The Pod Bay

Antzi

00:00

I wonder if there is a kind of abort system not to waste a barge if the rocket figure out it won't land properly

kim holder

@duzzy :] i'll just let that pass. i'm out of steam on that one

TildalWave

anyway there's 2nd burn of upper stage coming up which is the primary mission

in about a minute

qasdfdsaq

Who cares about "primary mission" :-P

duzzy

@Antzi They'll just repair it again.

Russell Borogove

They'ev had, what, three blow up on the barge?

Brian Lynch

00:01

@qasdfdsaq +1

lol

TildalWave

@qasdfdsaq anyone that put some money into it?

we're just observers :P

Russell Borogove

before today

PearsonArtPhoto

I'm sure there is some kind of an abort system, but it seems like they don't use it that much, and it's pretty robust.

duzzy

These barges have taken a beating already anyway.

Antzi

yeah

Brian Lynch

00:02

probably quite difficult to abort -- you're either coming in close enough you hope for a landing, otherwise it won't even hit anyway, once it's almost landing there probably isn't much you can do

Russell Borogove

second stage venting chilldown?

TildalWave

looks like it

and ignition

qasdfdsaq

This observer only cares about the ground-breaking cutting edge stuff. That "primary mission" business is just routine launching that happens every other week

Russell Borogove

boom!

TildalWave

and inside the RP-1 tank

@RussellBorogove what boom? :P

duzzy

00:03

@RussellBorogove Don't say "boom" in a space exploration chat!!

:P

qasdfdsaq

Electronics inside a rocket fuel tank, man they're ballsy

TildalWave

that was RP-1 sloshing

Russell Borogove

hahah

sorry. Whoosh!

qasdfdsaq

Well my thought was also along the lines of "Did something explode or has the rocket gone weird"

kim holder

that was the stargate

TildalWave

00:03

@qasdfdsaq I believe it's just an optical cable with a lens head

qasdfdsaq

I guess the internal cam is also what helped them figure out how the fuel tank supports failed when that last ISS mission blew up

TildalWave

kinda like at surgeries

qasdfdsaq

@TildalWave Clever.

PearsonArtPhoto

Falcon 9 booster landing tests

The Falcon 9 first stage landing tests are a series of controlled-descent flight tests conducted by SpaceX beginning in 2013 which continued through December 2015.The program objective was to execute a controlled-descent re-entry into Earth's atmosphere after Falcon 9 rocket first stages complete the boost phase of an orbital flight. Some tests included an attempt at softly landing the first stage of the rocket in the ocean, or on an Autonomous spaceport drone ship—commissioned by SpaceX to provide a hard landing surface on a floating vessel—or on terra firma at Landing Zone 1 on the east coast...

qasdfdsaq

747's have been known to blow up due to electronics in the fuel tanks :-P

PearsonArtPhoto

00:04

So 4 attempts before today.

kim holder

was the first 'full-thrust'? with the densified fuel?

PearsonArtPhoto

No

The successful one was a full thrust.

kim holder

ah.

TildalWave

@qasdfdsaq yeah they have same also in the LOX tank (you can identify which one they're showing by color, LOX is electric blue, RP-1 is mostly clear, slightly yellow or pink depends on temperature and such)

PearsonArtPhoto

This would be the first exploded full thrust one, however.

(Assuming that's what happened)

TildalWave

00:06

anyway, if it works within LOX then within the RP-1 tank shouldn't be a problem

kim holder

they always get to have some kind of first :)

TildalWave

ain't that great?

qasdfdsaq

P.S. Hi I'm new, @duzzy dragged me in here

TildalWave

we haven't had "a first" for years before SpaceX, just "a thirst"

PearsonArtPhoto

Dust, interesting...

kim holder

00:07

@qasdfdsaq Welcome! and good for duzzy!

Antzi

space snow:p

Brian Lynch

does anyone else find it really friggin annoying how these guys are always laughing?

kim holder

so success?

Brian Lynch

I prefer that guys on his own sitting at the computer

TildalWave

@kimholder yup

Antzi

00:08

Success for space X at least

kim holder

i was watching the tech broadcast

qasdfdsaq

Now show us what happened to the booster :-(

Brian Lynch

class action lawsuit after we all get dried out eyeballs?

