Why was the engine of the launch vehicle recently tested in Iran “not a very good missile engine”?
$begingroup$
The NPR News item What's Iran Up To With Recent Rocket Launch Attempt? by NPR's Geoff Brumfiel, about a recent launch test in Iran includes the following:
Earlier this week, Iran attempted to launch a rocket carrying a satellite into space. The Trump administration says their goal is really to develop long-range weapons. NPR's Geoff Brumfiel looks into what Iran is up to.
[...]
Markus Schiller is the founder of ST Analytics, an independent consultancy in Germany. He's spent a lot of time looking at Iran's space program, and he says there are links to the military. For example, the engines Iran uses on its space rockets have a military origin.
MARKUS SCHILLER: It's actually a missile engine.
BRUMFIEL/NPR: But Schiller says it's not a very good missile engine. It's an old design from the Soviet Union, picked up by the North Koreans and later transferred to Iran. It's clunky and inefficient. To get even a small payload into space requires the rocket to be huge. It takes weeks to set up.
Also, Schiller says, based on photos, Iran's space rocket can't work as a missile. The second stage is just too small. To him, the launch looks nonthreatening.
Question: What actual engine are they talking about, and in what way is it "not a very good missile engine"? Why would this engine require "the rocket to be huge"?
engines launch-vehicle iran
asked 2 days ago
uhohuhoh
36k18127449
$endgroup$
|
show 6 more comments
$begingroup$
The NPR News item What's Iran Up To With Recent Rocket Launch Attempt? by NPR's Geoff Brumfiel, about a recent launch test in Iran includes the following:
Earlier this week, Iran attempted to launch a rocket carrying a satellite into space. The Trump administration says their goal is really to develop long-range weapons. NPR's Geoff Brumfiel looks into what Iran is up to.
[...]
Markus Schiller is the founder of ST Analytics, an independent consultancy in Germany. He's spent a lot of time looking at Iran's space program, and he says there are links to the military. For example, the engines Iran uses on its space rockets have a military origin.
MARKUS SCHILLER: It's actually a missile engine.
BRUMFIEL/NPR: But Schiller says it's not a very good missile engine. It's an old design from the Soviet Union, picked up by the North Koreans and later transferred to Iran. It's clunky and inefficient. To get even a small payload into space requires the rocket to be huge. It takes weeks to set up.
Also, Schiller says, based on photos, Iran's space rocket can't work as a missile. The second stage is just too small. To him, the launch looks nonthreatening.
Question: What actual engine are they talking about, and in what way is it "not a very good missile engine"? Why would this engine require "the rocket to be huge"?
engines launch-vehicle iran
asked 2 days ago
uhohuhoh
36k18127449
$endgroup$
6
$begingroup$
taking weeks to set up would make it a very poor missile engine -- the Thor missiles the UK bought from the US were criticised for their 15 minute launch time.
$endgroup$
– JCRM
2 days ago
3
$begingroup$
an inefficient engine requires more fuel, requiring exponentially larger fuel tanks because of the rocket equation.
$endgroup$
– JCRM
2 days ago
1
$begingroup$
your source said it was inefficient, not undersized. Insufficient thrust can be worked around by using multiple engines or a kick stage
$endgroup$
– JCRM
2 days ago
1
$begingroup$
@jamesqf it goes into the trade space because an engine with bad Isp causes the vehicle to get larger for a given mission. So the missiles' launchers, fueling systems, etc, etc all get bigger. But which is cheaper, building a big launch trailer or developing a better engine?
$endgroup$
– Organic Marble
2 days ago
2
$begingroup$
Wouldn't it be more threatening if you're testing an "orbital" rocket design with an engine that has a very low hope of getting anything useful into space? That sounds like a passable IRBM then.
$endgroup$
– Nick T
2 days ago
|
show 6 more comments
$begingroup$
The NPR News item What's Iran Up To With Recent Rocket Launch Attempt? by NPR's Geoff Brumfiel, about a recent launch test in Iran includes the following:
Earlier this week, Iran attempted to launch a rocket carrying a satellite into space. The Trump administration says their goal is really to develop long-range weapons. NPR's Geoff Brumfiel looks into what Iran is up to.
[...]
Markus Schiller is the founder of ST Analytics, an independent consultancy in Germany. He's spent a lot of time looking at Iran's space program, and he says there are links to the military. For example, the engines Iran uses on its space rockets have a military origin.
MARKUS SCHILLER: It's actually a missile engine.
BRUMFIEL/NPR: But Schiller says it's not a very good missile engine. It's an old design from the Soviet Union, picked up by the North Koreans and later transferred to Iran. It's clunky and inefficient. To get even a small payload into space requires the rocket to be huge. It takes weeks to set up.
