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00:01
anyone know when the next F9R landing attempt will be? (hopefully in daylight)
in fact, would be nice to have a method for quickly figuring out if any upcoming mission would support a landing -- I know we've had previous discussions about this based on the mission parameters
@Hohmannfan, I was just looking at that question about launchers using external power/thrust systems and wondering why nobody has added anything about air-breathing engines -- you should add that to your answer to strengthen the question and answer (I was going to add it as another answer but am kind of lazy)
00:33
@BrianLynch great idea, thanks!
00:44
@BrianLynch Thanks for this, cute story!
auch danke für kein verderben :)
01:18
I got the moderator tools, and I am kinda not comfortable with it. Is this the time to scream and run?
Oh! There is a page about that at the help centre, never mind
@BrianLynch -- Jason-3 launch out of Vandenberg on January 17, barge landing attempt. That's a F9 1.1 not a Full Thrust.
Then on January 23, a Full Thrust launch out of Canaveral, that might be a return to launch site.
This is a list of missions, historic and planned, for the SpaceX Falcon 9 family of launch vehicles. The four versions of the rocket are the Falcon 9 v1.0 (now retired), currently-operational Falcon 9 v1.1, Falcon 9 v1.1 Full Thrust, and the in-development Falcon Heavy. == Notable missions == === Maiden launch === The Falcon 9 maiden launch occurred on June 4, 2010 and was deemed a success, placing the test payload within 1 percent of the intended orbit. The second stage engine performed a short second burn to demonstrate its multiple firing capability. The rocket experienced, "a littl...
Primary payload's about 4 tons, so if they aren't carrying much else, they should be able to do RTLS
Oh, hmm, it's going to GTO, though, so will need more oomph.
01:43
> One year after pioneering this technique on flight 16, Falcon will again launch two Boeing 702SP electric-propulsion satellites in a dual-stack configuration,[74] with the same customers sharing the rocket and mission costs.
the "pioneering" part there is the all-electric propulsion sats, not the dual-stack config as the text suggests... nothing "pioneering" about that
e.g. all Galileo sats are launched in couples
but there were many others launched like that before
02:44
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^ (on 15th, Jason-3 Prelaunch News Conference & Mission Science Briefing, on NASA TV nasa.gov/multimedia/nasatv, more info: nasa.gov/press-release/…)
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^ (on 17th, Launch of SpaceX Falcon 9 rocket deploying Jason-3 ocean altimetry sattelite for NASA and NOAA, same links as above, SpaceX will webcast at spacex.com/webcast)
 
2 hours later…
04:47
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^ (on 20th, Smithsonian Air & Space "Mission to Mars" presentaton w/ John Grant on NASA’s ongoing Mars rover missions, airandspace.si.edu/explore-and-learn/whats-new-aerospace)
05:00
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^ (all four, 19th-22nd, University of Southampton's 2nd Stardust Global Virtual Workshop (4 days), ocs.soton.ac.uk/index.php/Stardust-GVWII/Stardust-GVWII, webcast: livestream.com/UniversityofSouthampton/StardustGVW2)
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^ (on 21st, 2nd Stardust GVW's Public Lecture: Orbital Debris and Breaking Cognitive Biases w/ Dr. Darren McKnight, same links as above + ocs.soton.ac.uk/index.php/Stardust-GVWII/index/pages/view/…)
05:51
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^ (both, Feb. 1st-2nd, NASA OPAG (Outer Planets Assessment Group) Winter Meeting 2016 (2 days), lpi.usra.edu/planetary_news/2016/01/08/…, Adobe Connect link TBA)
06:16
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^ (both, Mar. 2nd-3rd, 31st MEPAG (Mars Exploration Program Analysis Group) Meeting (2 days), mepag.nasa.gov/meetings.cfm?expand=m31, Adobe Connect link TBA but most likely connect.arc.nasa.gov/mepag, times are best guess based on same format previous meeting, also TBA)
 
2 hours later…
08:15
@TildalWave haha I got danke and fur, but admittedly had to google translate that... no problem, I forget the ending anyway :)
@RussellBorogove sweet, just what I was hoping!
 
