[simne]

Very good article, but have few shortcomings.

1. Only first generations of "Soyuz" used H2O2 propellant, because it have very limited time before use (for "Soyuz", guaranteed 6 months), and because it have relatively high melting temperature.

First chose H2O2, because "Soyuz" planned as independent ship, to fly relatively short missions around Moon (it is near impossible to withstand even 6 months in so small volume).

When "Soyuz" primary role become companion ship for space station, it switched to hydrazine type propellant.

2. In pressure fed engines used almost all possible propellants and oxidizers. This is not error just clarification.

3. Exists three-propellant engines. For example, exists soviet engine for "spiral" system, which used kerosene+LOX+LH. First it run on mostly kerosene+LOX, with small percent of LH, than switched to pure LOX+LH (sure, LOX share also other).

4. Exists simpler bipropellant engines than mentioned, unfortunately with worse efficiency. - First Britain satellite flown on H2O2+RP1 Black Arrow rocket.

[avmich]

Soyuz rocket uses 82% H2O2 for all first and second stage engines.

Soyuz spacecraft uses H2O2 for capsule control during reentry.

Soyuz spacecraft uses a variant of hydrazine fuel for orbital maneuvers.

All of this is true for all versions of Soyuz rocket (except Soyuz 2-1v) and Soyuz spacecraft, since 1950-s to today.

[wumpus]

I've frequently read in news articles that the lifetime of the Soyuz spacecraft on orbit is limited by H2O2. You appear to be saying that's false.

A while ago I looked at Wikipedia and saw that the Soyuz spacecraft article didn't mention what the reaction control system uses for propellant.

Perhaps you can point at a source?

[simne]

> I've frequently read in news articles that the lifetime of the Soyuz spacecraft on orbit is limited by H2O2. You appear to be saying that's false

May be I misunderstood, what said by insiders. As I remember, first "Soyuz" spacecrafts was maid with H2O2 system, but than they made lot of changes, including new reaction control system.

But looks logically, system used in space separated from system used on atmosphere. And because "Soyuz" landing on dry land, and because accuracy of landing is its weak side, it is also logical to not use toxic components.

I think you remember, how long astronauts stay inside "Dragon" once, because sensors shown hydrazine fuel vapor near ship.

- American ships

> Perhaps you can point at a source?

Sorry, it is not easy now.

It is not secret. Before approximately 2005 I talked a lot on Russian forums, and there was specialists from Russian space industry, and they shared extremely interest info, and I even considered to go work there. Plus books, mostly from Russian authors.

After ~2005, appeared serious tension in talks, so I avoid them, to save my own psychic health.

I cannot be sure, but looks like, it was another step in preparing for big war.

And you are right, that open information on Russian technologies is very limited. This is partially, because they considered nearly all space technologies as semi-military, so some information just classified. Other part is that Russians extremely conservative in business behaviors, and one thing, they inherit form Soviets - very big love to close nearly all information, even harmless and useless, just to show only good info, to look better, to look winner.

What I mean about Soviets - typically, they made launches without announces, and only talk about them if success.

Because of this exists "kosmos" satellites, some of which was planned to flight with this designation, but mostly these are unsuccessful satellites, which reach orbit (and appeared in NORAD list) but does not function from beginning.

If satellite not reached orbit (for example because of malfunction of rocket), and NORAD don't catch it, nothing said at all. If reached some orbit, but malfunction - appears new "kosmos". Because of this behavior, in late USSR was about 1500 "kosmos" sats, and now this number more than 2000.