SpaceX Dragon Ship Falls Back to Earth | Hacker News Reader

SpaceX Dragon Ship Falls Back to Earth

bbc.co.uk

102 pointssparknlaunch49 comments

Was I the only person who read the headline and thought "Wait, was it meant to?". The word "falls" has very negative connotations and could have been chosen better surely? :-)

Agreed. Especially since all that stuff that's in orbit around us (like the ISS and Dragon) is falling all the time. They just happen to be going at the right speed to just keep from actually coming down.

The ISS is constantly falling, by about 90 metres a day. They have to periodically boost it back up to a higher orbits. And pretty much everything up there is actually falling all the time and would come down without corrective action.

http://en.wikipedia.org/wiki/Orbital_station-keeping http://www.msnbc.msn.com/id/17630218/ns/technology_and_scien...

Chosen better for what? They certainly chose a good title to get people to click...

They certainly chose a good title to get people to click...

And I'd like to keep "get people to click" type of content away from HN.

We tend to frown upon sensationalism here; it tends to correlate positively with bullshit.

The incidence of headline editing (vs using the original headline) seems to be on the rise. This original article didn't have the greatest headline either: "SpaceX Dragon ship aims for Earth" but would have been better and slightly more accurate. Dragon had not begun its fall when this was submitted.

Oddly enough if it did just fall, relative to the Earth's rotation, instead of slam into the atmosphere at thousands of meters per second it would be less stressful on the capsule.

Though, if the angle of re-entry is too shallow, it would skip off the atmosphere (like a rock would across water).

And if Earth is this basketball, and the Odyssey CM is this baseball, they have to hit a re-entry interface no thicker than this piece of computer paper.

(At least that's what Apollo 13 [the movie] said.)

"Returns to Earth" would have been accurate and rather less sensational.

"The firm has a $1.6bn (£1bn; 1.3bn-euro) contract with the US space agency (Nasa) waiting to be triggered on the successful recovery of Dragon from the ocean."

So.. no pressure or anything.

> $1.6bn (£1bn; 1.3bn euro)

How much in bitcoins?

Well, at roughly $5/bc and only 8 million bitcoins in existence the answer would be "more than all of them".

"You know Fred, if that software has a bug that messes up reentry, we don't get the $1.6bn......"

I find it hard to believe that they didn't negotiate a contract which would provide partial credit if things happen to go pear-shaped (or rather, pancake-shaped) at this point.

I believe up to this point they have milestone contracts. I'm not familiar with which milestones those trigger, but they did negotiate a failsafe in case it got to some point successfully but then failed. From here on out though, their forthcoming contracts are not milestone.

Expected timetable as best as I can work it out:

* 13:00 UTC, 08:00 CT, update from NASA

* 14:15 UTC, 09:15 CT, Coverage restarts on NASA TV

* 14:51 UTC, 09:51 CT, De-orbit burn

* 15:09 UTC, 10:09 CT, Dragon's trunk is jettisoned

* 15:35 UTC, 10:35 CT, Drogue chutes deployment

* 15:36 UTC, 10:36 CT, Main chute deployment

* 15:44 UTC, 10:44 CT, Splashdown

Dragon has unberthed, has been released from the ISS's robotic arm, and has completed its final separation burn . Remaining tasks: deorbit burn, separation from the trunk, reentry, and recovery.

Live stream on right now here:

http://www.ustream.tv/nasahdtv

As watching the mission control center of SpaceX: where are the computers? Are they running thin clients? I just see a lot of monitors and 1 or 2 two laptops but no actual PCs.

First parachutes just deployed...

"Dragon is in the water."

"OH GOD NO, FIRE THE TORPEDOES"

"THE DRAGON IS FRIENDLY. REPEAT: THE DRAGON. IS FRIENDLY."

> "Scientists say that the vessel will splashdown in the Pacific Ocean several hours later in what they are describing as “a very challenging phase of the flight”."

Impressed how space junk etc fall to Earth and almost always land in the ocean. Not hard when 70% of the Earth surface is covered by water. However what is the level of accuracy? I assume that it is planned to aim for a large body of water and get within an x% threshold?