7 hours later…
15:39
The 2nd 3rd and 4th answer to this question: space.stackexchange.com/questions/3012/…
Do they actually add anything valuable to the site?
15:53
@Hohmannfan they're deleted, you just see deleted posts now
one troll post per year on a lunar landing "how did they do it" question isn't even that bad :)
Sorry! I now realized what the red frame was :)
it does look a bit untidy ... I think it would be better if there was just a text link under kept answers, something like "this question has 3 deleted answers, click here to display them all", similar to how you can expand comments if there's more than 5
or at least some user setting, like "hide deleted answers with last activity older than x months"
basically, so recently deleted ones would still display by default to high rep members, in case there was something fishy going on and needs restoring, but if nothing has changed for them in, say, 3 months, then don't display the whole deleted posts but just a link to expand
(unless you came there through search)
I'm thinking on my feet here LOL
4
Q: Is it possible to use zinc powder as a NTR propellant?

HohmannfanThe ISP of a propellant is important when mass is the limiting factor, however, that is not exactly the case when launching a rocket. For the first part of the flight, the density of the propellant is also important. Higher density -> more propellant in the same tank -> higher mass ratio -> more...

@Hohmannfan This is a bit wrong, especially the Higher density -> more propellant in the same tank -> higher mass ratio -> more Δv
not more Δv, but higher thrust (mass flow rate)
you get more Δv with low molar mass propellants
because 1/2mv^2
this is actually the same regardless of the method how exhaust is energized
chemical, ion, magnetothermodynamic, dissociation (NTR),...
16:25
has vapor pressure for Zinc, compare that to Xenon at the top left
basically, you'd have to invest exponential amount of energy to energize linearly increasing mass of exhaust products
and as per 1/2mv^2, velocity matters more than mass
16:43
@TildalWave Am I too unclear in my question? I know low molar mass is best, but "Higher density -> more propellant in the same tank -> higher mass ratio -> more Δv" is actually correct. Consider a 1kg rocket with a 1L propellant tank. I have two propellants, one 1kg/L and 1000m/s, and one 2kg/L 700m/s. The denser actually gives a higher delta-v, despite having a lover exhaust velocity.
@Hohmannfan it's correct assuming same Isp, which it wouldn't be
at some point you also get to T/W < 1 so not the best choice for first stages then (depends where)
6
Q: Why do lower molar mass rocket exhaust products give higher specific impulse?

Brinn BelyeaI tried to work this out. My thinking is as follows. If the same amount of energy is given to a low mass particle and a high mass particle, the low mass particle is faster. A particle with a mass of 1 will be twice as fast as a particle with a mass of 4 but the momentum of the particle with a mas...

@TildalWave But higher density may outweight lower ISP. Density impulse is a COMBINED metric, denisty*ISP!
The first seconds=density impulse, the last seconds=specific impulse. Everything in between is a trade-off, where hydrogen eventually gets the advantage
you're confusing the matters there with that density impulse
you know it well
ISP is the "V_e" part, density is affects the ln(m_0/m_1) part.
you mean because it's easier to store so you have less dead weight?
I very much doubt it because you'll also have to deal with much higher exhaust temperature, and either case it would only be a small improvement.... and density in m_0/m_1 doesn't really matter (density/volume = mass, so you only potentially save a bit the wrapping of that volume)
again, higher exhaust temperature will offset that into a disadvantage
find a similar chart for vapor pressure for hydrogen, you'll see why
IIRC H2 dissociated at 3500K gives Isp of about 1,400 seconds
at 4000K I think it gives 1,700
NTR of heavier metals on its own won't have a very good Isp, I doubt it's much over 500 seconds at 4,000 K
it might be interesting to see what happens in a VASIMR tho
I think there were some attempts to use led for high thrust ion thrusters
17:05
NTR on zinc is 130s
oh that's bad
But take a look at the edit, density means a lot
at what temperature?
3100 K ish
OK so I was generous by about 2x :)
17:06
usual 68 to 1 atm expansion, 1.67 heat ratio
500s is more like ammonia
you're using extremely small volume of 10 cubic meters and 10 metric tons tank mass?
Just to show the point
Not just tank, engine as well
yeah I know but if you now plug much higher mass fraction into it, it will give H2 advantage over H2O at wet-to-dry mass ratio of only 7
But if you increase the size of the tank to 100m³, water is still better :P
...and the delta-v for the water rocket is then actually high enough to get into orbit
at 1000 m^3 (only 70,870 kg of hydrogen) you already get better delta-v for H2
so mass ratio of 7:1
that would be quite an awful mass ratio for any rocket stage wouldn't it?
17:20
at 1000m³ they both have a delta-v of about 18 km/s
much more than any existing stage
Updated tank volume to 100m³. But why not use water first, then hydrogen? The best from two worlds.
17:57
you're applying too many things at the same time when trying to understand fundamentals
Use water as what? For NTR? It takes too much energy to dissociate compared to hydrogen and you'll also have flow rate problems but that's already engineering and adding more things to it
water is usually mixed in hydrogen to lower exhaust temperature... there's that nuclear salt water rocket by Zubrin that adds high molar mass products to it for thrust, but that doesn't really increase specific impulse (the opposite)
mind, "salt" there is Uranium or Plutonium LOL
"water as what?" propellant! "for NTR?" Yes. BTW, water does only slightly disassociate at 3100 K.
18:14
and how is that an advantage?
you want it to dissociate as much as possible
9
A: Nuclear thermal rocket specific impulse calculation uses 1 amu, is that wrong?

