Author Topic: SpaceX Falcon 9 / Dragon 2 : SpX-DM1 : March 2, 2019 : DISCUSSION  (Read 587247 times)

Offline John Santos

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"the first new space vehicle designed for humans in over 40 years"

America designed plenty of space vehicles in the past 40 years. All of them got cancelled though - some while actually in flight testing (X-38). If America had the determination and foresight to actually follow through on one of these designs, then they wouldn't be in the ridiculous situation they found themselves in till now.

Also, Orion already had 1 testflight, although on a non human-rated launch vehicle. One could argue that that was designed over the last 40 years.
As did Buran, which I think was much closer to being habitable than Orion EFT-1 was.

Offline Jcc

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Folks here only need to compare the Stage 2 telemetry numbers with those of the average GTO mission. In doing so it will become quite clear that Demo-1 very much flew a lofted trajectory: the average GTO mission stages at an altitude of ~ 68 km with a velocity of ~ 8300 km/h, whereas Demo-1 staged at an altitude of 88 km and a velocity of just ~ 6700 km/h. So, staging was 20 km higher than a GTO mission and 1600 km/h slower than a GTO mission.

So yes, very much a lofted trajectory: trading speed for altitude in the early phase of the mission.

There's also the fact that the 1st stage landed 10 minutes after launch, which IIRC is the longest delay ever, additional hint that it was flying a lofted trajectory.

And the reason to fly a lofted trajectory? That is so in an abort Dragon would land closer to shore, allowing the rescue ships to get there sooner.

Online ugordan

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And the reason to fly a lofted trajectory? That is so in an abort Dragon would land closer to shore, allowing the rescue ships to get there sooner.

I'm not sure about that reasoning especially since an abort can theoretically happen at any point during boost phase so you could theoretically end up anywhere in the Atlantic. On a F9, the primary consideration for an early abort is probably some failure at stage separation/MVac ignition as those are the single, discrete events that happen on a launch. For a crew recovery, I'd think you'd prefer a shallower trajectory at MECO, one that gives you more prograde than upward velocity as that would ensure Dragon would reenter shallower and thus limit max G-s the crew would experience on reentry. Basically, the same reasoning that was once used against Atlas V and its "black zones".

Burning the 1st stage longer than on a typical LEO launch made sense to me, toward that goal of attaining more prograde velocity, but not in conjunction with a very lofted trajectory that seems to have been flown. Maybe I'm overinflating the reentry G concern based on Atlas V as Atlas V CCB burns out at a much higher velocity than F9 and the Centaur is much more underpowered for LEO launches so those two "lofted" trajectories are not nearly as comparable. Of note here is that the 2nd stage coasted to 221 km before falling down to 198 km at SECO, that kind of a trajectory is usually seen on "underpowered" 2nd stages, I don't recall seeing that amount of drop on other F9 launches.

I think we need some of the trajectory modelling wizards to crank some simulations to understand this better.
« Last Edit: 03/04/2019 11:26 am by ugordan »

Online FutureSpaceTourist

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Roscosmos have published one blog article so far about DM-1:

https://www.roscosmos.ru/26164/

Interesting that they should decide to focus on the first ever use of gas masks on the ISS ...

Google translate:

Quote
Crew Dragon arrives at the International Space Station
03/04/2019 3:03 pm

On March 3, the new spacecraft Crew Dragon arrived at the International Space Station. He was met by Oleg Kononenko, Ann McClain and David San-Jacques. A couple of hours after docking, hatches were opened between the ISS and the spacecraft.
For the first time in the history of the station, the crew worked in Russian-made IPK (Space Isolating Gas Mask) gas masks. They are designed to protect the astronauts' respiratory organs and eyes from toxic gas and vapor products. Oleg Kononenko and David San-Jacques took air samples at the Dragon, tested gas masks and reported to the Earth how they felt in them.
As the astronaut notes, in this expedition he managed for the first time to test a space gas mask and a fire extinguisher, which we wrote about earlier .
We add that Oleg Kononenko is not the first to meet on board the ISS a new ship. In May 2012, the first private Dragon “truck” was docked, he was met by the crew of the ISS-31 expedition under the command of Oleg Kononenko.

Offline gdelottle

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Today, human advancement of exploration continues, as the first new space vehicle designed for humans in over 40 years arrived at our front door,...

