably more than a capsule loss.

SpaceX can build a crew capsule historically cheaply.  Building one more isn't going to kill them.  Ideally they'll keep the abort rate down below the normal wear & tear replacement rate, even in the event they transition to substantially lower prices which require re-use.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 08/08/2014 06:25 PM
So you are talking about first the need of an abort and then an abort gone badly wrong. Wow.
No, I am saying that I have no reason to believe that the Dragon capsule will be required to splash down into water (instead of landing on land) when using chutes in case of
a) the SD thrusters failing on normal descent
b) a launch abort
Instead I am quite certain that the Dragon v2 can (but not necessarily will) perform a landing on solid ground with parachutes, in either case with little to no significant damage to the capsule and no harm to the crew.
Now, I may be wrong with this, but I interpret the statements made by various SpaceX people that way and I have not seen any convincing argument that indicates otherwise.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 08/08/2014 06:43 PM
So you are talking about first the need of an abort and then an abort gone badly wrong. Wow.
No, I am saying that I have no reason to believe that the Dragon capsule will be required to splash down into water (instead of landing on land) when using chutes in case of

You are making a differentiation without a difference. In case of abort the sea is very near. A trajectory into the sea is both the safest and the easiest. There is no reason at all to consider anything else in the abort case.

I am not disagreeing that Dragon can safely get people to the ground with parachutes in case that the engines fail the last test before the decision parachute or powered landing is made. And hopefully in the case that the engines fail a few seconds later upon landing but that is a close call IMO.

Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 08/08/2014 07:17 PM
You are making a differentiation without a difference. In case of abort the sea is very near. A trajectory into the sea is both the safest and the easiest. There is no reason at all to consider anything else in the abort case.
As I said "it can", but I don't think it will have to.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 08/09/2014 01:50 AM
There's the very simple case of Dragon coming in for a powered landing, and the SDs failing the startup test.   At that point you get parachute landing on land.

However, at 2.5 g, the impact should not break anything.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: fregate on 08/09/2014 04:12 AM
My $0.05 IMHO after landing on parachutes capsule would not be able to reused on the next flight (at least not without rigorous verification). AFAIK it was RSC Energia policy for VA PTK landing on backup parachute system.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 08/09/2014 05:05 AM
My $0.05 IMHO after landing on parachutes capsule would not be able to reused on the next flight (at least not without rigorous verification). AFAIK it was RSC Energia policy for VA PTK landing on backup parachute system.

All they need to do is record the acceleration during impact.  If above a certain level, it will trigger further inspections.  This is standard practice when shipping sensitive items via truck, for example.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: CuddlyRocket on 08/09/2014 07:45 AM
If something goes wrong and there is either a launch or a powered descent abort, the spacecraft becomes expendable, and the only priority becomes saving the passengers.

The overriding priority becomes saving the passengers; but if there's things you can do in the design or otherwise that don't increase the risk to passengers but do increase the chances of saving the spacecraft, then why not?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: hrissan on 08/12/2014 03:14 PM
SuperDracos have how much fuel? For accelerating to 100-200m/s, right? Then keeping 5% of that fuel during abort will allow to fully cushion the impact of parachute landing on the land.

Why everybody insist on spending ALL propellant during abort? Because you used to solid rocket LAS? :)

And as 0.5 meters of travel in the legs is enough to stop from 5m/s @ 2.5g I cannot understand why the capsule should be damaged by this more than by abort itself @ 10+g
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Giovanni DS on 08/12/2014 04:17 PM
While landing under parachutes the capsule probably would  not have the right attitude for a quick burn, if I remember well, the Dragon (v1) hits the water with an steep angle.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 08/12/2014 04:38 PM
While landing under parachutes the capsule probably would  not have the right attitude for a quick burn, if I remember well, the Dragon (v1) hits the water with an steep angle.

They could still do a burn, not using the one cluster that is highest - or starting it later when the Dragon reaches horizontal position.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: JasonAW3 on 08/12/2014 04:48 PM
While landing under parachutes the capsule probably would  not have the right attitude for a quick burn, if I remember well, the Dragon (v1) hits the water with an steep angle.

They could still do a burn, not using the one cluster that is highest - or starting it later when the Dragon reaches horizontal position.

Probably easier to use differential throttling.  Lower throttling on the high side at first until level, then normal throttling until landing.

But is it definately confirmed that they are going to use both parachutes and the Super Draco engines for land landings?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: SpunkyEnigma on 08/12/2014 05:00 PM

....

But is it definately confirmed that they are going to use both parachutes and the Super Draco engines for land landings?

No.  By default land landings will be SD only.   Pad aborts will always use parachutes for main braking, some possibility of SD burn similar to Soyuz burn on landing.

If you have to abort orbital landing and use parachutes, there's a good chance you're going to come down on land and will need to survive that.  Will available SDs fire in the last seconds?  That's the question, but I believe that you wouldn't because you already have a suspect SD system, and wouldn't want to trust it while swinging on the chutes.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Giovanni DS on 08/12/2014 06:26 PM
There is another aspect to consider, after an abort, if the capsule is going to land on solid terrain (much more like a controlled crash) you wouldn't want any residual propellants in tanks. The outer ring would be the first thing to break and tanks are there.

In order to avoid this failure case they should burn to depletion on abort. I wonder if RCS capability is still needed after breaking free.

Giovanni
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Dudely on 08/12/2014 07:07 PM
There is another aspect to consider, after an abort, if the capsule is going to land on solid terrain (much more like a controlled crash) you wouldn't want any residual propellants in tanks. The outer ring would be the first thing to break and tanks are there.

In order to avoid this failure case they should burn to depletion on abort. I wonder if RCS capability is still needed after breaking free.

Giovanni

The parachutes will be able to handle the job of flipping a tumbling stage to the proper attitude. Earlier tests have proven this capability.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: douglas100 on 08/12/2014 11:09 PM
In the case of a launch abort the Dragon will land in the sea. A parachute only landing is ok in these circumstances. Where there might be concern is if an SD failure results in a hard landing on a solid surface. You would not want the extra risk of tanks or lines breaking on impact. Hopefully SD redundancy will make this scenario unlikely.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: docmordrid on 08/19/2014 09:51 AM
Here we go....

Final FAA DragonFly Environmental Assessment

August 8, 2014

Link...(PDF) (http://www.faa.gov/about/office_org/headquarters_offices/ast/media/DragonFly_Final_EA_sm.pdf)

Quote
DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

Office of Commercial Space Transportation; Finding of No Significant Impact

AGENCY:  Federal Aviation Administration (FAA)

ACTION:  Finding of No Significant Impact (FONSI)
>
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cartman on 08/19/2014 02:05 PM
Quote
To support the DragonFly RLV activities under the experimental permit, SpaceX would construct a 40 foot by 40 foot launch pad.

Quote
SpaceX anticipates that the DragonFly RLV program would require up to 2 years to complete (2014 –2015). Therefore, the Proposed Action considers one new permit and one potential permit renewal. A maximum of 30 annual operations are proposed in each year of operation

Quote
The DragonFly RLV weighs approximately 14,000 pounds (lsb) un-fueled, with a height of 17ft and a base width of 13ft....maximum operational propellant load of approximately 400 gallons

They also have to notify Charles Graham Cattle Company 24h in advance of each operation  :)
They must also watch for whooping cranes (an endangered species) during migration periods, and cease activities ultil they have left the area.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Jet Black on 08/19/2014 02:48 PM
Is that the company that owns the infamous cows that we see running around in front of Grasshopper/F9R tests?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: RubberToe on 08/19/2014 03:07 PM
They also have to notify Charles Graham Cattle Company 24h in advance of each operation  :)
They must also watch for whooping cranes (an endangered species) during migration periods, and cease activities until they have left the area.

Someone should send a nice letter or e-mail to Charles and tell him that there are about 46,876 frothing Space-X fanboys who would really like to have him pass along that 24h notice to Chris here. If it helps at all, let him know that I have consumed several of his herd at the local Houston's here...

RT
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 08/19/2014 03:40 PM
How does the Full Propulsive Hopping differ from an abort situation? I assume that the acceleration by the SuperDracos is not the same? Seems like those SuperDracos can throttle very well.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: rpapo on 08/19/2014 03:59 PM
How does the Full Propulsive Hopping differ from an abort situation? I assume that the acceleration by the SuperDracos is not the same? Seems like those SuperDracos can throttle very well.
It helps when you can use 4 or 8 or 16 of them and still be stable.

EDIT: My mistake...
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Scylla on 08/19/2014 04:07 PM
Quote
It helps when you can use 4, 8, or 16 of them and still be stable.

16? ???  Doesn't the Dragon V2 have four clusters with 2 SuperDracos each?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 08/19/2014 04:12 PM
Quote
It helps when you can use 4, 8, or 16 of them and still be stable.

16? ???  Doesn't the Dragon V2 have four clusters with 2 SuperDracos each?
Indeed.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: JasonAW3 on 08/19/2014 04:56 PM
They also have to notify Charles Graham Cattle Company 24h in advance of each operation  :)
They must also watch for whooping cranes (an endangered species) during migration periods, and cease activities until they have left the area.

Someone should send a nice letter or e-mail to Charles and tell him that there are about 46,876 frothing Space-X fanboys who would really like to have him pass along that 24h notice to Chris here. If it helps at all, let him know that I have consumed several of his herd at the local Houston's here...

RT

Heck, Some of us, if we got 24h notice before a test would love to come see that!  Charles gould do BIG business with a steakhouse with a big picture windo to watch the tests.  Call it the "Roadhouse Blockhouse."
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lar on 08/19/2014 09:56 PM
They also have to notify Charles Graham Cattle Company 24h in advance of each operation  :)
They must also watch for whooping cranes (an endangered species) during migration periods, and cease activities until they have left the area.

Someone should send a nice letter or e-mail to Charles and tell him that there are about 46,876 frothing Space-X fanboys who would really like to have him pass along that 24h notice to Chris here. If it helps at all, let him know that I have consumed several of his herd at the local Houston's here...

RT

Heck, Some of us, if we got 24h notice before a test would love to come see that!  Charles gould do BIG business with a steakhouse with a big picture windo to watch the tests.  Call it the "Roadhouse Blockhouse."

Probably more suited to the general McGregor thread but ya, that's just a crazy enough idea that it might work as a business plan. Probably not but it'd be neat.  Serve all steaks with Tang.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: woods170 on 08/20/2014 07:37 AM
They also have to notify Charles Graham Cattle Company 24h in advance of each operation  :)
They must also watch for whooping cranes (an endangered species) during migration periods, and cease activities until they have left the area.

Someone should send a nice letter or e-mail to Charles and tell him that there are about 46,876 frothing Space-X fanboys who would really like to have him pass along that 24h notice to Chris here. If it helps at all, let him know that I have consumed several of his herd at the local Houston's here...

RT

Heck, Some of us, if we got 24h notice before a test would love to come see that!  Charles gould do BIG business with a steakhouse with a big picture windo to watch the tests.  Call it the "Roadhouse Blockhouse."

Probably more suited to the general McGregor thread but ya, that's just a crazy enough idea that it might work as a business plan. Probably not but it'd be neat.  Serve all steaks with Tang.
What? You just took a direct dig at Jim? Shame on you! ;)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: yg1968 on 08/20/2014 03:15 PM
Final report on the environmental assessment of Dragonfly was recently released:
http://www.faa.gov/about/office_org/headquarters_offices/ast/media/DragonFly_Final_EA_sm.pdf
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 08/20/2014 03:51 PM
Final report on the environmental assessment of Dragonfly was recently released:
http://www.faa.gov/about/office_org/headquarters_offices/ast/media/DragonFly_Final_EA_sm.pdf

Nice.
Quote
DragonFly RLV program would require up to two years to complete (2014-2015). Therefore, the Proposed Action considers one new permit and one potential permit renewal. A maximum of 30 annual operations are proposed in each year of operation.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Roy_H on 10/13/2014 03:39 PM
So has there been any sign of activity at McGregor? Any sightings of Dragon V2 or Dragonfly? Getting close to Pad abort test, and I would think that there would be several hops of Dragonfly first.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: douglas100 on 10/13/2014 03:58 PM
I don't think there's any need for  a Dragonfly flight before the abort test.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: RonM on 10/13/2014 04:12 PM
No need for Dragonfly tests before the abort test. The abort will use up the fuel and Dragon will land with parachutes. Hopefully with a splash in the ocean instead of a splat on land.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Llian Rhydderch on 10/13/2014 04:12 PM
They also have to notify Charles Graham Cattle Company 24h in advance of each operation  :)
They must also watch for whooping cranes (an endangered species) during migration periods, and cease activities until they have left the area.

Someone should send a nice letter or e-mail to Charles and tell him that there are about 46,876 frothing Space-X fanboys who would really like to have him pass along that 24h notice to Chris here. If it helps at all, let him know that I have consumed several of his herd at the local Houston's here...

RT

Heck, Some of us, if we got 24h notice before a test would love to come see that!  Charles gould do BIG business with a steakhouse with a big picture windo to watch the tests.  Call it the "Roadhouse Blockhouse."

Probably more suited to the general McGregor thread but ya, that's just a crazy enough idea that it might work as a business plan. Probably not but it'd be neat.  Serve all steaks with Tang.

Or Charles might be able to rent out some cots in the bunkhouse via Airbnb (https://www.airbnb.com/) and make a decent return.  I'm guessing beds inside a nearby house, or with steak and eggs for breakfast would go for $500 a night.
 
Title: Re: SpaceX DragonFly Discussion Thread
Post by: nimbostratus on 10/13/2014 05:29 PM
No need for Dragonfly tests before the abort test. The abort will use up the fuel and Dragon will land with parachutes. Hopefully with a splash in the ocean instead of a splat on land.


I don't think there's any need for  a Dragonfly flight before the abort test.

Agree.

But I have a new idea: integrade the pad abort test with the propulsive assisted landing test, to cut numbers of test and to save the expense of the helicopter.


Abort test is similar to a hop, with a difference in the ascending g force.

So I think abort tests bad better wait till the hop tests succeed, because hops are more like hovering and relatively less resky.

While the propulsive assisted landing tests can be intergrated with the abort test, because propulsive landing test are of high risk too if conducted seperately. Also test numbers are cut and the expense of the helicopter is saved.




Title: Re: SpaceX DragonFly Discussion Thread
Post by: Nindalf on 10/13/2014 05:43 PM
No need for Dragonfly tests before the abort test.
They might not need them, but they also might prefer to do some more cautious and gentle flight testing before trying such an extreme maneuver as an abort.

Or they could go the other way, and prefer to do simpler full-throttle abort testing (and prove that it works properly) before attempting delicate propulsive landing, with a significant probability of failure (which shouldn't ground the vehicle, just prevent the use of propulsive landing on working flights).
Title: Re: SpaceX DragonFly Discussion Thread
Post by: kch on 10/13/2014 05:51 PM
No need for Dragonfly tests before the abort test. The abort will use up the fuel and Dragon will land with parachutes. Hopefully with a splash in the ocean instead of a splat on land.


I don't think there's any need for  a Dragonfly flight before the abort test.

Agree.

But I have a new idea: integrade the pad abort test with the propulsive assisted landing test, to cut numbers of test and to save the expense of the helicopter.

A propulsive assisted landing test with no fuel (and therefore no propulsion)?  Ouch ...  :(
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Roy_H on 10/13/2014 09:17 PM
A propulsive assisted landing test with no fuel (and therefore no propulsion)?  Ouch ...  :(

We don't know that for sure. There must be enough fuel for an abort at MaxQ, and I would imagine that it would take somewhat more fuel for that than a pad abort, so there may be enough fuel left to land.

However it is required that they test the parachutes (open fully at this low altitude) and water landing, so it is a moot point.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Robotbeat on 10/14/2014 04:30 AM
DragonFly test hops wouldn't be a terrible idea, though... Might be a lower-key test than the abort test and would help sanity check everything.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: nimbostratus on 10/14/2014 04:45 AM
No need for Dragonfly tests before the abort test. The abort will use up the fuel and Dragon will land with parachutes. Hopefully with a splash in the ocean instead of a splat on land.


I don't think there's any need for  a Dragonfly flight before the abort test.

Agree.

But I have a new idea: integrade the pad abort test with the propulsive assisted landing test, to cut numbers of test and to save the expense of the helicopter.

A propulsive assisted landing test with no fuel (and therefore no propulsion)?  Ouch ...  :(

Not likely.

Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 10/14/2014 07:17 AM
DragonFly test hops wouldn't be a terrible idea, though... Might be a lower-key test than the abort test and would help sanity check everything.

Maybe not a terrible idea. But a really bad idea IMO. A hop is significantly more complex than the abort. Why put it on the critical path to something that is essential for program success? They have proposed parachute landing for a reason. Even though we all hope - and I personally believe - they can achieve fully propulsive landing before commercial service begins.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Robotbeat on 10/14/2014 01:46 PM
It WOULDN'T be on the critical path, that's the point.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 10/14/2014 02:27 PM
It WOULDN'T be on the critical path, that's the point.

If you want to do it before Pad Abort it is on the critical path. Especially if it is the only vehicle at the time - VERY critical. ;)

Edit: If you are thinking of a separate vehicle, there is none at this time, at least this is a very safe assumption.

Title: Re: SpaceX DragonFly Discussion Thread
Post by: Zardar on 10/14/2014 02:38 PM
It WOULDN'T be on the critical path, that's the point.

If you want to do it before Pad Abort it is on the critical path. Especially if it is the only vehicle at the time - VERY critical. ;)

Edit: If you are thinking of a separate vehicle, there is none at this time, at least this is a very safe assumption.

Even if it was a separate vehicle, if you test that in McGregor, and on the small, but non-zero chance that it goes off like a draco-powered catherine wheel through the local herd, you can be sure it will land itself into the critical path with quite an impressive and toxic boom.

In fact, if any separate vehicle test(s) don't go 100% nominally, they would almost certainly delay the Pad Abort.
(I wouldn't expect any less from spacex)

Title: Re: SpaceX DragonFly Discussion Thread
Post by: douglas100 on 10/14/2014 03:41 PM
I think it is very likely that the Dragonfly test vehicle will be different from the Dragon doing both abort demos. If they are one and the same then I think the abort tests must come first since they are critical milestones.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 10/14/2014 08:18 PM
I think it is very likely that the Dragonfly test vehicle will be different from the Dragon doing both abort demos.
Why would it be?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: douglas100 on 10/14/2014 11:15 PM
To be clear I meant that I think that the Dragonfly tests will use a different vehicle from the abort tests. That would reduce the chances that a failure in one set of tests would impact on the other.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 10/15/2014 01:39 AM
To be clear I meant that I think that the Dragonfly tests will use a different vehicle from the abort tests. That would reduce the chances that a failure in one set of tests would impact on the other.
Ahh, ok that makes more sense. "Different" as in "separate"...
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Owlon on 10/15/2014 05:42 AM
What I could see happening is that the pad abort vehicle is also used to do the in-flight abort, and then used as the DragonFly vehicle while a new Dragon is built for the unmanned and manned orbital tests with finished insides. The abort test/DragonFly vehicle would have a non-flight inside; this could be as unfinished as the Dragon we saw at the V2 unveiling, or it could be simply prototype ECLSS and whatnot.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: ChefPat on 01/26/2015 08:17 PM
I wonder what the announcement of the Pad Abort test today will relate to for Dragonfly testing?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: baldusi on 05/06/2015 04:11 PM
Now that there's been a successful Dragon v2 Pad Abort test, and they are so close to landing on CRS-7 that they have converted F9Dev3 to the In-flight abort LV, the next step should be to test and retest those SuperDracos for landing, so they can earn confidence and iron out any anomalies.
Which brought me a funny idea, what if they launch the DragonFly from one of the recovered stages? They put it on top, with no upper stage, launch it as high as they are allowed and then let it get down on a powered descent. It would both help validate and certify Dragon for powered descent... and one up Blue Origin if they get their core back  :P
Title: Re: SpaceX DragonFly Discussion Thread
Post by: kevinof on 05/06/2015 04:23 PM
Would love to see it happen but it wont. I think SX is just too busy designing, building and testing what's currently on their plate. Adding in additional flights, testing and cost would just not work.

Would love to see it. I've no doubt the s/w for landing isn't ready  yet. Maybe another 6/12 months.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: deruch on 05/06/2015 04:42 PM
According to the totally unreliable FAA website, DragonFly doesn't yet have an experimental permit (neither does the F9R-dev since its permit expired earlier this year). 

https://www.faa.gov/data_research/commercial_space_data/permits/
Title: Re: SpaceX DragonFly Discussion Thread
Post by: baldusi on 05/06/2015 05:14 PM
Well, SpaceX appears to have done away with the plans at Airport America, since the ASDS experience has that envelop covered. And even if they want to test flown stages, McGregor can hardly push a km or so of height and lacks the sound suppression for a full 9 engine burn. They are amazing at doing acceptance testing, but they must be itching to do something like the DragonFly.
Crew Dragon won't even try propulsive landing without a robust certification plan with lots of testing. And Cargo Dragon will stay on the v1 platform for a while. Also, it would seem that the SD didn't perform 100% nominally in the Pad Abort Test. Thus, I would expect DragonFly to happen three months or so after In-Flight Abort at McGregor.
Launching a Dragon on a recovered stage would need to be done in Airport America because of the top cieling limitations. And it was actually a joke. If CRS-7 returns safely to the ASDS, that's more than enough upmanship.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: SVBarnard on 05/07/2015 08:38 AM
Will someone please explain to me whats going on here? So the certification that was issued last year for dragonfly has now expired? Why didn't spacex just start testing already? Why would they wait for the F9R to complete? We're gonna be waiting til next year the rate things are going!
Title: Re: SpaceX DragonFly Discussion Thread
Post by: JamesH on 05/07/2015 11:44 AM
Will someone please explain to me whats going on here? So the certification that was issued last year for dragonfly has now expired? Why didn't spacex just start testing already? Why would they wait for the F9R to complete? We're gonna be waiting til next year the rate things are going!

I'd guess at a lack of people/cash/time to do everything at once. They presumably have a timescale that gets them where they want to go, within budget.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: baldusi on 05/07/2015 02:25 PM
Will someone please explain to me whats going on here? So the certification that was issued last year for dragonfly has now expired? Why didn't spacex just start testing already? Why would they wait for the F9R to complete? We're gonna be waiting til next year the rate things are going!
Well, I believe that now that they have priced and won their crew services with expendable F9 and water landing, their top priority is to get the flag before Boeing. DragonFly will be the icing on the cake. I suspect that there were quite a few issues in the PA, which is expected and logical. But why rush it if they can feed back and do a further set of iterations to get the IFA right, and also help the certification.
My guess is that the reusable F9 will be solved by the simple pass of time, since CRS-7 or the ORBCOMM flights should be returned. By the end of 2017, they might have a couple of reflown stages. But in the end, launching on reusable F9 is just about cost for SpaceX, the price is fixed in their bid.
Land landing, on the other hand, is one of the "weaknesses" of their proposal. I will take a stab and assume that for now they want to iron out all the issues for IFA, but nothing gives the SD a good shake like the DragonFly program. So I will assume that DF will happen NLT by H1 2016.
I guess that if they can certify the land landing after the demo mission, they'll try to get the certification for the 2018 flights. Besides, by that time the CRS-2 contract should start and they might send a gutted Dragon v2 as cargo and use it as demonstrator of the landing capabilities.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cscott on 05/07/2015 02:27 PM
Will someone please explain to me whats going on here? So the certification that was issued last year for dragonfly has now expired? Why didn't spacex just start testing already? Why would they wait for the F9R to complete? We're gonna be waiting til next year the rate things are going!

