SpaceX Falcon 9 / Dragon 2 : SpX-DM1 : March 2, 2019 : DISCUSSION

[joseph.a.navin]

Here is my completed DM-1 article which I talked about back in Jan or Feb! This one took more research but I am overall very proud of it. Enjoy!
https://pfhstheroar.com/7144/news/other-news/the-dawn-of-a-new-era-in-human-spaceflight/#

[freddo411]

Have we heard anything from NASA/SpaceX about the performance and interaction of the 4 chutes? 

No.  Probably will have to wait for the next ASAP meeting to see if it gets discussed.  I don't think we're likely to get many specific statements from SpaceX or NASA on technical matters or systems performance beyond just, "Everything went well."  Or generalizations about "few minor issues being worked through," etc.

The more chutes you add the more weird interactions between them you are liable to get. Even ASAP should realize that eventually.

I wonder if a one parachute, and landing rocket system would have the most predictable and safest landing.   ASAP doesn't seem to object to that for Soyuz.

[Vettedrmr]

The more chutes you add the more weird interactions between them you are liable to get. Even ASAP should realize that eventually.

Agreed.  Normally when you add redundancy you're adding complexity that can be fairly well characterized (weight, power, space, software,etc.), but with the chutes you have the aerodynamics as well.

IIRC, D2's chute system requires 2 for safe landing, Spx went to 3 for redundancy, and ASAP required a 4th for some reason.  But, I can't remember what that reason was.

Thanks for the response, and have a good one,
Mike

[freda]

Here is my completed DM-1 article which I talked about back in Jan or Feb! This one took more research but I am overall very proud of it. Enjoy!
https://pfhstheroar.com/7144/news/other-news/the-dawn-of-a-new-era-in-human-spaceflight/#

A good read. I also see other space articles there by you. Thanks for posting and letting us see what you create. Write more.

[woods170]

The more chutes you add the more weird interactions between them you are liable to get. Even ASAP should realize that eventually.

Agreed.  Normally when you add redundancy you're adding complexity that can be fairly well characterized (weight, power, space, software,etc.), but with the chutes you have the aerodynamics as well.

IIRC, D2's chute system requires 2 for safe landing, Spx went to 3 for redundancy, and ASAP required a 4th for some reason.  But, I can't remember what that reason was.

Thanks for the response, and have a good one,
Mike

D2's chute system requires 2 for survivable landing. Safe landing requires 3 chutes.

Fourth chute was not required by ASAP. ASAP is not in a position to require/demand anything.

The fourth chute is there because NASA talked SpaceX out of propulsive landing. That had the undesired effect of Crew Dragon splashing down with a fairly substantial load of propellant still on-board (unused abort propellant that would otherwise have been spent during propulsive landing). The vehicle is thus a lot heavier than previously anticipated. To add extra redundancy to counter for this weight increase a fourth chute was added to the system, by SpaceX.

[Vettedrmr]

D2's chute system requires 2 for survivable landing. Safe landing requires 3 chutes.

Sorry, that's my old job's language coming out.  In the safety-critical environment, "safe" means "safe recovery of the crew", but damage to the vehicle may occur.  "Operational" means, well, exactly how it sounds.

That said, it sounds to me that Crew Dragon requires 3 chutes for normal ops, but can have absorb one failure safely.

Thanks for the info, and have a good one,
Mike

[Rocket Science]

The more chutes you add the more weird interactions between them you are liable to get. Even ASAP should realize that eventually.

Agreed.  Normally when you add redundancy you're adding complexity that can be fairly well characterized (weight, power, space, software,etc.), but with the chutes you have the aerodynamics as well.

IIRC, D2's chute system requires 2 for safe landing, Spx went to 3 for redundancy, and ASAP required a 4th for some reason.  But, I can't remember what that reason was.

Thanks for the response, and have a good one,
Mike

D2's chute system requires 2 for survivable landing. Safe landing requires 3 chutes.

Fourth chute was not required by ASAP. ASAP is not in a position to require/demand anything.

The fourth chute is there because NASA talked SpaceX out of propulsive landing. That had the undesired effect of Crew Dragon splashing down with a fairly substantial load of propellant still on-board (unused abort propellant). The vehicle is thus a lot heavier than previously anticipated. To add extra redundancy to counter for this weight increase a fourth chute was added to the system, by SpaceX.

Just curious, why don't they just dump the prop on entry?

[Alexphysics]

The more chutes you add the more weird interactions between them you are liable to get. Even ASAP should realize that eventually.

Agreed.  Normally when you add redundancy you're adding complexity that can be fairly well characterized (weight, power, space, software,etc.), but with the chutes you have the aerodynamics as well.

IIRC, D2's chute system requires 2 for safe landing, Spx went to 3 for redundancy, and ASAP required a 4th for some reason.  But, I can't remember what that reason was.

Thanks for the response, and have a good one,
Mike

D2's chute system requires 2 for survivable landing. Safe landing requires 3 chutes.

Fourth chute was not required by ASAP. ASAP is not in a position to require/demand anything.