Also, Schiller says, based on photos, Iran's space rocket can't work as a missile. The second stage is just too small. To him, the launch looks nonthreatening.
Question: What actual engine are they talking about, and in what way is it "not a very good missile engine"? Why would this engine require "the rocket to be huge"?
engines launch-vehicle iran
asked 2 days ago
uhohuhoh
36k18127449
$endgroup$
The NPR News item What's Iran Up To With Recent Rocket Launch Attempt? by NPR's Geoff Brumfiel, about a recent launch test in Iran includes the following:
Earlier this week, Iran attempted to launch a rocket carrying a satellite into space. The Trump administration says their goal is really to develop long-range weapons. NPR's Geoff Brumfiel looks into what Iran is up to.
[...]
Markus Schiller is the founder of ST Analytics, an independent consultancy in Germany. He's spent a lot of time looking at Iran's space program, and he says there are links to the military. For example, the engines Iran uses on its space rockets have a military origin.
MARKUS SCHILLER: It's actually a missile engine.
BRUMFIEL/NPR: But Schiller says it's not a very good missile engine. It's an old design from the Soviet Union, picked up by the North Koreans and later transferred to Iran. It's clunky and inefficient. To get even a small payload into space requires the rocket to be huge. It takes weeks to set up.
Also, Schiller says, based on photos, Iran's space rocket can't work as a missile. The second stage is just too small. To him, the launch looks nonthreatening.
Question: What actual engine are they talking about, and in what way is it "not a very good missile engine"? Why would this engine require "the rocket to be huge"?
engines launch-vehicle iran
engines launch-vehicle iran
asked 2 days ago
uhohuhoh
36k18127449
asked 2 days ago
uhohuhoh
36k18127449
edited 2 days ago
uhoh
asked 2 days ago
uhohuhoh
36k18127449
asked 2 days ago
uhohuhoh
36k18127449
asked 2 days ago
uhohuhoh
36k18127449
36k18127449
6
$begingroup$
taking weeks to set up would make it a very poor missile engine -- the Thor missiles the UK bought from the US were criticised for their 15 minute launch time.
$endgroup$
– JCRM
2 days ago
3
$begingroup$
an inefficient engine requires more fuel, requiring exponentially larger fuel tanks because of the rocket equation.
$endgroup$
– JCRM
2 days ago
1
$begingroup$
your source said it was inefficient, not undersized. Insufficient thrust can be worked around by using multiple engines or a kick stage
$endgroup$
– JCRM
2 days ago
1
$begingroup$
@jamesqf it goes into the trade space because an engine with bad Isp causes the vehicle to get larger for a given mission. So the missiles' launchers, fueling systems, etc, etc all get bigger. But which is cheaper, building a big launch trailer or developing a better engine?
$endgroup$
– Organic Marble
2 days ago
2
$begingroup$
Wouldn't it be more threatening if you're testing an "orbital" rocket design with an engine that has a very low hope of getting anything useful into space? That sounds like a passable IRBM then.
$endgroup$
– Nick T
2 days ago
|
show 6 more comments
6
$begingroup$
taking weeks to set up would make it a very poor missile engine -- the Thor missiles the UK bought from the US were criticised for their 15 minute launch time.
$endgroup$
– JCRM
2 days ago
3
$begingroup$
an inefficient engine requires more fuel, requiring exponentially larger fuel tanks because of the rocket equation.
$endgroup$
– JCRM
2 days ago
1
$begingroup$
your source said it was inefficient, not undersized. Insufficient thrust can be worked around by using multiple engines or a kick stage
$endgroup$
– JCRM
2 days ago
1
$begingroup$
@jamesqf it goes into the trade space because an engine with bad Isp causes the vehicle to get larger for a given mission. So the missiles' launchers, fueling systems, etc, etc all get bigger. But which is cheaper, building a big launch trailer or developing a better engine?
$endgroup$
– Organic Marble
2 days ago
2
$begingroup$
Wouldn't it be more threatening if you're testing an "orbital" rocket design with an engine that has a very low hope of getting anything useful into space? That sounds like a passable IRBM then.
$endgroup$
– Nick T
2 days ago
6
6
$begingroup$
taking weeks to set up would make it a very poor missile engine -- the Thor missiles the UK bought from the US were criticised for their 15 minute launch time.
$endgroup$
– JCRM
2 days ago
$begingroup$
taking weeks to set up would make it a very poor missile engine -- the Thor missiles the UK bought from the US were criticised for their 15 minute launch time.
$endgroup$
– JCRM
2 days ago
3
3
$begingroup$
an inefficient engine requires more fuel, requiring exponentially larger fuel tanks because of the rocket equation.
$endgroup$
– JCRM
2 days ago
$begingroup$
an inefficient engine requires more fuel, requiring exponentially larger fuel tanks because of the rocket equation.