I'd guess at a lack of people/cash/time to do everything at once. They presumably have a timescale that gets them where they want to go, within budget.
And my understanding is that Spaceport America (probably more accurately "the neighboring air force range") has proven to be a little less accommodating to SpaceX's plans than originally hoped.
So a combination of other testing going better than planned, Spaceport America testing being more complicated than planned, the loss of F9R1, and probably the results of NASA/range negotiations regarding flyback at the Cape/Vandenberg and where Dragon 2 propulsive landing fits in the contracts.

Lots of factors, but it seems that Spaceport America testing isn't on the "hurry up and do it" critical path right now, and the hardware that might be sent to Spaceport America is more critically needed elsewhere.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: deruch on 05/07/2015 02:50 PM
Will someone please explain to me whats going on here? So the certification that was issued last year for dragonfly has now expired? Why didn't spacex just start testing already? Why would they wait for the F9R to complete? We're gonna be waiting til next year the rate things are going!

They've never had an FAA Permit to start DragonFly testing.  Nothing expired (in relation to this test program).  Last year they got final approval of the DragonFly Environmental Assessment.  A Finding of No Significant Impacts by the FAA.  Which was a prerequisite for getting an Experimental Permit.  That EA, by the way, included a proviso that no further F9R-dev flights would be occurring at McGregor.  i.e. DragonFly had to wait until F9R-dev testing was finished in Texas.  After the failure of the F9R-dev1, that program got put on hold for a while but they originally were planning to test fly F9R-dev2 at least once in Texas before sending it to New Mexico for further testing.  All of which got overtaken by events--they found they could do the needed testing on actual launches.

So, to recap the position.  As far as we know, they haven't yet submitted an application for an Experimental Permit.  Though it's also possible that they actually do have one now but the FAA's website hasn't been updated to show that yet (their site is not reliable when it comes to timely updating of permits and licenses, etc.).  Or their application could be pending/under review.  SpaceX aren't in a major hurry to do this testing.  Dragon 2 won't be attempting propulsive landings for NASA launches in the beginning so there's no need to fast track it.  SpaceX has a HUGE amount of stuff going on, DragonFly is probably pretty low on the priority list.   The "rate things are going" is amazingly fast when you consider all the different things they have going on.  Yes.  I wouldn't be at all surprised if they didn't start DragonFly until well after the 1st launch (unmanned) of the Dragon 2 to the ISS.  Though they did include propulsive landing tests as a milestone for CCtCap, so maybe it'll start before that.  Who knows?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: clongton on 05/08/2015 08:43 PM
Will someone please explain to me whats going on here? We're gonna be waiting til next year the rate things are going!

And that is important why?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sanman on 05/09/2015 03:05 PM
I see that on that testflight roster it mentions 8 rounds of "Propulsive Assist Hopping" before later doing the "Full Propulsive Hopping". Why do you need so many testflights for "Propulsive Assist Hopping"? Is there any scenario where that capability is an end unto itself, or isn't "Propulsive Assist Hopping" merely supposed to be a prelude to the "Full Propulsive Hopping"?

And actually, when would "Full Propulsive Hopping" itself be used? Would that ever be used here on Earth, or would it mainly be meant for hopping around on the Moon/Mars/etc?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 05/09/2015 04:07 PM
I see that on that testflight roster it mentions 8 rounds of "Propulsive Assist Hopping" before later doing the "Full Propulsive Hopping". Why do you need so many testflights for "Propulsive Assist Hopping"? Is there any scenario where that capability is an end unto itself, or isn't "Propulsive Assist Hopping" merely supposed to be a prelude to the "Full Propulsive Hopping"?

Propulsive assist landing is much more likely to be certified early by NASA than full propulsive landing.

And actually, when would "Full Propulsive Hopping" itself be used? Would that ever be used here on Earth, or would it mainly be meant for hopping around on the Moon/Mars/etc?

Never ever. It is a test program to prepare for land landing.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sanman on 05/09/2015 05:14 PM
I see that on that testflight roster it mentions 8 rounds of "Propulsive Assist Hopping" before later doing the "Full Propulsive Hopping". Why do you need so many testflights for "Propulsive Assist Hopping"? Is there any scenario where that capability is an end unto itself, or isn't "Propulsive Assist Hopping" merely supposed to be a prelude to the "Full Propulsive Hopping"?

Propulsive assist landing is much more likely to be certified early by NASA than full propulsive landing.

Hi, I wasn't referring to "Propulsive Assist Landing", I was referring to the "Propulsive Assist Hopping" testflights which are listed. Or are you saying that demonstrating "Propulsive Assist Hopping" is a prerequisite for certification on "Propulsive Assist Landing"?

Quote from: guckyfan
And actually, when would "Full Propulsive Hopping" itself be used? Would that ever be used here on Earth, or would it mainly be meant for hopping around on the Moon/Mars/etc?

Never ever. It is a test program to prepare for land landing.

So the hopping flight demonstrations are a prerequisite for being certified for propulsive landing? Why wouldn't you just focus on demonstrating the propulsive landing? Why would you want to demonstrate hopping at all, if you weren't going to use it?
I'm referring to what was posted on the first page of the thread:

Some pretty awesome details in there. They anticipate the program taking two years (2014-2015), and there are four different flight profiles they will be testing.

(http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=34800.0;attach=584633;image)

That's a whole lot of hopping going on.

Or does it ultimately just become cheaper to use propulsive hopping as a way to test propulsive landing?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 05/09/2015 05:47 PM
Once they are confident of landing, I think hopping is faster and cheaper than helicopter drops. So yes, IMO the hopping is for the landing.

Plus my wild uneducated speculation, that they may want to discontinue using the trunk for stabilization on abort. If they are confident of stable flight without trunk they can load more payload in the trunk. Hopping would provide stability data. I am looking forward to those hops. If they would expend a trunk on every hop it may not be so cheap compared to helicopter dropping.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sanman on 05/09/2015 06:03 PM
At some point, once the objectives of demonstrating propulsive landings has been achieved, could they modify DragonFly into other configurations, in order to demonstrate (here on Earth) the ability to do propulsive landings on the Moon?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: TrevorMonty on 05/09/2015 06:07 PM
Once they are confident of landing, I think hopping is faster and cheaper than helicopter drops. So yes, IMO the hopping is for the landing.

Plus my wild uneducated speculation, that they may want to discontinue using the trunk for stabilization on abort. If they are confident of stable flight without trunk they can load more payload in the trunk. Hopping would provide stability data. I am looking forward to those hops. If they would expend a trunk on every hop it may not be so cheap compared to helicopter dropping.
They need trunk to stabilize flight after the engines cut out. Look what happens to dragon in LAS test once trunk separates.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 05/09/2015 06:15 PM
They need trunk to stabilize flight after the engines cut out. Look what happens to dragon in LAS test once trunk separates.

Not at all. Without propulsion Dragon will find a stable condition with the heatshield/bottom going first. What we saw after engine cut off was Dragon seeking to find that stable orientation but the time was too short to find it. I expect that Dragon during those hops will also not have time enough to find that orientation so will fly under constant engine thrust.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Robotbeat on 05/09/2015 07:11 PM
I wonder if they'll bother with tethered flight tests?

I probably would.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Eerie on 05/09/2015 07:12 PM
Not at all. Without propulsion Dragon will find a stable condition with the heatshield/bottom going first. What we saw after engine cut off was Dragon seeking to find that stable orientation but the time was too short to find it.

When you are using the escape system to, you know, escape, you may want to fly with the pointy end forward for a while.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cscott on 05/09/2015 07:21 PM
I think its more likely they'll eventually add a small parachute to recover the trunk for propulsive hop tests.  They can afford to hop lower/slower during the hop tests, since they don't need to duplicate the pad abort conditions.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Eerie on 05/09/2015 07:53 PM
I think its more likely they'll eventually add a small parachute to recover the trunk for propulsive hop tests.  They can afford to hop lower/slower during the hop tests, since they don't need to duplicate the pad abort conditions.

Why would there be a trunk during propulsive hop tests? Crew dragon is going to lose the trunk before re-entering anyway, its not part of a normal landing.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 05/09/2015 08:18 PM
Not at all. Without propulsion Dragon will find a stable condition with the heatshield/bottom going first. What we saw after engine cut off was Dragon seeking to find that stable orientation but the time was too short to find it.

When you are using the escape system to, you know, escape, you may want to fly with the pointy end forward for a while.

We were not talking about an abort. We were talking about DragonFly hops.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: ChrisWilson68 on 05/09/2015 08:55 PM
Once they are confident of landing, I think hopping is faster and cheaper than helicopter drops. So yes, IMO the hopping is for the landing.

Plus my wild uneducated speculation, that they may want to discontinue using the trunk for stabilization on abort. If they are confident of stable flight without trunk they can load more payload in the trunk. Hopping would provide stability data. I am looking forward to those hops. If they would expend a trunk on every hop it may not be so cheap compared to helicopter dropping.

The trunk is there for stability in the coast phase on abort.  Remember, in abort they use up all their prop in about 5 seconds, then coast for 15-20 seconds before dropping the trunk and deploying the drogue chute.

I'm sure they're very stable without the trunk while descending and while the Super Dracos are firing, but not while ascending.  In fact, the whole design is to make the capsule want to put the heat shield first, which is great when re-entering but not so much in the coast phase after an abort where you want the pointy end to keep pointing up.

I'm sure they won't use a trunk in the hopping tests because they're not testing abort, they're testing landing.  So, no need for a long coast phase without power.

They need trunk to stabilize flight after the engines cut out. Look what happens to dragon in LAS test once trunk separates.

Not at all. Without propulsion Dragon will find a stable condition with the heatshield/bottom going first. What we saw after engine cut off was Dragon seeking to find that stable orientation but the time was too short to find it. I expect that Dragon during those hops will also not have time enough to find that orientation so will fly under constant engine thrust.

And that's the problem -- on abort, there's no time for it to get to a stable orientation during coast and it's going fast through the thick atmosphere starting pointing the wrong way, which won't happen while coming in from orbit because in that case it has time in the thin atmosphere to stabilize.  On abort, it will probably tumble too much without the trunk in the coast phase.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 05/09/2015 09:13 PM
The trunk is there for stability in the coast phase on abort.  Remember, in abort they use up all their prop in about 5 seconds, then coast for 15-20 seconds before dropping the trunk and deploying the drogue chute.

I'm sure they're very stable without the trunk while descending and while the Super Dracos are firing, but not while ascending.  In fact, the whole design is to make the capsule want to put the heat shield first, which is great when re-entering but not so much in the coast phase after an abort where you want the pointy end to keep pointing up.

I'm sure they won't use a trunk in the hopping tests because they're not testing abort, they're testing landing.  So, no need for a long coast phase without power.

The trunk is used to provide stability during the boost phase, not or only secondary during the coast phase.

After the boost phase is completed in an abort situation Dragon can reorient itself aerodynamically for flying heatshield first. I don't see a problem with that. I may be wrong on this part but I don't think so.

So I wonder how the hops would be done. With or without trunk in the boost phase? Will there be a coast phase or will they go directly from boost up into the landing phase? I believe those things have not been discussed yet because the trunk with fins on abort was not known before.

Title: Re: SpaceX DragonFly Discussion Thread
Post by: Jim on 05/09/2015 09:40 PM

The trunk is used to provide stability during the boost phase, not or only secondary during the coast phase.
I believe those things have not been discussed yet because the trunk with fins on abort was not known before.


Wrong, it is there for the coast phase.  It is not needed for the boost phase, the vehicle has active control.  If it was not needed for the coast phase, it would not fly at all much less have fins.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 05/09/2015 10:04 PM
Not at all. Without propulsion Dragon will find a stable condition with the heatshield/bottom going first. What we saw after engine cut off was Dragon seeking to find that stable orientation but the time was too short to find it.

When you are using the escape system to, you know, escape, you may want to fly with the pointy end forward for a while.

In the hypothetical case that it aborts with no trunk, it will fly "pointy end forward" during the powered phase, which already puts it hundreds of meters and 5.5 seconds away from the rocket.  Once the thrusters are off, it will do what it did on trunk separation - flip around.

The risk is that it will not stop flipping.  There are many solutions in which spin doesn't damp out, and that would be fatal.

What the trunk does is keep the vehicle from spinning between the powered flight and parachute time.  So unless you want to force the capsule to deploy the parachutes right after the SDs cut off (you don't), you need the trunk with you.

Keep in mind though - the trunk looks heavy, but it's actually just big and light.  There's no harm carrying it with the capsule.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 05/09/2015 10:14 PM
Keep in mind though - the trunk looks heavy, but it's actually just big and light.  There's no harm carrying it with the capsule.

True, as long as you don't put payload there. I would like to be able to put payload there, however, for reasons related to servicing private space stations. But discussing that is OT for this thread. So no more from me.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: TomH on 05/10/2015 12:04 AM
After the failure of the F9R-dev1, that program got put on hold for a while but they originally were planning to test fly F9R-dev2 at least once in Texas before sending it to New Mexico for further testing.  All of which got overtaken by events--they found they could do the needed testing on actual launches.

SpaceX has a HUGE amount of stuff going on, DragonFly is probably pretty low on the priority list.   The "rate things are going" is amazingly fast when you consider all the different things they have going on.  Yes.  I wouldn't be at all surprised if they didn't start DragonFly until well after the 1st launch (unmanned) of the Dragon 2 to the ISS.  Though they did include propulsive landing tests as a milestone for CCtCap, so maybe it'll start before that.  Who knows?

Speaking of doing testing on actual (existing) flights, I wonder how hard it would be to begin using a model of Dragon 2 that is similar to the one just used in the pad abort test as the vehicle for later CRS missions. The thing already gets sent to LEO. It already undergoes an actual reentry. I realize some issues would be approaching ISS with that much hypergolic prop on board in a Dragon variant that has never been to ISS. Maybe the first of these would need to approach and berth with no prop for the SuperDracos. There is also the issue of getting approval of a landing site. Places that come to mind are Spaceport America, Mojave Desert around Edwards, maybe Kazakhstan, though were I Elon, I wouldn't want any chance of proprietary hardware falling into the wrong hands. Maybe even land the first ones on the ocean surface like Falcon stage 1 just to show it can be done.

This is just off the top of the head thinking, I realize there would be substantial issues to deal with. OTOH, it would be somewhat like using existing launches to test stage 1 landings. Thoughts?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Zed_Noir on 05/10/2015 12:35 AM

Speaking of doing testing on actual (existing) flights, I wonder how hard it would be to begin using a model of Dragon 2 that is similar to the one just used in the pad abort test as the vehicle for later CRS missions. The thing already gets sent to LEO. It already undergoes an actual reentry. I realize some issues would be approaching ISS with that much hypergolic prop on board in a Dragon variant that has never been to ISS. Maybe the first of these would need to approach and berth with no prop for the SuperDracos. There is also the issue of getting approval of a landing site. Places that come to mind are Spaceport America, Mojave Desert around Edwards, maybe Kazakhstan, though were I Elon, I wouldn't want any chance of proprietary hardware falling into the wrong hands. Maybe even land the first ones on the ocean surface like Falcon stage 1 just to show it can be done.

This is just off the top of the head thinking, I realize there would be substantial issues to deal with. OTOH, it would be somewhat like using existing launches to test stage 1 landings. Thoughts?

Somehow the lack of a CBM hatch on the Dragon 2 (aka Dragon V2, crewed Dragon, Dragonrider, etc) make it very unlikely.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: docmordrid on 05/10/2015 02:58 AM
One would think that depends on the size of the cargo containers on a particular mission. If they're smaller than an IDA's hatch, why not?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 05/10/2015 05:48 AM

The trunk is used to provide stability during the boost phase, not or only secondary during the coast phase.
I believe those things have not been discussed yet because the trunk with fins on abort was not known before.


Wrong, it is there for the coast phase.  It is not needed for the boost phase, the vehicle has active control.  If it was not needed for the coast phase, it would not fly at all much less have fins.

Thanks, I learned something. I wonder if I was the only one with that misunderstanding.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cosmicvoid on 05/10/2015 06:40 AM
Somehow the lack of a CBM hatch on the Dragon 2 (aka Dragon V2, crewed Dragon, Dragonrider, etc) make it very unlikely.

Not to mention lack of a grapple fixture.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Zed_Noir on 05/10/2015 09:28 AM
Somehow the lack of a CBM hatch on the Dragon 2 (aka Dragon V2, crewed Dragon, Dragonrider, etc) make it very unlikely.

Not to mention lack of a grapple fixture.

Why would you need a grapple fixture when you have an IDA docking hatch.  ::)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 05/10/2015 12:28 PM
I wonder if they'll bother with tethered flight tests?

I probably would.

They probably won't.

The drop tests should validate precision control. Take-offs from the pad for parachute-assisted landings will validate take-off control. Hopping should round out the envelope.

Their testing boldness continues to increase as shown by just-completed pad abort where eight engine performance was demo'd 24 hrs before live launch from a pad they have fully booked.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: baldusi on 05/10/2015 04:37 PM

Speaking of doing testing on actual (existing) flights, I wonder how hard it would be to begin using a model of Dragon 2 that is similar to the one just used in the pad abort test as the vehicle for later CRS missions. The thing already gets sent to LEO. It already undergoes an actual reentry. I realize some issues would be approaching ISS with that much hypergolic prop on board in a Dragon variant that has never been to ISS. Maybe the first of these would need to approach and berth with no prop for the SuperDracos. There is also the issue of getting approval of a landing site. Places that come to mind are Spaceport America, Mojave Desert around Edwards, maybe Kazakhstan, though were I Elon, I wouldn't want any chance of proprietary hardware falling into the wrong hands. Maybe even land the first ones on the ocean surface like Falcon stage 1 just to show it can be done.

This is just off the top of the head thinking, I realize there would be substantial issues to deal with. OTOH, it would be somewhat like using existing launches to test stage 1 landings. Thoughts?

Somehow the lack of a CBM hatch on the Dragon 2 (aka Dragon V2, crewed Dragon, Dragonrider, etc) make it very unlikely.
CRS-2 actually allowed for IDA equipped vehicles. And I doubt that they'll will waste the uncrewed demonstration flight and thus it won't flight empty. I wouldn't be surprised if SpaceX actually wins a fat contract in CRS-2 (a likely outcome), they might offer an uncrewed Dragon v2 as a one-off mission. For CRS-2 it will offer cargo without the cost of crew time required for training and actual berthing operation, and it wouldn't conflict with any CBM CVV. It could also sand unpressurized cargo that's not well behaved in an abort situation. And it would allow to certify the propulsive (assited?) landing. Size limited unpressurized cargo might be manifested on a different flight.
Now, how does this affects DragonFly? Well, I believe that the cheapest opportunity to certify the Crewed Dragon for propulsive landing would be the Uncrewed Flight. But it would seem like they won't go that route and DragonFly might actually happen after it. Besides, they must have a mountain of certificates in development for water landing and redoing it for propulsive landing will take a while. And SpaceX wants that flag!
Thus, I would assume, that the next cheapest and safest way is to do the DragonFly program after Uncrewed Flight, and once all the kinks are out, they can negotiate a single Dragon v2 flight within their CRS-2 program, with the specific purpose of demonstrating the propulsive landing. It would also allow for a significant amount of downmass with a relatively gentle landing and could probably be in the hands of investigators at L+4hrs. Nothing that CST-100 Cargo wouldn't offer. But a nice thing to have if it doesn't cost anything.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Robotbeat on 05/10/2015 05:25 PM
I wonder if they'll bother with tethered flight tests?

I probably would.

They probably won't.

The drop tests should validate precision control. Take-offs from the pad for parachute-assisted landings will validate take-off control. Hopping should round out the envelope.

Their testing boldness continues to increase as shown by just-completed pad abort where eight engine performance was demo'd 24 hrs before live launch from a pad they have fully booked.
I don't expect them to fly tethered tests. But I certainly would as that's a lot cheaper than building a new expensive spacecraft.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 05/10/2015 06:29 PM
I wonder if they'll bother with tethered flight tests?

I probably would.

They probably won't.

The drop tests should validate precision control. Take-offs from the pad for parachute-assisted landings will validate take-off control. Hopping should round out the envelope.

Their testing boldness continues to increase as shown by just-completed pad abort where eight engine performance was demo'd 24 hrs before live launch from a pad they have fully booked.
I don't expect them to fly tethered tests. But I certainly would as that's a lot cheaper than building a new expensive spacecraft.

What they can do is start with T/w<1, and see how weight is controllably taken off the legs, without ever leaving the ground.

Then T/w>1 for a brief period / hover, staying within what the legs can take if they were to suddenly shutdown all engines.

At that point you're gotten quite a bit of information.

Then T/w>1 for a couple of seconds, getting to parachute height, so you can abort by parachute.  Might not be pretty, but better than crashing.

Then they can start using it go get lunch downtown without getting caught in traffic.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Zed_Noir on 05/10/2015 07:09 PM


Somehow the lack of a CBM hatch on the Dragon 2 (aka Dragon V2, crewed Dragon, Dragonrider, etc) make it very unlikely.
CRS-2 actually allowed for IDA equipped vehicles. And I doubt that they'll will waste the uncrewed demonstration flight and thus it won't flight empty. I wouldn't be surprised if SpaceX actually wins a fat contract in CRS-2 (a likely outcome), they might offer an uncrewed Dragon v2 as a one-off mission. For CRS-2 it will offer cargo without the cost of crew time required for training and actual berthing operation, and it wouldn't conflict with any CBM CVV. It could also sand unpressurized cargo that's not well behaved in an abort situation. And it would allow to certify the propulsive (assited?) landing. Size limited unpressurized cargo might be manifested on a different flight.
Now, how does this affects DragonFly? Well, I believe that the cheapest opportunity to certify the Crewed Dragon for propulsive landing would be the Uncrewed Flight. But it would seem like they won't go that route and DragonFly might actually happen after it. Besides, they must have a mountain of certificates in development for water landing and redoing it for propulsive landing will take a while. And SpaceX wants that flag!
Thus, I would assume, that the next cheapest and safest way is to do the DragonFly program after Uncrewed Flight, and once all the kinks are out, they can negotiate a single Dragon v2 flight within their CRS-2 program, with the specific purpose of demonstrating the propulsive landing. It would also allow for a significant amount of downmass with a relatively gentle landing and could probably be in the hands of investigators at L+4hrs. Nothing that CST-100 Cargo wouldn't offer. But a nice thing to have if it doesn't cost anything.

What you suggest seems doable with a restricted cargo manifest. However don't think NASA will go for it.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: TomH on 05/11/2015 02:24 AM
What you suggest seems doable with a restricted cargo manifest. However don't think NASA will go for it.