TildalWave

@BrianLynch not so much as with some really catastrophic news and anchors with plastic surgery done to not be even able not to smile

Antzi

Did you guys saw the news about the russian crowd founded reflector satellite ?

duzzy

00:10

It is kind of lame that they end without saying anything about the first stage.

Brian Lynch

@TildalWave haha yea true

PearsonArtPhoto

0

Q: What was all of the junk in the SES satellite deployment?

In the SES launch, when the satellite deployed, there was quite a bit of junk that was released when the satellite was released. What was that?

TildalWave

@Antzi I haven't, link please

duzzy

@Antzi I saw a headline, and astronomers angry about light pollution.

PearsonArtPhoto

They probably don't know that much about the first stage.

TildalWave

00:11

@PearsonArtPhoto isn't this a dupe? :P

PearsonArtPhoto

You'd think they'd have something that would work, but...

Brian Lynch

@duzzy my guess is they are actively trying to prop up the real mission and emphasize that is the true success

duzzy

@BrianLynch That makes sense.

PearsonArtPhoto

Is it?

Antzi

boomstarter.ru/projects/shaenko/kosmicheskiy_sputnik_mayak

Brian Lynch

00:11

which is annoying because I feel like everyone there and everyone here mostly just cares about the landing

duzzy

When they kept having those failed landing attempts, everyone just kept talking about how SpaceX keeps blowing up rockets.

Antzi

arstechnica.com/information-technology/2016/02/…

PearsonArtPhoto

I bet they are as annoyed as we are.

Of course, news doesn't flow as fast on a Friday evening, so...

Russell Borogove

I care about the landings more because putting satellites up is more or less a solved problem.

TildalWave

@PearsonArtPhoto dunno, I thought it might be but now I can't find what I was looking for

qasdfdsaq

00:14

Yeah, the whole point of SpaceX isn't just to do routine launches forever. They want to bring down the cost in the long term which won't happen without groundbreaking science

The commercial launches are just how the fund the science

PearsonArtPhoto

There's been some similar questions before.

But I don't remember seeing this much junk in a deployment before.

duzzy

But they might be concerned about peoples' perception that they keep "failing" when the landing attempts don't go well.

Russell Borogove

It's great for SpaceX and great for the customer when the primary mission goes well.

qasdfdsaq

@duzzy Well science isn't all about succeeding every time.

duzzy

If the perception is that they keep blowing up rockets all the time, people might start to question why NASA pays them for launches.

@qasdfdsaq True, but politics.

qasdfdsaq

00:16

I hate politiks :(

duzzy

Me too.

Antzi

Why would SpaceX need to worry about people not understanding them ?

qasdfdsaq

Rocket science beats politics anyday

duzzy

Because people put pressure on Congress. Congress decides the budget for NASA. NASA pays SpaceX for launches.

qasdfdsaq

Nobody's gonna save humanity through politics. Oh wait...

kim holder

00:17

@duzzy other launchers lose those stages every time.

Antzi

Hmm, they did blew up one cargo to the ISS once...

duzzy

Right, but it's the perception.

When it just splashes down in the ocean as it's meant to, nobody notices.

qasdfdsaq

@kimholder Other launchers don't live stream those stages exploding?

TildalWave

SES-9 Technical Webcast

►

duzzy

When it blows up on a barge during a landing attempt, people see it as a failure.

TildalWave

00:17

if you wanna embed it... link is embedding-friendly already ;)

duzzy

When they had those failed landing attempts in the beginning, I kept seeing people complaining about how many times SpaceX keeps wasting money on blowing up rockets.

qasdfdsaq

That's not dust, that's SPACE GLITTER!

Antzi

Oh really ? Did they not bothered to read the full story ?

duzzy

I think what Brian said about emphasizing successful missions, rather than blowed-up boosters, makes sense.

Antzi

Yeah it does

duzzy

00:19

@Antzi When does anyone ever read the full anything?

:P

Brian Lynch

tl dr right

Antzi

I don't understand. People don't have time to read 3 more paragraphs but somehow hollywood managed to get us to watch 1.30h+ of additional crap on each of its movies ?