The fourth chute is there because NASA talked SpaceX out of propulsive landing. That had the undesired effect of Crew Dragon splashing down with a fairly substantial load of propellant still on-board (unused abort propellant). The vehicle is thus a lot heavier than previously anticipated. To add extra redundancy to counter for this weight increase a fourth chute was added to the system, by SpaceX.

Just curious, why don't they just dump the prop on entry?

See ASTP and, for the nth time, if the conversation is focused on propulsive landing, there's a thread for that...

[Rocket Science]

The more chutes you add the more weird interactions between them you are liable to get. Even ASAP should realize that eventually.

Agreed.  Normally when you add redundancy you're adding complexity that can be fairly well characterized (weight, power, space, software,etc.), but with the chutes you have the aerodynamics as well.

IIRC, D2's chute system requires 2 for safe landing, Spx went to 3 for redundancy, and ASAP required a 4th for some reason.  But, I can't remember what that reason was.

Thanks for the response, and have a good one,
Mike

D2's chute system requires 2 for survivable landing. Safe landing requires 3 chutes.

Fourth chute was not required by ASAP. ASAP is not in a position to require/demand anything.

The fourth chute is there because NASA talked SpaceX out of propulsive landing. That had the undesired effect of Crew Dragon splashing down with a fairly substantial load of propellant still on-board (unused abort propellant). The vehicle is thus a lot heavier than previously anticipated. To add extra redundancy to counter for this weight increase a fourth chute was added to the system, by SpaceX.

Just curious, why don't they just dump the prop on entry?

See ASTP and, for the nth time, if the conversation is focused on propulsive landing, there's a thread for that...

Wasn't even on my mind, but thanks anyway...

[woods170]

The more chutes you add the more weird interactions between them you are liable to get. Even ASAP should realize that eventually.

Agreed.  Normally when you add redundancy you're adding complexity that can be fairly well characterized (weight, power, space, software,etc.), but with the chutes you have the aerodynamics as well.

IIRC, D2's chute system requires 2 for safe landing, Spx went to 3 for redundancy, and ASAP required a 4th for some reason.  But, I can't remember what that reason was.

Thanks for the response, and have a good one,
Mike

D2's chute system requires 2 for survivable landing. Safe landing requires 3 chutes.

Fourth chute was not required by ASAP. ASAP is not in a position to require/demand anything.

The fourth chute is there because NASA talked SpaceX out of propulsive landing. That had the undesired effect of Crew Dragon splashing down with a fairly substantial load of propellant still on-board (unused abort propellant). The vehicle is thus a lot heavier than previously anticipated. To add extra redundancy to counter for this weight increase a fourth chute was added to the system, by SpaceX.

Just curious, why don't they just dump the prop on entry?

See ASTP and, for the nth time, if the conversation is focused on propulsive landing, there's a thread for that...

Conversation is not focused on propulsive landing. Just pointing out that the fourth parachute is there exactly because there is no propulsive landing on the current design of Crew Dragon.

But I much appreciate your attempt to keep the discussion focused on aspects of DM-1.

[Rocket Science]

And my comment to to reduce landing weight under chutes...

[Steven Pietrobon]

Here is my completed DM-1 article which I talked about back in Jan or Feb! This one took more research but I am overall very proud of it. Enjoy!
https://pfhstheroar.com/7144/news/other-news/the-dawn-of-a-new-era-in-human-spaceflight/#

One minor correction. The abort booster will be B1048.4, as it will be on its fourth flight.

[joseph.a.navin]

Ok thanks for the correction, I will edit that one error if I can. If you read it was the article overall well rounded?

[tyrred]

Ok thanks for the correction, I will edit that one error if I can. If you read it was the article overall well rounded?

Great job!  I only wish we had such reporting at my old high school...

[tyrred]

Is there any further information on why there was an aluminum grid fin on this booster?  Was the opposite grid fin also aluminum?  I must admit, I didn't notice this on any earlier coverage.

[Alexphysics]

Is there any further information on why there was an aluminum grid fin on this booster?  Was the opposite grid fin also aluminum?  I must admit, I didn't notice this on any earlier coverage.

There were no aluminum grid fins on this one

[Steven Pietrobon]

Ok thanks for the correction, I will edit that one error if I can. If you read it was the article overall well rounded?

Yes, it was well rounded and well written.

[RotoSequence]

Isn't there supposed to be a post-mission briefing at some point?

[woods170]

Isn't there supposed to be a post-mission briefing at some point?

When they actually start flying astronauts than yes.

[meekGee]

Have we heard anything from NASA/SpaceX about the performance and interaction of the 4 chutes? 

No.  Probably will have to wait for the next ASAP meeting to see if it gets discussed.  I don't think we're likely to get many specific statements from SpaceX or NASA on technical matters or systems performance beyond just, "Everything went well."  Or generalizations about "few minor issues being worked through," etc.

The more chutes you add the more weird interactions between them you are liable to get. Even ASAP should realize that eventually.

Exactly.

My thought was that three circles (think three pennies on a table) have one stable configuration.

Four circles can clearly do the rhombus dance we've seen.