my subscriptions
POPULAR-ALL-RANDOM | LOADING...MORE »
Translathor 2 points

!doublecheck

Going up the mountain and down with the skis

Into the ski hut and the hands up in the air

Out with the bunny1 and down goes the Jagertee2

Man, that's nice!

1 - leaving with a hot girl. Not a literal bunny, of course.

2 - drinking Jagertee (black tea & rum)

Seemed like a nice holiday :D

edit: formatting

hallowatisdeze 2 points

Excellent, these lyrics explain the accessory dance of the song. Thank you!

And now that I got your attention. What is the play on words in this Johnny Däpp song? I'm not sure what Däpp means. https://youtu.be/IJUnRR_oXpk

hallowatisdeze commented on a post in r/HighStakesSpaceX
hallowatisdeze 5 points

Funny, below news comes in only 3 days after this bet has been offered!

EM-1 officially slips into 2020 and EM-2 into 2023. And Europa Clipper into Q4 2025 (prev 2022) https://twitter.com/SpcPlcyOnline/status/963172689358868480 https://twitter.com/jeff_foust/status/963172944880066561

hallowatisdeze commented on a post in r/spacex
4.6k
hallowatisdeze 9 points

Everybody (including the mods) is so hyped, that the "Select Upcoming Events" in the sidebar is still not updated, 24 hours after liftoff! :P

hallowatisdeze 10 points

So perhaps the landing algorithms were not that easy to update for a heavily modified booster, which the center core is. But probably they can learn a lot from this!

hallowatisdeze commented on a post in r/spacex
237
hallowatisdeze 6 points

About the Tesla Roadster going to 'Mars orbit'. The consensus seems to be now that we assume that the Roadster will not go to a Mars orbit, but only do a flyby of Mars and stay in a solar orbit with aphelion at Mars's orbit and perihelion at Earth's orbit. However, I didn't read any convincing reason for this assumption. As a matter of fact, this assumption does contradict the original tweet of Elon saying that the Roadster will go to Mars orbit, nothing else.

Why do we all assume that a ballistic capture to a high altitude Mars is not the case? ( https://en.wikipedia.org/wiki/Ballistic_capture ) Is this not possible with the low attitude control of the Tesla Roadster? Why not? It doesn't require any deep space insertion burn which the second stage can't execute. I can agree that it is a challenging task to do the Earth escape burn so accurate that the trajectory will lead to a ballistic Mars capture. But they can at least try it? I can't understand arguments I read that this is unrealistic because the spacecraft will not be sterilized, as a ballistic trajectory leads to a high altitude orbit with no chance of deorbiting any time soon. (An inaccurate Earth escape burn might lead to a 'contaminating' crash at Mars, but this risk is still valid when just a flyby is attempted)

Sorry for long post, I hope someone can give me some more information why a ballistic capture is realistic or why not.

theinternetftw 18 points

From this article by Phil Plait:

So I decided to contact Musk. He got back to me, and gave me the info.

[...]

No, it’s not going to Mars. It’s going near Mars. He said it’ll be placed in “a precessing Earth-Mars elliptical orbit around the sun.” What he means by this is what’s sometimes called a Hohmann transfer orbit, an orbit around the Sun that takes it as close to the Sun as Earth and as far out as Mars. This is a low-energy orbit; that is, it takes the least amount of energy to put something in this orbit from Earth. That makes sense for a first flight.

So that answers why we assume no ballistic capture.

this risk [of crashing] is still valid when just a flyby is attempted

Not if you're aiming so far away from Mars that even calling it a flyby is a stretch. It'll be interesting to see the expected closest approach distance (both this year and later years). The phrase "going near Mars" in the article above is Phil Plait's editorialization, and it may be generous.

To get past planetary protection (which Elon says they complied with), all of this had to be reckoned with.

hallowatisdeze 1 point

Thanks for that, I completely missed that article.

hallowatisdeze commented on a post in r/spacex
hallowatisdeze 34 points

This way, could they give the second stage a bit more energy, so that the second stage can cut off a bit earlier, which means that there is some fuel left for testing a controlled re-entry of that second stage?

hallowatisdeze commented on a post in r/Arianespace
hallowatisdeze 8 points

Too bad there is an abort! Some speculation of the cause:

After main (liquid fueled) engine ignition the computers calculate the generated thrust. They do this either by measuring the force on the hold-down clamps or by measuring the combustion chamber pressure (or both?).

When it is found that the engine thrust is too low, they decide to not let go of the hold-down clamps and shut down the liquid engine. This is all before the solid booster ignition, as they obviously cannot be stopped once fired.

A reason for the too low thrust can be too high propellant temperature. If this temperature is high, the density decreases. As the turbo pump works at a certain volume rate, this means that less mass of propellant is pumped to the engine for decreased propellant density. This could lead to not enough thrust. (Not relevant for Ariane, see below)

As said: this is all speculation. Maybe something completely different is the cause. SpaceX's Falcon 9 had an abort last year which looked very similar, I think that abort was caused by what I just speculated.

