Why aren't air breathing engines used as small first stages
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I am wondering why we don't use jet engines as first stages. Most small rockets, like the Electron, can lift off with a small thrust. In the Electron's case, 192 kN. Why can't we replace the 9 Rutherford engines on the Electron with a/some jet engine(s), like a ram/scramjet with an equal amount of thrust? In a rocket/spaceflight simulator (KSP), I have tried replacing the first stage with a small first stage with a hybrid jet engine with 200 kN of thrust. This works, so why doesn't NASA or other aerospace companies use this?
engines rocketlab electron kerbal-space-program ramjet
asked 3 hours ago
18ballz18ballz
157
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show 3 more comments
$begingroup$
I am wondering why we don't use jet engines as first stages. Most small rockets, like the Electron, can lift off with a small thrust. In the Electron's case, 192 kN. Why can't we replace the 9 Rutherford engines on the Electron with a/some jet engine(s), like a ram/scramjet with an equal amount of thrust? In a rocket/spaceflight simulator (KSP), I have tried replacing the first stage with a small first stage with a hybrid jet engine with 200 kN of thrust. This works, so why doesn't NASA or other aerospace companies use this?
engines rocketlab electron kerbal-space-program ramjet
asked 3 hours ago
18ballz18ballz
157
New contributor
18ballz is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
$begingroup$
Someone else will post a detailed answer, but humans have not yet been able to make a working scramjet. That limits air breathing engines to < Mach 5 which is not a big help. Conventional first stages simply work better.
$endgroup$
– Organic Marble
3 hours ago
$begingroup$
Oh, in the KSP simulator, the hybrid jet engine can go up to Mach 4, where it loses thrust. However, it has a good high-altitude performance. Is there any jet engine that can do this?
$endgroup$
– 18ballz
3 hours ago
$begingroup$
The highest altitude high-speed aircraft engine I know of is the Pratt and Whitney J58. It could run at around Mach 3 at around 85,000 ft. There are some developments like the Sabre engine that could do better if they actually are built and work.
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– Organic Marble
2 hours ago
$begingroup$
That's good! So what thrust does the J58 have?
$endgroup$
– 18ballz
2 hours ago
$begingroup$
Roughly 30,000 lbf.
$endgroup$
– Organic Marble
2 hours ago
|
show 3 more comments
$begingroup$
I am wondering why we don't use jet engines as first stages. Most small rockets, like the Electron, can lift off with a small thrust. In the Electron's case, 192 kN. Why can't we replace the 9 Rutherford engines on the Electron with a/some jet engine(s), like a ram/scramjet with an equal amount of thrust? In a rocket/spaceflight simulator (KSP), I have tried replacing the first stage with a small first stage with a hybrid jet engine with 200 kN of thrust. This works, so why doesn't NASA or other aerospace companies use this?
engines rocketlab electron kerbal-space-program ramjet
asked 3 hours ago
18ballz18ballz
157
New contributor
18ballz is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
I am wondering why we don't use jet engines as first stages. Most small rockets, like the Electron, can lift off with a small thrust. In the Electron's case, 192 kN. Why can't we replace the 9 Rutherford engines on the Electron with a/some jet engine(s), like a ram/scramjet with an equal amount of thrust? In a rocket/spaceflight simulator (KSP), I have tried replacing the first stage with a small first stage with a hybrid jet engine with 200 kN of thrust. This works, so why doesn't NASA or other aerospace companies use this?
engines rocketlab electron kerbal-space-program ramjet
engines rocketlab electron kerbal-space-program ramjet
asked 3 hours ago
18ballz18ballz
157
New contributor
18ballz is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 3 hours ago
18ballz18ballz
157
New contributor
18ballz is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 3 hours ago
18ballz18ballz
157
New contributor
18ballz is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 3 hours ago
18ballz18ballz
157
asked 3 hours ago
18ballz18ballz
157
157
New contributor
18ballz is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
18ballz is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
18ballz is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$begingroup$
Someone else will post a detailed answer, but humans have not yet been able to make a working scramjet. That limits air breathing engines to < Mach 5 which is not a big help. Conventional first stages simply work better.
$endgroup$
– Organic Marble
3 hours ago
$begingroup$
Oh, in the KSP simulator, the hybrid jet engine can go up to Mach 4, where it loses thrust. However, it has a good high-altitude performance. Is there any jet engine that can do this?
$endgroup$
– 18ballz
3 hours ago
$begingroup$
The highest altitude high-speed aircraft engine I know of is the Pratt and Whitney J58. It could run at around Mach 3 at around 85,000 ft. There are some developments like the Sabre engine that could do better if they actually are built and work.
$endgroup$
– Organic Marble
2 hours ago
$begingroup$
That's good! So what thrust does the J58 have?