$endgroup$
– JCRM
2 days ago
1
1
$begingroup$
your source said it was inefficient, not undersized. Insufficient thrust can be worked around by using multiple engines or a kick stage
$endgroup$
– JCRM
2 days ago
$begingroup$
your source said it was inefficient, not undersized. Insufficient thrust can be worked around by using multiple engines or a kick stage
$endgroup$
– JCRM
2 days ago
1
1
$begingroup$
@jamesqf it goes into the trade space because an engine with bad Isp causes the vehicle to get larger for a given mission. So the missiles' launchers, fueling systems, etc, etc all get bigger. But which is cheaper, building a big launch trailer or developing a better engine?
$endgroup$
– Organic Marble
2 days ago
$begingroup$
@jamesqf it goes into the trade space because an engine with bad Isp causes the vehicle to get larger for a given mission. So the missiles' launchers, fueling systems, etc, etc all get bigger. But which is cheaper, building a big launch trailer or developing a better engine?
$endgroup$
– Organic Marble
2 days ago
2
2
$begingroup$
Wouldn't it be more threatening if you're testing an "orbital" rocket design with an engine that has a very low hope of getting anything useful into space? That sounds like a passable IRBM then.
$endgroup$
– Nick T
2 days ago
$begingroup$
Wouldn't it be more threatening if you're testing an "orbital" rocket design with an engine that has a very low hope of getting anything useful into space? That sounds like a passable IRBM then.
$endgroup$
– Nick T
2 days ago
|
show 6 more comments
3 Answers
3
active
oldest
votes
$begingroup$
What actual engine are they talking about
Organic Marble has identified it as the S5.2/9D21.
in what way is it "not a very good missile engine"?
It uses a propellant combination, kerosene/IRFNA, common for military missiles in the 1950s-1960s, but now considered obsolete, which yields a poor specific impulse (233 seconds at sea level, or effective exhaust velocity of 2285 m/s).
Why would this engine require "the rocket to be huge"?
Rearranging the rocket equation:
$$Delta v = v_text{e} ln frac {m_0} {m_f}$$
to
$$e ^ frac {Delta v} { v_text{e} } = frac {m_0} {m_f}$$
shows that the mass of a rocket is proportional to the exponential of (delta-v divided by effective exhaust velocity). Small changes in the exhaust velocity can yield large changes in mass.
Assuming ~9400 m/s delta-v required to reach orbit, a 233 second engine requires an initial-mass-to-final-mass ratio of around 60; a good modern kerosene/LOX engine like the RD-180 of Atlas V has a specific impulse of 311 seconds at sea level, which requires a mass ratio of around 20 -- a 3x lighter rocket from a 33% more efficient engine.
The statement "not a very good missile engine" needs qualification; it's not a very good long-range missile engine (which, to be fair, is an important question about Iranian engines if you're a German analyst) because of the low specific impulse. The SCUD series the engine is derived from is a ~300km range tactical missile; for such a short flight the required ∆v is much lower; it's thus in a shallower part of the exponential curve and the penalty for poor specific impulse is much smaller.
answered 2 days ago
Russell BorogoveRussell Borogove
84.5k3283367
$endgroup$
$begingroup$
tag-teams? is the gamification of SE moving to a new level? ;-)
$endgroup$
– uhoh
2 days ago
3
$begingroup$
@uhoh now you can edit all three together and post the perfect answer you seek!
$endgroup$
– Organic Marble
2 days ago
3
$begingroup$
You know I can't pass up a chance to link the rocket equation and specific impulse WP pages.
$endgroup$
– Russell Borogove
2 days ago
$begingroup$
Your last sentence provides a lot of insight.
$endgroup$
– uhoh
2 days ago
1
$begingroup$
I said the propellant combo was obsolete, but, I mean, yeah? Russia fields solid-fueled rockets in the short-range ballistic role these days. SS-21, SS-23, SS-26 for example. Solids are much safer to operate.
$endgroup$
– Russell Borogove
yesterday
|
show 2 more comments
$begingroup$
Supplemental answer: Scud missiles were powered by the S5.2/9D21 engine, burning inhibited red fuming nitric acid and kerosene.
Thrust is 132 kN, Isp is "2285 Nskg" or ~233 seconds.
Sources: 1,2,3
answered 2 days ago
Organic MarbleOrganic Marble
54.6k3145233
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2
$begingroup$
Ns/kg is newton-seconds per kilogram, the “correct” SI unit for specific impulse, equivalent to meters per second. Divide by 9.806 to get ISP in seconds.
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– Russell Borogove
2 days ago
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Thanks. I was just looking at the wikipedia article and found that in there as well.