Brian Lynch

youtube and wikipedia lol

oh man I love anything cool and new, but that solar reflector project makes me cringe -- is it really so great to reflect sunlight to light cities at night? You either need a constellation that provides continuous light or a geo version, which is probably ridiculous to hope for

TildalWave

@Antzi I like it, it's like a novel use for gossamer drag augmentation and it'll also look cool for a while

if sats used such devices to deorbit faster once dead (I guess they could be made to self-deploy) it would also be much easier to track them and predict or maybe even select reentry location

Russell Borogove

Unconfirmed tweet asserts loss of first stage confirmed by SpaceX

#Falcon9 booster did not survive landing, confirmed by #SpaceX. #SES9

Tweeted by MatthewBTravis on March 5, 2016 at 12:09 AM

No source given

qasdfdsaq

00:32

RIP poor booster :-(

Antzi

Tidal: yeah provided the satellite is not too high :)

Russell Borogove

i cannot confirm that I relayed an unconfirmed tweet however

qasdfdsaq

The tweet confirms that it confirms itself

TildalWave

@Antzi sure, but this would work where it's most needed

Antzi

Anyway the project already reached its first goal so hopefully we'll see it within a few years :)

TildalWave

00:34

qasdfdsaq

It's all about space lazers.

The Russians want to use the sun as a space lazer to attack the U.S.

Russell Borogove

Hey, a thread on the spacex subreddit has a number of people claiming they did a three-engine landing burn, the theory being the terminal burn could be higher-g, thereby shorter, and save gravity losses. Anyone here heard that before?

TildalWave

I didn't but it makes sense as long as you're dead on target

Russell Borogove

(That could certainly explain the difference in precision, if they had less decel time)

qasdfdsaq

The theory is sound but I can't think the savings would be any more than minimal

Antzi

00:38

Qasd: I'm waiting for the Gundam 00 orbiting solar farm before talking space lasers

qasdfdsaq

I'm thinking like. 0.5% difference at best.

Russell Borogove

It fits with the whole tone of uncertainty they've had about the landing, if they were testing a new strategy

0.5% based on what? Going from ~1.5g to ~4.5g terminal decel would change the burn time hugely.

If I weren't doing 3 other things right now I'd do some rocket math

You know how I love doing rocket math

qasdfdsaq

Based on the terminal burn being only a few seconds long. Then again I might be confusing it with the boostback.

TildalWave

@RussellBorogove about 15.4 seconds shorter burn

Russell Borogove

Wow seriously?

qasdfdsaq

00:43

Oh. That'd be quite a bit then... how log is the landing burn anyway?

Russell Borogove

What are the before and after times?

I guess 7 sec vs 22 sec?

TildalWave

7.7 and 23.1 ... it's 1:3 anyway

qasdfdsaq

Huh, must have misread the graph

So 23s at 1.5G, the landing burn basically uses 340m/s of delta-v

kim holder

@Antzi just wonderin' if you know you can ping someone in particular by putting the @ before their name... or you can hover over the left side of a message and a triangle will come up that you can click, and then there is a menu where you can choose to reply to that message

qasdfdsaq

Of which, 225m/s would be gravity losses.

Those numbers don't sound right.

(I did fail maths at school three times, so I expect to be wrong)

Now IF the landing burn is a 23 second, 1.5G burn, then going to 4.5G would cut it down to 3.3 seconds, not 7.7

duzzy

00:54

Rocket landed hard on the droneship. Didn't expect this one to work (v hot reentry), but next flight has a good chance.

Tweeted by elonmusk on March 5, 2016 at 12:48 AM

qasdfdsaq

Unconfirmed confirmation tweet confirmed!

duzzy

:P

qasdfdsaq

But seriously, if I did the math right, going from 23s down to 3.3s is a huge difference, and that can't be right cause I'm sure the video lit up for more than 3.3 seconds

PearsonArtPhoto

What is "Hot Reentry?

kim holder

@qasdfdsaq if you show your math someone can say if the formula is right

or you can ask it as a question on the main site. it would make a good question, actually.

qasdfdsaq

00:56

Well 23s at 1.5G = 23x1.5x9.8=338.1m/s

23s of 1.0G gravity = 225.4m/s. 338.1-225.4 = 112.7m/s that the rocket is actually travelling at at the beginning of the landing burn

TildalWave

@PearsonArtPhoto I'm guessing high reentry speed, lots of friction heating

qasdfdsaq

Maybe I'm used to KSP where everything of mine takes off at 200m/s

112.7m/s sounds awfully slow for a rocket at terminal velocity.