$endgroup$
– 18ballz
2 hours ago
$begingroup$
Roughly 30,000 lbf.
$endgroup$
– Organic Marble
2 hours ago
|
show 3 more comments
$begingroup$
Someone else will post a detailed answer, but humans have not yet been able to make a working scramjet. That limits air breathing engines to < Mach 5 which is not a big help. Conventional first stages simply work better.
$endgroup$
– Organic Marble
3 hours ago
$begingroup$
Oh, in the KSP simulator, the hybrid jet engine can go up to Mach 4, where it loses thrust. However, it has a good high-altitude performance. Is there any jet engine that can do this?
$endgroup$
– 18ballz
3 hours ago
$begingroup$
The highest altitude high-speed aircraft engine I know of is the Pratt and Whitney J58. It could run at around Mach 3 at around 85,000 ft. There are some developments like the Sabre engine that could do better if they actually are built and work.
$endgroup$
– Organic Marble
2 hours ago
$begingroup$
That's good! So what thrust does the J58 have?
$endgroup$
– 18ballz
2 hours ago
$begingroup$
Roughly 30,000 lbf.
$endgroup$
– Organic Marble
2 hours ago
$begingroup$
Someone else will post a detailed answer, but humans have not yet been able to make a working scramjet. That limits air breathing engines to < Mach 5 which is not a big help. Conventional first stages simply work better.
$endgroup$
– Organic Marble
3 hours ago
$begingroup$
Someone else will post a detailed answer, but humans have not yet been able to make a working scramjet. That limits air breathing engines to < Mach 5 which is not a big help. Conventional first stages simply work better.
$endgroup$
– Organic Marble
3 hours ago
$begingroup$
Oh, in the KSP simulator, the hybrid jet engine can go up to Mach 4, where it loses thrust. However, it has a good high-altitude performance. Is there any jet engine that can do this?
$endgroup$
– 18ballz
3 hours ago
$begingroup$
Oh, in the KSP simulator, the hybrid jet engine can go up to Mach 4, where it loses thrust. However, it has a good high-altitude performance. Is there any jet engine that can do this?
$endgroup$
– 18ballz
3 hours ago
$begingroup$
The highest altitude high-speed aircraft engine I know of is the Pratt and Whitney J58. It could run at around Mach 3 at around 85,000 ft. There are some developments like the Sabre engine that could do better if they actually are built and work.
$endgroup$
– Organic Marble
2 hours ago
$begingroup$
The highest altitude high-speed aircraft engine I know of is the Pratt and Whitney J58. It could run at around Mach 3 at around 85,000 ft. There are some developments like the Sabre engine that could do better if they actually are built and work.
$endgroup$
– Organic Marble
2 hours ago
$begingroup$
That's good! So what thrust does the J58 have?
$endgroup$
– 18ballz
2 hours ago
$begingroup$
That's good! So what thrust does the J58 have?
$endgroup$
– 18ballz
2 hours ago
$begingroup$
Roughly 30,000 lbf.
$endgroup$
– Organic Marble
2 hours ago
$begingroup$
Roughly 30,000 lbf.
$endgroup$
– Organic Marble
2 hours ago
|
show 3 more comments
2 Answers
2
active
oldest
votes
$begingroup$
Take a look at the SABRE engine. The goal is to achieve single stage to orbit with a hybrid engine capable of breathing air at low altitude but switching to stored oxidizer and operating like a rocket when it is no longer practical to use ambient air.
The limitations of an air-breathing engine for space launch are that
- You can't go very high before the air gets very thin - not a lot of oxygen
- You can't go very fast before things start to get very hot from either friction or compression or both.
That said, the SABRE attempts to address these problems to a degree with some rather innovative ideas.
answered 1 hour ago
Anthony XAnthony X
9,50513681
$endgroup$
add a comment |
$begingroup$
There are two major barriers: one is that thrust-to-weight ratio of jet engines is pretty poor (2 J58s massing more than 15 times what 9 Rutherfords do), the other is that it's hard to make an engine that performs efficiently over the wide range of speeds and altitudes that a first stage wants to cover.
That said, Boeing at one point toyed with a concept using recoverable jet-powered modules as the first stage of a three-stage-to-orbit reusable launcher.
answered 2 hours ago
Russell BorogoveRussell Borogove
89.3k3300384
$endgroup$
$begingroup$
I'm not advocating the concept, but you might save some mass by not carrying oxidizer for the jet engines.
$endgroup$
– Organic Marble
2 hours ago
$begingroup$
Absolutely -- that's the most attractive thing about using jet engines. On orbital ascent, though, the useful run time of air-breathers is so short that the added weight of the engine almost eats up the oxidizer savings.
$endgroup$
– Russell Borogove
2 hours ago
$begingroup$
Agree completely.