$endgroup$
– Organic Marble
2 days ago
2
$begingroup$
And a hell of an oxidizer to handle in the field! Wow.
$endgroup$
– Organic Marble
2 days ago
1
$begingroup$
adding that even under ideal conditions that ISP could only get about 1.5% of launch mass to orbit (and this isn't an ideal rocket) would make this a complete answer.
$endgroup$
– uhoh
2 days ago
4
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I rolled back the edit because the units on Isp are exactly what was in the source document, hence the quote marks.
$endgroup$
– Organic Marble
2 days ago
|
show 1 more comment
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According to Gunter's web site, this launcher originated in the Shahab-5 IRBM, which is a continuation of the Scud-D / No-dong-A, No-dong-B and Shahab-5 / 6 / Taep’o-dong-2B / Unha-2
And Scud-D is originated in Soviet R-17 military missle
answered 2 days ago
Pavel BernshtamPavel Bernshtam
2,759926
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1
$begingroup$
Is it possible to name the engine itself or at least say something about its capability in terms of orbital applications?
$endgroup$
– uhoh
2 days ago
add a comment |
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3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
What actual engine are they talking about
Organic Marble has identified it as the S5.2/9D21.
in what way is it "not a very good missile engine"?
It uses a propellant combination, kerosene/IRFNA, common for military missiles in the 1950s-1960s, but now considered obsolete, which yields a poor specific impulse (233 seconds at sea level, or effective exhaust velocity of 2285 m/s).
Why would this engine require "the rocket to be huge"?
Rearranging the rocket equation:
$$Delta v = v_text{e} ln frac {m_0} {m_f}$$
to
$$e ^ frac {Delta v} { v_text{e} } = frac {m_0} {m_f}$$
shows that the mass of a rocket is proportional to the exponential of (delta-v divided by effective exhaust velocity). Small changes in the exhaust velocity can yield large changes in mass.
Assuming ~9400 m/s delta-v required to reach orbit, a 233 second engine requires an initial-mass-to-final-mass ratio of around 60; a good modern kerosene/LOX engine like the RD-180 of Atlas V has a specific impulse of 311 seconds at sea level, which requires a mass ratio of around 20 -- a 3x lighter rocket from a 33% more efficient engine.
The statement "not a very good missile engine" needs qualification; it's not a very good long-range missile engine (which, to be fair, is an important question about Iranian engines if you're a German analyst) because of the low specific impulse. The SCUD series the engine is derived from is a ~300km range tactical missile; for such a short flight the required ∆v is much lower; it's thus in a shallower part of the exponential curve and the penalty for poor specific impulse is much smaller.
answered 2 days ago
Russell BorogoveRussell Borogove
84.5k3283367
$endgroup$
$begingroup$
tag-teams? is the gamification of SE moving to a new level? ;-)
$endgroup$
– uhoh
2 days ago
3
$begingroup$
@uhoh now you can edit all three together and post the perfect answer you seek!
$endgroup$
– Organic Marble
2 days ago
3
$begingroup$
You know I can't pass up a chance to link the rocket equation and specific impulse WP pages.
$endgroup$
– Russell Borogove
2 days ago
$begingroup$
Your last sentence provides a lot of insight.
$endgroup$
– uhoh
2 days ago
1
$begingroup$
I said the propellant combo was obsolete, but, I mean, yeah? Russia fields solid-fueled rockets in the short-range ballistic role these days. SS-21, SS-23, SS-26 for example. Solids are much safer to operate.
$endgroup$
– Russell Borogove
yesterday
|
show 2 more comments
$begingroup$
What actual engine are they talking about
Organic Marble has identified it as the S5.2/9D21.
in what way is it "not a very good missile engine"?
It uses a propellant combination, kerosene/IRFNA, common for military missiles in the 1950s-1960s, but now considered obsolete, which yields a poor specific impulse (233 seconds at sea level, or effective exhaust velocity of 2285 m/s).
Why would this engine require "the rocket to be huge"?
Rearranging the rocket equation:
$$Delta v = v_text{e} ln frac {m_0} {m_f}$$
to
$$e ^ frac {Delta v} { v_text{e} } = frac {m_0} {m_f}$$
shows that the mass of a rocket is proportional to the exponential of (delta-v divided by effective exhaust velocity). Small changes in the exhaust velocity can yield large changes in mass.
Assuming ~9400 m/s delta-v required to reach orbit, a 233 second engine requires an initial-mass-to-final-mass ratio of around 60; a good modern kerosene/LOX engine like the RD-180 of Atlas V has a specific impulse of 311 seconds at sea level, which requires a mass ratio of around 20 -- a 3x lighter rocket from a 33% more efficient engine.