The author of that speech forgot about Shenzhou, New Glenn, SpaceShipOne and SpaceShipTwo!


Not necessarily, if you interpret that statement all together: not just "the first new space vehicle", but "the first new space vehicle [...] arrived at our front door".

BTW, if I am not wrong, more than from any other visible aspect, I am really impressed by the internal "design" of Dragon. This is the very first case in which industrial design become a basic requirement in an operative space vehicle, apart a few small details of previous spaceships, like logos.

Another change of reference, "made in SpaceX".

 
« Last Edit: 03/04/2019 11:50 am by gdelottle »

Offline Alexphysics

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It was what I told you the other day. Even though we were told this was not a lofted trajectory it was indeed a lofted trajectory. Compare any of those numbers with a GTO mission and you'll see those go lower and faster which means they fly a shallower trajectory.

I don't think anyone official told us this was not a lofted trajectory, in fact Hans made it clear it is a lofted trajectory in the press conference, it's just nobody here believes him...

Well, actually, for Atlas V we were told that. "Centaur has two engines to allow a shallower trajectory". We just extrapolated that to Falcon 9 and thought it will do the same but it's clear it didn't and so now the question is why the two fly such different trajectories.

Offline niwax

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It was what I told you the other day. Even though we were told this was not a lofted trajectory it was indeed a lofted trajectory. Compare any of those numbers with a GTO mission and you'll see those go lower and faster which means they fly a shallower trajectory.

I don't think anyone official told us this was not a lofted trajectory, in fact Hans made it clear it is a lofted trajectory in the press conference, it's just nobody here believes him...

Well, actually, for Atlas V we were told that. "Centaur has two engines to allow a shallower trajectory". We just extrapolated that to Falcon 9 and thought it will do the same but it's clear it didn't and so now the question is why the two fly such different trajectories.

Atlas flies very lofted as it is, so shallow for Atlas may well be what SpaceX is doing anyways. We would need to compare the trajectories directly, and even then the capsules have different abort and reentry characteristics.
Which booster has the most soot? SpaceX booster launch history! (discussion)

Offline AS-503

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And the reason to fly a lofted trajectory? That is so in an abort Dragon would land closer to shore, allowing the rescue ships to get there sooner.

I'm not sure about that reasoning especially since an abort can theoretically happen at any point during boost phase so you could theoretically end up anywhere in the Atlantic. On a F9, the primary consideration for an early abort is probably some failure at stage separation/MVac ignition as those are the single, discrete events that happen on a launch. For a crew recovery, I'd think you'd prefer a shallower trajectory at MECO, one that gives you more prograde than upward velocity as that would ensure Dragon would reenter shallower and thus limit max G-s the crew would experience on reentry. Basically, the same reasoning that was once used against Atlas V and its "black zones".

Burning the 1st stage longer than on a typical LEO launch made sense to me, toward that goal of attaining more prograde velocity, but not in conjunction with a very lofted trajectory that seems to have been flown. Maybe I'm overinflating the reentry G concern based on Atlas V as Atlas V CCB burns out at a much higher velocity than F9 and the Centaur is much more underpowered for LEO launches so those two "lofted" trajectories are not nearly as comparable. Of note here is that the 2nd stage coasted to 221 km before falling down to 198 km at SECO, that kind of a trajectory is usually seen on "underpowered" 2nd stages, I don't recall seeing that amount of drop on other F9 launches.

I think we need some of the trajectory modelling wizards to crank some simulations to understand this better.

I've attached Wayne Hale's blog posts on black zones where he uses the the words "flat" or "depressed" to describe typical manned trajectories and "lofted" to describe non-manned trajectories. This thread has me confused over the word choice to describe the DM-1 trajectory as "lofted", when we know that the parabolic arc of the first stage was in fact long and wide (not lofted). Thus the down range landing. Are we getting semantically tangled up over what these words mean with respect to this (and other) flight(s)? Are we repeating some one elses technically incorrect wording for this trajectory?

Houston just asked David for an estimate of the temp on Dragon to confirm the readings they have on console I assume. They asked if the temp felt like it was around 82-ish, David confirmed that it felt warmer in Dragon than in Node 2. (I was listening to the feed on https://www.nasa.gov/multimedia/nasatv/iss_ustream.html which has audio)

Someone who attended Nasa social spoke to someone from the ISS program. They were really surprised that someone even listens to the space to ground loop.
I think there are lots of us that do.