Perhaps at a lower price. NASA gets some cargo up at a lower price, SpaceX gets some remuneration.  I could see the first CST-100 doing this and the first Dragon2 doing it sans prop for the SDracos. Later, after several manned Dragon2s have visited ISS, another unmanned with small sized cargo could be used for the first retropulsive landing. May as well get a little more out of these flights if they're going to ISS anyway.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: TomH on 07/28/2015 05:05 AM
Chris' article indicates that the first unmanned Dragon2 will carry cargo to ISS:
http://www.nasaspaceflight.com/2015/07/saving-spaceship-dragon-contingency-chute/
In fact, there may be a second unmanned Dragon2 which would also carry cargo.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: TomH on 07/28/2015 05:48 AM
So Chris' latest article http://www.nasaspaceflight.com/2015/07/saving-spaceship-dragon-contingency-chute/  indicates that the first uncrewed Dragon2 will carry cargo, and that there may also be a second uncrewed Dragon2 which would also carry cargo. My question is this, being that the vehicle is uncrewed, how likely is it that the SuperDracos could be tested in a DragonFly landing scenario? Or would the first docking attempt of the spacecraft with ISS be too risky to carry the hypergolics aboard? What if the first flight is done successfully with no hypergolics, if there is a second uncrewed Dragon2, might they try a DragonFly landing on that flight? Or is DragonFly too far down the line to attempt it so early? After enough manned Dragon2 vehicles fly, I assume the first DragonFly landing will have to be an unmanned test. It just seems that the initial unmanned flight of Dragon2 to ISS would also be a good opportunity to test the powered landing ability of DragonFly.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: TrevorMonty on 07/28/2015 05:48 AM
Can SpaceX use Dragon2 on a CRS mission?
 Would have smaller hatch, limiting cargo options but that is a small price to pay for extra flight testing of a crew capsule.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: TomH on 07/28/2015 05:55 AM
They have to fly it unmanned to test it. It will go to ISS. Why send it empty when smaller cargo items that are able to fit through the hatch can be carried to the station? This would not be a regular resupply mission, but at the cost/Kg of cargo, sending it empty rather than with cramming it full of smaller cargo just doesn't make sense.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 07/28/2015 06:11 AM
They have to fly it unmanned to test it. It will go to ISS. Why send it empty when smaller cargo items that are able to fit through the hatch can be carried to the station? This would not be a regular resupply mission, but at the cost/Kg of cargo, sending it empty rather than with cramming it full of smaller cargo just doesn't make sense.

It is clear that the big size of the berthing port is needed for ISS supply. But on which percentage of  flights do they really transport big items? I would guess it is not that many. Am I wrong?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: docmordrid on 07/28/2015 06:32 AM
Dragon 1 has a 127x127 cm CBM hatch.  AIUI Cygnus uses a 94x94 cm CBM hatch, but IDA's tunnel is only 80 cm.  A tad tight.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Req on 07/28/2015 10:37 AM
So Chris' latest article http://www.nasaspaceflight.com/2015/07/saving-spaceship-dragon-contingency-chute/  indicates that the first uncrewed Dragon2 will carry cargo, and that there may also be a second uncrewed Dragon2 which would also carry cargo. My question is this, being that the vehicle is uncrewed, how likely is it that the SuperDracos could be tested in a DragonFly landing scenario? Or would the first docking attempt of the spacecraft with ISS be too risky to carry the hypergolics aboard? What if the first flight is done successfully with no hypergolics, if there is a second uncrewed Dragon2, might they try a DragonFly landing on that flight? Or is DragonFly too far down the line to attempt it so early? After enough manned Dragon2 vehicles fly, I assume the first DragonFly landing will have to be an unmanned test. It just seems that the initial unmanned flight of Dragon2 to ISS would also be a good opportunity to test the powered landing ability of DragonFly.

The first, and probably the first several V2 flights will be chute/ocean landing because they need to prove that system works as a primary objective of the program.  They will not bypass that notch on their belt to try to leap ahead to propulsive landing, they will mimic the entire mission that humans will be going on exactly.

The first Dragon V2 to visit the ISS will have a full load of hypergolics, because even when they are eventually doing propulsive landing, it's actual primary purpose is for abort.  And much like the chute landings, they will fly with a full load because they will be proving that the spacecraft works how humans will be using it, so that humans can begin using it.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Chris Bergin on 10/16/2015 04:53 PM
By the way, per L2's McGregor Photos and Update Section, Dragonfly has been photographed at McGregor, as has a big, big crane. I've asked SpaceX if they want to talk to us about the upcoming test objectives, but we'll be writing an article next week regardless.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Okie_Steve on 10/16/2015 05:55 PM
When SpaceX first started work on landing stages there was a lot if nay saying in some quarters, but for "DragonFly" you can hear the crickets chirping. They are being take *much* more seriously now, and for good reason.

I've got to admit, that pending a successful 'chute landing on the first (un)crew test it would be exciting to see a  propulsive landing test on the second, probably filled with trash bags or very low value down mass.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: wannamoonbase on 10/16/2015 06:04 PM
When SpaceX first started work on landing stages there was a lot if nay saying in some quarters, but for "DragonFly" you can hear the crickets chirping. They are being take *much* more seriously now, and for good reason.

I've got to admit, that pending a successful 'chute landing on the first (un)crew test it would be exciting to see a  propulsive landing test on the second, probably filled with trash bags or very low value down mass.

If they are doing drops from a crane it will be very interesting. Even the worlds largest crane doesn't give them much of a drop distance. 

I expected to see them start with hold down tests over a grated surface with simulated inputs.  But maybe they've done this out of site.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: joek on 10/16/2015 06:53 PM
For initial tests, that crane height looks like it should not be a limitation; from the  recent FAA experimental permit (https://www.faa.gov/about/office_org/headquarters_offices/ast/licenses_permits/media/Dragonfly%20Experimental%20Permit%20EP%2015-011%20All%20Documents%20%28Final%29.pdf), 29-Jul-2015:
Quote
Altitude: SpaceX may operate the Dragonfly vehicle to an altitude that does not exceed 80 feet AGL, in accordance with its application.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: oiorionsbelt on 10/16/2015 07:49 PM
If they are doing drops from a crane it will be very interesting. Even the worlds largest crane doesn't give them much of a drop distance. 

Probably not "drops" but tethered test flights such as those done by  Morpheus.

http://www.dailymotion.com/video/x2voskw
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 10/17/2015 09:56 PM
If they are doing drops from a crane it will be very interesting. Even the worlds largest crane doesn't give them much of a drop distance. 

Probably not "drops" but tethered test flights such as those done by  Morpheus.

http://www.dailymotion.com/video/x2voskw

Exactly - these are to validate and fine tune the flight model, so the control rules are right.

If the vehicle is responding in the way the computer is expecting it to, then within what's possible, the different maneuvers should be similar from a "difficulty" standpoint.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sghill on 10/18/2015 08:03 PM
For initial tests, that crane height looks like it should not be a limitation; from the  recent FAA experimental permit (https://www.faa.gov/about/office_org/headquarters_offices/ast/licenses_permits/media/Dragonfly%20Experimental%20Permit%20EP%2015-011%20All%20Documents%20%28Final%29.pdf), 29-Jul-2015:
Quote
Altitude: SpaceX may operate the Dragonfly vehicle to an altitude that does not exceed 80 feet AGL, in accordance with its application.
A tethered unmanned aircraft (or one flown indoors) doesn't need an airworthiness certificate.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Space Ghost 1962 on 10/18/2015 08:18 PM
If they are doing drops from a crane it will be very interesting. Even the worlds largest crane doesn't give them much of a drop distance. 

Probably not "drops" but tethered test flights such as those done by  Morpheus.

http://www.dailymotion.com/video/x2voskw

Exactly - these are to validate and fine tune the flight model, so the control rules are right.

If the vehicle is responding in the way the computer is expecting it to, then within what's possible, the different maneuvers should be similar from a "difficulty" standpoint.

Think both tethered flight (inertial platform, thruster fall-off issues) and drops (combustion instabilities, closed loop feedback issues).

Think of Grasshopper. They incrementally expanded the flight envelope, and then did simulated landings (or drops).

Unlike Grasshopper, where you'd never be able to have such a crane nor get to terminal velocity, you might get enough to be helpful in accelerating development of flight avionics/inertial platform/software for landing.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: joek on 10/18/2015 08:37 PM
A tethered unmanned aircraft (or one flown indoors) doesn't need an airworthiness certificate.

No tether exemption for DragonFly due to toxic propellants CFR §400.2(c)(1)(iii) (http://www.ecfr.gov/cgi-bin/text-idx?SID=88f8ae30c1feba92dd1bd21bfa8cf226&mc=true&node=se14.4.400_12&rgn=div8).
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sghill on 10/19/2015 04:51 PM
A tethered unmanned aircraft (or one flown indoors) doesn't need an airworthiness certificate.

No tether exemption for DragonFly due to toxic propellants CFR §400.2(c)(1)(iii) (http://www.ecfr.gov/cgi-bin/text-idx?SID=88f8ae30c1feba92dd1bd21bfa8cf226&mc=true&node=se14.4.400_12&rgn=div8).

Nice!  See, that's what I love about NSF.  I learn new stuff everyday from this site.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Chris Bergin on 10/21/2015 06:57 PM
By the way, per L2's McGregor Photos and Update Section, Dragonfly has been photographed at McGregor, as has a big, big crane. I've asked SpaceX if they want to talk to us about the upcoming test objectives, but we'll be writing an article next week regardless.

Here's the article - with L2 photos and some cool L2 renderings by Nathan :)

http://www.nasaspaceflight.com/2015/10/spacex-dragonfly-arrives-mcgregor-testing/

When they start the testing at McGregor we'll set up an update thread.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: DatUser14 on 10/21/2015 07:02 PM
Is the DragonFly  modified from the Pad Abort vehicle or a new build? sorry, my search fu is not very high.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: MattMason on 10/21/2015 07:17 PM
By the way, per L2's McGregor Photos and Update Section, Dragonfly has been photographed at McGregor, as has a big, big crane. I've asked SpaceX if they want to talk to us about the upcoming test objectives, but we'll be writing an article next week regardless.

Here's the article - with L2 photos and some cool L2 renderings by Nathan :)

http://www.nasaspaceflight.com/2015/10/spacex-dragonfly-arrives-mcgregor-testing/

When they start the testing at McGregor we'll set up an update thread.

Ooooh! That rendering  by Nathan of the Dragonfly with the crane in the background completely fooled me into thinking this already happened. He needs some watermarks or disclaimers or something!

"How to Train Your Dragon 2": I see what you did there. :) Nice story!
Title: Re: SpaceX DragonFly Discussion Thread
Post by: NovaSilisko on 10/21/2015 07:32 PM
"How to Train Your Dragon 2": I see what you did there. :) Nice story!

Thank okan for that one, he came up with that as a title for the lead image.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: PahTo on 10/21/2015 08:00 PM

Perhaps better suited to the "Rocket Engine QnA" thread, but since mentioned in the article--given the toxicity of the fuel and oxidizer, are the combustion byproducts of MMH and NTO toxic as well?  I know they're really hot, but any toxicity?  I wonder how they'll do the crane (remote control, or operator raise the vehicle, then get 3,000' away?--gotta' believe remotely operated...)
 
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 10/21/2015 08:02 PM
So Dragon can rise 7000ft, over 2km and still do a fully propulsive landing? WOW.

Title: Re: SpaceX DragonFly Discussion Thread
Post by: BrianNH on 10/21/2015 08:32 PM
I wouldn't be surprised if Dragonfly was modified to do that - using up some of the living/cargo space for extra fuel tanks.  That isn't a capability that Dragon 2 would need.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Comga on 10/21/2015 08:37 PM
I wouldn't be surprised if Dragonfly was modified to do that - using up some of the living/cargo space for extra fuel tanks.  That isn't a capability that Dragon 2 would need.

To do what?
Fly to 7000 ft?  It has that capability.
Carry cargo instead of passengers?  It has that capability.  (Technically Dragonfly won't carry passengers.  That was a comment for Dragon V2.)
There is no evidence that SpaceX is considering a modified Crew Dragon for anything, other than the rumored SAA for Red Dragon.
Of course, we won't be surprised if SpaceX does any of a number of wild things, because they have in the past. ;)

edit: clarity
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Alpha Control on 10/21/2015 08:38 PM

Perhaps better suited to the "Rocket Engine QnA" thread, but since mentioned in the article--given the toxicity of the fuel and oxidizer, are the combustion byproducts of MMH and NTO toxic as well?  I know they're really hot, but any toxicity?  I wonder how they'll do the crane (remote control, or operator raise the vehicle, then get 3,000' away?--gotta' believe remotely operated...)
 

In the Shuttle era, one of the main concerns post landing was any leaks from the RCS jets. They used the ground team in SCAPE suits equipped with "sniffers" to check for any MMH/NTO leaks. Would SpaceX use the same process, after each test? Seems reasonable to do that before allowing ground crews to approach the DragonFly.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars-J on 10/22/2015 12:08 AM
So Dragon can rise 7000ft, over 2km and still do a fully propulsive landing? WOW.

No. An abort uses up all the propellant, making a water landing a necessity. Dragon 2 is only has enough propellant for:
1) Abort
or
2) on-orbit ops and propulsive landing.
Not both.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: NovaSilisko on 10/22/2015 12:11 AM
Keep in mind for the hop test it won't be hauling the trunk, either. I'd venture it starts as a quick kick at full throttle to get going, then a very low (perhaps lowest throttle) thrust level afterward, until it reaches apogee and begins descent again, at which point it throttles back up. Almost exactly like Dev1's flight profile, minus the hover. It will be a far gentler ride than an abort.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: RocketmanUS on 10/22/2015 12:41 AM
So Dragon can rise 7000ft, over 2km and still do a fully propulsive landing? WOW.

No. An abort uses up all the propellant, making a water landing a necessity. Dragon 2 is only has enough propellant for:
1) Abort
or
2) on-orbit ops and propulsive landing.
Not both.
From the article the second hope test will be propulsive to about 7,000 ft and then propulsive landing ( engines throttled down ). For 12.5 seconds up and 12.5 seconds down the engines will not be at full power for the fully propulsive hop test.

But for an in flight or pad abort all or most of the propellant would be used.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: BrianNH on 10/22/2015 02:22 AM
I wouldn't be surprised if Dragonfly was modified to do that - using up some of the living/cargo space for extra fuel tanks.  That isn't a capability that Dragon 2 would need.

To do what?
Fly to 7000 ft?  It has that capability.
Carry cargo instead of passengers?  It has that capability.  (Technically Dragonfly won't carry passengers.  That was a comment for Dragon V2.)
There is no evidence that SpaceX is considering a modified Crew Dragon for anything, other than the rumored SAA for Red Dragon.
Of course, we won't be surprised if SpaceX does any of a number of wild things, because they have in the past. ;)

edit: clarity

As Lars pointed out, Dragon would not be expected to have enough fuel for both a propulsive high altitude launch and a propulsive landing.  It would not be unreasonable to add extra tanks to cover the fuel needed for the launch portion.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: yg1968 on 10/22/2015 03:41 AM
By the way, per L2's McGregor Photos and Update Section, Dragonfly has been photographed at McGregor, as has a big, big crane. I've asked SpaceX if they want to talk to us about the upcoming test objectives, but we'll be writing an article next week regardless.

Here's the article - with L2 photos and some cool L2 renderings by Nathan :)

http://www.nasaspaceflight.com/2015/10/spacex-dragonfly-arrives-mcgregor-testing/

When they start the testing at McGregor we'll set up an update thread.

I am confused. Is the grasshopper in the image still active? Is there still a grasshopper program?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: llanitedave on 10/22/2015 03:48 AM
It's retired.  Quite literally put out to pasture.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 10/22/2015 06:54 AM
As Lars pointed out, Dragon would not be expected to have enough fuel for both a propulsive high altitude launch and a propulsive landing.  It would not be unreasonable to add extra tanks to cover the fuel needed for the launch portion.

That sounds right. And the design might just be what is needed to land Red Dragon with a heavy payload on Mars too.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Chris Bergin on 10/22/2015 10:40 AM
Is the DragonFly  modified from the Pad Abort vehicle or a new build? sorry, my search fu is not very high.

Added a few words to the article to confirm this is the former Pad Abort vehicle that's now DragonFly (albeit it scrubbed clean, rebuilt and ready to go again).
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Req on 10/22/2015 10:59 AM
Is the DragonFly  modified from the Pad Abort vehicle or a new build? sorry, my search fu is not very high.

Added a few words to the article to confirm this is the former Pad Abort vehicle that's now DragonFly (albeit it scrubbed clean, rebuilt and ready to go again).

Which, it's worth reiterating for the sake of verbosity, actually started out as a cargo dragon, not a crew dragon(aka v2).
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Arb on 10/22/2015 02:37 PM
From the article the second hope test will be propulsive to about 7,000 ft and then propulsive landing ( engines throttled down ). For 12.5 seconds up and 12.5 seconds down the engines will not be at full power for the fully propulsive hop test.
Any one able to calculate what that equates to in delta-v?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Jet Black on 10/22/2015 03:14 PM
Is the DragonFly  modified from the Pad Abort vehicle or a new build? sorry, my search fu is not very high.

Added a few words to the article to confirm this is the former Pad Abort vehicle that's now DragonFly (albeit it scrubbed clean, rebuilt and ready to go again).

Do you have any idea how much rebuilding has been done? i.e. are they the same SuperDracos? any other notable differences?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: NovaSilisko on 10/22/2015 07:08 PM
They would probably hang it from the uppermost parachute mounting point. A place it's designed already to take hanging loads. We've seen the parachute deployment test of Dragon 2 a long time ago, which kept the nose cap in place.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: ClayJar on 10/22/2015 08:05 PM
From the article the second hope test will be propulsive to about 7,000 ft and then propulsive landing ( engines throttled down ). For 12.5 seconds up and 12.5 seconds down the engines will not be at full power for the fully propulsive hop test.
Any one able to calculate what that equates to in delta-v?

Would it be a reasonable napkin approximation to consider it simply a net of 25 seconds of gravity losses, with the initial and final positions and velocities being zero?  That would put it at g*25s, or 245m/s, right?  (Of course, this completely glosses over pretty much everything important, but hey.  ;D)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: manboy on 10/23/2015 01:58 AM
By the way, per L2's McGregor Photos and Update Section, Dragonfly has been photographed at McGregor, as has a big, big crane. I've asked SpaceX if they want to talk to us about the upcoming test objectives, but we'll be writing an article next week regardless.

Here's the article - with L2 photos and some cool L2 renderings by Nathan :)

http://www.nasaspaceflight.com/2015/10/spacex-dragonfly-arrives-mcgregor-testing/

When they start the testing at McGregor we'll set up an update thread.

"These include the “Propulsive assist landing” test – which will see DragonFly dropped from helicopter (an Erickson E‐model or equivalent) aided by three parachutes. This will be followed by the “Fully propulsive landing” test – again utilizing a helicopter and parachutes, concluding with a five-second firing of the SuperDracos for a smooth landing."

This doesn't sound correct.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars-J on 10/23/2015 02:20 AM
Why doesn't it sound correct?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: TrevorMonty on 10/23/2015 03:15 AM
As much as I like fully propulsive landing, the  propulsive assist landing on land seems safer plus it gives redundancy if there is parachute failure.

Let the cargo version use fully propulsive landing.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: CameronD on 10/23/2015 03:19 AM
Why doesn't it sound correct?

Most likely because a "fully propulsive landing” test shouldn't, logically, require parachutes?

(Note: I'm not, and I'm not suggesting anybody is, saying it's not factual.. but he's right - it doesn't sound correct)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Comga on 10/23/2015 03:33 AM
As much as I like fully propulsive landing, the  propulsive assist landing on land seems safer plus it gives redundancy if there is parachute failure.

Let the cargo version use fully propulsive landing.

It has always looked like a compromise would be optimum, at least for the interim: Drogue chutes and propulsive assist.  Plenty of time to test the SuperDracos after drogue deployment,  much less velocity to kill allowing for lower thrust over a longer time while eating the gravity loss, much less time than parachutes so less drift. No need to use the big chutes if all goes well.

However, this has never been discussed, to my knowledge.  Why?

edit: Corrected the wording
Title: Re: SpaceX DragonFly Discussion Thread
Post by: CameronD on 10/23/2015 07:02 AM
As much as I like fully propulsive landing, the  propulsive assist landing on land seems safer plus it gives redundancy if there is parachute failure.

Let the cargo version use fully propulsive landing.

It has always looked like a compromise would be optimum, at least for the interim: Drogue chutes and propulsive assist.  Plenty of time to test the SuperDracos after drogue deployment,  much less velocity to kill allowing for lower thrust over a longer time while eating the gravity loss, much less time than parachutes so less drift. No need to use the big chutes if all goes well.

However, this has never been discussed, to my knowledge.  Why?

Maybe drag from the drogue chutes / any chutes would interfere with GNC of the capsule using the SDs?


Title: Re: SpaceX DragonFly Discussion Thread
Post by: The Amazing Catstronaut on 10/23/2015 08:47 AM
As much as I like fully propulsive landing, the  propulsive assist landing on land seems safer plus it gives redundancy if there is parachute failure.

Let the cargo version use fully propulsive landing.

Above some critical altitude, can't the parachute also provide a level of redundancy in case of propulsion failure? The engines have a lot of engine out capability before that becomes a requirement.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: douglas100 on 10/23/2015 09:29 AM
As much as I like fully propulsive landing, the  propulsive assist landing on land seems safer plus it gives redundancy if there is parachute failure.

Let the cargo version use fully propulsive landing.

It has always looked like a compromise would be optimum, at least for the interim: Drogue chutes and propulsive assist.  Plenty of time to test the SuperDracos after drogue deployment,  much less velocity to kill allowing for lower thrust over a longer time while eating the gravity loss, much less time than parachutes so less drift. No need to use the big chutes if all goes well.

However, this has never been discussed, to my knowledge.  Why?

Maybe drag from the drogue chutes / any chutes would interfere with GNC of the capsule using the SDs?

Also, there may be a possibility of the SD plumes damaging any deployed parachute. That wouldn't matter if they were just using the SD's to kill the landing impact under parachutes.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Req on 10/23/2015 09:40 AM
This has been discussed ad naseam, and I'm not going to go dig up all of the links, but the officially stated idea behind a fully-propulsive crew landing is that the superdracos get tested at a high enough altitude that the main chutes can still deploy to save the mission in the event of a failure in the superdraco system.

"That the main chutes can still deploy to save the mission" implies a flight regime where the main chutes can still deploy and guarantee a chute landing - regardless of whether this particular flight regime required drogues to achieve or not.

The sequence for a crew fully-propulsive landing will be:

1) Enter regime where propulsive or main chutes will be effective
2) Fire SDs to ensure positive response
3a) SDs did not give positive response, initiate main chute landing profile
3b) SDs gave positive response, initiate propulsive landing profile

Drogues(or not) are independent of these decisions, and happen either as part of item #1 or item #3a AIUI.

Edit - clarity
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 10/23/2015 10:04 AM
Can you point to a discussion? I thought I have read everything about this on NSF and I have never seen a reference to drogues for propulsive landing.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Req on 10/23/2015 10:06 AM
Can you point to a discussion? I thought I have read everything about this on NSF and I have never seen a reference to drogues for propulsive landing.

I was intentionally vague on drogues because I can't think of a specific discussion on drogues with respect to Dragon landing profiles either.  What I am pointing out, though, is that it's irrelevant as part of the current debate, based on what has been publicly stated and discussed quite a bit here on NSF.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 10/23/2015 10:13 AM
Can you point to a discussion? I thought I have read everything about this on NSF and I have never seen a reference to drogues for propulsive landing.

I was intentionally vague on drogues because I can't think of a specific discussion on drogues with respect to Dragon landing profiles either.  What I am pointing out, though, is that it's irrelevant as part of the current debate, based on what has been publicly stated and discussed quite a bit here on NSF.

You changed your post after my request. You had unequivocally stated that droges would be part of any descent, parachutes or full SD powered landing. That is why I requested a pointer.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: JamesH on 10/23/2015 10:43 AM
Can you point to a discussion? I thought I have read everything about this on NSF and I have never seen a reference to drogues for propulsive landing.

I was intentionally vague on drogues because I can't think of a specific discussion on drogues with respect to Dragon landing profiles either.  What I am pointing out, though, is that it's irrelevant as part of the current debate, based on what has been publicly stated and discussed quite a bit here on NSF.

You changed your post after my request. You had unequivocally stated that droges would be part of any descent, parachutes or full SD powered landing. That is why I requested a pointer.