$endgroup$
– Organic Marble
2 hours ago
add a comment |
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2 Answers
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active
oldest
votes
2 Answers
2
active
oldest
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active
oldest
votes
$begingroup$
Take a look at the SABRE engine. The goal is to achieve single stage to orbit with a hybrid engine capable of breathing air at low altitude but switching to stored oxidizer and operating like a rocket when it is no longer practical to use ambient air.
The limitations of an air-breathing engine for space launch are that
- You can't go very high before the air gets very thin - not a lot of oxygen
- You can't go very fast before things start to get very hot from either friction or compression or both.
That said, the SABRE attempts to address these problems to a degree with some rather innovative ideas.
answered 1 hour ago
Anthony XAnthony X
9,50513681
$endgroup$
add a comment |
$begingroup$
Take a look at the SABRE engine. The goal is to achieve single stage to orbit with a hybrid engine capable of breathing air at low altitude but switching to stored oxidizer and operating like a rocket when it is no longer practical to use ambient air.
The limitations of an air-breathing engine for space launch are that
- You can't go very high before the air gets very thin - not a lot of oxygen
- You can't go very fast before things start to get very hot from either friction or compression or both.
That said, the SABRE attempts to address these problems to a degree with some rather innovative ideas.
answered 1 hour ago
Anthony XAnthony X
9,50513681
$endgroup$
add a comment |
$begingroup$
Take a look at the SABRE engine. The goal is to achieve single stage to orbit with a hybrid engine capable of breathing air at low altitude but switching to stored oxidizer and operating like a rocket when it is no longer practical to use ambient air.
The limitations of an air-breathing engine for space launch are that
- You can't go very high before the air gets very thin - not a lot of oxygen
- You can't go very fast before things start to get very hot from either friction or compression or both.
That said, the SABRE attempts to address these problems to a degree with some rather innovative ideas.
answered 1 hour ago
Anthony XAnthony X
9,50513681
$endgroup$
Take a look at the SABRE engine. The goal is to achieve single stage to orbit with a hybrid engine capable of breathing air at low altitude but switching to stored oxidizer and operating like a rocket when it is no longer practical to use ambient air.
The limitations of an air-breathing engine for space launch are that
- You can't go very high before the air gets very thin - not a lot of oxygen
- You can't go very fast before things start to get very hot from either friction or compression or both.
That said, the SABRE attempts to address these problems to a degree with some rather innovative ideas.
answered 1 hour ago
Anthony XAnthony X
9,50513681
answered 1 hour ago
Anthony XAnthony X
9,50513681
answered 1 hour ago
Anthony XAnthony X
9,50513681
answered 1 hour ago
Anthony XAnthony X
9,50513681
9,50513681
add a comment |
add a comment |
$begingroup$
There are two major barriers: one is that thrust-to-weight ratio of jet engines is pretty poor (2 J58s massing more than 15 times what 9 Rutherfords do), the other is that it's hard to make an engine that performs efficiently over the wide range of speeds and altitudes that a first stage wants to cover.
That said, Boeing at one point toyed with a concept using recoverable jet-powered modules as the first stage of a three-stage-to-orbit reusable launcher.
answered 2 hours ago
Russell BorogoveRussell Borogove
89.3k3300384
$endgroup$
$begingroup$
I'm not advocating the concept, but you might save some mass by not carrying oxidizer for the jet engines.
$endgroup$
– Organic Marble
2 hours ago
$begingroup$
Absolutely -- that's the most attractive thing about using jet engines. On orbital ascent, though, the useful run time of air-breathers is so short that the added weight of the engine almost eats up the oxidizer savings.
$endgroup$
– Russell Borogove
2 hours ago
$begingroup$
Agree completely.
$endgroup$
– Organic Marble
2 hours ago
add a comment |
$begingroup$
There are two major barriers: one is that thrust-to-weight ratio of jet engines is pretty poor (2 J58s massing more than 15 times what 9 Rutherfords do), the other is that it's hard to make an engine that performs efficiently over the wide range of speeds and altitudes that a first stage wants to cover.
That said, Boeing at one point toyed with a concept using recoverable jet-powered modules as the first stage of a three-stage-to-orbit reusable launcher.
answered 2 hours ago
Russell BorogoveRussell Borogove
89.3k3300384
$endgroup$
$begingroup$
I'm not advocating the concept, but you might save some mass by not carrying oxidizer for the jet engines.
$endgroup$
– Organic Marble
2 hours ago
$begingroup$
Absolutely -- that's the most attractive thing about using jet engines. On orbital ascent, though, the useful run time of air-breathers is so short that the added weight of the engine almost eats up the oxidizer savings.
$endgroup$
– Russell Borogove
2 hours ago
$begingroup$
Agree completely.