Geoffrey LandisSome of the hydrogen will be disassociated. For the reaction mass that is not dissociated, and passes through the engine in the form of diatomic hydrogen, in addition to the three translational degrees of freedom, heat energy is also put into the vibrational and rotational energy of the hydrogen ...

18:31
@TildalWave I did not say it was an advantage, I just stated the fact. Your previous post seemed to imply I had not considered if the propellants disassociated or not.
Yeah OK I'll admit I'm not giving this my full attention and thought we're having a casual chat. I'm doing other things now and this won't change today nor probably for the rest of the week. :P
the answer to your question is yes, it's possible ... I'm just not sure that NTR is the best way of going about it and it won't increase Isp not delta-v for a given specific energy density .... but there might be engineering solutions that I'm not aware of that can energize zinc more efficiently ... NSWR is the closest I can think of and in a sense it's a NTR, or maybe high thrust plasma drives could do that better, dunno
BTW I think that Zubrin's NSWR suffers from some basic flaw there, I get exhaust temperature at nearly 1 billion K LOL
(a bit over 1 million K for the lower Isp version)
18:56
@TildalWave Sorry TildalWave, I may have been a little too aggressive, it so easy to not care about what I am writing in a chat. Please bear with me. You are the one that is on-topic, helpful and point out the holes in my arguments. You are doing an enormous job here on the site, and was the person who took the time to learn me how SE really worked. Keep up the good work! (I also ask this question again: Do you really sleep?)
oww no no I didn't mean that there's any apology necessary, I was just explaining that I might be taking this a bit too casual because I can't dedicate much time to it ... and yes, I do sleep LOL not much during week days but I make up for that during weekends ... frankly, I'm not sure I feel completely awake now LOL
BTW why zinc?
ah OK you mention that in the question
And not mercury :) I have a lot of unpublished stuff on alternate NTR propellants, but sadly, it is all in Norwegian.
usually, when you mix high molar mass additives to your propellant you're doing that to increase mass flow rate (thrust), but Isp will decrease
That too
For a NTR, thrust is inversely proportional with ISP
or you might wanna combine that with some other benefit, such as chemical catalyst ... aluminum nanopowder is most commonly used for that
I don't know much about zinc to be honest... not for such applications at least
19:05
All my data is in Norwegian! I can't give you all the NTR analyses I have
and that NSWR still bothers me
I think that Zubrin is there just assuming that adding more massive particles to it will keep same exhaust velocity
or I just don't get it
or ... he's basically thinking of a sustained thermonuclear explosion
that would then explain where I get those ludicrous temperatures from
but I have no idea how to work with that then
(I don't know what design to apply for exhaust temperature of the Sun LOL)
My internet connection is dying, bye!
19:29
@TildalWave Aluminum nanopowder? Sounds like a great match for some iron oxide
yeah actually I should say aluminum oxide nanopowder
any half decent rocket scientist like I'm not should know that :P
@TildalWave If you're not a great scientist I don't know who is.
bah I'm just some IT guy ;)
anyway it's tricky to have pure aluminum nanopowder because it either oxidizes or cold welds ... so you'd have to have it suspended in something that prevents oxidation
it would be cool to play with pure aluminum nanolattice tho
that thing probably goes in a real nice flash :))
I think it would be awesome to play with anything that has the word "nano" in the name
get a hexbug nano
19:46
@BrianLynch I put a laser pointer on one and sent my friend's cat into a curious rage
nice
^my dog playing with one