The statement "not a very good missile engine" needs qualification; it's not a very good long-range missile engine (which, to be fair, is an important question about Iranian engines if you're a German analyst) because of the low specific impulse. The SCUD series the engine is derived from is a ~300km range tactical missile; for such a short flight the required ∆v is much lower; it's thus in a shallower part of the exponential curve and the penalty for poor specific impulse is much smaller.
answered 2 days ago
Russell BorogoveRussell Borogove
84.5k3283367
$endgroup$
$begingroup$
tag-teams? is the gamification of SE moving to a new level? ;-)
$endgroup$
– uhoh
2 days ago
3
$begingroup$
@uhoh now you can edit all three together and post the perfect answer you seek!
$endgroup$
– Organic Marble
2 days ago
3
$begingroup$
You know I can't pass up a chance to link the rocket equation and specific impulse WP pages.
$endgroup$
– Russell Borogove
2 days ago
$begingroup$
Your last sentence provides a lot of insight.
$endgroup$
– uhoh
2 days ago
1
$begingroup$
I said the propellant combo was obsolete, but, I mean, yeah? Russia fields solid-fueled rockets in the short-range ballistic role these days. SS-21, SS-23, SS-26 for example. Solids are much safer to operate.
$endgroup$
– Russell Borogove
yesterday
|
show 2 more comments
$begingroup$
What actual engine are they talking about
Organic Marble has identified it as the S5.2/9D21.
in what way is it "not a very good missile engine"?
It uses a propellant combination, kerosene/IRFNA, common for military missiles in the 1950s-1960s, but now considered obsolete, which yields a poor specific impulse (233 seconds at sea level, or effective exhaust velocity of 2285 m/s).
Why would this engine require "the rocket to be huge"?
Rearranging the rocket equation:
$$Delta v = v_text{e} ln frac {m_0} {m_f}$$
to
$$e ^ frac {Delta v} { v_text{e} } = frac {m_0} {m_f}$$
shows that the mass of a rocket is proportional to the exponential of (delta-v divided by effective exhaust velocity). Small changes in the exhaust velocity can yield large changes in mass.
Assuming ~9400 m/s delta-v required to reach orbit, a 233 second engine requires an initial-mass-to-final-mass ratio of around 60; a good modern kerosene/LOX engine like the RD-180 of Atlas V has a specific impulse of 311 seconds at sea level, which requires a mass ratio of around 20 -- a 3x lighter rocket from a 33% more efficient engine.
The statement "not a very good missile engine" needs qualification; it's not a very good long-range missile engine (which, to be fair, is an important question about Iranian engines if you're a German analyst) because of the low specific impulse. The SCUD series the engine is derived from is a ~300km range tactical missile; for such a short flight the required ∆v is much lower; it's thus in a shallower part of the exponential curve and the penalty for poor specific impulse is much smaller.
answered 2 days ago
Russell BorogoveRussell Borogove
84.5k3283367
$endgroup$
What actual engine are they talking about
Organic Marble has identified it as the S5.2/9D21.
in what way is it "not a very good missile engine"?
It uses a propellant combination, kerosene/IRFNA, common for military missiles in the 1950s-1960s, but now considered obsolete, which yields a poor specific impulse (233 seconds at sea level, or effective exhaust velocity of 2285 m/s).
Why would this engine require "the rocket to be huge"?
Rearranging the rocket equation:
$$Delta v = v_text{e} ln frac {m_0} {m_f}$$
to
$$e ^ frac {Delta v} { v_text{e} } = frac {m_0} {m_f}$$
shows that the mass of a rocket is proportional to the exponential of (delta-v divided by effective exhaust velocity). Small changes in the exhaust velocity can yield large changes in mass.
Assuming ~9400 m/s delta-v required to reach orbit, a 233 second engine requires an initial-mass-to-final-mass ratio of around 60; a good modern kerosene/LOX engine like the RD-180 of Atlas V has a specific impulse of 311 seconds at sea level, which requires a mass ratio of around 20 -- a 3x lighter rocket from a 33% more efficient engine.
The statement "not a very good missile engine" needs qualification; it's not a very good long-range missile engine (which, to be fair, is an important question about Iranian engines if you're a German analyst) because of the low specific impulse. The SCUD series the engine is derived from is a ~300km range tactical missile; for such a short flight the required ∆v is much lower; it's thus in a shallower part of the exponential curve and the penalty for poor specific impulse is much smaller.
answered 2 days ago
Russell BorogoveRussell Borogove
84.5k3283367
edited yesterday
answered 2 days ago
Russell BorogoveRussell Borogove
84.5k3283367
answered 2 days ago
Russell BorogoveRussell Borogove
84.5k3283367
answered 2 days ago
Russell BorogoveRussell Borogove
84.5k3283367
84.5k3283367
$begingroup$
tag-teams? is the gamification of SE moving to a new level? ;-)
$endgroup$
– uhoh
2 days ago
3
$begingroup$
@uhoh now you can edit all three together and post the perfect answer you seek!
