
Antares rocket explosion: The question of using decades-old Soviet engines - coreymgilmore
http://www.washingtonpost.com/news/morning-mix/wp/2014/10/29/antares-rocket-explosion-the-question-of-using-decades-old-soviet-engines/
======
joshAg
To answer the question of why even use them at all, it's because on paper they
still compare very well to the other options.

Specific impulse is basically an efficiency measure, like mpg for cars. The
higher it is, the more efficient the rocket engine is.

SpaceX's Merlin 1d has a thrust-to-weight ratio (twr) of 150, and a specific
impulse (I_sp) at sea level of 2.73 km/s. I doubt this was an option for
orbital sciences to use in their rockets.

The NK33, which is the soviet engine that was used, has a twr of 137 and an
I_sp at sea level of 2.91 km/s.

The atlas V rockets by boeing and lockheed use an rd180, also russian built
btw, which has a twr of 78.44 and an I_sp at sea level of 3.05 km/s.

The delta IV rockets by boeing us an rs68 or rs68a have a twr of 51.2 and an
I_sp of 3.58 km/s. I'm not sure if these are available for commercial use,
though, since boeing shut down the commercial delta IV launch program. The US
military still uses them though, so they are still being produced. Also, these
use liquid hydrogen instead of RP1 (rocket grade kerosine) like all the rest
of the engines here.

The Saturn V used five F1 engines (also 1960s tech, but no longer available).
Each of those have a twr of 82.27 and an I_sp of 2.58 km/s.

~~~
jessriedel
Isn't this much more a question of reliability and track record than 10%
performance differences?

~~~
avmich
Both reliability and performance. And also reliability is something which you
estimate, calculate basing on some models - it's probability, not a guarantee.
How would you estimate the reliability of an engine which run over 3 hours on
a test stand? Of course you might prefer a well known fuels, industry-proven
range of pressures and other engineering solutions, and you test them on Earth
first - but after that you have to fly.

Track records are tricky for rocket systems. Since the first Sputnik, over the
57 years the humanity had may be - roughly - 4000 launches of space rockets of
all kinds, with many different fuels, engines, sizes etc. It's relatively rare
when you have a good track record which is measured by many tens of flights -
let alone hundreds. When a system flew 20 times it's already considered rather
mature - double so if those were all successful flights. So it's quite usual
to use a new engine in a new design of rocket - in fact it's rare when you
have many different rockets with the same engine type or many different
engines used on the same rocket. Rockets and engines are usually optimized to
each other - particularly rockets are built around engines, since margins are
quite thin.

------
hindsightbias
The NK-33 may be old, but it offers equal or superior performance to anything
made in the US. Another engine, the RD-180 is used in the Atlas. US industries
have the rights to manufacture, but want $800M and 4 years to build it or
create a new engine. That tells you the state of US tech.

[http://aviationweek.com/defense/aerojet-rocketdyne-
targets-2...](http://aviationweek.com/defense/aerojet-rocketdyne-
targets-25-million-pair-ar-1-engines)

Video on Russian/Ukranian engines:
[http://www.youtube.com/watch?v=TMbl_ofF3AM](http://www.youtube.com/watch?v=TMbl_ofF3AM)

------
gedmark
Not sure what proper HN etiquette on this is, but I made a comment on the
launch news story on this exact subject:

[https://news.ycombinator.com/item?id=8525057](https://news.ycombinator.com/item?id=8525057)

TLDR- Those engines may be 50 years old, but they're a technological marvel.
Using them is a little crazy, but I'm sure Orbital saw it as the "least crazy"
of three options: building a new engine from scratch, buying prohibitively
expensive engines from Rocketdyne, or buying risky but cheap engines from
Russia.

~~~
rst
The design is a technical marvel, but it won't keep the metal from corroding,
and this isn't the first sign of trouble -- a few months ago, a different
AJ-26 blew up on a test stand. It isn't yet clear that the engine was at fault
in the Antares fire (trouble in the tankage or fuel lines could have cascaded
down, among other fun possibilities) -- but if the engine does turn out to be
at fault, the remaining stock will certainly get more attention.

------
hamitron
Well the CEO of a rocket company should have a better response than "I wish
there were better engines to use." Maybe with that multi billion dollar
contract you can, oh I don't know, build one?

~~~
SEJeff
SpaceX certainly built their own and they seem to be working quite well
thusfar.

~~~
wdewind
To be fair SpaceX's last launch (Aug 22) exploded too. It was a test, not a
real mission, but to quote Elon: "Rockets are tricky."

~~~
will_hughes
For starters, that wasn't an actual launch to orbit, that's just the low
altitude testing frames for landing/reusability.

It was deliberately destroyed as a safety measure because the rocket was
moving out of the testing zone and the onboard system wasn't able to
compensate fast enough.

Apparently Elon and a few others were a little annoyed that more (appropriate)
risk wasn't being taken in those test flights, because they'd been 100%
successful.

Secondly, their launches of the production Falcon 9's have been 100%
successful (with one launch not achieving a secondary objective).
Additionally, after the first three Falcon 1's, they were also 100%
successful.