Why wouldn't drogues be part of any descent? They are a cheap and cheerful way of reducing speed, and therefore would result in less fuel being required in the case of propulsive landing, and would be required anyway for parachute landing to stabilise the Dragon prior to main chute deploy. So they are always on board, as they are needed for abort scenarios.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Req on 10/23/2015 10:54 AM
Can you point to a discussion? I thought I have read everything about this on NSF and I have never seen a reference to drogues for propulsive landing.

I was intentionally vague on drogues because I can't think of a specific discussion on drogues with respect to Dragon landing profiles either.  What I am pointing out, though, is that it's irrelevant as part of the current debate, based on what has been publicly stated and discussed quite a bit here on NSF.

You changed your post after my request. You had unequivocally stated that droges would be part of any descent, parachutes or full SD powered landing. That is why I requested a pointer.

Why wouldn't drogues be part of any descent? They are a cheap and cheerful way of reducing speed, and therefore would result in less fuel being required in the case of propulsive landing, and would be required anyway for parachute landing to stabilise the Dragon prior to main chute deploy. So they are always on board, as they are needed for abort scenarios.

Because they may not be necessary to reach terminal velocity at the desired altitude to test for propulsive/chute profiles, or to obtain the required stabilization to deploy one or both.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Semmel on 10/23/2015 10:58 AM
Landing takes much less fuel than the abort. Since the engines need to do both, a drogue is not required. It would just reduce payload.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: hkultala on 10/23/2015 11:05 AM
Landing takes much less fuel than the abort. Since the engines need to do both, a drogue is not required. It would just reduce payload.

No, the engines do not need to do BOTH (on same flight). They need to do EITHER.

In case of abort, use all fuel to abort and then land to sea using parachutes.
In case of succesful launch and deorbit, land to land using engines.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Req on 10/23/2015 11:11 AM
Landing takes much less fuel than the abort. Since the engines need to do both, a drogue is not required. It would just reduce payload.

Main chute landing is and will be considered the primary landing method for crew(with propulsive landing becoming an increasingly common "exception") until well after it is no longer the norm.  That's why I called it #3a instead of #3b.  Drogues will be included as part of the dry mass if the CHUTE landing system(not the propulsive landing system) needs them for decades to come, regardless of how it usually lands.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Semmel on 10/23/2015 11:33 AM
ok, let me rephrase.

Landing takes much less fuel than the abort. Since the engines need to be able to do both, a drogue is not required. It would just reduce payload.

Also, for propulsive landings, I dont know why you would use a drogue, makes things just more complicated. Of course landing by chutes is the abort scenario of propulsive landing. And landing per chutes is the scenario after a launch abort. But the fact stands, the use of drogues do not reduce launch mass.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: rpapo on 10/23/2015 11:55 AM
As long as the SuperDracos and all their fuel are needed for abort, there will always be a requirement for the Dragon capsule to have parachutes.  They may not need them for landing, but they will be there.  And since they are there, they provide a good backup to the propulsive landing system.

There are two costs to having parachutes: weight, and the cost of repacking or replacing them if they are used.  And since they have to be there, the weight is not optional.

For cargo flights, that may or may not be the case, depending on the decisions taken from the CRS-7 accident.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: MattMason on 10/23/2015 12:07 PM
Friends, friends, it seems we're doing "The White Zone is For Loading, There is No Stopping in the Yellow Zone" (https://www.youtube.com/watch?v=FyOX4G7TmE0) stuff. Wasn't this settled over a year ago?

Try Chris B.'s 8/2014 article where NASA and SpaceX says how typical Crew Dragon landings are to be done (http://www.nasaspaceflight.com/2014/08/dragon-v2-rely-parachutes-landing/).
Title: Re: SpaceX DragonFly Discussion Thread
Post by: JamesH on 10/23/2015 12:37 PM
Friends, friends, it seems we're doing "The White Zone is For Loading, There is No Stopping in the Yellow Zone" (https://www.youtube.com/watch?v=FyOX4G7TmE0) stuff. Wasn't this settled over a year ago?

Try Chris B.'s 8/2014 article where NASA and SpaceX says how typical Crew Dragon landings are to be done (http://www.nasaspaceflight.com/2014/08/dragon-v2-rely-parachutes-landing/).

Read it, must have missed the bit about whether a propulsive landing also used drogues to do initial slowdown and stabilisation, and in order to save fuel.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: TrueBlueWitt on 10/23/2015 02:21 PM
Friends, friends, it seems we're doing "The White Zone is For Loading, There is No Stopping in the Yellow Zone" (https://www.youtube.com/watch?v=FyOX4G7TmE0) stuff. Wasn't this settled over a year ago?

Try Chris B.'s 8/2014 article where NASA and SpaceX says how typical Crew Dragon landings are to be done (http://www.nasaspaceflight.com/2014/08/dragon-v2-rely-parachutes-landing/).

Read it, must have missed the bit about whether a propulsive landing also used drogues to do initial slowdown and stabilisation, and in order to save fuel.

Also.. Having the drogue already deployed should significantly reduce reaction time to deploy mains in an emergency.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: yg1968 on 10/23/2015 02:35 PM
Friends, friends, it seems we're doing "The White Zone is For Loading, There is No Stopping in the Yellow Zone" (https://www.youtube.com/watch?v=FyOX4G7TmE0) stuff. Wasn't this settled over a year ago?

Try Chris B.'s 8/2014 article where NASA and SpaceX says how typical Crew Dragon landings are to be done (http://www.nasaspaceflight.com/2014/08/dragon-v2-rely-parachutes-landing/).

Read it, must have missed the bit about whether a propulsive landing also used drogues to do initial slowdown and stabilisation, and in order to save fuel.

The 2014 article doesn't say that. Were you being sarcastic?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: JamesH on 10/23/2015 02:41 PM
Friends, friends, it seems we're doing "The White Zone is For Loading, There is No Stopping in the Yellow Zone" (https://www.youtube.com/watch?v=FyOX4G7TmE0) stuff. Wasn't this settled over a year ago?

Try Chris B.'s 8/2014 article where NASA and SpaceX says how typical Crew Dragon landings are to be done (http://www.nasaspaceflight.com/2014/08/dragon-v2-rely-parachutes-landing/).

Read it, must have missed the bit about whether a propulsive landing also used drogues to do initial slowdown and stabilisation, and in order to save fuel.

The 2014 article doesn't say that. Were you being sarcastic?

Yes. Sorry, sarcasm  doesn't come across very well except in my head. Point being, drogues were not mentioned at all in the article, so we don't know is they are used for all types of descent.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars-J on 10/23/2015 05:25 PM
Friends, friends, it seems we're doing "The White Zone is For Loading, There is No Stopping in the Yellow Zone" (https://www.youtube.com/watch?v=FyOX4G7TmE0) stuff. Wasn't this settled over a year ago?

Try Chris B.'s 8/2014 article where NASA and SpaceX says how typical Crew Dragon landings are to be done (http://www.nasaspaceflight.com/2014/08/dragon-v2-rely-parachutes-landing/).

Read it, must have missed the bit about whether a propulsive landing also used drogues to do initial slowdown and stabilisation, and in order to save fuel.

Also.. Having the drogue already deployed should significantly reduce reaction time to deploy mains in an emergency.

The new parachute system - as demonstrated in the Dragon 2 pad abort - is designed to deploy much faster (and at lower altitude) than the Dragon 1 parachutes.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: yg1968 on 10/23/2015 06:43 PM
By the way, per L2's McGregor Photos and Update Section, Dragonfly has been photographed at McGregor, as has a big, big crane. I've asked SpaceX if they want to talk to us about the upcoming test objectives, but we'll be writing an article next week regardless.

Here's the article - with L2 photos and some cool L2 renderings by Nathan :)

http://www.nasaspaceflight.com/2015/10/spacex-dragonfly-arrives-mcgregor-testing/

When they start the testing at McGregor we'll set up an update thread.

"These include the “Propulsive assist landing” test – which will see DragonFly dropped from helicopter (an Erickson E‐model or equivalent) aided by three parachutes. This will be followed by the “Fully propulsive landing” test – again utilizing a helicopter and parachutes, concluding with a five-second firing of the SuperDracos for a smooth landing."

This doesn't sound correct.

It has now been corrected. The four types of tests are described at the beginning of this thread:
http://forum.nasaspaceflight.com/index.php?topic=34800.0
Title: Re: SpaceX DragonFly Discussion Thread
Post by: oiorionsbelt on 10/23/2015 06:46 PM
Friends, friends, it seems we're doing "The White Zone is For Loading, There is No Stopping in the Yellow Zone" (https://www.youtube.com/watch?v=FyOX4G7TmE0) stuff. Wasn't this settled over a year ago?

Try Chris B.'s 8/2014 article where NASA and SpaceX says how typical Crew Dragon landings are to be done (http://www.nasaspaceflight.com/2014/08/dragon-v2-rely-parachutes-landing/).

Read it, must have missed the bit about whether a propulsive landing also used drogues to do initial slowdown and stabilisation, and in order to save fuel.

Also.. Having the drogue already deployed should significantly reduce reaction time to deploy mains in an emergency.

The new parachute system - as demonstrated in the Dragon 2 pad abort - is designed to deploy much faster (and at lower altitude) than the Dragon 1 parachutes.
Yes they use mortars to deploy the drogues on D2. Im not sure if that was the case for D1 or not.
 (Hmmm, Do mortars qualify as a pyrotechnic?)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars-J on 10/23/2015 06:47 PM
Friends, friends, it seems we're doing "The White Zone is For Loading, There is No Stopping in the Yellow Zone" (https://www.youtube.com/watch?v=FyOX4G7TmE0) stuff. Wasn't this settled over a year ago?

Try Chris B.'s 8/2014 article where NASA and SpaceX says how typical Crew Dragon landings are to be done (http://www.nasaspaceflight.com/2014/08/dragon-v2-rely-parachutes-landing/).

Read it, must have missed the bit about whether a propulsive landing also used drogues to do initial slowdown and stabilisation, and in order to save fuel.

Also.. Having the drogue already deployed should significantly reduce reaction time to deploy mains in an emergency.

The new parachute system - as demonstrated in the Dragon 2 pad abort - is designed to deploy much faster (and at lower altitude) than the Dragon 1 parachutes.
Yes they use mortars to deploy the drogues on D2. Im not sure if that was the case for D1 or not.
 (Hmmm, Do moratrs qualify as a pyrotechnic?)

The old ones used mortars too. But the new system (and location on capsule) is supposed to be more reliable and quicker, even when the capsule is tumbling.

Avoiding to fire the mortars and not having to repack parachutes is certainly part of the desire to do an all-propulsive landing.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: oiorionsbelt on 10/23/2015 06:59 PM
The skills developed with the DragonFly hops seems like something that would be useful for getting around on the surface of Mars as well.

If DragonFly strays too far from it's flight path on one of these hops, what type of "range safety" will it have?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: mme on 10/23/2015 07:01 PM
Friends, friends, it seems we're doing "The White Zone is For Loading, There is No Stopping in the Yellow Zone" (https://www.youtube.com/watch?v=FyOX4G7TmE0) stuff. Wasn't this settled over a year ago?

Try Chris B.'s 8/2014 article where NASA and SpaceX says how typical Crew Dragon landings are to be done (http://www.nasaspaceflight.com/2014/08/dragon-v2-rely-parachutes-landing/).

Read it, must have missed the bit about whether a propulsive landing also used drogues to do initial slowdown and stabilisation, and in order to save fuel.

The 2014 article doesn't say that. Were you being sarcastic?

Yes. Sorry, sarcasm  doesn't come across very well except in my head. Point being, drogues were not mentioned at all in the article, so we don't know is they are used for all types of descent.

Drogues are not needed for stabilization, the capsule is aerodynamically stable flying bottom first unless the trunk is attached.  The only time drogues would stabilize a reentering capsule is if it is tumbling before reentry and that is not nominal (to say the least).  And the capsule has no problem decelerating to terminal velocity.  Elon and others have explicitly mentioned firing the SDs early to test and confirm propulsive landing will be successful.  The only SpaceX animations we've ever seen of propulsive landings do not use drogues.

I don't know what interim steps will be involved in the process of perfecting propulsive landing and getting people comfortable with it.  But all evidence is that nominal propulsive landings will be 100% propulsive and drogues are an unnecessary complexity.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 10/23/2015 07:20 PM
As an intermediate I would be perfectly happy with full parachute landing and engines for making it a soft landing. When they demonstrate that to the satisfaction of NASA they can do land landing instead of water landing. That would facilitate reuse of Dragon.

After that they can work on fully powered landing as needed for Red Dragon.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Chris Bergin on 10/23/2015 08:09 PM
By the way, per L2's McGregor Photos and Update Section, Dragonfly has been photographed at McGregor, as has a big, big crane. I've asked SpaceX if they want to talk to us about the upcoming test objectives, but we'll be writing an article next week regardless.

Here's the article - with L2 photos and some cool L2 renderings by Nathan :)

http://www.nasaspaceflight.com/2015/10/spacex-dragonfly-arrives-mcgregor-testing/

When they start the testing at McGregor we'll set up an update thread.

"These include the “Propulsive assist landing” test – which will see DragonFly dropped from helicopter (an Erickson E‐model or equivalent) aided by three parachutes. This will be followed by the “Fully propulsive landing” test – again utilizing a helicopter and parachutes, concluding with a five-second firing of the SuperDracos for a smooth landing."

This doesn't sound correct.

It has now been corrected. The four types of tests are described at the beginning of this thread:
http://forum.nasaspaceflight.com/index.php?topic=34800.0

Yeah, I got a bit carried away with the chutes. The one stray additional chute reference removed with the wave of a tiny trim of a few words. Taa Dah! ;D
Title: Re: SpaceX DragonFly Discussion Thread
Post by: docmordrid on 12/25/2015 03:51 AM
Still, the DragonFly FAA permit runs out on July 28, 2016.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 12/25/2015 08:53 AM
On a site not to be mentioned here a mod claimed insider knowledge that the first test on a crane has been successfully done already and video of it will be released in january.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: xpete on 12/25/2015 03:38 PM
http://www.nasa.gov/feature/15-in-15-nasas-commercial-crew-program-moves-closer-to-flight/

Quote
SpaceX Conducted Propulsive Landing Tests – SpaceX is building its Crew Dragon capsule to return to Earth and land as safely and precisely as a helicopter by using thrusters instead of parachutes. The company's engineers began testing the propulsion system at facilities in Texas in late 2015. Early flights for NASA with astronauts aboard will come home under parachutes for water landings, but successful testing now could clear the way to later flights ending on a landing pad where the astronauts will step out on solid ground and the spacecraft will be processed for another flight.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: NovaSilisko on 12/25/2015 03:52 PM
"Testing the propulsion system" sounds more like the usual testing of the SuperDracos, to me.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cscott on 12/25/2015 04:59 PM
Crane testing would be a logical first step, and not-very-impressive to look at, so makes sense they'd wait until after RTF to quietly release the video --- for SpaceX superfans, not a big press release.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Robotbeat on 12/25/2015 05:15 PM
Honestly, I think crane tests of Dragon hovering would be PLENTY impressive! :) Pairs well with the booster landing as this is sort of tech is what would be needed for a reusable upper stage.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cscott on 12/25/2015 11:56 PM
Impressive to us, not so impressive to general public.  Hence not worthy of a big to-do, just a quiet release of the test videos to YouTube.  IMHO.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lar on 01/18/2016 07:29 PM
Some less than NSF quality posts were trimmed.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: dbush on 01/21/2016 09:03 PM
SpaceX has just posted this Vine of a crane test:

https://vine.co/v/iepOLZvMBYz

Edit: YouTube video too:
http://youtu.be/07Pm8ZY0XJI
Title: Re: SpaceX DragonFly Discussion Thread
Post by: mme on 01/21/2016 09:28 PM
SpaceX has just posted this Vine of a crane test:

https://vine.co/v/iepOLZvMBYz

Edit: YouTube video too:
http://youtu.be/07Pm8ZY0XJI

They say this test is part of a Commercial Crew milestone.

Quote
Published on Jan 21, 2016
On November 24, SpaceX’s Dragon 2, powered by eight SuperDraco engines, executed a picture-perfect propulsive hover test at the company’s rocket development facility in McGregor, Texas.

Eight SuperDraco thrusters, positioned around the perimeter of the vehicle in pairs called “jet packs”, fired up simultaneously to raise the Crew Dragon spacecraft for a five-second hover, generating approximately 33,000 lbs of thrust before returning the vehicle to its resting position. This test was the second of a two-part milestone under NASA’s Commercial Crew Program. The first test—a short firing of the engines intended to verify a healthy propulsion system—was completed November 22, and the longer burn two-days later demonstrated vehicle control while hovering.

I guess that's for the "soft touchdown" under parachutes.  Also, since it's hovering, I guess that means that the test article is about 33,000 lbs.  Any ideas how much of that is ballast?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lar on 01/21/2016 09:32 PM
Link to another image on Instagram

https://www.instagram.com/p/BA0Rksxl8Ud/
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AnalogMan on 01/21/2016 09:53 PM
And another.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Chris Bergin on 01/21/2016 10:07 PM
Great to see her dancing :)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Kabloona on 01/21/2016 10:10 PM
Quote
I guess that's for the "soft touchdown" under parachutes.  Also, since it's hovering, I guess that means that the test article is about 33,000 lbs.  Any ideas how much of that is ballast?

Must be a lot. Even if you add a few thousand pounds to the advertised V1 weight of 9300 lbs for SuperDracos and plumbing, environmental controls, crew, etc, that's still less than half of 33,000 lbs. So I'd guess more than half of that is ballast, and the thrust level represents a "perceived" 2-3g or so landing deceleration in unballasted configration. (By "perceived" I mean what the crew would feel in the seats of their pants).

Edit: quote from Lars_J from first page of this thread:

Quote
Hmm, interesting information about the "DragonFly RLV" in that PDF:

 - up to four steel landing legs
 - weighs 14000 lbs unfueled
 - maximum proplellant load is 400 gallons
Title: Re: SpaceX DragonFly Discussion Thread
Post by: The man in the can on 01/21/2016 10:45 PM
According to NASA:

SpaceX recently tested its ability to fire engines that will be used to land a human-rated spacecraft safely on the ground with the accuracy of a helicopter at the company’s test facility in McGregor, Texas. SpaceX envisions returning people to Earth from space on the power of thrust instead of beneath parachutes. Working with NASA’s Commercial Crew Program, SpaceX is in the early phases of analysis. In November, the company conducted two tethered tests of a full-size Crew Dragon mock-up attached to a crane so engineers could refine the landing software and systems on the spacecraft. The Crew Dragon spacecraft will be equipped with eight SuperDraco thrusters that would be used to slow the vehicle’s return to Earth through the atmosphere and ultimately set the spacecraft and its crew down gently.

Propulsive landing will not be used initially for missions with NASA astronauts to the International Space Station.The Crew Dragon will splash down safely in the ocean under parachutes as its passengers return from the space station.

https://blogs.nasa.gov/commercialcrew/2016/01/21/spacex-tests-superdraco-descent-landing-capability/ (https://blogs.nasa.gov/commercialcrew/2016/01/21/spacex-tests-superdraco-descent-landing-capability/)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 01/21/2016 10:52 PM
I've been having a generally good day here, but this video just kicked it up another 2-3 notches...

Watch and smile...   Paraphrasing: Those crazy young kids in their flying machines.  :)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Space Ghost 1962 on 01/21/2016 10:57 PM
Note the slight rotation in the vine. And you can see gimbal or differential thrust movements.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Coastal Ron on 01/21/2016 11:02 PM
Note the slight rotation in the vine. And you can see gimbal or differential thrust movements.

I saw the slight rotation, but does their engine layout allow for controlling rotation?  Based on the layout I would assume they don't care what orientation the spacecraft is in when it lands, since there is no real "front" or "back".  Their biggest concern is "bottom down", but the CG takes care of that.

It sure looked steady throughout the entire thrust sequence.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: QuantumG on 01/21/2016 11:11 PM
Roll nullification is usually the last thing you do when you do tether testing. This is one of the first tests, yes?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: ugordan on 01/21/2016 11:13 PM
I saw the slight rotation, but does their engine layout allow for controlling rotation?

It has to, no system is perfectly aligned and there'll always be a residual amount of torque present. You do not want to land with a significant roll rate.

The individual SDs in a pod are canted very slightly to one another so I assume differentially throttling them controls roll. Normal Dracos are a no-go in the atmospheric pressure.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 01/21/2016 11:37 PM
Bravo. Why reinvent the wheel on how to do tests?
Not saying they should.. just hoping that everyone is aware of the pioneers.

Of course SpaceX didn't invent VTVL....  But context matters - this is part of a manned orbital system...

My eyes are watching the video, but my brain is seeing it happening at LZ-1, after it fell to Earth...
Title: Re: SpaceX DragonFly Discussion Thread
Post by: QuantumG on 01/21/2016 11:50 PM
Of course SpaceX didn't invent VTVL....  But context matters - this is part of a manned orbital system...

My eyes are watching the video, but my brain is seeing it happening at LZ-1, after it fell to Earth...

My eyes are watching the video and my brain is saying: they're only on the first tether test? What have they been doing?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 01/21/2016 11:59 PM
Of course SpaceX didn't invent VTVL....  But context matters - this is part of a manned orbital system...

My eyes are watching the video, but my brain is seeing it happening at LZ-1, after it fell to Earth...

My eyes are watching the video and my brain is saying: they're only on the first tether test? What have they been doing?
Yeah, I actually went through that too...  This test has been literally years in the making....

Priorities, I guess.  Still though.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sanman on 01/22/2016 12:05 AM
Here - just embedding in the thread directly for ease of viewing:

https://www.youtube.com/watch?v=07Pm8ZY0XJI

How many mach diamonds can you count, kids?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Chris Bergin on 01/22/2016 12:06 AM
The video is from tests a few months ago, I'm told (not sure if that's noted already). And they are moving through a long test series. Seen responses to twitter thinking the test was from this week and that they've been delayed. Nope, that was from about November.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: The man in the can on 01/22/2016 12:12 AM
November 24 according to the text published with the video on Youtube
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sanman on 01/22/2016 12:16 AM
Anybody have a top-down or bottom-up view of the Dragon v2? I just wanted to see how the thrusters are positioned around the craft.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Space Ghost 1962 on 01/22/2016 12:18 AM
For passive stability, you'd want a means to insure that propulsion is uniform across all SD's, so that at the engine controller level, the vehicle would maintain stable flight in the plane. All this prior to vehicle flight tests.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Chris Bergin on 01/22/2016 12:26 AM
November 24 according to the text published with the video on Youtube

Oh, there we go then. I'll go back into my shed! ;D
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars-J on 01/22/2016 12:32 AM
Of course SpaceX didn't invent VTVL....  But context matters - this is part of a manned orbital system...

My eyes are watching the video, but my brain is seeing it happening at LZ-1, after it fell to Earth...

My eyes are watching the video and my brain is saying: they're only on the first tether test? What have they been doing?

Yeah, what else does SpaceX do, does anyone know?  ;D
Title: Re: SpaceX DragonFly Discussion Thread
Post by: QuantumG on 01/22/2016 12:40 AM
Yeah, what else does SpaceX do, does anyone know?  ;D

Umm.. if you bother to read the thread you'll discover that my confusion was perfectly valid. This is a video from two months ago.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: MP99 on 01/22/2016 01:02 AM
For passive stability, you'd want a means to insure that propulsion is uniform across all SD's, so that at the engine controller level, the vehicle would maintain stable flight in the plane. All this prior to vehicle flight tests.
Pulsing in the SDs seems pretty apparent in the 1/4 speed version. I'm surprised just how stably the thing seems to hover.

Cheers, Martin
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Norm38 on 01/22/2016 01:33 AM
Good to see some flight tests.  The grasshopper years were such fun to watch, can't wait to see this really fly.