$endgroup$
– Organic Marble
2 days ago
3
$begingroup$
You know I can't pass up a chance to link the rocket equation and specific impulse WP pages.
$endgroup$
– Russell Borogove
2 days ago
$begingroup$
Your last sentence provides a lot of insight.
$endgroup$
– uhoh
2 days ago
1
$begingroup$
I said the propellant combo was obsolete, but, I mean, yeah? Russia fields solid-fueled rockets in the short-range ballistic role these days. SS-21, SS-23, SS-26 for example. Solids are much safer to operate.
$endgroup$
– Russell Borogove
yesterday
|
show 2 more comments
$begingroup$
tag-teams? is the gamification of SE moving to a new level? ;-)
$endgroup$
– uhoh
2 days ago
3
$begingroup$
@uhoh now you can edit all three together and post the perfect answer you seek!
$endgroup$
– Organic Marble
2 days ago
3
$begingroup$
You know I can't pass up a chance to link the rocket equation and specific impulse WP pages.
$endgroup$
– Russell Borogove
2 days ago
$begingroup$
Your last sentence provides a lot of insight.
$endgroup$
– uhoh
2 days ago
1
$begingroup$
I said the propellant combo was obsolete, but, I mean, yeah? Russia fields solid-fueled rockets in the short-range ballistic role these days. SS-21, SS-23, SS-26 for example. Solids are much safer to operate.
$endgroup$
– Russell Borogove
yesterday
$begingroup$
tag-teams? is the gamification of SE moving to a new level? ;-)
$endgroup$
– uhoh
2 days ago
$begingroup$
tag-teams? is the gamification of SE moving to a new level? ;-)
$endgroup$
– uhoh
2 days ago
3
3
$begingroup$
@uhoh now you can edit all three together and post the perfect answer you seek!
$endgroup$
– Organic Marble
2 days ago
$begingroup$
@uhoh now you can edit all three together and post the perfect answer you seek!
$endgroup$
– Organic Marble
2 days ago
3
3
$begingroup$
You know I can't pass up a chance to link the rocket equation and specific impulse WP pages.
$endgroup$
– Russell Borogove
2 days ago
$begingroup$
You know I can't pass up a chance to link the rocket equation and specific impulse WP pages.
$endgroup$
– Russell Borogove
2 days ago
$begingroup$
Your last sentence provides a lot of insight.
$endgroup$
– uhoh
2 days ago
$begingroup$
Your last sentence provides a lot of insight.
$endgroup$
– uhoh
2 days ago
1
1
$begingroup$
I said the propellant combo was obsolete, but, I mean, yeah? Russia fields solid-fueled rockets in the short-range ballistic role these days. SS-21, SS-23, SS-26 for example. Solids are much safer to operate.
$endgroup$
– Russell Borogove
yesterday
$begingroup$
I said the propellant combo was obsolete, but, I mean, yeah? Russia fields solid-fueled rockets in the short-range ballistic role these days. SS-21, SS-23, SS-26 for example. Solids are much safer to operate.
$endgroup$
– Russell Borogove
yesterday
|
show 2 more comments
$begingroup$
Supplemental answer: Scud missiles were powered by the S5.2/9D21 engine, burning inhibited red fuming nitric acid and kerosene.
Thrust is 132 kN, Isp is "2285 Nskg" or ~233 seconds.
Sources: 1,2,3
answered 2 days ago
Organic MarbleOrganic Marble
54.6k3145233
$endgroup$
2
$begingroup$
Ns/kg is newton-seconds per kilogram, the “correct” SI unit for specific impulse, equivalent to meters per second. Divide by 9.806 to get ISP in seconds.
$endgroup$
– Russell Borogove
2 days ago
$begingroup$
Thanks. I was just looking at the wikipedia article and found that in there as well.
$endgroup$
– Organic Marble
2 days ago
2
$begingroup$
And a hell of an oxidizer to handle in the field! Wow.
$endgroup$
– Organic Marble
2 days ago
1
$begingroup$
adding that even under ideal conditions that ISP could only get about 1.5% of launch mass to orbit (and this isn't an ideal rocket) would make this a complete answer.
$endgroup$
– uhoh
2 days ago
4
$begingroup$
I rolled back the edit because the units on Isp are exactly what was in the source document, hence the quote marks.
$endgroup$
– Organic Marble
2 days ago
|
show 1 more comment
$begingroup$
Supplemental answer: Scud missiles were powered by the S5.2/9D21 engine, burning inhibited red fuming nitric acid and kerosene.
Thrust is 132 kN, Isp is "2285 Nskg" or ~233 seconds.
