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Comment by kibwen | Hacker News Reader

I was about to say that launching so far from the equator sounds very fuel-inefficient, but it turns out that their launchpad's latitude (39 degrees south) is nearer the equator than Russia's primary launch site, the Baikonur Cosmodrome (45 degrees north). For reference, Cape Canaveral is 28 degrees north.

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TBF Baikonur is known to be a fairly bad location from an efficiency perspective if you're trying for GTO/GEO: using pretty much the same rocket, you can send 6~7t to GTO from Baikonur while you can send 10 from Kourou (on 5N).

That's why as time went on, China kept building their new launch facilities more and more southernly (Jiuquan was built on 40N in the 50s, the recently opened Wenchang sits on 19N).

It gets worse than that. The russian site also has to not fly over chinese territory, further increasing their minimum inclination. Chinese dont want thier stinking rockets falling on china. (Literally. Russian rockets use some nasty stuff that groups like SpaceX have stayed far away from.)

> Russian rockets use some nasty stuff

Do you have a source for that? What sort of "stuff"?

They probably mean hydrazine. The Russian Proton rocket uses it, though it’s being discontinued. This isn’t a uniquely Russian oddity, by the way; the European Ariane IV and US Titan IV were still in use into the last decade.

UDMH is not hydrazine, and is said to be worse as it doesn't biodegrade as readily as hydrazine.

UDMH, hydrazine, and MMH are all very different beasts.

UDMH and MMH are both hydrazine derivatives, classified as hydrazines, and either picked or mixed (Aerozine 50 is a 50/50 mix of hydrazine and UDMH) depending on the specific chemical and performance tradeoffs you want to make.

UDMH, hydrazine and MMH are slightly different beasts.

UDMH. This is why Musk can stand beside a crashed falcon rocket while a crashed russian rocket must be approached in suits.

Depends on the rocket. The Soyuz main stage only uses refined kerosene, liquid oxygen and hydrogen peroxide. The upper stages almost always use some hydrazine compound, but that’s pretty common. Almost all satellites use a storeable propellant.

>must be approached in suits

Locals make a living scavenging the toxic parts and have awful health problems as a result. http://blogs.discovermagazine.com/crux/2018/06/07/in-russia-...

As long as it didn't crash with a Dragon anyway (that uses MMH).

I'm guessing they're referring to the hypergolic propellants used on the Proton rocket? Which are, indeed, notoriously toxic.

In which case, they're not something SpaceX has shyed away from; they are indeed not used on the Falcon, but hypergols will power the SuperDraco engines on the Dragon 2.

When you need storable propellants (either for a launch escape system that needs to be ready to go at any time, or for ICBMs that can be kept in a launch-ready state), and a solid rocket won't do for whatever reason, there's just nothing else that will do the job.

> When you need storable propellants (either for a launch escape system that needs to be ready to go at any time, or for ICBMs that can be kept in a launch-ready state), and a solid rocket won't do for whatever reason, there's just nothing else that will do the job.

That is, if you don't count Soyuz landing capsule, which carries about 30 kg of hydrogen peroxide and keeps that for up to 210 days flight before landing. And if you don't count Zarya spacecraft, which - never built, but was designed to use hydrogen peroxide for powered landing ( https://en.wikipedia.org/wiki/Zarya_(spacecraft) ), also after long flights. And Buran spaceplane, which used LOX and kerosine for maneuver engines able to word in a month-long flight. And Kliper spacecraft designs with propulsion on LOX and ethanol.

Even hydrogen can be made working after weeks of flight if you have large enough tanks - there was design of upper stage of N-1 with that. With Lockheed works on space tanker ( https://en.wikipedia.org/wiki/Advanced_Cryogenic_Evolved_Sta... ) the time range can be extended even more. I think we can leave those toxic propellants aside when we want.

>Do you have a source for that? What sort of "stuff"?

Russians are still using hypergolic fuels rather than the methane/oxygen that most new generation launch vehicles are using.

Those methane-based launchers all have not yet left the design stage.

Probably UDMH and nitrogen tetroxide or nitric acid referred to as Devil's Venom in Russia apparently https://en.wikipedia.org/wiki/Devil%27s_venom

The same mix was what blew up in Damascus Titan missile explosion as told in the book Command and Control. Luckily the 9-megaton warhead didn't go off.