Jef-F 4 points

reason for the too low thrust can be too high propellant temperature.

AFAIK Ariane uses fuel and oxidizer at boiling temperatures, so they can't warm up higher than that. For F9 with sub-chilled LOX this is a problem, yes.

hallowatisdeze 1 point

Good point! I forgot about this difference between those launch vehicles. Ariane doesn't use 'superchilled' propellants like Falcon 9.

I'll strike it in my post.

hallowatisdeze commented on a post in r/spacex
NowanIlfideme 23 points

This bot always pops up, it'd probably be best for mods to contact the creator and ask to blacklist replying to u/decronym...

hallowatisdeze 9 points

That sounds like a good idea to me. However, I do appreciate this bot in typical cases. It saves me several clicks and loading times a day.

hallowatisdeze commented on a post in r/spacex
bertcox 41 points

Meme's are not allowed on /r/spacex, even the creation of meme's is banned here. Take that meme stuff to the kid pool where everything belongs. Only peer reviewed articles done by dual PHD's from Harvard's school of Philosophy are allowed here.

hallowatisdeze 14 points

Watch out, you're creating a meme.

hallowatisdeze commented on a post in r/spacex
danweber 10 points

Why is that more useful than ground-based detection?

hallowatisdeze 42 points

I don't think Putin would agree if the US tried to place a detector in Siberia.

danweber 38 points

The test-ban-treaty was a godsend for geologists, because the technology you use for detecting nuclear detonations is basically the same as for detecting earthquakes, and so there are detectors all over the globe.

You can't blow up a nuclear bomb in secret. And if you somehow got it buried deep enough that it wasn't detectable by earth-based sensors (which probably is not possible), you definitely aren't going to notice it from space.

hallowatisdeze 8 points

The detectors on the GPS sats are aiming for atmospheric nuclear detonations. I'm not sure if these are also that detectable with seismographic sensors?

Here an example of what in orbit detectors can cause: https://en.m.wikipedia.org/wiki/Vela_Incident For me, that's a very intriguing article.

hallowatisdeze commented on a post in r/spacex
431
hallowatisdeze 35 points

This is just me nitpicking:

Reading 'NROL launch' here in the comments makes me laugh. That's like saying 'LCD display', 'URL link' or 'USB bus'. :P

Kare11en 45 points

Ahem. URL.

hallowatisdeze 7 points

TIL learned what URL really stands for.

hallowatisdeze commented on a post in r/spacex
ethan829 26 points

SpaceX has always said that government missions on Falcon 9 are around $90 million. GPS III satellites are pretty light at 3,880 kg, and don't require vertical integration as far as I know.

hallowatisdeze 16 points

I'm pretty sure GPS-sats don't need vertical integration. It's basically 'just' a signal transmitter with a really accurate clock.

DoD-sats that require vertical integration are probably (as they're classified) very sensitive optical divices (lenses, mirrors...?), which must be taken more care of. Hence the vertical integration, which basically means that the sat can only take loads in one dimension/direction.

hallowatisdeze commented on a post in r/spacex
2A_is_the_best_A 24 points

They are owned by SpaceX, made mostly by the company I work for (www.orbitalsystems.com). They use several types of antennae, mostly 3m and 3.7m sized units, but they just ordered our second production 5m system.

These are located all over the place, the cape, vandy, africa, new england, bermuda. We're working on 2 additional systems for the cape to support falcon heavy right now, the'll be outside for testing at the factory next week-ish.

hallowatisdeze 2 points

Thanks, that's some interesting information!

What's the main benefit of taking the 5m ones instead of the current smaller size antennae? Is it also a useful upgrade for LEO communications, or is this another signal (haha signal, get it?) that SpaceX is really focusing on deep(er) space?

2A_is_the_best_A 2 points

A Bigger dish means more gain, so you can track things farther away or things with lower power transmitters. Or keep everything the same and use a higher bandwidth (if FCC approves) and get a higher data rate.

hallowatisdeze 1 point

Aha, thanks again for your reply. So I understand the bigger dish does not really point to specific applications. It just has better overall performance.

hallowatisdeze commented on a post in r/spacex
326
hallowatisdeze 4 points

Thanks for the analysis. I like the method just as much as the results.

My question: I understand the calculations done in MATLAB, but how did you do the tracking of the top and bottom of the stage? Do you also do this in MATLAB with some kind of image recognition tool?

view more:
next ›
12,209 Karma
9,460 Post Karma
2,749 Comment Karma

Following this user will show all the posts they make to their profile on your front page.

About hallowatisdeze

  • Reddit Birthday

    January 12, 2015

Other Interesting Profiles

    Want to make posts on your
    own profile?

    Sign up to test the Reddit post to profile beta.

    Sign up