Can't the super dracos deep throttle?  So why does the Dragon have to be balasted?  Instead of just not testing at full throttle?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 01/22/2016 01:36 AM
Good to see some flight tests.  The grasshopper years were such fun to watch, can't wait to see this really fly.

Can't the super dracos deep throttle?  So why does the Dragon have to be balasted?  Instead of just not testing at full throttle?

Five seconds is the deceleration burn duration listed in the license back at start of this thread.  Maybe test is to check stability and thrust level attained for that burn... this would make the ballast equivalent to (a proxy of) momentum that had to be shed.

(This burn for parachute landing assist.)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: OxCartMark on 01/22/2016 02:00 AM
For those that have access, my previous comments on the three cable system still stand.
http://forum.nasaspaceflight.com/index.php?topic=38409.msg1436880#msg1436880

So it sounds like this went down in November which correlates with {***} in L2.  Does anyone that's following the McGregor spy shots know if the crane is still set up for these tests or how long it was up?

For those calling out rotation about the "rope axis", I would expect this behavior since the (unsuper)Draco engines don't seem to be "on" for this test and they are the only way that it could stabilize itself around that axis.

Normal Dracos are a no-go in the atmospheric pressure.
  Really?  I didn't know that.  Do we really know that?

See the blast wall between the test article and the crane cab?  Doesn't it remind you of the blast wall they have on the ASDSs?

That's some serious illumination they have inside that capsule.  Not too much different from the illimination coming from the SDs.  I wonder if its for high speed photography?  I wonder if they've got that marlboro man from the Grasshopper tests in there?  Listening to Johnny Cash's "Ring Of Fire" as he flies.

NASA's release refers to it as "Crew Dragon", SpaceX calls it a V2 rocket or somesuch (dumb) and in this test sequence its DragonFly.  SpaceX has a serious problem with name drift for everything it does.  Perhaps if they could just name something once and consistently it would save them program time and their corporate time dialation factor could be closer to 1:1.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: docmordrid on 01/22/2016 02:17 AM
It would be nice if the Anne McCaffrey estate would let them use DragonRider, but these days unlikely. The term DragonFly is used all over, but Dean Space is using it as a potential asteroid miner. Dunno there's a rights issue given the space context.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: CameronD on 01/22/2016 02:40 AM
NASA's release refers to it as "Crew Dragon", SpaceX calls it a V2 rocket or somesuch (dumb) and in this test sequence its DragonFly.  SpaceX has a serious problem with name drift for everything it does.  Perhaps if they could just name something once and consistently it would save them program time and their corporate time dialation factor could be closer to 1:1.

You're suggesting SpaceX need a PAO??  ;D
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Hauerg on 01/22/2016 04:50 AM
Good to see some flight tests.  The grasshopper years were such fun to watch, can't wait to see this really fly.

Can't the super dracos deep throttle?  So why does the Dragon have to be balasted?  Instead of just not testing at full throttle?
This is not even close to full throttle. Remember thT pad abort test? That was what happens when you step on the gas. Not really fitting for a tethered flight.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: clegg78 on 01/22/2016 05:04 AM

That's some serious illumination they have inside that capsule.  Not too much different from the illimination coming from the SDs.  I wonder if its for high speed photography?

It's actually not illumination for the window, its a gold coating/covering on the window.   Look at previous shots of the V2 Dragon and you'll see they had gold covered windows as well.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: 411rocket on 01/22/2016 05:10 AM
Good to see some flight tests.  The grasshopper years were such fun to watch, can't wait to see this really fly.

Can't the super dracos deep throttle?  So why does the Dragon have to be balasted?  Instead of just not testing at full throttle?
This is not even close to full throttle. Remember the pad abort test? That was what happens when you step on the gas. Not really fitting for a tethered flight.

The ballasting, is to bring it to estimated flight weight in various locations internally, instead of just the previous ballasting, done for the pad abort test. As I had read elsewhere, that the revised ballasting had included, the top of the dragon, which means the flight control area I'm guessing.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Garrett on 01/22/2016 07:57 AM
Am I correct in interpreting from the YouTube text that the hover test closes out milestone number 2:
"2. Initial Propulsion Module Testing Complete - April 2015"

The helicopter release tests (parachute and then freefall) would then fall under milestone 6:
"6. Propulsive Land Landing Test Complete - Sept 2015"

So about 7 months behind so far. I suppose that's not too bad. If the five month gap between milestones 2 and 6 is respected, then that could mean helicopter release tests in the March to May timeframe.

(source of milestones: http://www.parabolicarc.com/2015/03/04/spacex-cctcap-milestones/)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: JamesH on 01/22/2016 08:21 AM
Considering that appears to be the first 'flight' (ignoring the abort test), that looks like a pretty solid result to me. Very stable.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Antilope7724 on 01/22/2016 08:26 AM
Wonder what the interior noise level is for crew members, with 8 firing engines encircling them from only a few feet away?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: KelvinZero on 01/22/2016 08:50 AM
NASA's release refers to it as "Crew Dragon", SpaceX calls it a V2 rocket or somesuch (dumb) and in this test sequence its DragonFly.  SpaceX has a serious problem with name drift for everything it does.  Perhaps if they could just name something once and consistently it would save them program time and their corporate time dialation factor could be closer to 1:1.
Are they going to phase out the current Dragon? That would make Dragon V2 the ideal name, and eventually it could just become Dragon again. Historians can refer to Dragon v1 if they need to.

(I dont have any info about that but I like the idea of this vehicle being used for cargo also so it gets as much testing as possible)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: malenfant on 01/22/2016 09:07 AM
Are they going to phase out the current Dragon? That would make Dragon V2 the ideal name, and eventually it could just become Dragon again. Historians can refer to Dragon v1 if they need to.

(I dont have any info about that but I like the idea of this vehicle being used for cargo also so it gets as much testing as possible)

That's been debated.  I expect a dragon v2 cargo varient with CBM for the crs2 flights (if not before).  Testing on an actual orbital return is a higher fidelity test than dropping from a helicopter at terminal velocity.  Others disagree.  Personally I don't see them being allowed to try the brown trouser maneuver on people without experience from multiple actual flights and they will want an anchor customer for those tests.

EDIT: Ignore me, Garett has the up to date answer below.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: mme on 01/22/2016 09:08 AM
...
NASA's release refers to it as "Crew Dragon", SpaceX calls it a V2 rocket or somesuch (dumb) and in this test sequence its DragonFly.  SpaceX has a serious problem with name drift for everything it does.  Perhaps if they could just name something once and consistently it would save them program time and their corporate time dialation factor could be closer to 1:1.
For what it's worth, SpaceX calls it "Dragon 2".  They dropped the "V" quite a while ago.  I'm pretty sure that DragonFly is the name of the testing program to develop propulsive landing, it's not the name of the capsule.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Garrett on 01/22/2016 09:11 AM
NASA's release refers to it as "Crew Dragon", SpaceX calls it a V2 rocket or somesuch (dumb) and in this test sequence its DragonFly.  SpaceX has a serious problem with name drift for everything it does.  Perhaps if they could just name something once and consistently it would save them program time and their corporate time dialation factor could be closer to 1:1.
Are they going to phase out the current Dragon? That would make Dragon V2 the ideal name, and eventually it could just become Dragon again. Historians can refer to Dragon v1 if they need to.

(I dont have any info about that but I like the idea of this vehicle being used for cargo also so it gets as much testing as possible)
For the next cargo resupply contract (CRS2), they have proposed a mixture of V1 and V2:
"SpaceX – yet to release a statement on the CRS2 award – will utilize its Dragon spacecraft, in two configurations, during CRS2, with both the berthed Dragon spacecraft – as currently being employed during CRS1 – and the upgraded Dragon 2, which can dock directly with the ISS."
http://www.nasaspaceflight.com/2016/01/nasa-awards-crs2-spacex-orbital-atk-sierra-nevada/
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Star One on 01/22/2016 10:21 AM
I assume this will be used for cargo return over many flights before any humans are let anywhere near the inside of it.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: darkenfast on 01/22/2016 11:01 AM
Anybody have a top-down or bottom-up view of the Dragon v2? I just wanted to see how the thrusters are positioned around the craft.

I think they are at roughly 2 and 4 o'clock, and 8 and 10 o'clock.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: 411rocket on 01/22/2016 11:14 AM
I assume this will be used for cargo return over many flights before any humans are let anywhere near the inside of it.

Maybe, if they fit the Super Draycos into the current Dragons. As CRS 2 starts in 2019 & Crew Dragon occupied flight, currently starts next year. Remember, this test article is built on a modified Dragon 1 pressure hull, so it is possible.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Kabloona on 01/22/2016 11:18 AM
Good to see some flight tests.  The grasshopper years were such fun to watch, can't wait to see this really fly.

Can't the super dracos deep throttle?  So why does the Dragon have to be balasted?  Instead of just not testing at full throttle?
This is not even close to full throttle. Remember thT pad abort test? That was what happens when you step on the gas. Not really fitting for a tethered flight.

Using SpaceX's figure of 120,000 lbf max axial thrust, 33,000 lbf is about 28% of full throttle, with 20% being their stated lower limit, so it's pretty close to the minimum.

Quote
Five seconds is the deceleration burn duration listed in the license back at start of this thread.  Maybe test is to check stability and thrust level attained for that burn... this would make the ballast equivalent to (a proxy of) momentum that had to be shed.

For some ballpark figures, if we assumed an unballasted capsule landing weight of 16,500* lbf, then the 4 second firing at 33,000 lbf would have reduced speed by about 128 fps.

*(picking that figure somewhat arbitrarily because it's exactly half the test thrust and should be close to the stated Dragonfly capsule weight of 14,000 lbf plus 400 gallons propellant)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 01/22/2016 11:40 AM
Are they going to phase out the current Dragon? That would make Dragon V2 the ideal name, and eventually it could just become Dragon again. Historians can refer to Dragon v1 if they need to.

(I dont have any info about that but I like the idea of this vehicle being used for cargo also so it gets as much testing as possible)

That's been debated.  I expect a dragon v2 cargo varient with CBM for the crs2 flights (if not before).  Testing on an actual orbital return is a higher fidelity test than dropping from a helicopter at terminal velocity.  Others disagree.  Personally I don't see them being allowed to try the brown trouser maneuver on people without experience from multiple actual flights and they will want an anchor customer for those tests.

EDIT: Ignore me, Garett has the up to date answer below.

Testing is good and will be extensive before crew flights. Cargo returns are full-up tests and so useful.
But this is the only system with back-up capability -- parachutes and full propulsion.  It should be the safest ever flown.  The fact that they will first land in the ocean is an overly-conservative imposition when compared to the experience base and lack of back-up the other two craft will rely upon.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Star One on 01/22/2016 11:51 AM

I assume this will be used for cargo return over many flights before any humans are let anywhere near the inside of it.

Maybe, if they fit the Super Draycos into the current Dragons. As CRS 2 starts in 2019 & Crew Dragon occupied flight, currently starts next year. Remember, this test article is built on a modified Dragon 1 pressure hull, so it is possible.

It would just seem a sensible course and I am sure both NASA and those who are going to travel in it would welcome the reassurance this would bring.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 01/22/2016 12:06 PM

I assume this will be used for cargo return over many flights before any humans are let anywhere near the inside of it.

Maybe, if they fit the Super Draycos into the current Dragons. As CRS 2 starts in 2019 & Crew Dragon occupied flight, currently starts next year. Remember, this test article is built on a modified Dragon 1 pressure hull, so it is possible.

It would just seem a sensible course and I am sure both NASA and those who are going to travel in it would welcome the reassurance this would bring.

Would anything stop them from flying SuperDracos on some of remaining 8-10 CRS-1 flights?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: OnWithTheShow on 01/22/2016 12:11 PM

That's some serious illumination they have inside that capsule.  Not too much different from the illimination coming from the SDs.  I wonder if its for high speed photography?

It's actually not illumination for the window, its a gold coating/covering on the window.   Look at previous shots of the V2 Dragon and you'll see they had gold covered windows as well.

From what I recall from the pad abort test its just a gold sticker and this vehicle doesn't actually have a window.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: malenfant on 01/22/2016 12:17 PM
...
But this is the only system with back-up capability -- parachutes and full propulsion.  It should be the safest ever flown.  The fact that they will first land in the ocean is an overly-conservative imposition when compared to the experience base and lack of back-up the other two craft will rely upon.

Do chutes provide full backup capability for every phase of the landing cycle?  There is a maximum impact speed above which the landing becomes potentially injurious.  There is a minimum altitude below which chutes cannot open and provide meaningful deceleration.  Are we sure their aren't points late in the landing sequence where a multiple SD failure becomes fatal?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: malenfant on 01/22/2016 12:29 PM
...But this is the only system with back-up capability...

FWIW Soyuz has chutes backed up by chutes.  Not sure about  cst-100 or Orion but I suspect they also have some redundancy?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sanman on 01/22/2016 12:32 PM
They need to bring back that Cowboy - I liked to call him "Chuck Norris" - and strap him into a seat to show what the interior situation looks like during a test flight. It's a capsule this time, so interior matters.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Jarnis on 01/22/2016 12:52 PM
...But this is the only system with back-up capability...

FWIW Soyuz has chutes backed up by chutes.  Not sure about  cst-100 or Orion but I suspect they also have some redundancy?

Isn't the redundancy basically that one of the mains can fail/get torn up and the landing is still survivable, or do some of these actually have a full set of backup chutes that never deploy on a nominal landing?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 01/22/2016 12:57 PM
Do chutes provide full backup capability for every phase of the landing cycle?  There is a maximum impact speed above which the landing becomes potentially injurious.  There is a minimum altitude below which chutes cannot open and provide meaningful deceleration.  Are we sure their aren't points late in the landing sequence where a multiple SD failure becomes fatal?

Not every phase. My understanding is that there will be a SuperDraco test fire at the altitude where parachutes still can be safely deployed. At that point, when the SuperDraco are all OK they commit to powered landing. After that several SuperDraco, I think one in every engine pod will have to work.

Title: Re: SpaceX DragonFly Discussion Thread
Post by: Herb Schaltegger on 01/22/2016 01:17 PM
Wonder what the interior noise level is for crew members, with 8 firing engines encircling them from only a few feet away?

That was my first thought as well - the internal acoustic environment has got to be challenging to say the least. I wonder if SpaceX's crew helmet design includes active noise suppression, or if there is some other kind of "secret sauce" for cabin noise isolation?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: malenfant on 01/22/2016 01:26 PM
...
Isn't the redundancy basically that one of the mains can fail/get torn up and the landing is still survivable, or do some of these actually have a full set of backup chutes that never deploy on a nominal landing?

Soyuz has a backup that is not deployed on a nominal landing.  I believe Apollo was as you describe.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: OxCartMark on 01/22/2016 04:15 PM
My understanding is that there will be a SuperDraco test fire at the altitude where parachutes still can be safely deployed. At that point, when the SuperDraco are all OK they commit to powered landing.

That's my understanding as well but isn't there a problem with parachutes being incompatible with hypergolly fuel (Apollo 15)?  I know its being burned but wouldn't there be some residual parachute eating nastiness left?  Or just the plume of hot gas that the parachutes would go through?  Or if one or more of the SDs only squirted out one of the two fluids, (a failure which would require the parachutes) wouldn't that be a bad scenario for the parachutes?

...
Isn't the redundancy basically that one of the mains can fail/get torn up and the landing is still survivable, or do some of these actually have a full set of backup chutes that never deploy on a nominal landing?

Soyuz has a backup that is not deployed on a nominal landing.  I believe Apollo was as you describe.
  If Apollo CM had backup parachutes I want to hear more about it.  But I think you're saying that Apollo could stand failure of one parachute which is correct.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 01/22/2016 05:12 PM
When F9 comes in, the retro burn starts at about 30 seconds out and 5000' up, IIRC. 

If Dragon is anything similar, that's plenty of time to abort and go for parachutes.

So it's not just a brief test, its actually beginning the retro burn, making sure all is going well, and then committing to continue the burn.

I don't think there ever was anything as safe.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: rpapo on 01/22/2016 05:30 PM
When F9 comes in, the retro burn starts at about 30 seconds out and 5000' up, IIRC. 

If Dragon is anything similar, that's plenty of time to abort and go for parachutes.
You sure about that?  In the pad abort test, at about a mile up, the Dragon had relatively little vertical velocity at that point.  Coming back from the stratosphere it should be falling quite a bit faster, thereby making the required altitude for chute deployment somewhat higher.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 01/22/2016 05:36 PM
When F9 comes in, the retro burn starts at about 30 seconds out and 5000' up, IIRC. 

If Dragon is anything similar, that's plenty of time to abort and go for parachutes.
You sure about that?  In the pad abort test, at about a mile up, the Dragon had relatively little vertical velocity at that point.  Coming back from the stratosphere it should be falling quite a bit faster, thereby making the required altitude for chute deployment somewhat higher.
Right, but it also left the pad at 5g or so.

It's just a matter of working out the terminal velocity and assuming a landing acceleration.

If the terminal velocity is similar, 300 m/s or so, and decelerating by 10 m/s, that's your 30 seconds.

Then take half the speed (150) and multiply back by 30, and that the starting altitude.

(Roughly, of course)

Title: Re: SpaceX DragonFly Discussion Thread
Post by: nadreck on 01/22/2016 05:38 PM
When F9 comes in, the retro burn starts at about 30 seconds out and 5000' up, IIRC. 

If Dragon is anything similar, that's plenty of time to abort and go for parachutes.
You sure about that?  In the pad abort test, at about a mile up, the Dragon had relatively little vertical velocity at that point.  Coming back from the stratosphere it should be falling quite a bit faster, thereby making the required altitude for chute deployment somewhat higher.
Right, but it also left the pad at 5g or so.

It's just a matter of working out the terminal velocity and assuming a landing acceleration.

If the terminal velocity is similar, 300 m/s or so, and decelerating by 10 m/s, that's your 30 seconds.

Then take half the speed (150) and multiply back by 30, and that the starting altitude.

(Roughly, of course)

so 5000m vs 5000'
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 01/22/2016 05:41 PM
When F9 comes in, the retro burn starts at about 30 seconds out and 5000' up, IIRC. 

If Dragon is anything similar, that's plenty of time to abort and go for parachutes.
You sure about that?  In the pad abort test, at about a mile up, the Dragon had relatively little vertical velocity at that point.  Coming back from the stratosphere it should be falling quite a bit faster, thereby making the required altitude for chute deployment somewhat higher.
Right, but it also left the pad at 5g or so.

It's just a matter of working out the terminal velocity and assuming a landing acceleration.

If the terminal velocity is similar, 300 m/s or so, and decelerating by 10 m/s, that's your 30 seconds.

Then take half the speed (150) and multiply back by 30, and that the starting altitude.

(Roughly, of course)

so 5000m vs 5000'
This is all out of memory here..  But terminal velocity for F9 was supersonic, right?  So definitely not 300 fps..

I'm sure someone upthread appropriated Dragon's terminal velocity...
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sghill on 01/22/2016 06:22 PM
When F9 comes in, the retro burn starts at about 30 seconds out and 5000' up, IIRC. 

If Dragon is anything similar, that's plenty of time to abort and go for parachutes.
You sure about that?  In the pad abort test, at about a mile up, the Dragon had relatively little vertical velocity at that point.  Coming back from the stratosphere it should be falling quite a bit faster, thereby making the required altitude for chute deployment somewhat higher.
Right, but it also left the pad at 5g or so.

It's just a matter of working out the terminal velocity and assuming a landing acceleration.

If the terminal velocity is similar, 300 m/s or so, and decelerating by 10 m/s, that's your 30 seconds.

Then take half the speed (150) and multiply back by 30, and that the starting altitude.

(Roughly, of course)

so 5000m vs 5000'
This is all out of memory here..  But terminal velocity for F9 was supersonic, right?  So definitely not 300 fps..

I'm sure someone upthread appropriated Dragon's terminal velocity...

Around 100m/sec depending on how loaded up it is coming home.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 01/22/2016 07:18 PM
100 m/s seems slow, but this stukk yields (quickly) 10 seconds, 500m, 1500' -  lower than I thought, but still enough to open chutes.

The point is, I don't think they have to test the engines and then decide whether to power-land.

I think they can start the landing burn, and then decide whether to continue with it or abandon it in favor of parachutes, and that the decision can be made pretty far down the timeline.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cambrianera on 01/22/2016 07:31 PM
Dragon has quite the same frontal section of F9, and approx 1/4 of the mass.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 01/22/2016 08:01 PM
Dragon has quite the same frontal section of F9, and approx 1/4 of the mass.

Also much more ability to throttle -- or hover.
Probably could start landing burn at 5-10km and know well in advance if they had solid propulsion.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: RocketGoBoom on 01/22/2016 08:16 PM
Does anyone know when we might see a free flying Dragon 2 doing a test propulsive landing?

I know you guys follow all of these details more closely than the casual fanboys like me. Any mention of propulsive landing test, perhaps dropped from a high altitude?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Kabloona on 01/22/2016 08:17 PM
100 m/s seems slow, but this stukk yields (quickly) 10 seconds, 500m, 1500' -  lower than I thought, but still enough to open chutes.

Are you saying you would wait until 1500' to fire up the engines and then decide whether to deploy chutes instead?? I'm no parachutist, but that sounds like a death wish if you're in a 15,000+ lb capsule at terminal velocity. And it takes time for the chutes to deploy, during which time you just lost another 500' altitude and are awfully close to becoming a pancake.

Why on earth would you not test fire the SD's for a second at a safely high altitude and give yourself plenty of margin on the go/no go decision for powered landing?

Quote
I think they can start the landing burn, and then decide whether to continue with it or abandon it in favor of parachutes, and that the decision can be made pretty far down the timeline.

10 seconds or less before impact is probably too late.  ???
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Hauerg on 01/22/2016 08:27 PM
Test firing them higher up is exactly what Elon said they would do. Long time ago.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 01/22/2016 09:14 PM
Probably could start landing burn at 5-10km and know well in advance if they had solid propulsion.

Phrasing!!!!
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Kabloona on 01/22/2016 09:40 PM
Probably could start landing burn at 5-10km and know well in advance if they had solid propulsion.

Phrasing!!!!

Yes,  they will know well in advance that they have *liquid* propulsion. (That had me confused, too.)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: rpapo on 01/22/2016 09:54 PM
Probably could start landing burn at 5-10km and know well in advance if they had solid propulsion.

Phrasing!!!!

Yes,  they will know well in advance that they have *liquid* propulsion. (That had me confused, too.)
How about simply "reliable" propulsion?  Solid and liquid have other primary meanings in this forum...
Title: Re: SpaceX DragonFly Discussion Thread
Post by: nadreck on 01/22/2016 09:56 PM
Probably could start landing burn at 5-10km and know well in advance if they had solid propulsion.

Phrasing!!!!

Yes,  they will know well in advance that they have *liquid* propulsion. (That had me confused, too.)
How about simply "reliable" propulsion?  Solid and liquid have other primary meanings in this forum...

"if propulsion was nominal"
Title: Re: SpaceX DragonFly Discussion Thread
Post by: AncientU on 01/22/2016 10:20 PM
Probably could start landing burn at 5-10km and know well in advance if they had solid propulsion.

Phrasing!!!!

Context!!!!
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Kabloona on 01/22/2016 10:30 PM
Probably could start landing burn at 5-10km and know well in advance if they had solid propulsion.

Phrasing!!!!

Context!!!!

To a rocket scientist, "solid propulsion" never means "reliable liquid propulsion."  ;)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 01/22/2016 11:13 PM
Test firing them higher up is exactly what Elon said they would do. Long time ago.

They can test high, but my point is that (it looks to me like) they still have time to decide after the primary burn starts.