PearsonArtPhoto

You've got to be careful about relying too much on KSP.

KSP gives you a pretty good grasp of a number of things, but there are quite a few things that aren't accurate at all.

qasdfdsaq

Well this is with Ferram's "realistic" aerodynamics. Regardless, lets ignore the numbers not "sounding" right then

PearsonArtPhoto

That's better, but still...

qasdfdsaq

01:01

112.7m/s is 252 miles per hour, random example from Wikipedia suggests human terminal velocity is 122mph to 200mph.

Russell Borogove

The 1.5g figure I pulled directly ex recto

qasdfdsaq

So actually 112.7m/s sounds... reasonable.

TildalWave

@qasdfdsaq you won't be able to calculate gravity losses as easily as that, because mass also changes ... no other way that I'd know of than to integrate it

qasdfdsaq

@TildalWave True, but I'm assuming by the time it lands it's got a negligible fuel fraction.

Russell Borogove

The rocket is mostly empty space at that point, so Vt should be pretty low

TildalWave

01:03

@qasdfdsaq well you'd get a decent approximation, but remember that the rate of change is 1:3 so that ratio should follow you however you calculate it

if you haven't that ratio between the two results, or close to it, you're off somewhere

qasdfdsaq

5

A: What's the thrust to weight ratio of Falcon 9 at landing?

From Wikipedia, we gain the following value at launch (Pounds deliberately chosen because both are units of force, instead of kg, which is a unit of mass) 1,530,000 lbf thrust 1,194,000 lb weight Thus, the TWR at launch is 1.28. The maximum is 5, because Falcon 9 will start shutting engines d...

> Landing- 1.8-2.05 (Estimated maximum, actual could be lower if there is remaining fuel)

So the 1.5G ex-recto figure isn't that far off.

kim holder

my google translate is telling me 'ab anus' is a better latin translation...

TildalWave

@qasdfdsaq EX RECTO :))

(from the ass)

qasdfdsaq

Yes, I know.

For a figure derived from that part of the human anatomy, being within 20% is pretty close.

The 0.5% figure I pulled out from my rear end is probably off by a factor of 10.

kim holder

anything involving my anus that is 20% off i am firmly opposed to

TildalWave

01:07

small numbers ex recto sound better :D

qasdfdsaq

Aaanyway. Let's say you have a TWR of 2.0G at landing cause that's what the answer suggests the peak landing TWR is going to be with a small amount of fuel left.

And that it doesn't change significantly over the course of the landing burn, because that amount of math would make my head explode

At that rate a 23s burn would kill 225.4m/s of velocity. To do the same with 3 engines @ 6G's would take 4.6 seconds accounting for gravity at a constant 9.8m/s.

TildalWave

we also need speed, it should be slightly higher than Mach 1 because we heard the booms

qasdfdsaq

Your gravity losses (again assuming constant mass and acceleration) would drop from 225.4m/s to 45.08m/s

I'm assuming if it goes from 225.4m/s at the start of the burn to 0m/s at the end, then 225 is the speed.

But then, yeah that's not fast enough to make sonic booms.

For it to be travelling faster than the speed of sound at the start of the landing burn you'd have to have far more TWR than 2.0 and/or a far longer burn than 23s.

(I have no idea where the 23s figure came from)

TildalWave

from my ex recto :)

just a rough estimate

qasdfdsaq

Well if that was ex-recto as well...

To be fair that's also within about 20% :-P

SpaceX's own publication says landing burn starts "about 30 seconds before touchdown"

duzzy

01:14

lol looks like T has a new favorite phrase. :P

TildalWave

neah

I just didn't really use it since college

latus rectum maybe

kim holder

recto means right in latin. same as in spanish.

qasdfdsaq

Anyway, going from 2G to 6G on a 23s landing burn would save you 180m/s or around 3-6% of the first stage's total.

See, my ex-recto figure was off by a factor of 10x, yours only by 0.2x

All hail the highly precise rectum.

kim holder

(no respect for latin around here...)