Sources: 1,2,3
answered 2 days ago
Organic MarbleOrganic Marble
54.6k3145233
$endgroup$
2
$begingroup$
Ns/kg is newton-seconds per kilogram, the “correct” SI unit for specific impulse, equivalent to meters per second. Divide by 9.806 to get ISP in seconds.
$endgroup$
– Russell Borogove
2 days ago
$begingroup$
Thanks. I was just looking at the wikipedia article and found that in there as well.
$endgroup$
– Organic Marble
2 days ago
2
$begingroup$
And a hell of an oxidizer to handle in the field! Wow.
$endgroup$
– Organic Marble
2 days ago
1
$begingroup$
adding that even under ideal conditions that ISP could only get about 1.5% of launch mass to orbit (and this isn't an ideal rocket) would make this a complete answer.
$endgroup$
– uhoh
2 days ago
4
$begingroup$
I rolled back the edit because the units on Isp are exactly what was in the source document, hence the quote marks.
$endgroup$
– Organic Marble
2 days ago
|
show 1 more comment
$begingroup$
Supplemental answer: Scud missiles were powered by the S5.2/9D21 engine, burning inhibited red fuming nitric acid and kerosene.
Thrust is 132 kN, Isp is "2285 Nskg" or ~233 seconds.
Sources: 1,2,3
answered 2 days ago
Organic MarbleOrganic Marble
54.6k3145233
$endgroup$
Supplemental answer: Scud missiles were powered by the S5.2/9D21 engine, burning inhibited red fuming nitric acid and kerosene.
Thrust is 132 kN, Isp is "2285 Nskg" or ~233 seconds.
Sources: 1,2,3
answered 2 days ago
Organic MarbleOrganic Marble
54.6k3145233
edited 2 days ago
answered 2 days ago
Organic MarbleOrganic Marble
54.6k3145233
answered 2 days ago
Organic MarbleOrganic Marble
54.6k3145233
answered 2 days ago
Organic MarbleOrganic Marble
54.6k3145233
54.6k3145233
2
$begingroup$
Ns/kg is newton-seconds per kilogram, the “correct” SI unit for specific impulse, equivalent to meters per second. Divide by 9.806 to get ISP in seconds.
$endgroup$
– Russell Borogove
2 days ago
$begingroup$
Thanks. I was just looking at the wikipedia article and found that in there as well.
$endgroup$
– Organic Marble
2 days ago
2
$begingroup$
And a hell of an oxidizer to handle in the field! Wow.
$endgroup$
– Organic Marble
2 days ago
1
$begingroup$
adding that even under ideal conditions that ISP could only get about 1.5% of launch mass to orbit (and this isn't an ideal rocket) would make this a complete answer.
$endgroup$
– uhoh
2 days ago
4
$begingroup$
I rolled back the edit because the units on Isp are exactly what was in the source document, hence the quote marks.
$endgroup$
– Organic Marble
2 days ago
|
show 1 more comment
2
$begingroup$
Ns/kg is newton-seconds per kilogram, the “correct” SI unit for specific impulse, equivalent to meters per second. Divide by 9.806 to get ISP in seconds.
$endgroup$
– Russell Borogove
2 days ago
$begingroup$
Thanks. I was just looking at the wikipedia article and found that in there as well.
$endgroup$
– Organic Marble
2 days ago
2
$begingroup$
And a hell of an oxidizer to handle in the field! Wow.
$endgroup$
– Organic Marble
2 days ago
1
$begingroup$
adding that even under ideal conditions that ISP could only get about 1.5% of launch mass to orbit (and this isn't an ideal rocket) would make this a complete answer.
$endgroup$
– uhoh
2 days ago
4
$begingroup$
I rolled back the edit because the units on Isp are exactly what was in the source document, hence the quote marks.
$endgroup$
– Organic Marble
2 days ago
2
2
$begingroup$
Ns/kg is newton-seconds per kilogram, the “correct” SI unit for specific impulse, equivalent to meters per second. Divide by 9.806 to get ISP in seconds.
$endgroup$
– Russell Borogove
2 days ago
$begingroup$
Ns/kg is newton-seconds per kilogram, the “correct” SI unit for specific impulse, equivalent to meters per second. Divide by 9.806 to get ISP in seconds.
$endgroup$
– Russell Borogove
2 days ago
$begingroup$
Thanks. I was just looking at the wikipedia article and found that in there as well.
$endgroup$
– Organic Marble
2 days ago
$begingroup$
Thanks. I was just looking at the wikipedia article and found that in there as well.
$endgroup$
– Organic Marble
2 days ago
2
2
$begingroup$
And a hell of an oxidizer to handle in the field! Wow.
$endgroup$
– Organic Marble
2 days ago
$begingroup$
And a hell of an oxidizer to handle in the field! Wow.