$endgroup$
– Organic Marble
2 hours ago
add a comment |
$begingroup$
There are two major barriers: one is that thrust-to-weight ratio of jet engines is pretty poor (2 J58s massing more than 15 times what 9 Rutherfords do), the other is that it's hard to make an engine that performs efficiently over the wide range of speeds and altitudes that a first stage wants to cover.
That said, Boeing at one point toyed with a concept using recoverable jet-powered modules as the first stage of a three-stage-to-orbit reusable launcher.
answered 2 hours ago
Russell BorogoveRussell Borogove
89.3k3300384
$endgroup$
There are two major barriers: one is that thrust-to-weight ratio of jet engines is pretty poor (2 J58s massing more than 15 times what 9 Rutherfords do), the other is that it's hard to make an engine that performs efficiently over the wide range of speeds and altitudes that a first stage wants to cover.
That said, Boeing at one point toyed with a concept using recoverable jet-powered modules as the first stage of a three-stage-to-orbit reusable launcher.
answered 2 hours ago
Russell BorogoveRussell Borogove
89.3k3300384
edited 2 hours ago
answered 2 hours ago
Russell BorogoveRussell Borogove
89.3k3300384
answered 2 hours ago
Russell BorogoveRussell Borogove
89.3k3300384
answered 2 hours ago
Russell BorogoveRussell Borogove
89.3k3300384
89.3k3300384
$begingroup$
I'm not advocating the concept, but you might save some mass by not carrying oxidizer for the jet engines.
$endgroup$
– Organic Marble
2 hours ago
$begingroup$
Absolutely -- that's the most attractive thing about using jet engines. On orbital ascent, though, the useful run time of air-breathers is so short that the added weight of the engine almost eats up the oxidizer savings.
$endgroup$
– Russell Borogove
2 hours ago
$begingroup$
Agree completely.
$endgroup$
– Organic Marble
2 hours ago
add a comment |
$begingroup$
I'm not advocating the concept, but you might save some mass by not carrying oxidizer for the jet engines.
$endgroup$
– Organic Marble
2 hours ago
$begingroup$
Absolutely -- that's the most attractive thing about using jet engines. On orbital ascent, though, the useful run time of air-breathers is so short that the added weight of the engine almost eats up the oxidizer savings.
$endgroup$
– Russell Borogove
2 hours ago
$begingroup$
Agree completely.
$endgroup$
– Organic Marble
2 hours ago
$begingroup$
I'm not advocating the concept, but you might save some mass by not carrying oxidizer for the jet engines.
$endgroup$
– Organic Marble
2 hours ago
$begingroup$
I'm not advocating the concept, but you might save some mass by not carrying oxidizer for the jet engines.
$endgroup$
– Organic Marble
2 hours ago
$begingroup$
Absolutely -- that's the most attractive thing about using jet engines. On orbital ascent, though, the useful run time of air-breathers is so short that the added weight of the engine almost eats up the oxidizer savings.
$endgroup$
– Russell Borogove
2 hours ago
$begingroup$
Absolutely -- that's the most attractive thing about using jet engines. On orbital ascent, though, the useful run time of air-breathers is so short that the added weight of the engine almost eats up the oxidizer savings.
$endgroup$
– Russell Borogove
2 hours ago
$begingroup$
Agree completely.
$endgroup$
– Organic Marble
2 hours ago
$begingroup$
Agree completely.
$endgroup$
– Organic Marble
2 hours ago
add a comment |
18ballz is a new contributor. Be nice, and check out our Code of Conduct.
18ballz is a new contributor. Be nice, and check out our Code of Conduct.
18ballz is a new contributor. Be nice, and check out our Code of Conduct.
18ballz is a new contributor. Be nice, and check out our Code of Conduct.
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$begingroup$
Someone else will post a detailed answer, but humans have not yet been able to make a working scramjet. That limits air breathing engines to < Mach 5 which is not a big help. Conventional first stages simply work better.
$endgroup$
– Organic Marble
3 hours ago
$begingroup$
Oh, in the KSP simulator, the hybrid jet engine can go up to Mach 4, where it loses thrust. However, it has a good high-altitude performance. Is there any jet engine that can do this?
$endgroup$
– 18ballz
3 hours ago
$begingroup$
The highest altitude high-speed aircraft engine I know of is the Pratt and Whitney J58. It could run at around Mach 3 at around 85,000 ft. There are some developments like the Sabre engine that could do better if they actually are built and work.
$endgroup$
– Organic Marble
2 hours ago
$begingroup$
That's good! So what thrust does the J58 have?
$endgroup$
– 18ballz
2 hours ago
$begingroup$
Roughly 30,000 lbf.
$endgroup$
– Organic Marble
2 hours ago