unending entertainment
@BrianLynch God that's hysterical
such a cool little toy too
20:00
@BrianLynch So that is a 'nano' bug, is a regular bug about 30,000 km then?
yes, they are working on that one
er I mean, no my dog is really really small
is there a description of today's space show?
the most I can find is the one-liner in the notification bar here
No description on the live365 page either
and right now i'm getting ambient pop music
same here
^ that's the website of one of the guests
john strickland does a lot of writing for the space review
20:05
nice, was just looking at that
trying to read the paper quickly haha
it's an overview really
lol after what you said earlier now I am second guessing my assumption of what COTS means
and I can't find them listing the acronym anywhere
not even on lunarCOTS.com
PEBKAC
its that same reference, commercial orbital transfer, uh, service i think
it's more a reference to that public private partnership approach
i've talked to him at length and exchanged a couple of emails
this is the thing, he's a medical doctor and doesn't really have the time to focus on this
@Hohmannfan i had to look that up...
@BrianLynch hehehhee that is a lot of fun
I'm eager to ask him about teleoperation delay and how that affects trade-off between manual operation and autonomy
since he talks about his experience with teleop surgery
aha so it isn't commercial-off-the-shelf!
lol I guess not so generic music
20:22
The Space Show w/ Dr. D. Plata & J. Strickland on cislunar space development, technology and economics is now podcast live. More info in the newsletter
soz for delay, I was out :P
the lack of full justification in the cislunarone.com paper is making me cringe though lol
ah they haven't started yet?
no tech difficulties
@kimholder How is moonwards progressing?
20:24
i'm working on updating models with improved designs right now
i have several to do
@kimholder what is your opinion of the "first woman on the Moon"
image on the last page of that paper?
i decided to let that pass...
:P
lol
kind of made me face-palm
he pulls these images from elsewhere
oh yea I would assume so
20:27
but he does have a sort of protective stance about women
oh really?
he plans to send two married couples. but the men go first, and their wives come later
of course he also lists "the first couple" and "the first pet" along with "metals & glass produced"
I like that stuff a bit since it makes space exploration feel closer to being part of day-to-day life... but also makes my eyes roll when I just want to hear about the actual science and technology
oww David has put up a new newsletter for the upcoming week ... I'll have to find the description of today's show in my mail then
hmmm just that one line
he's especially interested in establishing a community. he is attracted to considering the reproductive issues and how to overcome them
20:33
really? wow
why is that "first woman on the moon" shown with a helmet off? :OO
we don't even do that in Antarctica!
lol cuz she doesn't want to ruin her hair Tildal
she's big! :)
20:33
hahaha
that picture is like something out of an adult anime show
it's awful
yea I couldn't believe that was in the appendix
OK we're live with the show
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^ (tomorrow, The Space Show w/ Dr. Louis Freedman re his book "Human Spaceflight: From Mars to the Stars", more info: thespaceshow.com/newsletter, podcast: thespaceshow.com/content/listen-live)
20:42
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^ (on 12th/13th, The Space Show w/ Jim Muncy, President and founder of PoliSpace, same links as above)
OK I found the description for today's show here thespaceshow.com/newsletter?page=1
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^ (on 15th, The Space Show w/ Steve Wolfe & James Causey re NTP's SpaceCom Space Commerce Conference and Exposition, same links as above)
I'll schedule the John Batchelor show on 13th when more info is available
 