I recommend the book Ignition if you are interested in these things (free pdf http://library.sciencemadness.org/library/books/ignition.pdf)

That book is one of the best things ever.

" And if you, gentle reader, have never seen a nervous rocket mechanic, complete with monkey suit, being buzzed by nine thousand demented bats and trying to beat them off with a shovel, there is something missing from your experience."

Only the Chinese get to drop rockets on their towns.

https://www.youtube.com/watch?v=DJRZ-eyncVk

The Red Plume you see is Hypergolic fuels - the aforementioned "bad stuff". Highly toxic and carcinogenic.

Hypergolic doesn't mean "bad stuff", "highly toxic" or "carcinogenic" though, it just means "ignites on its own" (it's usually though not necessarily a combination of a fuel and an oxidiser[0])

Then again, hypergolic components are generally extremely toxic or ridiculously corrosive or both.

[0] generally because e.g. Chlorine Trifluoride is such a strong oxidiser it's famously[1] hypergolic with stuff not usually considered "fuel" like cloth, people, water, sand or asbestos

[1] http://blogs.sciencemag.org/pipeline/archives/2008/02/26/san...

The word hypergolic doesn't mean that, but in spaceflight the term refers to a fairly specific group of compounds; Dinitrogen tetroxide and unsymmetrical dimethylhydrazine or monomethylhydrazine (UDMH / MMH).

mmh+nto is the only thing still being used in the west outside of missiles. even spacex use it for module maneuver. I think. not even sure why I know that.

but china probably use the lesser hypergolic combinations for actuall lift off.

> but china probably use the lesser hypergolic combinations for actuall lift off.

Yep, Long March 2, 3 and 4 use YF-20 engines (and its derivatives) which are UDMH-powered.

They're switching to LOX/Kerosene for LM5.

It's been worse...

https://www.airspacemag.com/history-of-flight/disaster-at-xi...

Possibly next-gen small fission reactors will have them looking for close-to-deep-ocean far-from-large-population launch sites again.

https://www.nasa.gov/press-release/demonstration-proves-nucl...

If you're launching into sun-synchronous and highly inclined or polar orbits, you want to be as far north or south as possible. They're not going for low inclination orbits, but rather the opposite, if you look at the ground track of an Iridium satellite, that's a perfect example of a polar orbit.

Spire is one of their customers, that's earth observation, perfect use case example for polar orbit.

https://en.wikipedia.org/wiki/Polar_orbit

To avoid dropping the first stage on a populated area if you're launching into a polar orbit, you also need a very empty area of land or an ocean under your flightpath. For example Israel has a domestic satellite launch capability (they're one of the few countries that launches LEO stuff westbound, to retrograde orbits) because they both can't drop first stages on the eastern neigbours, and can't launch heading north or south.

For what it's worth, this specific launch was polar, I believe. But yes, for equatorial launches, it will take a lot more dV to flatten it out.

I do like their little kick stage on top that finalizes payload delivery, though. That will be useful for this sort of thing.

This has always bothered me especially given their plans to send a rover to the moon. Launching from Tokelau, Niue or the Cook Islands would make more longterm sense.

If you think about it, the added starting velocity from launching on the equator is nice but is still only ~6% of the total velocity required to get into low Earth orbit. (0.0625 = 1.5 / 24 given orbital period in LEO is ~90 minutes and rotation period is 24 hours). Even at 45 degrees latitude you're only losing 0.707*6=4.4% of your target velocity.

The problem is not the starting velocity (which is indeed minor, and not an issue for LEO launches) it's the inclination burns you need to reach GTO/GEO.

With roughly equivalent rockets, there's a 30~40% difference in payload mass between Kourou (5°N) and Baikonur (45°N): Proton can launch 23t to LEO and 7t to GTO while Ariane 5 can send 21t to LEO and 10t to GTO.

That makes sense, I hadn't really thought about it in this context but I guess geostationary orbits kind of have to be equatorial.

Percentage of velocity is highly misleading. The rocket equation is nasty, and a small increase in velocity means a large increase in fuel requirements, or a large decrease in payload capacity.

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