Online ugordan

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This thread has me confused over the word choice to describe the DM-1 trajectory as "lofted", when we know that the parabolic arc of the first stage was in fact long and wide (not lofted). Thus the down range landing. Are we getting semantically tangled up over what these words mean with respect to this (and other) flight(s)? Are we repeating some one elses technically incorrect wording for this trajectory?

No, we're not getting semantically tangled up. Check out OneSpeed's excellent visualization of CRS-16 (RTLS!) vs DM1- 1st stage trajectories. It is clear that DM-1 flew a more lofted trajectory than typical for F9 standards. In Wayne Hale's words, CRS-16 flew a more flat/depressed trajectory, even though it was doing a RTLS.

Offline woods170

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Folks here only need to compare the Stage 2 telemetry numbers with those of the average GTO mission. In doing so it will become quite clear that Demo-1 very much flew a lofted trajectory: the average GTO mission stages at an altitude of ~ 68 km with a velocity of ~ 8300 km/h, whereas Demo-1 staged at an altitude of 88 km and a velocity of just ~ 6700 km/h. So, staging was 20 km higher than a GTO mission and 1600 km/h slower than a GTO mission.

So yes, very much a lofted trajectory: trading speed for altitude in the early phase of the mission.

There's also the fact that the 1st stage landed 10 minutes after launch, which IIRC is the longest delay ever, additional hint that it was flying a lofted trajectory.

Yeah... the stage had to pass through (at least) 20 additional kilometers of altitude (compared to the average GTO launch) on its way back to the drone ship. That takes a little extra time.

Online ugordan

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There's also the fact that the 1st stage landed 10 minutes after launch, which IIRC is the longest delay ever, additional hint that it was flying a lofted trajectory.

I stand corrected, the longest delay until landing was actually on the Formosat-5 launch, MECO was at 6800 kmh at 86 km, 1st stage landed at around T+10:45 after launch, the trajectory was so lofted that by the time the reentry burn started, the exhaust wasn't even glowing yet when hitting the hypersonic airflow. That wasn't a Block 5 though, so not directly comparable.

Offline Star One

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Will they in future be using the Dragon 2 when it’s docked to the ISS as part of the living space of the station being as unlike Soyuz it is quite roomy?

The Soyuz is quite roomy with the orbital module.

I thought it being put into orbital hibernation precluded its use.

I'm just responding to someone who implied that the Soyuz wasn't roomy. I have no idea wether either spacecraft can be used when docked.

I should have added to my question does orbital hibernation preclude the use of Dragon 2 for living space.

Offline Rocket Science

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Houston just asked David for an estimate of the temp on Dragon to confirm the readings they have on console I assume. They asked if the temp felt like it was around 82-ish, David confirmed that it felt warmer in Dragon than in Node 2. (I was listening to the feed on https://www.nasa.gov/multimedia/nasatv/iss_ustream.html which has audio)

Someone who attended Nasa social spoke to someone from the ISS program. They were really surprised that someone even listens to the space to ground loop.
I think there are lots of us that do.
Welcome to the forum! :)
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Offline gongora

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Landing with SuperDracos has nothing to do with DM-1 (or any of the mission threads.)  That discussion is being split into a new thread in the SpaceX General secion.

Offline DigitalMan

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Those are some weird looking external survey pictures in the update thread.  I suppose I hadn't noticed all those spots like that, any thoughts?

Offline Roy_H

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Those are some weird looking external survey pictures in the update thread.  I suppose I hadn't noticed all those spots like that, any thoughts?
I would like to know what all those yellow spots that look like glue are, and their purpose.
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Offline CorvusCorax

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Those are some weird looking external survey pictures in the update thread.  I suppose I hadn't noticed all those spots like that, any thoughts?
I would like to know what all those yellow spots that look like glue are, and their purpose.

Crazy speculation mode on:

1. Micrometeorite Impact Craters.
2. Deliberate little dents to detach airflow and decrease drag - like on a golfball.
3. Screw/Bolt-holes filled with paint/thermal/ablative/insulating coating.
4. Dragon-warts.
5. ???

Offline Herb Schaltegger

Number 3.
Ad astra per aspirin ...

Offline HVM

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Number 3.
I’ll have two number 9s, a number 9 large, a number 6 with extra dip, a number 7, two number 45s, one with cheese, and a large soda.

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