1 hour later…
21:57
@BrianLynch, Lovely beautiful rottie you got there.
@MyOtherHead thanks! he is pretty adorable, rotties are so awesome :)
holy the population in here reached double digits!
I have to say I am not very impressed by Plata's arguments
in decimal system, it's 4 digits in binary :P
lol very true!
or 1 digit if you were born with a polydactylism
22:04
I had to google that word :))
oh yea me too haha
I wasn't even close with "my" spelling of it
how was Star Wars?
@BrianLynch Never had the pleasure of being an owner, but I was an "uncle" to a late close friend's rottie, whose name escapes me at the moment. The rottie was like his owner. I know I'm missing the Space Show, but I was doing work-work when it started, and І don't like to come into the middle/end of a show.
I tried to calculate the ideal velocity for a vertical ascent, and surprisingly ended up with terminal velocity. I spent half an hour writing a question about it offline, was just about to post......And then I found that somebody had asked about that before. LOL
oh dear, sounds like you need sleep :)
22:19
@TildalWave But there are a lot more trajectory optimization left!
The terminal velocity thing has some strange implications though, the rocket must actually slow down a bit after a while, if it looses mass faster than the atmospheric density decrease.
one thing to remember about escape velocity is that it's also the impact speed at free fall towards the body with no atmosphere, if that fall started at 0 relative velocity at infinity ... it's just a different way of saying the same thing, but is useful sometimes
escape velocity?
@TildalWave Do you need to sleep too?
ah damnit I was reading it wrong didn't I?
yeah LOL
but it would be for a body with no atmosphere :P
I mean, ideal velocity for a vertical ascent
tho granted, for terminal velocity you do need an atmosphere :))
@BrianLynch oh, good on you - mention those credentials man!
lol I hate how he reads that, that's just an automated signature
gonna have to delete them for future questions
22:26
@BrianLynch i understand it completely, it looks good on the program too :)
yea maybe he wants to read it so he can tout an educated audience hehe
exactly....
and it is already building you up for when i use you as a reference :]
haha the higher you climb though...
I'm so sick of hearing about cost
at least as a driving requirement
tell me about it
we'll end up with Walmart launch vehicles
if you're going to do it, do it right
and stop wasting money on F-35s
or drug wars
22:37
that's where you need a ground-swell of popular support
which points the issue straightly at public awareness and education
yea it's true, the public will scoff at _any_dollar amount for a program they don't like
@BrianLynch could not agree more on that one...
the short-range visions that the public gets really makes the subject far far duller than it really is
^and then no more whining about space costing too much
people just need to understand that we're not burning the money needed to get to space, we're spending it here on Earth and it stays here
and for my fav, the drug income of all the mexican cartels together is double to triple NASA's annual budget
22:41
@TildalWave very very true
didn't think about it like that
@kimholder wonder if they'll move from submarines to suborbital vehicles
are not submarines already suborbital? :P
rockets are too easy to track, unfortunately
ok sure, but then so am I when I get on a trampoline
@Hohmannfan not if they're in orbit :P
@TildalWave Dean drive reference?
22:44
neah, didn't think of that
Put the Dean machine on a submarine
google images for submarines in space
there's a long Japanese anime tradition in that
Space Battleship Yamato
yea I love those art concepts
22:49
OK that's a battleship, but I've seen submarines too
geez that's as old as I am
(the manga versions)
why does YouTube want me to sign in to confirm my age when I wanna play Star Blazers?
@TildalWave koliko si star?
is that because it contains certain keywords like manga?
@Hohmannfan too old LOL
you're using Google translate?
Nope, Yandex tranlate
yeah it keeps same structure as you typed it in, it's OK but not exactly correct
23:43
I am maybe half a year late.... But I am in if a few more of you do it. Bounty January. 3 each?
@PearsonArtPhoto
Jun 24 '15 3:24 PM
Challenge: Let's bring our unanswered questions to 0. I'm personally putting forward some of my reputation to accomplish this, but I can only set 3 bounties at a time. I challenge those with high reputations, including @TildalWave and @geoffc to do the same. Let's see what we can accomplish!
We've done that before and will do it again. I stand by my position tho that I'd rather award bounty to really good answers than offer it with no guarantee that the question will get answers worthy of it.
I've awarded 1,900 rep in bounties so far, not counting some that didn't get any answers or I eventually ended up answering them myself
and i very much agree
^I echo that sentiment
also T has said before it would be better for the highest rep people to offer bounties rather than those of us below 20 000
I think we're doing just fine when it comes to percentage of answered questions
I'd even dare say we're doing great in that regard
23:48
is it possible for a moderator to force an answer to a question?
many graduated sites have lower stats on that
sorry an accepted answer I mean
nope
only OP can accept
gotcha
there were one or two I remember seeing where the OP clearly was happy with an answer but just upvoted it because they don't know how the site works
Or they are just gone...
23:50
oh don't be bothered by that, it's same rules of the game for all of us
we all have a fair share of answers like that
oh I mean more because I feel like having the green check mark makes it more useful for visitors
it shouldn't, the hover text on the accept says what it's there for
"The question owner accepted this as the best answer"
well I know how SE works but yet I still trust answers more that have the accepted check
give it time... :]
i.e., when I'm trying to solve problems with git or C++
23:52
hahaha exactly... give it time
at one point you're gonna double facepalm at which answer was accepted
oh yea I've been doing that already
to be honest I don't come here to get my questions answered lol
i get the feeling it is easier to be clear and precise about both questions and answers on the SE sites regarding coding.
yes exactly
I rely on those for direct answers with no bs
whereas SEx is just for fun
(sorry I couldn't resist)
I think I'd like to close my question on whether The Expanse is realistic in terms of trajectories and timelines, and start a new question about the exact same thing but without any reference to The Expanse
but should I just edit the original question instead?

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