TildalWave

@kimholder no I think it's right, rectum (behind, trailing,...), of rectum, recto... or maybe recti hmmm

kim holder

01:18

google translate says right. and that feels right, because it is in fact the same word in spanish.

anus is what you want

TildalWave

that's just rude!! :D

qasdfdsaq

> English: from rectum
Latin: de recto

Alternatively, my maths are "eruerunt mihi asinum"

kim holder

did you get that from a translator?

qasdfdsaq

Google Translate, yes.

kim holder

try it in reverse. it says right.

which seems strange if they used the same word for both things

TildalWave

01:22

@qasdfdsaq doesn't sound right

extrahi asinum?

qasdfdsaq

@TildalWave I don't speak latin so I have no idea

TildalWave

I'm supposed to speak some, but it's been like 20 years

qasdfdsaq

TildalWave

and I always hated it :P

qasdfdsaq

Meh :-/

> Etymology[edit]
From New Latin rectum, abbreviation of Latin rectum intestinum ‎(“the straight intestine”), rectum, neuter of rectus ‎(“straight”). See right.

So it really is the same word in Latin

kim holder

01:24

TildalWave

BTW asinum is more like arse, not ass

and it doesn't quite work

qasdfdsaq

Eh don't we have a language SE site this might be more suited for? :-P

@TildalWave Arse, Ass, same difference in the UK.

kim holder

anus, not asinum

TildalWave

why not just say it was a proctological solution to a problem?

qasdfdsaq

Assuming you're referring to the rear end in both cases and not the donkey.

I think I should go back to KSP before I derail this chat room entirely...

kim holder

01:28

oh, this is a standard rail for it

in fact the combination of rocket math and bathroom humor fits it especially well

2

ok, not always...

qasdfdsaq

Huh. And I thought my usual hangout (Root Access) was bad...

kim holder

try sec.se

wow

qasdfdsaq

As in security.stackexchange?

kim holder

yeah

qasdfdsaq

I get random people from security.stackexchange coming to RA and calling me a troll :-/

kim holder

01:30

really???

qasdfdsaq

Usually because I get flagged for saying something as offensive as "I wish I sudo worked on women"

TildalWave

surely not from the DMZ

kim holder

ah yes, the dmz. that's what i meant

TildalWave

we're suckers for toilet humor there

erm, bathroom humor apparently

or either, what's the difference?

kim holder

either one

potty humor

qasdfdsaq

01:32

@kimholder Yup

in Root Access, Mar 1 at 17:47, by Mark Buffalo

@qasdfdsaq You keep annoying and disrupting users here. Please stop trolling.

kim holder

huh.

qasdfdsaq

@TildalWave Isn't the politically correct term "Humour associated with excretory bodily functions"

TildalWave

@qasdfdsaq seems to me a case of mistaken identity

kim holder

well, gotta make dinner and maybe struggle some more with coding the website. ciao for now.

qasdfdsaq

Cya

TildalWave

01:38

yeah I'm off too I have some baddies to kill with a wrench

qasdfdsaq

People still use a wrench as a weapon these days?

I thought it was all railguns and space lasers now

Brian Lynch

02:47

check it out y'all :) ckwstv.com/2016/03/04/brian-lynch

3

duzzy

03:20

That's pretty cool! You're on TV!

We have a famous person among us!

Russell Borogove

Good grief, what have I started in here

Brian Lynch

haha yea don't think BBC will pick it up anytime soon though lol

Russell Borogove

03:41

I was going to let my domain registration exrecto.com lapse since I haven't done anything with it in the (mumble) years I've had it, but now I'm thinking I better hang onto it

kim holder

14:45

@BrianLynch hey, that's fun. you are more laid back there than i imagined. you have a sort of hobbit eye-twinkle going on in your profile pic.

Antzi

20:02

@kimholder Oh I did't knew about the reply to this message thing.

kim holder

i thought not. wasn't sure tho.

but clearly you have it now :)

Antzi

Thanks:)

kim holder

no prob. there are a few more hints if you click on the little blue 'help' text in the bottom right corner. at least, it's there if you are on a desktop. i didn't notice that until a couple of weeks ago...

Space Exploration Meta

23:10

0

Q: Is "here I googled it for you, please google this topic for more information" the best quality answers we can give?

In my recent question here: What advancements towards Mars were made during Scott Kelly and Mikhail Kornienko's "1 year" journey? 2 answers have come in yet to me they read like: "I googled some stuff which I will quote here and by the way there is a thing called google and that's how I was abl...

discussion

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