And finally, they launched two Falcon 9's since August 22nd: September 7th:
Asiasat 6 launch (Geosync), and September 21st - Dragon CRS-4 (ISS).

~~~
avmich
Agree. And those Merlin-1D seem to be very efficient from economical point of
view. Technically they are also good - record setting for open cycle engines.

However, NK-33 are closed cycle and have better Isp. Economically they also
made a lot of sense for Orbital, since they were bought as already made for
another project. It can be justified.

------
brandonmenc
The B-52 is just as old, and is expected to have served for almost a century
once retired. It's not the same as rockets, but "oh it's old" isn't as
compelling of an argument as failure rate, which - how many have there been
using these engines?

Is that data available?

~~~
venomsnake
"We saw rust and crack, so we repaired them" seems like the culprit. Not the
age.

~~~
alf
Which begs the question... If they don't know enough about rockets to build
them, how can they possibly know how to safely repair them?

~~~
avmich
I don't know enough about computers to make my own PC from scratch. I however
can fix some problems with PC. So you can have one without another.

------
pbreit
My admittedly uninformed opinion is that it just doesn't make any sense. I
don't care how good the Russians are/were at making rockets. First of all,
surely there has been significant progress in all aspects of the design and
manufacturing of such an item. And second, who knows how well the engines have
been stored, cared for, maintained and transported over the past 40 years. I
would think you'd want to have more visibility into such a thing for this type
of component.

Elon: It “has a contract to resupply the International Space Station, and
their rocket honestly sounds like the punch line to a joke,” he said. “It uses
Russian rocket engines that were made in the ’60s. I don’t mean their design
is from the ’60s — I mean they start with engines that were literally made in
the ’60s and, like, packed away in Siberia somewhere.”

Orbital: "we did discover there were some effects of aging since they had been
in storage for awhile, including some stress corrosion cracking,”

I could see Elon offering to supply Orbital with some US-made engines. But
maybe that wouldn't satisfy NASA's desire for diversity.

~~~
avmich
Uninformed, yes :( .

There are theoretical limits for how high Isp - the specific impulse, defined
as how much thrust, in, say, pounds of force, you can get from a unit of fuel
flow, going into the engine, in, say, pounds of mass per second. The engines
created in '60s are already rather close to that theoretical limit - so saying
that you can do much better just because decades has passed is similar to
saying "well, surely we had SR-71 flying back in '70s already - by today we
ought to have all civil aviation routinely doing at least Mach 2".

So - no, it's pretty hard, including for fundamental reasons, to make engines
much better that NK-33 by Isp. And that parameter is of paramount importance
for a rocket engine.

Mind you, this is still not the only parameter. After all, you probably care a
lot about economic efficiency. Elon Musk seems to understand that pretty well
- and SpaceX engines, while lacking technically, could be in a much better
position economically. Next, you're right that design and manufacturing aren't
standing still. Both control of materials parameters and the ability to
convert the raw material into an engineered device substantially rose -
talking about, say, 3D printing engines or parts, which happens rather
frequently now, but didn't in '70s.

So it's a complicated matter. However, NK-33 still have good technical
parameters, and were bought inexpensively - in '90s, when Russia was severely
starved for cash. Why not to use something which is already there, and not
expensive? That's quite a rational decision Orbital - and Aerojet before them
- took.

Regarding the second part, about storage. Surely this is unprecedented case.
That's why the engines were tested - many times, both in Russia and in USA,
and also analysed, trying to predict how several decades of storage could
affect engines. The results were apparently positive - of course you and I
don't have the original raw data which was used to make that decision. But
don't think the engines just were, say, buried underground; their storage
history is roughly known and isn't that different from other products of heavy
machinery industry.

So I think Elon is habitually being overreacting in regard to Orbital usage of
those engines. May be it has something to do with Elon's unsuccessful attempts
to strike a deal with Russian space industry back when SpaceX was really young
- or may be it's just a tradition for him, Elon sometimes says something out
of proportions, even though SpaceX real - smaller - results are undeniable.
Elon misses the point - it's only for uninformed the phrase "rocket engines
made in USSR 40 years ago" would mean "unacceptable variant". George Sutton,
author of "History of Liquid Propellant Rocket Engines" mentions that USSR
spent far more towards rocket engine research than all other countries
combined, and NK-33 is one of the serious achievements of Soviet rocket
school. Don't discount something off hand just because it's old and foreign.

~~~
pbreit
The only thing I was not referring to were the technical parameters.

~~~
avmich
They are important to make a good decision. Efficiency, mass, reliability,
price... You can't just ignore them.

------
njsteinsund
I can highly recommend these two books for an engaging introduction to getting
things right in the rocket business: Ignition! An informal history of liquid
rocket propellants
[http://www.goodreads.com/book/show/677285.Ignition_](http://www.goodreads.com/book/show/677285.Ignition_)
and Space Systems Failures: Disasters and Rescues of Satellites, Rocket and
Space Probes
[http://www.goodreads.com/book/show/1015478.Space_Systems_Fai...](http://www.goodreads.com/book/show/1015478.Space_Systems_Failures)

------
ijk
Also note that we don't know yet if the NK-33/AJ-26 engine was the cause of
failure. Sometimes the most visible possibility wasn't the original cause of
the problem.

------
ianstallings
I don't think it's so much about age as it is about design. From my
understanding the original NK 33 rocket engines used a unique oxygen-rich fuel
turbo-pump mechanism that the west considered too dangerous. Aerojet-
Rocketdyne took these engines and refurbished them and therein lies the
question. But I think it might be premature to ask this given they haven't
told us what happened.

The thing is they are very powerful engines and the price was right.