Also don't forget - Musk was trying to give a short answer to a safety question...  The way he said it, it reads better and is more comforting to someone who really doesn't like the idea of propulsive landings...
Title: Re: SpaceX DragonFly Discussion Thread
Post by: docmordrid on 01/22/2016 11:25 PM
Just so everyone can be on the same page, the DragonFly EIS lays out the test series and altitudes.

Chopper drop propulsive landings are from 10,000 feet, then there's free fall, and the SD's fire up at an unmentioned altitude

Grasshopper/Dev-1 style hops go ground to 7,000 feet, then it decends to a propulsive landing.

Is it reasonable to assume the SD test fire for the propulsive landing go/no-go happens at or near 7,000 feet, and if no-go the parachute mortar fires?

http://www.faa.gov/about/office_org/headquarters_offices/ast/media/DragonFly_Final_EA_sm.pdf
Title: Re: SpaceX DragonFly Discussion Thread
Post by: gongora on 01/22/2016 11:32 PM

I assume this will be used for cargo return over many flights before any humans are let anywhere near the inside of it.

Maybe, if they fit the Super Draycos into the current Dragons. As CRS 2 starts in 2019 & Crew Dragon occupied flight, currently starts next year. Remember, this test article is built on a modified Dragon 1 pressure hull, so it is possible.

It would just seem a sensible course and I am sure both NASA and those who are going to travel in it would welcome the reassurance this would bring.

It's not really sensible for NASA to delay the Commercial Crew project a couple years and try to cram in a few hundred million dollars of extra cargo missions before flying humans in it.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Kabloona on 01/23/2016 12:51 AM
Just so everyone can be on the same page, the DragonFly EIS lays out the test series and altitudes.

Chopper drop propulsive landings are from 10,000 feet, then there's free fall, and the SD's fire up at an unmentioned altitude

Grasshopper/Dev-1 style hops go ground to 7,000 feet, then it decends to a propulsive landing.

Is it reasonable to assume the SD test fire for the propulsive landing go/no-go happens at or near 7,000 feet, and if no-go the parachute mortar fires?

Sounds reasonable to me. I can't imagine them making the go/no-go call below 5,000 feet, which will be well before the landing burn begins.

And as pointed out upthread, the Dragon landing burn will have to be shorter and begin at lower altitude than the F9 S1 landing burn.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: 411rocket on 01/23/2016 01:27 AM

I assume this will be used for cargo return over many flights before any humans are let anywhere near the inside of it.

Maybe, if they fit the Super Draycos into the current Dragons. As CRS 2 starts in 2019 & Crew Dragon occupied flight, currently starts next year. Remember, this test article is built on a modified Dragon 1 pressure hull, so it is possible.

It would just seem a sensible course and I am sure both NASA and those who are going to travel in it would welcome the reassurance this would bring.

It's not really sensible for NASA to delay the Commercial Crew project a couple years and try to cram in a few hundred million dollars of extra cargo missions before flying humans in it.

How do you get, that Crew Dragon will get delayed, over propulsive landing? The current known plan, is water landings to start. I had suggested it is possible to gain flight experience, by fitting Super Draycos to the current CRS 1 Dragons. For all we know, that may be done in addition, to the inflight abort mode programming, after the Spx7 freefall.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 01/23/2016 02:17 AM
Just so everyone can be on the same page, the DragonFly EIS lays out the test series and altitudes.

Chopper drop propulsive landings are from 10,000 feet, then there's free fall, and the SD's fire up at an unmentioned altitude

Grasshopper/Dev-1 style hops go ground to 7,000 feet, then it decends to a propulsive landing.

Is it reasonable to assume the SD test fire for the propulsive landing go/no-go happens at or near 7,000 feet, and if no-go the parachute mortar fires?

Sounds reasonable to me. I can't imagine them making the go/no-go call below 5,000 feet, which will be well before the landing burn begins.

And as pointed out upthread, the Dragon landing burn will have to be shorter and begin at lower altitude than the F9 S1 landing burn.

I agree.  If the terminal velocity is indeed 100 m/s as surmised above, than 5000' is impact-minus-15-seconds if free falling (and 30 seconds if retro-burning at constant acceleration).   

But why not start the real burn and then make the decision?  Less things can go wrong if you're already on the braking burn than if you're only doing a test.  Zero ignitions instead of 8, for example. 

I don't mind doing a quick test at 7000' or 8000', but I'd feel safer if they can "abort to chutes" after the final burn begins.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Kabloona on 01/23/2016 02:33 AM
Quote
But why not start the real burn and then make the decision? 

That would make sense if you could start the burn at a high enough altitude.

Problem is, the SD's lowest throttle setting may not be low enough to extend the burn time beyond 10-20 seconds or so (depending on what values we assume for terminal velocity and capsule landing mass).

Which in turn means the landing burn can't start until around 3,500 ft altitude or lower,  too little margin for safe parachute deploy.

For example:

SD min axial thrust = 24,000 lbf (all 8 engines, with cosine loss)
Assume Dragon landing wt = 17,000 lbf
So T/W=1.41
Then deceleration = 13.2 ft/sec^2
Assume Terminal velocity = 300 ft/sec
Then burn time = 22.7 sec
So vertical distance traveled during burn = 3,405 ft (ie altitude at which burn must start)

And things get worse if landing Dragon is actually lighter than 17,000 lbf, because T/W goes up and therefore burn time is shorter and begins at lower altitude.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: KelvinZero on 01/23/2016 02:59 AM
It just occurred to me: I have always seen all engines firing, but aren't these massively overpowered for landing in order to be suitable for launch escape? I think I remember something about a 10g figure if used for escape. Did throttling down include using half the engines?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 01/23/2016 03:20 AM
Quote
But why not start the real burn and then make the decision? 

That would make sense if you could start the burn at a high enough altitude.

Problem is, the SD's lowest throttle setting may not be low enough to extend the burn time beyond 10-20 seconds or so (depending on what values we assume for terminal velocity and capsule landing mass).

Which in turn means the landing burn can't start until around 3,500 ft altitude or lower,  too little margin for safe parachute deploy.

For example:

SD min axial thrust = 24,000 lbf (all 8 engines, with cosine loss)
Assume Dragon landing wt = 17,000 lbf
So T/W=1.41
Then deceleration = 13.2 ft/sec^2
Assume Terminal velocity = 300 ft/sec
Then burn time = 22.7 sec
So vertical distance traveled during burn = 3,405 ft (ie altitude at which burn must start)

And things get worse if landing Dragon is actually lighter than 17,000 lbf, because T/W goes up and therefore burn time is shorter and begins at lower altitude.

We don't know much about the minimum throttle level.

We also don't know the minimum parachute deployment altitude.  Those whole-airplane parachutes (clearly smaller) work at a few hundreds of feet. 

Anyway - I think we're in agreement.   Best to be able to abort to chute after the real burn begins, but if it can't, it can't.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 01/23/2016 03:37 AM
Probably could start landing burn at 5-10km and know well in advance if they had solid propulsion.

Phrasing!!!!

Context!!!!

To a rocket scientist, "solid propulsion" never means "reliable liquid propulsion."  ;)
"All propulsion is gaseous*."


*Solid and liquid are just forms of storage
Title: Re: SpaceX DragonFly Discussion Thread
Post by: docmordrid on 01/23/2016 04:01 AM
Quote
But why not start the real burn and then make the decision? 

That would make sense if you could start the burn at a high enough altitude.

Problem is, the SD's lowest throttle setting may not be low enough to extend the burn time beyond 10-20 seconds or so (depending on what values we assume for terminal velocity and capsule landing mass).

Which in turn means the landing burn can't start until around 3,500 ft altitude or lower,  too little margin for safe parachute deploy.

For example:

SD min axial thrust = 24,000 lbf (all 8 engines, with cosine loss)
Assume Dragon landing wt = 17,000 lbf
So T/W=1.41
Then deceleration = 13.2 ft/sec^2
Assume Terminal velocity = 300 ft/sec
Then burn time = 22.7 sec
So vertical distance traveled during burn = 3,405 ft (ie altitude at which burn must start)

And things get worse if landing Dragon is actually lighter than 17,000 lbf, because T/W goes up and therefore burn time is shorter and begins at lower altitude.

We don't know much about the minimum throttle level.
>

http://www.spacex.com/news/2014/07/31/spacex-launches-3d-printed-part-space-creates-printed-engine-chamber-crewed

Quote
SuperDraco engine was fired in both a launch escape profile and a landing burn profile, successfully throttling between 20% and 100% thrust levels.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Kabloona on 01/23/2016 04:05 AM
Thanks, docmordrid. Yes, that's why I used 120,000 lbf x .2 = 24,000 lbf min thrust for 8 SD's, after cosine losses.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Earendil on 01/23/2016 07:28 AM
Thanks, docmordrid. Yes, that's why I used 120,000 lbf x .2 = 24,000 lbf min thrust for 8 SD's, after cosine losses.

Ok, so why not use 4 engines for twice longer time..  this will also lower the g during landing.. such an approach seems to me more like "future spacecraft landing", rather then burn in the last possible moment..
Stability issues if only 4 are fired?? .. Of course they know better than us :)

Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 01/23/2016 08:10 AM
Thanks, docmordrid. Yes, that's why I used 120,000 lbf x .2 = 24,000 lbf min thrust for 8 SD's, after cosine losses.

Ok, so why not use 4 engines for twice longer time..  this will also lower the g during landing.. such an approach seems to me more like "future spacecraft landing", rather then burn in the last possible moment..
Stability issues if only 4 are fired?? .. Of course they know better than us :)

I am quite sure they would fire all 8 to ensure their function. They could switch off 4 of them after verification. That would give them 4 engines for the landing burn plus 4 tested engines if one of the 4 burning fail, which is very unlikely. If only one of the 8 fails at testing altitude they use the parachutes.

I agree fully that beginning the landing burn while they can still go for parachute landing is desirable if it can be done.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Kaputnik on 01/23/2016 08:27 AM
Would pulsed firings be at all feasible? SD is pressure fed and smaller versions of the same type of thruster can be used in very tightly controlled pulses.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: MP99 on 01/23/2016 08:39 AM
Would pulsed firings be at all feasible? SD is pressure fed and smaller versions of the same type of thruster can be used in very tightly controlled pulses.
Listen to the soundtrack of the test, then try to tell me they're not doing that already.

Cheers, Martin
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 01/23/2016 08:49 AM
Would pulsed firings be at all feasible? SD is pressure fed and smaller versions of the same type of thruster can be used in very tightly controlled pulses.
Listen to the soundtrack of the test, then try to tell me they're not doing that already.

Cheers, Martin

Yes, but do they need pulsed firing to throttle to 20%? SuperDraco should be able to throttle to 20% without pulsing. Pulsing would be on top of that or am I wrong?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: JamesH on 01/23/2016 09:02 AM
Cross range capability.

I asked a similar question about the first stage, but what sort of cross range capability does the Dragon have? I presume it can be steered in a small way using thrusters to align the shell, and using its aero shape, and they will get some sort of directional ability once the SD start up, but I cannot see if being in the same range as the 1st stage.

So, how do they hit the landing pad accurately without something like grid fins?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Johnnyhinbos on 01/23/2016 11:49 AM

Cross range capability.

I asked a similar question about the first stage, but what sort of cross range capability does the Dragon have? I presume it can be steered in a small way using thrusters to align the shell, and using its aero shape, and they will get some sort of directional ability once the SD start up, but I cannot see if being in the same range as the 1st stage.

So, how do they hit the landing pad accurately without something like grid fins?
I think the capsule can be thought of like one large grid fin. AFAIK the grid fins are used to orient the body of the booster to achieve a glide slope. Likewise the capsule can be steered via body positioning via thrusters during descent. This was done during Apollo by inverting the center of gravity to change the angle of attack and thereby going sever hundred more miles downrange to avoid a storm. I believe dragon has much finer control of the craft's angle of attack.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 01/23/2016 12:27 PM
So, how do they hit the landing pad accurately without something like grid fins?

I recall some info from the Commercial Crew Contract release. Dragon does have an internal mechanism to shift the center of mass. That should give some significant steering capability. I remember it quite well because I immediately thought of application for steering the Red Dragon descent in a similar but more controllable way as Curiosity did with dropping tungsten ballast twice.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: jabe on 01/23/2016 12:31 PM
This was done during Apollo by inverting the center of gravity to change the angle of attack and thereby going sever hundred more miles downrange to avoid a storm. I believe dragon has much finer control of the craft's angle of attack.
a great vid explaining how Apollo capsule navigates entering atmosphere..amazing what they did with the hardware they had.  whole video is good  ..atmospheric interface starts at ~6:40
jb
https://www.youtube.com/watch?v=aW5ozq4Tqew
Title: Re: SpaceX DragonFly Discussion Thread
Post by: OxCartMark on 01/23/2016 03:00 PM
WRT the propulsion test altitude -

I presume that the falling (~directed flying) capsule is targeting the landing pad.  When the propulsive landing test is performed if its not good then I would expect that the system would use whatever SD capability is left to translate the capsule east so that the parachute landing will be into water.  It seems to me that the time and altitude required for this translation would drive the altitude of the SD test to one of the higher assumed altitudes rather than one of the lower guesses.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Robotbeat on 01/23/2016 03:15 PM
A landing should be survivable just fine under parachutes. The legs provide cushioning. Soyuz sometimes has its landing thrusters fail to fire. It's rough, but survivable. With legs, the situation may be much better.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: OxCartMark on 01/23/2016 03:35 PM
Yes, no, maybe.  A Russian or Blue Origin capsule will be landing on a flat nearly featureless surface.  SpaceX will be landing in an area that has (for instance) utility poles, ditches, fire hydrants, buildings, trees, etc.  Water is less lumpy.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 01/23/2016 03:38 PM
Yes, no, maybe.  A Russian or Blue Origin capsule will be landing on a flat nearly featureless surface.  SpaceX will be landing in an area that has (for instance) utility poles, ditches, fire hydrants, buildings, trees, etc.  Water is less lumpy.

No. If Dragon comes down under parachutes it would not land very near to the intended landing pad for powered descent. They would place that pad in an area where they can come down under parachutes.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sewebster on 01/23/2016 07:57 PM
Yes, no, maybe.  A Russian or Blue Origin capsule will be landing on a flat nearly featureless surface.  SpaceX will be landing in an area that has (for instance) utility poles, ditches, fire hydrants, buildings, trees, etc.  Water is less lumpy.

No. If Dragon comes down under parachutes it would not land very near to the intended landing pad for powered descent. They would place that pad in an area where they can come down under parachutes.

Would they really be able to divert when they figured out the engines didn't work? Especially without being able to use the engines to do so?

Also, I'm not sure such a clear area would actually be able to exist near where they would do propulsive landing? (other than the water, which probably makes sense)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Kabloona on 01/23/2016 08:11 PM
Would pulsed firings be at all feasible? SD is pressure fed and smaller versions of the same type of thruster can be used in very tightly controlled pulses.
Listen to the soundtrack of the test, then try to tell me they're not doing that already.

Cheers, Martin

Yes, but do they need pulsed firing to throttle to 20%? SuperDraco should be able to throttle to 20% without pulsing. Pulsing would be on top of that or am I wrong?

Pulsing would be on top of the 20% minimum.

Turns out that the 33,000 lbf axial thrust for the test is 27.5% of the 120,000 lbf max axial thrust advertised capability. So the test might have been run with 4 engines pulsing between 25% and 30% throttle, 180 degrees out of phase with the other 4 pulsing between the same levels, with the resulting average of 27.5% throttle.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 01/23/2016 10:43 PM
Thanks, docmordrid. Yes, that's why I used 120,000 lbf x .2 = 24,000 lbf min thrust for 8 SD's, after cosine losses.

Ok, so why not use 4 engines for twice longer time..  this will also lower the g during landing.. such an approach seems to me more like "future spacecraft landing", rather then burn in the last possible moment..
Stability issues if only 4 are fired?? .. Of course they know better than us :)

I always thought that was the plan, and having engine #2 on each block at standby, so it can kick in immediately.  Only if both engines in a block fail, do you switch over to parachutes, and I think these ballistic-opened chutes can operate it very very low altitudes
Title: Re: SpaceX DragonFly Discussion Thread
Post by: georgegassaway on 01/24/2016 06:09 AM
I always thought that was the plan, and having engine #2 on each block at standby, so it can kick in immediately.  Only if both engines in a block fail, do you switch over to parachutes, and I think these ballistic-opened chutes can operate it very very low altitudes
Ballistic chutes can, but every parachute system has operational limits / envelopes.  If a given ballistic chute system was meant to be fired at less than 200 mph, and the drogues fail for whatever reason so it comes in at say 250 mph, that could result in the ballistic chutes ripping off when they try to deploy (more than 50% aerodynamic load forces at 250 mph vs 200 mph).

Or, if failure for whatever reason of an entire quadrant failed, so that an aborted powered descent resulted in tumbling, that could set up a chain of events it could not recover from regardless of altitude. Such as the failure of an Orion recovery system test, video at end of message.

Now, I am not saying I don't think it can work. Just that it is not quite as simple to just deploy chutes the last few hundred feet in case of problems with powered descent.  Indeed, ballistic fast-opening chutes are sort of the opposite of what a heavy  fast-moving object needs, the usual method is drogues to slow a bit, and stabilize, then deploy the main but have it reefed and slowly open fully so as not to overstress the chute and/or the lines/connections. But of course, it requires a lot of altitude to do that, problematic for this purpose.  So, ballistic chutes make sense but there are some additional issues to solve due to the complications of not doing slowly un-reefed chutes.

The recovery system needs to be designed with worst-case scenarios (including tumbling), and a LOT of strength margins.

[edit update - have  added a successful Orion recovery system video.  Note the sequencing, main chute inflation, and giving time to slow itself more with the reefed deploy, and the disreef about 2:12. That is a lot of decleration over a relatively long period of time (and altitude of course) before the disreef, that a ballistic chute system would have to have the strength to deal with to get to that point. More likely, some compromise design with perhaps ballistically deployed drogues and even have ballistically deployed chutes reefed momentarily, which would require some more altitude than pure ballistic but not nearly the incredible deployment loads of  regular ballistically deployed chutes.]

- George Gassaway

https://www.youtube.com/watch?v=TVl6lCr1vCo


https://www.youtube.com/watch?v=bwdNQoAKBs4
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 01/24/2016 06:52 PM
I always thought that was the plan, and having engine #2 on each block at standby, so it can kick in immediately.  Only if both engines in a block fail, do you switch over to parachutes, and I think these ballistic-opened chutes can operate it very very low altitudes
Ballistic chutes can, but every parachute system has operational limits / envelopes.  If a given ballistic chute system was meant to be fired at less than 200 mph, and the drogues fail for whatever reason so it comes in at say 250 mph, that could result in the ballistic chutes ripping off when they try to deploy (more than 50% aerodynamic load forces at 250 mph vs 200 mph).

Or, if failure for whatever reason of an entire quadrant failed, so that an aborted powered descent resulted in tumbling, that could set up a chain of events it could not recover from regardless of altitude. Such as the failure of an Orion recovery system test, video at end of message.

Now, I am not saying I don't think it can work. Just that it is not quite as simple to just deploy chutes the last few hundred feet in case of problems with powered descent.  Indeed, ballistic fast-opening chutes are sort of the opposite of what a heavy  fast-moving object needs, the usual method is drogues to slow a bit, and stabilize, then deploy the main but have it reefed and slowly open fully so as not to overstress the chute and/or the lines/connections. But of course, it requires a lot of altitude to do that, problematic for this purpose.  So, ballistic chutes make sense but there are some additional issues to solve due to the complications of not doing slowly un-reefed chutes.

The recovery system needs to be designed with worst-case scenarios (including tumbling), and a LOT of strength margins.

[edit update - have  added a successful Orion recovery system video.  Note the sequencing, main chute inflation, and giving time to slow itself more with the reefed deploy, and the disreef about 2:12. That is a lot of decleration over a relatively long period of time (and altitude of course) before the disreef, that a ballistic chute system would have to have the strength to deal with to get to that point. More likely, some compromise design with perhaps ballistically deployed drogues and even have ballistically deployed chutes reefed momentarily, which would require some more altitude than pure ballistic but not nearly the incredible deployment loads of  regular ballistically deployed chutes.]

- George Gassaway

https://www.youtube.com/watch?v=TVl6lCr1vCo


https://www.youtube.com/watch?v=bwdNQoAKBs4

Sure, but air speed is your friend...  And if a jet malfunctions and they decide to abort to parachute, the cut-off will happen so fast there won't be time for the capsule to start spinning fast. 

This will be a computerized decision - if the system is not getting the right response from the thruster, than 0.1 seconds later the thruster are off and the mortar has fired.

The airframe parachute site is talking about sub-second timing for deploying the chute
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 01/25/2016 01:13 AM
Well, we know from the pad abort test that the parachutes of the Dragon v2 can handle deployment at less than 4,500 feet. Though the capsule had a relatively low vertical speed then. That said, even with some of the SDs failing, you can probably still slow down enough for the chutes to work deploy fine. I think it would be unlikely that all SDs fail. Plus the legs will do some cushioning and the capsule itself provides some crunch zone.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 01/25/2016 01:39 AM
Given all the forms of redundancy, the likeliest way to have a crash is if the flight software has a bug and under some unforeseen combination of inputs makes a dumb decision.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: alang on 01/25/2016 08:20 PM
I think this has all been said before but I'm curious if anyone thinks it is a good summary or if perceptions have changed recently:
The general view is that there is no doubt that they will get it to work. However, at what point will SpaceX want to risk someone's neck with a propulsive landing?
I don't doubt that there will be no shortage of volunteers but the publicity is still bad when things go wrong.
There's a cultural aspect here - our parents' generation and before had a different expectation with respect to physical danger - probably due to war, disease and workplace accidents.
Everybody knows why SpaceX is doing this : propulsive landings have to become normative in order to fulfill the SpaceX (or at least Elon Musk) spacefaring vision. In order to fulfil that vision you need general purpose spacraft without an Earth atmosphere focussed landing system. They need it to be the default approach.
However,  IMO, it will be a very long time before a person rather than cargo does a propulsive landing on earth except through parachute failure.
I would guess that you would have to prove that it was at least as safe as the Soyuz approach of parachute plus emergency parachute - people are convinced by experience. Unfortunately or fortunately Soyuz has a lot of experience.
When it comes to landing on the moon or Mars people's expectations will be different - it's meant to be dangerous.
The plus side is that when propulsive landing is shown to work regularly for cargo then the practicality of regular landings on the moon or mars will be clear to see by anyone.
I do think they will need cleaner propellant for regular propulsive landings though - I can't see the green laws getting any less demanding_ another source of bad publicity whatever else you may think about it.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 01/26/2016 01:12 AM
I don't understand why people think that propulsive landing is more dangerous than landing under parachutes. It is not like parachutes never fail.
It seems to me that propulsive landing is less dangerous since it adds another level of redundancy.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: georgegassaway on 01/26/2016 03:20 AM
Once a parachute system has successfully deployed, it’s safe for the rest of the ride down (unless something bizarre happens like a fire). 

Once a propulsive landing gets below some critical altitude and into a “dead zone” (too low to safely deploy chutes in time for a soft-enough landing), it HAS to keep working properly for 100% of the rest of the descent, otherwise a large risk of LOV/LOC.

I’m not saying it can’t be done safely and reliably. But in some ways not exactly redundant, either.  In some ways it is an additional criticality 1 failure mode (if during an abort the Super-Dracos only burned for 80% duration, it’d still probably abort safely..  80% duration burn then shutdown for some reason mid-air during landing….. probably a Bad Day).

