Sfrgttk

Should I discuss the type of campaign with my players?

What do you call a plan that's an alternative plan in case your initial plan fails?

When to stop saving and start investing?

Why don't the Weasley twins use magic outside of school if the Trace can only find the location of spells cast?

List *all* the tuples!

How to recreate this effect in Photoshop?

What happens to sewage if there is no river near by?

Examples of mediopassive verb constructions

What are the motives behind Cersei's orders given to Bronn?

Why one of virtual NICs called bond0?

The logistics of corpse disposal

Why does Python start at index 1 when iterating an array backwards?

When is phishing education going too far?

What is the correct way to use the pinch test for dehydration?

Java 8 stream max() function argument type Comparator vs Comparable

If 'B is more likely given A', then 'A is more likely given B'

How does a Death Domain cleric's Touch of Death feature work with Touch-range spells delivered by familiars?

Is 1 ppb equal to 1 μg/kg?

How can I make names more distinctive without making them longer?

If Jon Snow became King of the Seven Kingdoms what would his regnal number be?

What is the musical term for a note that continously plays through a melody?

What is the longest distance a 13th-level monk can jump while attacking on the same turn?

Right-skewed distribution with mean equals to mode?

What are the pros and cons of Aerospike nosecones?

Why aren't air breathing engines used as small first stages

2

1

$begingroup$

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

share|improve this question

asked 2 hours ago

18ballz18ballz

156

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
  2 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
  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
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Roughly 30,000 lbf.
  $endgroup$
  – Organic Marble
  2 hours ago
  

  
  
  
  

 | 
show 3 more comments

2

1

$begingroup$

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

share|improve this question

asked 2 hours ago

18ballz18ballz

156

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
  2 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
  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
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  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

share|improve this question

asked 2 hours ago

18ballz18ballz

156

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.

$endgroup$

share|improve this question

asked 2 hours ago

18ballz18ballz

156

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.

share|improve this question

asked 2 hours ago

18ballz18ballz

156

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 2 hours ago

18ballz18ballz

156

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 2 hours ago

18ballz18ballz

156

2 Answers
2

active

oldest

votes

3

$begingroup$

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

1. You can't go very high before the air gets very thin - not a lot of oxygen


2. 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.

share|improve this answer

answered 49 mins ago

Anthony XAnthony X

9,50513681

$endgroup$

add a comment | 

3

$begingroup$

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.

share|improve this answer

edited 2 hours ago

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
  1 hour ago
  

  
  
  
  

add a comment | 

Your Answer

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "508"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});

function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});


}
});

18ballz is a new contributor. Be nice, and check out our Code of Conduct.

draft saved

draft discarded

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Sign up using Google

Sign up using Facebook

Sign up using Email and Password

Post as a guest

Name

Email

Required, but never shown

StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fspace.stackexchange.com%2fquestions%2f35540%2fwhy-arent-air-breathing-engines-used-as-small-first-stages%23new-answer', 'question_page');
}
);

Post as a guest

Name

Email

Required, but never shown

3

$begingroup$

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

1. You can't go very high before the air gets very thin - not a lot of oxygen


2. 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.

share|improve this answer

answered 49 mins ago

Anthony XAnthony X

9,50513681

$endgroup$

add a comment | 

3

$begingroup$

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

1. You can't go very high before the air gets very thin - not a lot of oxygen


2. 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.

share|improve this answer

answered 49 mins 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

1. You can't go very high before the air gets very thin - not a lot of oxygen


2. 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.

share|improve this answer

answered 49 mins ago

Anthony XAnthony X

9,50513681

$endgroup$

share|improve this answer

answered 49 mins ago

Anthony XAnthony X

9,50513681

answered 49 mins ago

Anthony XAnthony X

9,50513681

answered 49 mins ago

Anthony XAnthony X

9,50513681

3

$begingroup$

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.

share|improve this answer

edited 2 hours ago

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
  1 hour ago
  

  
  
  
  

add a comment | 

3

$begingroup$

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.

share|improve this answer

edited 2 hours ago

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
  1 hour 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.

share|improve this answer

edited 2 hours ago

answered 2 hours ago

Russell BorogoveRussell Borogove

89.3k3300384

$endgroup$

share|improve this answer

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