~~~
avmich
It's not that unique - in Russian space school oxidizer-rich turbines are
routine. Proton, for example, used to have - until latest years - a pretty
solid track record, especially for first stage engines, and those engines use
N2O4 for turbines. Considering that N2O4 is burned with some amount of
(CH3)2N-NH2, making HNO3... the gas going to chamber from turbine is the
nitric acid. Still engines work just fine.

One of big reasons for Russians to use oxydizer-reach gas generators is that
on the rocket there usually much more oxidizer - by mass - than fuel, which
makes the flow through the turbine much bigger - several times. So efficiency
of turbopumps goes up. That justifies the complexity of having oxidizer-rich
gas flow before the chamber.

------
diminoten
For someone who doesn't know much about aerospace engineering, can someone
outline the actual challenge with getting something like this right?

What's the missing piece that'll effectively eliminate accidents like this? Or
is this one of those things that will just happen from time to time because
going to space takes a lot of math that we don't fully understand yet?

I was just under the impression that this was a very well known area of
science.

~~~
austinz
With these particular engines, you also have the variable factor of them being
stored for decades in a warehouse, and all the issues with metal corrosion,
fatigue, degradation, etc. that come with that.

I'm not a materials engineer, but I could imagine things like seasonal
temperature changes, humidity, rough handling, changes in the metallurgical
properties of the alloys they used over time could all affect the ability of
the engine components to withstand high temperatures and pressures.

------
marze
So these engines were built when Paul McCartney was 23 years old?

Apparently Orbital Sciences scoured the museums and antique shops in Russia
and picked up enough of these engines to base a new rocket on them.

The reason they were surplus was that the rocket that they were built for was
canceled, because the engines exploded on each of the four test launches
conducted.

Orbital Sciences was once a scrappy startup. Books were written about it.
However, this is just embarrassing.

~~~
avmich
Aerojet bought those engines from Russia - the original manufacturer - in
1990-s. No need for Orbital to scour museums.

No, engines didn't explode. Were actually never flown before the first Antares
lifted off. But performed pretty well on stands.

~~~
marze
Are you were claiming that there were no failures of the NK-33 engine on any
of the four N1 flights that exploded during first stage burn?

~~~
avmich
Yes.

NK-33 never flew on N-1. They were intended to fly on N-1 in its fifth flight
- which never happened, because Glushko closed the program after becoming the
head of the Energiya company.

~~~
marze
So before the engines were obtained by Orbital, the NK-33 had never even been
flight tested?

~~~
avmich
Before the engines flew for the first time, yes they never flew before. And
Antares is the first rocket where those engines have flied - though not the
only one rocket already.

------
mladenkovacevic
When all else fails, blame Russia.

~~~
Correctille
No one is blaming Russia.

We're blaming the age of rocket engines (that just happened to come from
Russia).

~~~
CmonDev
And why not prominently state "Soviet" in the title.

------
tomswartz07
Here's the thing: the rocket itself is not 'decades old'. The design is.

This is tantamount to saying "Oh, cars use a decades old design.. they must be
terrible!"

The article also completely overlooks the fact that Russia launched a rocket
with the supplies within 24 hours of the failure.
[http://news.yahoo.com/cause-sought-space-supply-
rocket-08252...](http://news.yahoo.com/cause-sought-space-supply-
rocket-082528475.html)

~~~
ChuckMcM
Not exactly. The engines themselves _are_ decades old, Orbital Science is
quoted as saying

 _" 'As we went through testing, we did discover there were some effects of
aging since they had been in storage for awhile, including some stress
corrosion cracking,' Culbertson conceded at the time. 'That’s what we
[corrected] with weld repairs and other inspections.'"_

They got the engines that were decades old, and they've been fixing problems
that they have found, and refurbishing them and installing them into rockets.
It doesn't say they have built new engines on the old designs. That would have
been better, because then you would have someone who had designed the engine
on staff and could understand it in a deep way.

Presumably Orbital is designing their own engines now, or contracting with
someone to do so, perhaps their go to market strategy was "Get some things
into space with these old surplus engines, use the revenue/time to
design/test/manufacture our own engines, and then continue on with our own
bespoke design." I don't know of course if that was their intention or not.

~~~
avmich
Orbital now has ATK experience on board. Feels natural to switch to all-solid
rockets - like other Orbital designs. However for now, the Antares is the
biggest Orbital rocket, and it's designed with NK-33. Definitely need to
investigate this event and make decisions.

It's better to use engines which were just created - or just manufactured -
but sometimes there are reasons to prefer old engines to new ones. Age is not
the only factor.