MOST interesting will be the first time that a Dragon does a normal re-entry, then fires the Super-Dracos for a propulsive landing.  I know they will be testing the h*** out of it before then, high-altitude drop tests and all that, but not enough of a test compared to a full re-entry first, then a propulsive landing.

- George Gassaway
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 01/26/2016 07:44 AM
Once a propulsive landing gets below some critical altitude and into a “dead zone” (too low to safely deploy chutes in time for a soft-enough landing), it HAS to keep working properly for 100% of the rest of the descent, otherwise a large risk of LOV/LOC.

I’m not saying it can’t be done safely and reliably. But in some ways not exactly redundant, either.  In some ways it is an additional criticality 1 failure mode (if during an abort the Super-Dracos only burned for 80% duration, it’d still probably abort safely..  80% duration burn then shutdown for some reason mid-air during landing….. probably a Bad Day).

As you wrote, once the parachute is deployed, it is safe. Yes but before that it is not so the whole procedure has a degree of uncertainty, however low.

True, as soon as you pass a threshold the landing is committed to propulsive, no way to switch to parachute. However the SuperDraco propulsion system is very highly redundant and committing to it was done after checking it seconds earlier. Given the combination of redundancy and the very high reliability of pressure fed hypergolic engines it is very safe.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Elmar Moelzer on 01/26/2016 09:15 AM
True, as soon as you pass a threshold the landing is committed to propulsive, no way to switch to parachute. However the SuperDraco propulsion system is very highly redundant and committing to it was done after checking it seconds earlier. Given the combination of redundancy and the very high reliability of pressure fed hypergolic engines it is very safe.
I agree and then I want to add that it seems equally unlikely to me that so many of the engines will suddenly fail at a low enough altitude to make make parachute deployment impossible. I would really like to know what sort of failure mode that would be.
I also don't quite see why you cant deploy the parachutes at a low altitude. Sure they by themselves would not be able to guarantee a safe landing, but they could provide additional -DeltaV to further slow down the capsule (which to this point had already been slowed down by the SDs). Combine that with slow down from whatever SDs are left working and you should have a good chance to make the landing/crash survivable. Lets not forget that there are also landing legs and quite a substantial amount of capsule material including the very low density heatshield to provide a nice crumbling zone. The capsule would be destroyed and people would probably be injured, but should have a good chance to survive.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 01/26/2016 01:22 PM
This whole thing boils down to a gut reaction.  It's not too different than the wings vs. VTVL arguments.  Everyone* has 100 technical reasons this way or that, but at the end of the day, there are simply "wing people" and "non-wing" people...


*Except me, of course.  I'm objective and reached my conclusion based on sound engineering arguments!
Title: Re: SpaceX DragonFly Discussion Thread
Post by: douglas100 on 01/26/2016 03:55 PM
Dragon has another potential failure mode if it ever makes a very hard landing for whatever reason. If the prop lines or tanks fracture and the hypergols mix, then there could be a nasty conflagration. Now I think this is a highly unlikely scenario and I agree with Musk's assertion that they've made it as safe as possible. But I don't think I've seen the possibility discussed.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: dhHopkins on 01/26/2016 04:25 PM
Just an observation from a long time lurker - very occasional poster.  This is still spaceflight, as much as we would like it to be routine, like air travel.  The astronauts flying these wonderful new machines know, are trained on, and accept the risk.  These are still ‘Right Stuff’ and ‘Let’s light this candle’ folks.  If the propulsive landing yields more favorable odds than a 2 in 130 or so LOV/LOC – it’s an improvement to the previous system, which early on was proved to be a 1 in 50 or so risk – and they still flew
I believe this new system will be orders of magnitude safer than STS, and am excited to see the potential of a truly reusable orbital spacecraft, that doesn’t have to be dunked in the ocean before it’s next flight, and lands like something currently out of science fiction (except for Falcon 9 and New Shepard).
Hey – I’m just a space fan, and have little technical knowledge.  Tear me up, and enlighten me, guys!
 :)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: chipguy on 01/26/2016 05:26 PM
Dragon has another potential failure mode if it ever makes a very hard landing for whatever reason. If the prop lines or tanks fracture and the hypergols mix, then there could be a nasty conflagration. Now I think this is a highly unlikely scenario and I agree with Musk's assertion that they've made it as safe as possible. But I don't think I've seen the possibility discussed.

I find it hard to comprehend that the propulsion system couldn't or wouldn't be designed with enough mechanical
robustness to remain fully intact in any landing scenario potentially survivable by the occupants. The meatbags are
the weakest link.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Space Ghost 1962 on 01/26/2016 06:03 PM
Dragon has another potential failure mode if it ever makes a very hard landing for whatever reason. If the prop lines or tanks fracture and the hypergols mix, then there could be a nasty conflagration. Now I think this is a highly unlikely scenario and I agree with Musk's assertion that they've made it as safe as possible. But I don't think I've seen the possibility discussed.

Actually more serious is making a "dumb", default system that always self orients and fails in such a way that it brakes enough to be survivable. Then you "harden" the system so that it "crumples" and degrades in a survivable way, at a point where much of the props self exhaust so you have minimal mass/leakage.

Realize that the parachute first and brake to land period of propulsive landing means that your terminal velocity/guidance/failure tolerance can be "babystepped" upward as your design methodology/strategy proves itself to greater degrees, so you don't have to get it "all a once".

Your later efforts that due, also brings in the complexity of GNC for precision, controllable landings either automated or by the PIC.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: johnnyhinbos01 on 01/26/2016 06:15 PM

Once a parachute system has successfully deployed, it’s safe for the rest of the ride down (unless something bizarre happens like a fire). 

Once a propulsive landing gets below some critical altitude and into a “dead zone” (too low to safely deploy chutes in time for a soft-enough landing), it HAS to keep working properly for 100% of the rest of the descent, otherwise a large risk of LOV/LOC.

I’m not saying it can’t be done safely and reliably. But in some ways not exactly redundant, either.  In some ways it is an additional criticality 1 failure mode (if during an abort the Super-Dracos only burned for 80% duration, it’d still probably abort safely..  80% duration burn then shutdown for some reason mid-air during landing….. probably a Bad Day).

MOST interesting will be the first time that a Dragon does a normal re-entry, then fires the Super-Dracos for a propulsive landing.  I know they will be testing the h*** out of it before then, high-altitude drop tests and all that, but not enough of a test compared to a full re-entry first, then a propulsive landing.

- George Gassaway
Not sure I agree 100% with the "once open 100% safe" statement. Landing under chutes means either a water landing or a land landing. Water landings add an additional risk of inversion or even water ingress. Land landings under parachutes can be, uh, impactful events that have their own risks and are often augmented with retro rockets at touchdown that can also fail. Add to that, you have basically no command authority when under chutes which adds restrictions to landing areas and conditions.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sewebster on 01/26/2016 06:42 PM
Regarding the redundancy of having lots of Superdracos... I am wondering exactly which ones they can have fail and still be able to have stable control. For instance, what if they lose a pair, can they still land properly? Just the loss of thrust might be fine (maybe a harder landing), but if the capsule tumbles... obviously they would program the control system for the contingencies, but there is some limit...?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 01/26/2016 06:59 PM
Regarding the redundancy of having lots of Superdracos... I am wondering exactly which ones they can have fail and still be able to have stable control. For instance, what if they lose a pair, can they still land properly? Just the loss of thrust might be fine (maybe a harder landing), but if the capsule tumbles... obviously they would program the control system for the contingencies, but there is some limit...?

I have been thinking about this. My best guess is they cannot lose both engines in one pod and need to make sure that one failure cannot take out both engines.

However they have a means to shift the center of mass. They could shift the center away from the failed pod, do the braking with the four engines on two opposing pods and do the balancing with short bursts of an engine opposed to the failed pod. Probably too complex to work in the real world.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: e of pi on 01/26/2016 08:19 PM
So at 5 seconds in this videothey show the same November flight video we've already seen, but from 14 to 33 second is what appears to me to be a different, longer flight. If it's not slow motion, then it's a roughly 19-second hover. That'd be something like 190 m/s equivalent. Anybody else have thoughts on it, or what can be gleaned from it?

Video (https://www.youtube.com/watch?v=6glAvN5APh4&t=0m5s)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sewebster on 01/26/2016 08:22 PM
However they have a means to shift the center of mass. They could shift the center away from the failed pod, do the braking with the four engines on two opposing pods and do the balancing with short bursts of an engine opposed to the failed pod. Probably too complex to work in the real world.

I was wondering if they could shut down the opposite pod entirely and just run on the other two... can they throttle the engines individually or only at a pod level? If individually then perhaps theoretically you could maintain control with two pods? Not sure if this would actually be possible.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: NovaSilisko on 01/26/2016 09:03 PM
If it's not slow motion, then it's a roughly 19-second hover. That'd be something like 190 m/s equivalent. Anybody else have thoughts on it, or what can be gleaned from it?

It's definitely slow motion. The sound has the same "stretched" quality that the other slow motion version of the test had, plus, look at the residual flames at the very end.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars-J on 01/26/2016 09:13 PM

However they have a means to shift the center of mass. They could shift the center away from the failed pod, do the braking with the four engines on two opposing pods and do the balancing with short bursts of an engine opposed to the failed pod. Probably too complex to work in the real world.

What means do they have to shift the center of mass? Having the crew lean over? :)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: JFARNS on 01/26/2016 09:24 PM
Crew Dragon’s systems were designed with a critical focus on safety and reliability and provide a precision controlled reentry from space. Dragon’s passively stable shape generates lift as it reenters the Earth’s atmosphere supersonically. In addition to the 8 SuperDraco engines onboard Crew Dragon, its 16 Draco thrusters provide 2-fault tolerant roll control during reentry for precision guidance on course for a soft touchdown on land. Additionally, a movable ballast sled allows the angle of attack to be actively controlled during entry to further provide precision landing control. The Crew Dragon’s SuperDraco engines are divided into four quads, each with
two SuperDracos and 4 Draco engines. The SuperDracos will activate to provide precision land landing capability. Nominally, only two quads are used for on-orbit propellant with the Dracos and two quads are reserved for propulsive landing using the SuperDracos. For aborts or on- orbit faults, all four quads are available for Draco or SuperDraco operations, increasing flexibility, robustness, and performance in these critical situations. In the event of any anomalies with the propulsion system, Dragon retains its parachute capability for a soft water landing, a technology that has been demonstrated repeatedly via cargo missions. 
http://science.house.gov/sites/republicans.science.house.gov/files/documents/HHRG-114-SY16-WState-GReisman-20150227.pdf
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 01/26/2016 09:42 PM
I wonder if that ballast would be mass that is on board anyway, like a battery pack.

When I read this for the first time I immediately thought of Red Dragon steering for Mars EDL. Curiosity shifted center of mass twice by ejecting heavy tungsten ballast. First to move center of mass off center then to move it back to center. A movable ballast enables more precise steering. That's why it stuck in my memory.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: docmordrid on 01/26/2016 09:50 PM
I wonder if that ballast would be mass that is on board anyway, like a battery pack.
>
A movable ballast enables more precise steering. That's why it stuck in my memory.

Last February Garrett Reisman testified before Congress that it has a movable ballast sled.

http://science.house.gov/sites/republicans.science.house.gov/files/documents/HHRG-114-SY16-WState-GReisman-20150227.pdf

Quote
Additionally, a movable ballast sled allows the angle of attack to be actively controlled during entry to further provide precision landing control.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars-J on 01/26/2016 10:02 PM

However they have a means to shift the center of mass. They could shift the center away from the failed pod, do the braking with the four engines on two opposing pods and do the balancing with short bursts of an engine opposed to the failed pod. Probably too complex to work in the real world.

What means do they have to shift the center of mass? Having the crew lean over? :)

Last February Garrett Reisman testified before Congress that it has a movable ballast sled.

http://science.house.gov/sites/republicans.science.house.gov/files/documents/HHRG-114-SY16-WState-GReisman-20150227.pdf

Quote
Additionally, a movable ballast sled allows the angle of attack to be actively controlled during entry to further provide precision landing control.

Ah, thanks for the reminder. But a 'sled' makes this sound like this is in one axis only, on a track. Presumably to shift the angle of attack.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sewebster on 01/26/2016 10:20 PM
Nominally, only two quads are used for on-orbit propellant with the Dracos and two quads are reserved for propulsive landing using the SuperDracos.

Hmm. So this is saying that the nominal propulsive landing would only use two pods (quads)? The hover test used all four... but I guess that wasn't a landing.  I find this a little confusing and unexpected, seems unstable.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: nadreck on 01/26/2016 10:21 PM

Ah, thanks for the reminder. But a 'sled' makes this sound like this is in one axis only, on a track. Presumably to shift the angle of attack.

roll a little for yaw control with it.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: docmordrid on 01/26/2016 10:22 PM
Absent diagrams I don't think we can assume that it's unidirectional. 2 dimensions is relatively easy and flat, think plotter head, but 3 dimensions is another matter.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meadows.st on 01/27/2016 02:30 AM
Nominally, only two quads are used for on-orbit propellant with the Dracos and two quads are reserved for propulsive landing using the SuperDracos.

Hmm. So this is saying that the nominal propulsive landing would only use two pods (quads)? The hover test used all four... but I guess that wasn't a landing.  I find this a little confusing and unexpected, seems unstable.

Parsing the original quote:
16 Draco thrusters = 4 quads.  There are an additional 8 SuperDraco Thrusters.  Note that "Two quads" (of Dracos) = 8 Dracos for on-orbit and another "two quads" (of Dracos) for use during propulsive landing (with 8 SuperDracos).
Title: Re: SpaceX DragonFly Discussion Thread
Post by: wannamoonbase on 01/27/2016 03:12 AM

However they have a means to shift the center of mass. They could shift the center away from the failed pod, do the braking with the four engines on two opposing pods and do the balancing with short bursts of an engine opposed to the failed pod. Probably too complex to work in the real world.

What means do they have to shift the center of mass? Having the crew lean over? :)

Last February Garrett Reisman testified before Congress that it has a movable ballast sled.

http://science.house.gov/sites/republicans.science.house.gov/files/documents/HHRG-114-SY16-WState-GReisman-20150227.pdf

Quote
Additionally, a movable ballast sled allows the angle of attack to be actively controlled during entry to further provide precision landing control.

Ah, thanks for the reminder. But a 'sled' makes this sound like this is in one axis only, on a track. Presumably to shift the angle of attack.

Makes sense that with roll control by thrusters that the sled can be on a one dimensional track.  The two work together should give all the control needed.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sewebster on 01/27/2016 05:27 AM
Hmm. So this is saying that the nominal propulsive landing would only use two pods (quads)? The hover test used all four... but I guess that wasn't a landing.  I find this a little confusing and unexpected, seems unstable.

Parsing the original quote:
16 Draco thrusters = 4 quads.  There are an additional 8 SuperDraco Thrusters.  Note that "Two quads" (of Dracos) = 8 Dracos for on-orbit and another "two quads" (of Dracos) for use during propulsive landing (with 8 SuperDracos).

Ok, thanks, that would make more sense!
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Kabloona on 01/27/2016 08:45 PM
I always thought that was the plan, and having engine #2 on each block at standby, so it can kick in immediately.  Only if both engines in a block fail, do you switch over to parachutes, and I think these ballistic-opened chutes can operate it very very low altitudes
Ballistic chutes can, but every parachute system has operational limits / envelopes.  If a given ballistic chute system was meant to be fired at less than 200 mph, and the drogues fail for whatever reason so it comes in at say 250 mph, that could result in the ballistic chutes ripping off when they try to deploy (more than 50% aerodynamic load forces at 250 mph vs 200 mph).

Or, if failure for whatever reason of an entire quadrant failed, so that an aborted powered descent resulted in tumbling, that could set up a chain of events it could not recover from regardless of altitude. Such as the failure of an Orion recovery system test, video at end of message.

Now, I am not saying I don't think it can work. Just that it is not quite as simple to just deploy chutes the last few hundred feet in case of problems with powered descent.  Indeed, ballistic fast-opening chutes are sort of the opposite of what a heavy  fast-moving object needs, the usual method is drogues to slow a bit, and stabilize, then deploy the main but have it reefed and slowly open fully so as not to overstress the chute and/or the lines/connections....

Following up on this discussion...Lars_J just posted this video in another thread. The chute deployment is similar to what we've seen in the past on cargo Dragon, ie slowly deployed chutes at relatively high altitude.

I count at least 10 seconds before the chutes are fully deployed, so I continue to doubt the notion that ballistic fast-opening chutes deployed at low altitude are going to have any role on Crew Dragon.

The test seems consistent with SpaceX's stated operational plan to test fire the SD's on an incoming Crew Dragon at high altitude to verify operation, and only then deploy the chutes as a backup if necessary.

https://www.youtube.com/watch?v=4PG438XSarg
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 01/27/2016 08:54 PM
I always thought that was the plan, and having engine #2 on each block at standby, so it can kick in immediately.  Only if both engines in a block fail, do you switch over to parachutes, and I think these ballistic-opened chutes can operate it very very low altitudes
Ballistic chutes can, but every parachute system has operational limits / envelopes.  If a given ballistic chute system was meant to be fired at less than 200 mph, and the drogues fail for whatever reason so it comes in at say 250 mph, that could result in the ballistic chutes ripping off when they try to deploy (more than 50% aerodynamic load forces at 250 mph vs 200 mph).

Or, if failure for whatever reason of an entire quadrant failed, so that an aborted powered descent resulted in tumbling, that could set up a chain of events it could not recover from regardless of altitude. Such as the failure of an Orion recovery system test, video at end of message.

Now, I am not saying I don't think it can work. Just that it is not quite as simple to just deploy chutes the last few hundred feet in case of problems with powered descent.  Indeed, ballistic fast-opening chutes are sort of the opposite of what a heavy  fast-moving object needs, the usual method is drogues to slow a bit, and stabilize, then deploy the main but have it reefed and slowly open fully so as not to overstress the chute and/or the lines/connections....

Following up on this discussion...Lars_J just posted this video in another thread. The chute deployment is similar to what we've seen in the past on cargo Dragon, ie slowly deployed chutes at relatively high altitude.

I count at least 10 seconds before the chutes are fully deployed, so I continue to doubt the notion that ballistic fast-opening chutes deployed at low altitude are going to have any role on Crew Dragon.

https://www.youtube.com/watch?v=4PG438XSarg
Agreed insofar that in order to do last minute chute deployment you need an actively deployed setup.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cscott on 01/27/2016 09:29 PM
Pad abort clearly used fast deploy.  Are you suggesting separate parachute systems for pad abort and for water landing?

IMO it's more likely that we're seeing an early test of the four parachute system, and the drogue mortar has not yet been integrated with this design.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sewebster on 01/27/2016 09:56 PM
The pad abort (main) chutes still stayed reefed for a significant time, just like these four...?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Kabloona on 01/27/2016 10:51 PM
Pad abort clearly used fast deploy.  Are you suggesting separate parachute systems for pad abort and for water landing?

IMO it's more likely that we're seeing an early test of the four parachute system, and the drogue mortar has not yet been integrated with this design.

When I said I counted about 10 seconds to fully deploy, I meant the time it took for the mains to expand to full diameter and thus reach maximum drag condition.

If you watch the pad abort video and compare with the Crew Dragon video, the chute deployment dynamics appear to be the same, ie the chutes do not open immediately, they take many seconds to fully open, and thus are not designed for low-altitude deployment like the ballistic fast-opening chutes meekgee is talking about.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cscott on 01/28/2016 12:39 AM
Pad abort chutes are designed for deployment below 1500m ( http://www.spacex.com/news/2015/05/04/5-things-know-about-spacexs-pad-abort-test ).  I'd call that a "low-altitude deployment" but I guess different folks are disagreeing on exactly how low is "low altitude".
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 01/28/2016 01:32 AM
Our definition here is "below the minimum height that DV2 can start its abort burn".

If we assumed 100 m/s terminal velocity, and 10 m/s2 deceleration, then 10 seconds is exactly what you have.

But we don't know the minimum deceleration (4 engines?  8?  how throttled are they?) and so we're just passing time guessing until more information comes to light.

 
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Kabloona on 01/28/2016 01:42 AM
Pad abort chutes are designed for deployment below 1500m ( http://www.spacex.com/news/2015/05/04/5-things-know-about-spacexs-pad-abort-test ).  I'd call that a "low-altitude deployment" but I guess different folks are disagreeing on exactly how low is "low altitude".

Remember that for pad abort, chutes are deployed at apogee where vertical velocity is zero, more or less, and 1500 m altitude gives plenty of time for chute deployment and deceleration.

Different situation for a re-entering Dragon where chutes will be deployed at terminal velocity, where 1500 m deployment altitude may be too close to the ground for comfort.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cscott on 01/28/2016 03:00 AM
Not actually deployed at apogee; if you look at the link I posted above, *trunk separation* is at apogee.  Drogue deployment is sometime after that, presumably because you want some amount of vertical velocity to ensure the chutes stay inflated after the mortar has done its job.

So pad abort is 1000-1500m at small velocity, and meekGee's numbers say 500m at 100m/s.  Yes, these are different regimes, but perhaps they are not *so* different that, with a bit of cleverness (different reefing schedules, say), the same parachute system might not be able to handle both.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 01/28/2016 03:26 AM
Not actually deployed at apogee; if you look at the link I posted above, *trunk separation* is at apogee.  Drogue deployment is sometime after that, presumably because you want some amount of vertical velocity to ensure the chutes stay inflated after the mortar has done its job.

So pad abort is 1000-1500m at small velocity, and meekGee's numbers say 500m at 100m/s.  Yes, these are different regimes, but perhaps they are not *so* different that, with a bit of cleverness (different reefing schedules, say), the same parachute system might not be able to handle both.

That's why I count in seconds-from-impact, not meters. 

Also, parachute inflation speed is a function of airspeed - it doesn't matter if you're going horizontally or vertically.
However, if you're going horizontally, the parachutes open sideways, and you swing a lot.

I think opening parachutes at S-10  (S for Splat) is very manageable.  Maybe even half that for fast parachutes.  The parachutes in the video did not look fast.

But.

They open in two stages.  What determines the transition from one phase to the other?  Is it another lanyard?  Because if that's the case, maybe they can open a lot faster - it's just that the test was looking at how they behave in "drogue mode".
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cscott on 01/28/2016 01:22 PM
@meekGee yes, agreed.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Wolfram66 on 02/11/2016 05:03 PM
Will Crewed Dragon possibly need grid-fins for precise maneuvering to LZ for Propulsive landing or will they rely solely on RCS for fine guidance to the landing pad? :o ;D :-\
Title: Re: SpaceX DragonFly Discussion Thread
Post by: nadreck on 02/11/2016 05:07 PM
Will Crewed Dragon possibly need grid-fins for precise maneuvering to LZ for Propulsive landing or will they rely solely on RCS for fine guidance to the landing pad? :o ;D :-\

Neither, they will supplement RCS controls with changing the attitude of the craft to "surf" on the heatshield by shifting the CG of the craft.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: OxCartMark on 02/12/2016 01:52 AM
Will Crewed Dragon possibly need grid-fins for precise maneuvering to LZ for Propulsive landing or will they rely solely on RCS for fine guidance to the landing pad? :o ;D :-\

Neither, they will supplement RCS controls with changing the attitude of the craft to "surf" on the heatshield by shifting the CG of the craft.
...by shifting a mass mounted on a sled within the V2 which exists for exactly that purpose.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: The Amazing Catstronaut on 02/12/2016 02:34 AM
The heat shield surfing technique is an old one that goes right back to the dawn of American manned spaceflight. Soyuz uses the same system - it's a very efficient way to provide reentry guidance, control your descent and maximise atmospheric lift to avoid dropping like a cartoon piano. It reduces G-loads too. It's part of the reason why capsules are shaped the way they are. You get aerocontrol with no output other than electricity or changing the mass of your capsule. All you are doing is shifting some of that mass.