I don't know how big the landing zone is but the last Dragon reentered within a mile of it's targeted location.

...and hit the water within something like 50 seconds of it's projected landing time IIRC O_O

And it looks like they are planning for a future Dragon to do precision landings on a landing pad:

http://www.youtube.com/watch?feature=player_embedded&v=m...

That is the manned Dragon, which will have an integral escape system allowing the capsule to be boosted away from the launcher during any part of flight. But that same system can be used to provide powered landings.

Yep - Elon talked about this about an hour ago in the post-splashdown press conference and said the future dragon will be able to do precision soft landings where there is little atmosphere or no atmosphere, so we can deliver payloads to other bodies in the Solar System. I love how he also said it's how spaceships simply should do a landing. (He didn't quite say that's how God and Heinlein would have wanted it, but same idea.)

I don't believe the implication here is that it's hard to aim to the ocean, but to actually survive the re-entry. You know, high speed, high temperature and all that.

According to this page:

http://www.spacex.com/press.php?page=20120530

It parachutes down from 10,000 feet, at 16 to 16 feet per second - which means it spends almost 10 minutes at the mercy of the wind (I'm guessing the re-entry thrusters probably don't get used while it's parachuting down?)

That means that even if they can drop it onto the atmosphere accurately, the actual splash-down point can't be determined any more accuracy than they can predict the wind velocity along the parachute path.

A back of the envelope worst case would be assume they are off by 50 MPH and it takes 10 minutes to fall 10,000 feet at 17feet per second. That seems like 5 miles in the worst case. But, the parachutes don't instantly slow the thing to 15-18 MPH and the wind does not instantly get it to match wind speed and normally it's not dropping into a steady 50 MPH wind from 10,000 feet to sea level.

It can be much, much more accurate than that if needed.

In 1960s America had spy satellites that dropped canisters with photo film, that were captured mid-air by planes.

See: http://en.wikipedia.org/wiki/Corona_(satellite)#Discoverer

Wow! Wonder if the weight of a canister and mobility of a plane may help in connecting the two together? Or make it harder? Awesome story.

The canisters had little parachutes, so it's not quite as amazing as it sounds.

http://youtu.be/9jOGicfF_vQ

Just barely less amazing. Still like finding one particular mosquito in Pittsburgh?

If the mosquito were two feet across and equipped with a radio transmitter, yeah.

And I assume this was all necessary because: (a) They wanted to see if it could be done. or (b) They couldn't yet build a digital camera and/or digital cameras didn't work in space because of some obscure issues with radiation?

It was 1960. No digital cameras. The CCD wouldn't be invented for nine more years!

They have those in Alaska.

No, Pittsburgh is a lot smaller than the reentry pattern of a falling satellite. By orders of magnitude. Thus the scaled comparison.

Back in 2004 the sample capsule from the Genesis spacecraft crashed into the ground after the planned in-air retrieval by a helicopter failed. The plan was to hook the parachute canopy.

Presumably aircraft have an advantage over helicopters in that they fly higher and give you more opportunities for capture.

http://www.astrobio.net/exclusive/1185/genesis-suffers-a-cra... http://en.wikipedia.org/wiki/Genesis_(spacecraft)#Recovery_p...

The Russians typically landed their recoverable craft in Kazakhstan if I'm not mistaken.

Often in Russia. You are right that it was (and is) intended for the on-land, not on-water, landing, although there are provisions for the on-water landings as well. See Wikipedia entries for Soyuz 23 and, more generally, splashdown.

It has to splash down near the recovery vessels to be recovered. It's a much smaller target than "the Pacific Ocean".

During the Apollo program the accuracy with which reentry could be predicted got to be very good. Initially, the practice was to sail an aircraft carrier to the projected splashdown point and wait for the command module to hit the water some miles away. This had to be changed due to the growing risk of the spacecraft hitting the carrier. Instead, the carrier parked a few miles away.

I don't know if the increase in accuracy was due to improvements in trajectory control during reentry, better aerodynamic modelling based on experience of real flights, or other factors. I assume that SpaceX would be pretty confident about their accuracy, but this is only the second flight of a Dragon.

Dragon coming back safe

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