$endgroup$
– Organic Marble
2 days ago
1
1
$begingroup$
adding that even under ideal conditions that ISP could only get about 1.5% of launch mass to orbit (and this isn't an ideal rocket) would make this a complete answer.
$endgroup$
– uhoh
2 days ago
$begingroup$
adding that even under ideal conditions that ISP could only get about 1.5% of launch mass to orbit (and this isn't an ideal rocket) would make this a complete answer.
$endgroup$
– uhoh
2 days ago
4
4
$begingroup$
I rolled back the edit because the units on Isp are exactly what was in the source document, hence the quote marks.
$endgroup$
– Organic Marble
2 days ago
$begingroup$
I rolled back the edit because the units on Isp are exactly what was in the source document, hence the quote marks.
$endgroup$
– Organic Marble
2 days ago
|
show 1 more comment
$begingroup$
According to Gunter's web site, this launcher originated in the Shahab-5 IRBM, which is a continuation of the Scud-D / No-dong-A, No-dong-B and Shahab-5 / 6 / Taep’o-dong-2B / Unha-2
And Scud-D is originated in Soviet R-17 military missle
answered 2 days ago
Pavel BernshtamPavel Bernshtam
2,759926
$endgroup$
1
$begingroup$
Is it possible to name the engine itself or at least say something about its capability in terms of orbital applications?
$endgroup$
– uhoh
2 days ago
add a comment |
$begingroup$
According to Gunter's web site, this launcher originated in the Shahab-5 IRBM, which is a continuation of the Scud-D / No-dong-A, No-dong-B and Shahab-5 / 6 / Taep’o-dong-2B / Unha-2
And Scud-D is originated in Soviet R-17 military missle
answered 2 days ago
Pavel BernshtamPavel Bernshtam
2,759926
$endgroup$
1
$begingroup$
Is it possible to name the engine itself or at least say something about its capability in terms of orbital applications?
$endgroup$
– uhoh
2 days ago
add a comment |
$begingroup$
According to Gunter's web site, this launcher originated in the Shahab-5 IRBM, which is a continuation of the Scud-D / No-dong-A, No-dong-B and Shahab-5 / 6 / Taep’o-dong-2B / Unha-2
And Scud-D is originated in Soviet R-17 military missle
answered 2 days ago
Pavel BernshtamPavel Bernshtam
2,759926
$endgroup$
According to Gunter's web site, this launcher originated in the Shahab-5 IRBM, which is a continuation of the Scud-D / No-dong-A, No-dong-B and Shahab-5 / 6 / Taep’o-dong-2B / Unha-2
And Scud-D is originated in Soviet R-17 military missle
answered 2 days ago
Pavel BernshtamPavel Bernshtam
2,759926
answered 2 days ago
Pavel BernshtamPavel Bernshtam
2,759926
answered 2 days ago
Pavel BernshtamPavel Bernshtam
2,759926
answered 2 days ago
Pavel BernshtamPavel Bernshtam
2,759926
2,759926
1
$begingroup$
Is it possible to name the engine itself or at least say something about its capability in terms of orbital applications?
$endgroup$
– uhoh
2 days ago
add a comment |
1
$begingroup$
Is it possible to name the engine itself or at least say something about its capability in terms of orbital applications?
$endgroup$
– uhoh
2 days ago
1
1
$begingroup$
Is it possible to name the engine itself or at least say something about its capability in terms of orbital applications?
$endgroup$
– uhoh
2 days ago
$begingroup$
Is it possible to name the engine itself or at least say something about its capability in terms of orbital applications?
$endgroup$
– uhoh
2 days ago
add a comment |
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6
$begingroup$
taking weeks to set up would make it a very poor missile engine -- the Thor missiles the UK bought from the US were criticised for their 15 minute launch time.
$endgroup$
– JCRM
2 days ago
3
$begingroup$
an inefficient engine requires more fuel, requiring exponentially larger fuel tanks because of the rocket equation.
$endgroup$
– JCRM
2 days ago
1
$begingroup$
your source said it was inefficient, not undersized. Insufficient thrust can be worked around by using multiple engines or a kick stage
$endgroup$
– JCRM
2 days ago
1
$begingroup$
@jamesqf it goes into the trade space because an engine with bad Isp causes the vehicle to get larger for a given mission. So the missiles' launchers, fueling systems, etc, etc all get bigger. But which is cheaper, building a big launch trailer or developing a better engine?
$endgroup$
– Organic Marble
2 days ago
2
$begingroup$
Wouldn't it be more threatening if you're testing an "orbital" rocket design with an engine that has a very low hope of getting anything useful into space? That sounds like a passable IRBM then.
$endgroup$
– Nick T
2 days ago