The lower and slower you get the less effective it is and the less lift it will provide. For the terminal phase superdracos should be able to get you millimetre accuracy for a fully powered landing. Parachutes won't get you that, but parachute accuracy within a mile of the optimum landing site has been heard of before.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Robotbeat on 02/12/2016 02:45 AM
A trim tab is more efficient than shifting weights, especially if you need to eject weights like MSL did to get the right off-set.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: abaddon on 02/12/2016 02:20 PM
A trim tab is more efficient than shifting weights, especially if you need to eject weights like MSL did to get the right off-set.
On the other hand, a trim tab is an aero surface external to the capsule, and when dealing with an orbital re-entering vehicle, that makes things way more complicated.  With the sled being fully internal to Dragon no weights are ejected and it should still give the capsule plenty of steering capability.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: meekGee on 02/12/2016 02:50 PM
A trim tab is more efficient than shifting weights, especially if you need to eject weights like MSL did to get the right off-set.
On the other hand, a trim tab is an aero surface external to the capsule, and when dealing with an orbital re-entering vehicle, that makes things way more complicated.  With the sled being fully internal to Dragon no weights are ejected and it should still give the capsule plenty of steering capability.
If you follow Motie design philosophy, the sled weight is not just a dead weight but something you have to carry anyway.

Title: Re: SpaceX DragonFly Discussion Thread
Post by: Robotbeat on 02/13/2016 12:14 AM
A trim tab is more efficient than shifting weights, especially if you need to eject weights like MSL did to get the right off-set.
On the other hand, a trim tab is an aero surface external to the capsule, and when dealing with an orbital re-entering vehicle, that makes things way more complicated.
Actually, it makes things simpler since you don't have to discard weights (another critical event), etc. It has good control authority, much lower mass, and overall is a great idea. The main reason it hasn't been done is because:
1) JPL didn't think of it first. JPL does NASA's Mars missions. Not Invented Here.
2) It has never been done before. (Yes, this last point is a little redundant.)
Title: Re: SpaceX DragonFly Discussion Thread
Post by: CuddlyRocket on 02/13/2016 05:34 AM
A trim tab is more efficient than shifting weights, especially if you need to eject weights like MSL did to get the right off-set.
On the other hand, a trim tab is an aero surface external to the capsule, and when dealing with an orbital re-entering vehicle, that makes things way more complicated.  With the sled being fully internal to Dragon no weights are ejected and it should still give the capsule plenty of steering capability.
If you follow Motie design philosophy, the sled weight is not just a dead weight but something you have to carry anyway.

Like a battery pack, perhaps?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: nadreck on 02/13/2016 06:24 AM
Actually, it makes things simpler since you don't have to discard weights (another critical event), etc.

Where does this idea that some weight has to be discarded come from. Original capsules simply were off centre and used roll to control lift (and yaw). The Dragon moves the mass rather than using roll.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 02/13/2016 06:45 AM
Where does this idea that some weight has to be discarded come from.

The curiosity rover landing used discarding tungsten ballast twice. First to have a mass offset then to balance it again for landing. Several hundred kg tungsten carried all the way to Mars just for that purpose.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 02/13/2016 07:21 AM
Dragon is not curiosity.

I responded to the question where the idea of shedding weight may come from. I am aware Dragon is not Curiosity.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: rpapo on 02/13/2016 10:04 AM
Discarding anything other than propellant mass doesn't go with SpaceX's reusability goal.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: guckyfan on 02/13/2016 10:17 AM
Original capsules simply were off centre and used roll to control lift (and yaw). The Dragon moves the mass rather than using roll.

Sounds like a combination of shifting mass and roll should give much steering authority for precision landing.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Lars-J on 02/13/2016 04:17 PM

Actually, it makes things simpler since you don't have to discard weights (another critical event), etc.

Where does this idea that some weight has to be discarded come from. Original capsules simply were off centre and used roll to control lift (and yaw). The Dragon moves the mass rather than using roll.

Dragon 2 will use both.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: nadreck on 02/13/2016 04:50 PM

Actually, it makes things simpler since you don't have to discard weights (another critical event), etc.

Where does this idea that some weight has to be discarded come from. Original capsules simply were off centre and used roll to control lift (and yaw). The Dragon moves the mass rather than using roll.

Dragon 2 will use both.

Do you have a source that says Dragon 2 will use detachable weights? This thread has been the first place I have seen this suggested.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sewebster on 02/13/2016 07:06 PM

Actually, it makes things simpler since you don't have to discard weights (another critical event), etc.

Where does this idea that some weight has to be discarded come from. Original capsules simply were off centre and used roll to control lift (and yaw). The Dragon moves the mass rather than using roll.

Dragon 2 will use both.

Do you have a source that says Dragon 2 will use detachable weights? This thread has been the first place I have seen this suggested.

I think the suggestion is that Dragon will use movable weights and roll thrusters. Rather than just movable weights alone.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: nadreck on 02/13/2016 07:21 PM

Actually, it makes things simpler since you don't have to discard weights (another critical event), etc.

Where does this idea that some weight has to be discarded come from. Original capsules simply were off centre and used roll to control lift (and yaw). The Dragon moves the mass rather than using roll.

Dragon 2 will use both.

Do you have a source that says Dragon 2 will use detachable weights? This thread has been the first place I have seen this suggested.

I think the suggestion is that Dragon will use movable weights and roll thrusters. Rather than just movable weights alone.
Yes that was my assumption based on putting the weight on a track that allowed it to shift along a single arc. The second axis of steering would be provided by rolling to shift that arc. However a number of people here seem to be saying that they will have external masses that are discarded which does not seem to be consistent with the development of Dragon or other capsules so far.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: sewebster on 02/13/2016 07:44 PM
Yes that was my assumption based on putting the weight on a track that allowed it to shift along a single arc. The second axis of steering would be provided by rolling to shift that arc. However a number of people here seem to be saying that they will have external masses that are discarded which does not seem to be consistent with the development of Dragon or other capsules so far.

I think things just got off track during discussion of an aero trim tab, with a comparison made to the MSL descent. Then people started responding to that. My guess is that MSL used discardable ballast because it was seen as easier overall than a track system to shift mass. But I don't know that anyone is really saying that Dragon 2 will discard ballast.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: 411rocket on 02/13/2016 07:45 PM
Yes that was my assumption based on putting the weight on a track that allowed it to shift along a single arc. The second axis of steering would be provided by rolling to shift that arc. However a number of people here seem to be saying that they will have external masses that are discarded which does not seem to be consistent with the development of Dragon or other capsules so far.

Only weight loss I can think of, from what is currently known, is expended fuel from Drayco thruster & Super Drayco firings.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cscott on 02/13/2016 08:08 PM
No discarded ballast. And no useless ballast, either.  Just a moveable sled holding some weighty portion of the equipment which dragon needs.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Robotbeat on 02/16/2016 03:02 AM
No discarded ballast. And no useless ballast, either.  Just a moveable sled holding some weighty portion of the equipment which dragon needs.
...so now you also need cables to that moving mass. Or contacts. In both cases, you have more wear mechanisms and more opportunities for things to go wrong than if that mass was some inert mass. So I would bet money it's inert mass on Dragon.

And yes, I was referring to Mars missions like MSL above that needed discarded weights since it needs to be balanced during cruise. It's true that Dragon doesn't quite have that problem, but my point still remains that a trim tab is not a bad solution, especially for MSL-like vehicles. The main argument against trim tab is lack of heritage, which is the same thing as "we shouldn't try it because we haven't tried it yet."
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Robotbeat on 02/16/2016 03:03 AM
Grid fins are like a more sophisticated version of a trim tab (i.e. a grid of aerosurfaces instead of just one).
Title: Re: SpaceX DragonFly Discussion Thread
Post by: JamesH on 02/16/2016 09:20 AM
No discarded ballast. And no useless ballast, either.  Just a moveable sled holding some weighty portion of the equipment which dragon needs.
...so now you also need cables to that moving mass. Or contacts. In both cases, you have more wear mechanisms and more opportunities for things to go wrong than if that mass was some inert mass. So I would bet money it's inert mass on Dragon.

And yes, I was referring to Mars missions like MSL above that needed discarded weights since it needs to be balanced during cruise. It's true that Dragon doesn't quite have that problem, but my point still remains that a trim tab is not a bad solution, especially for MSL-like vehicles. The main argument against trim tab is lack of heritage, which is the same thing as "we shouldn't try it because we haven't tried it yet."

Robust cables to moving masses are a solved problem. It's not as if they get any real usage anyway. Just a few movements on the way down. Nothing like a production line where there are cables moving around 24/7 for years on end without failing.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: matthewkantar on 02/16/2016 01:32 PM
A lead screw would work fine. No need to stick things out in the nastiness around a reentering capsule, thrusters for roll, and moveable weight to adjust CG gives all the control you need.

Matthew
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Jim on 02/16/2016 02:02 PM
.by shifting a mass mounted on a sled within the V2 which exists for exactly that purpose.

Where is this documented?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: cscott on 02/16/2016 02:07 PM

.by shifting a mass mounted on a sled within the V2 which exists for exactly that purpose.

Where is this documented?

Garrett Reisman's congressional testimony, a year ago:

http://www.hq.nasa.gov/legislative/hearings/2-27-15_REISMAN.pdf

He just says "ballast on a sled", not the contents of the ballast.  NSF opinion at the time was that batteries would make excellent ballast, but we have no direct statement from SpaceX about what exactly the ballast is (ie, whether it's an inert mass or otherwise-useful equipment).
Title: Re: SpaceX DragonFly Discussion Thread
Post by: LouScheffer on 02/20/2016 11:25 PM
The main argument against trim tab is lack of heritage, which is the same thing as "we shouldn't try it because we haven't tried it yet."
There's a fairly long discussion on this point in the book "The Right Kind of Crazy", which talks about the Mars missions.  My copy is at work, but as I recall the trim tab solution was seriously considered.  What did it in was that the CFD simulations were difficult and uncertain, and the experimental hypersonic facilities could not test a tab as big as was needed to make sure it could survive the heating loads.  So it was felt to be too risky.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Robotbeat on 02/21/2016 12:48 AM
The main argument against trim tab is lack of heritage, which is the same thing as "we shouldn't try it because we haven't tried it yet."
There's a fairly long discussion on this point in the book "The Right Kind of Crazy", which talks about the Mars missions.  My copy is at work, but as I recall the trim tab solution was seriously considered.  What did it in was that the CFD simulations were difficult and uncertain, and the experimental hypersonic facilities could not test a tab as big as was needed to make sure it could survive the heating loads.  So it was felt to be too risky.
Right. Nothing actually says it can't work or is inferior or too expensive or whatever, it's just the ol' conservatism argument. If someone flew it, most objections would pass.

...but I'm afraid I've brought us too far afield. The trim tab is most advantageous in a MSL type scenario where you're spin-stabilized during cruise (though still useful with a Dragon-type vehicle).
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Donosauro on 02/21/2016 09:45 PM
A trim tab is more efficient than shifting weights, especially if you need to eject weights like MSL did to get the right off-set.
On the other hand, a trim tab is an aero surface external to the capsule, and when dealing with an orbital re-entering vehicle, that makes things way more complicated.
Actually, it makes things simpler since you don't have to discard weights (another critical event), etc. It has good control authority, much lower mass, and overall is a great idea. The main reason it hasn't been done is because:
1) JPL didn't think of it first. JPL does NASA's Mars missions. Not Invented Here.
2) It has never been done before. (Yes, this last point is a little redundant.)

Actually, using the release of tungsten masses to shift the craft's center-of-gravity is simple and lends itself to the use of pyrotechnic actuation, which is extremely reliable, and whose timing can be precisely controlled, both very important considerations during Curiosity's very-fast-paced reentry:

http://www.jpl.nasa.gov/news/news.php?feature=3421
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Robotbeat on 02/22/2016 12:23 AM
A trim tab is more efficient than shifting weights, especially if you need to eject weights like MSL did to get the right off-set.
On the other hand, a trim tab is an aero surface external to the capsule, and when dealing with an orbital re-entering vehicle, that makes things way more complicated.
Actually, it makes things simpler since you don't have to discard weights (another critical event), etc. It has good control authority, much lower mass, and overall is a great idea. The main reason it hasn't been done is because:
1) JPL didn't think of it first. JPL does NASA's Mars missions. Not Invented Here.
2) It has never been done before. (Yes, this last point is a little redundant.)

Actually, using the release of tungsten masses to shift the craft's center-of-gravity is simple and lends itself to the use of pyrotechnic actuation, which is extremely reliable, and whose timing can be precisely controlled, both very important considerations during Curiosity's very-fast-paced reentry:

http://www.jpl.nasa.gov/news/news.php?feature=3421
Thank you for mansplaining to me the very basics of the procedure which I was well aware of. Again, the main argument is conservatism, which you're basically just reiterating. Additionally, JPL doesn't have internal proponents for the idea since it was developed elsewhere.

But this is now off-topic. Let's take it elsewhere if you want to continue.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: OxCartMark on 02/22/2016 09:14 PM
How's about this - The 5 second V2 rocket test was what, December?  And assumedly an early test in a multiple test sequence.  So who among you is going to satiate my thirst for more V2 test video???  Somebody'd better bring me something new on this or I'm not going to be happy.  Don't make me get angry.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: fthomassy on 02/22/2016 10:14 PM
How's about this - The 5 second V2 rocket test was what, December?  And assumedly an early test in a multiple test sequence.  So who among you is going to satiate my thirst for more V2 test video???  Somebody'd better bring me something new on this or I'm not going to be happy.  Don't make me get angry.
The actual test was 24 Nov so there's likely more video in the queue than you thought.  I think they just don't want YOU to see it.  :D
Title: Re: SpaceX DragonFly Discussion Thread
Post by: 411rocket on 02/24/2016 09:23 PM
How's about this - The 5 second V2 rocket test was what, December?  And assumedly an early test in a multiple test sequence.  So who among you is going to satiate my thirst for more V2 test video???  Somebody'd better bring me something new on this or I'm not going to be happy.  Don't make me get angry.

I have a few V2 pics & where I took them. I think you should refer, to the new Dragon as Dragon 2, as most already have.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: neoforce on 04/27/2016 09:06 PM
Figured I'd bump this thread with today's tweet of a dragonfly test.   

https://twitter.com/SpaceX/status/725395026583285761

There is a weird quality to this GIF (static smoke, moving flame) that I'm not sure how they photoshopped it.  But I'm more interested in what it says about the current testing of Dragonfly.  They haven't released too much in the way of video/GIF/pictures from any Dragonfly testing.

Looks like the vehicle is on a stand, not on its legs.  The GIF is cropped so close to the top that I can't tell if it is tethered or not.

Any thoughts from the experts here what this shows?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: MikeAtkinson on 04/27/2016 09:53 PM
Figured I'd bump this thread with today's tweet of a dragonfly test.   

https://twitter.com/SpaceX/status/725395026583285761

There is a weird quality to this GIF (static smoke, moving flame) that I'm not sure how they photoshopped it.  But I'm more interested in what it says about the current testing of Dragonfly.  They haven't released too much in the way of video/GIF/pictures from any Dragonfly testing.

Looks like the vehicle is on a stand, not on its legs.  The GIF is cropped so close to the top that I can't tell if it is tethered or not.

Any thoughts from the experts here what this shows?

Just a few frames from a high speed video, maybe 0.01 second in total, smoke would hardly move in that time.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Hirox on 04/27/2016 09:57 PM
Figured I'd bump this thread with today's tweet of a dragonfly test.   

https://twitter.com/SpaceX/status/725395026583285761

There is a weird quality to this GIF (static smoke, moving flame) that I'm not sure how they photoshopped it.  But I'm more interested in what it says about the current testing of Dragonfly.  They haven't released too much in the way of video/GIF/pictures from any Dragonfly testing.

Looks like the vehicle is on a stand, not on its legs.  The GIF is cropped so close to the top that I can't tell if it is tethered or not.

Any thoughts from the experts here what this shows?

Just a few frames from a high speed video, maybe 0.01 second in total, smoke would hardly move in that time.

I looks like a cinemagraph ( https://en.wikipedia.org/wiki/Cinemagraph )
example : http://i.imgur.com/6lm4jBv.gif
Title: Re: SpaceX DragonFly Discussion Thread
Post by: joek on 05/05/2016 05:15 AM
Anyone by chance have a copy of the original FAA DragonFly permit (not the EIS)?  Unfortunately my archives are a mess and I can't find it.  The current permit (EP 15-011 Order A Rev 1) (http://www.faa.gov/about/office_org/headquarters_offices/ast/licenses_permits/media/EP%2015-011%20(Order%20A%20Rev%201)%20SpaceX%20Dragonfly%20mod.pdf) 28-Oct-2015 mentions non-tethered operations, which I don't recall was part of the original permit.

The original permit restriction of 80 feet AGL remains, but the new permit also appears to allow for non-tethered operations, to adds verbiage restricting operations based on weather.  (Presumably to avoid toxics escaping from "within the bounds of the toxic risk analysis...")

In short, wondering if the FAA may have approved non-tethered DragonFly tests circa Oct-2015.  Or maybe I'm just imagining things.  Thanks in advance.

edit: found it.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Flying Beaver on 05/05/2016 05:39 AM
The original permit restriction of 80 feet AGL remains, but the new permit also appears to allow for non-tethered operations, to adds verbiage restricting operations based on weather.  (Presumably to avoid toxics escaping from "within the bounds of the toxic risk analysis...")

This makes sense seeing that the Dracos are fueled by highly toxic Hydrazine.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: joek on 05/05/2016 06:03 AM
This makes sense seeing that the Dracos are fueled by highly toxic Hydrazine.

Yes, which is why the tether exemption for permits (https://forum.nasaspaceflight.com/index.php?topic=34800.msg1437287#msg1437287) does not apply in the case of DragonFly.  Question is: Did the revision of the FAA permit allow for non-tethered flight?  Or was that in the original permit... I don't think it was, but I may be mistaken?[1]  (Might explain some of the activity we have seen.)


[1] edit: Because that would (or should) require a license (not a permit), which there is no indication of.  Or it may simply be because the FAA is slow updating their information, which would not be surprising.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: joek on 05/05/2016 06:28 PM
Found the original DragonFly permit (Jul-2015); it does not mention non-tethered flights.  The update (Oct-2015) explicitly mentions "non-tethered operations".  Altitude limit of 80 feet AGL is the same.  Attached both for posterity.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Chris Bergin on 05/25/2016 12:38 AM
SpaceX's Garrett Reisman at Space Tech Expo: "First Dragonfly vehicle tether tested in Texas has been retired."
Title: Re: SpaceX DragonFly Discussion Thread
Post by: The Amazing Catstronaut on 05/25/2016 01:13 AM
SpaceX's Garrett Reisman at Space Tech Expo: "First Dragonfly vehicle tether tested in Texas has been retired."

A good sign?

Are they moving onto a more complete vehicle, or is there simply no internal need for tethered testing anymore now they've ticked the item off D2 list?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: dsobin on 05/25/2016 08:38 PM
SpaceX's Garrett Reisman at Space Tech Expo: "First Dragonfly vehicle tether tested in Texas has been retired."

A good sign?

Are they moving onto a more complete vehicle, or is there simply no internal need for tethered testing anymore now they've ticked the item off D2 list?

Or, did that referenced vehicle suffer damage during testing and entered a forced retirement?

That wouldn't be terrible, since that's what testing is for. The curious just wonder why it was retired.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: MattMason on 05/25/2016 08:42 PM
SpaceX's Garrett Reisman at Space Tech Expo: "First Dragonfly vehicle tether tested in Texas has been retired."

A good sign?

Are they moving onto a more complete vehicle, or is there simply no internal need for tethered testing anymore now they've ticked the item off D2 list?

Or, did that referenced vehicle suffer damage during testing and entered a forced retirement?

That wouldn't be terrible, since that's what testing is for. The curious just wonder why it was retired.

The most likely reason why it's retired is because another Crew Dragon test article(s), one that is less structural test article and closer to the final vehicle, is now ready for use for phase 2 of DragonFly, not to mention the in-flight abort test (which, if you haven't heard, is not the old three engine F9-Dev2, but a second-stageless first stage that will be recovered in that test).
Title: Re: SpaceX DragonFly Discussion Thread
Post by: woods170 on 05/26/2016 08:13 AM
SpaceX's Garrett Reisman at Space Tech Expo: "First Dragonfly vehicle tether tested in Texas has been retired."

A good sign?

Are they moving onto a more complete vehicle, or is there simply no internal need for tethered testing anymore now they've ticked the item off D2 list?
Very likely the retirement is related to this: http://forum.nasaspaceflight.com/index.php?topic=39832.msg1538623#msg1538623
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Chris Bergin on 08/04/2016 05:13 PM
Seems this got lost in the McGregor thread, but:

http://tinyurl.com/zb4aplq

FAA on Dragonfly.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: rpapo on 08/04/2016 05:21 PM
Interesting.  Clear for one kilometer around, but it can only fly up to 80' (~25m) above the ground?  And here I thought the new lease with the city of MacGregor said they couldn't go flying around at all.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: abaddon on 08/04/2016 05:44 PM
Interesting.  Clear for one kilometer around, but it can only fly up to 80' (~25m) above the ground?  And here I thought the new lease with the city of MacGregor said they couldn't go flying around at all.
A lease with the city and an FAA permit would not be the same things, a city ordinance could still deny things allowed in the FAA permit.  I would imagine SpaceX negotiated something similar with the city though.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Kabloona on 08/04/2016 07:14 PM
Interesting.  Clear for one kilometer around, but it can only fly up to 80' (~25m) above the ground?  And here I thought the new lease with the city of MacGregor said they couldn't go flying around at all.
A lease with the city and an FAA permit would not be the same things, a city ordinance could still deny things allowed in the FAA permit.  I would imagine SpaceX negotiated something similar with the city though.

Here's what was reported about the agreement with the city.

Quote
In addition, the actual launching of any vehicle into the atmosphere or into space is specifically prohibited at the McGregor facility.

http://www.kwtx.com/content/news/McGregor--City-modifies-SpaceX-rocket-testing-rules-378857891.html

However, we've seen that the press is not always entirely accurate, so maybe there's an allowance for low-altitude Dragonfly hops.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: fthomassy on 08/04/2016 08:28 PM
Perhaps
Quote
... actual launching of any vehicle into the atmosphere or into space ...
is interpreted as flying outside the property boundaries.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: Kabloona on 08/04/2016 09:37 PM
Perhaps
Quote
... actual launching of any vehicle into the atmosphere or into space ...
is interpreted as flying outside the property boundaries.

Flight outside the property boundaries would never be allowed anyway by FAA, so I don't think that's what the clause meant. It seems more likely directed at Grasshopper/F9RDev flights. There were talks of moving F9RDev flights to Spaceport America before SpaceX mothballed the program.
Title: Re: SpaceX DragonFly Discussion Thread
Post by: CuddlyRocket on 08/05/2016 01:42 AM
Quote
In addition, the actual launching of any vehicle into the atmosphere or into space is specifically prohibited at the McGregor facility.

There'll probably be some definitional sections somewhere that have a bearing on this. After all, on the face of it 'any vehicle' prohibits getting to and from the site by helicopter. Also, no more drone camera shots! And what does 'into the atmosphere' mean? Off the ground or above a certain height?
Title: Re: SpaceX DragonFly Discussion Thread
Post by: winkhomewinkhome on 10/02/2016 04:55 PM
Any updates on DragonFly testing?  Yes BIG Mars plans and RTF aside, should there be some concern with the silence?