Mixing
Does anyone know how to calculate the KG per second of RP-1 and LOX from the 9 Merlin 1D engines?
Clash Royale CLAN TAG#URR8PPP
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as can be seen from the title, I have been through at least 1,000 chrome tabs in the last few hours trying to find some form of definitive answer, but I've found absolutely nothing. Could anyone help me with a calculation from its 7,607kn to Fuel consumption KG/s
spacex rockets falcon-9 merlin-1d
asked Sep 6 at 11:21
UndefinedUsername
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UndefinedUsername is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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up vote
6
down vote
favorite
as can be seen from the title, I have been through at least 1,000 chrome tabs in the last few hours trying to find some form of definitive answer, but I've found absolutely nothing. Could anyone help me with a calculation from its 7,607kn to Fuel consumption KG/s
spacex rockets falcon-9 merlin-1d
asked Sep 6 at 11:21
UndefinedUsername
504
New contributor
UndefinedUsername is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |Â
up vote
6
down vote
favorite
up vote
6
down vote
favorite
as can be seen from the title, I have been through at least 1,000 chrome tabs in the last few hours trying to find some form of definitive answer, but I've found absolutely nothing. Could anyone help me with a calculation from its 7,607kn to Fuel consumption KG/s
spacex rockets falcon-9 merlin-1d
asked Sep 6 at 11:21
UndefinedUsername
504
New contributor
UndefinedUsername is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
as can be seen from the title, I have been through at least 1,000 chrome tabs in the last few hours trying to find some form of definitive answer, but I've found absolutely nothing. Could anyone help me with a calculation from its 7,607kn to Fuel consumption KG/s
spacex rockets falcon-9 merlin-1d
asked Sep 6 at 11:21
UndefinedUsername
504
New contributor
UndefinedUsername is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked Sep 6 at 11:21
UndefinedUsername
504
New contributor
UndefinedUsername is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked Sep 6 at 11:21
UndefinedUsername
504
asked Sep 6 at 11:21
UndefinedUsername
504
504
New contributor
UndefinedUsername is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
UndefinedUsername is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
UndefinedUsername is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |Â
add a comment |Â
2 Answers
2
active
oldest
votes
up vote
11
down vote
accepted
As @RussellBorogove points out in his excellent answer, Isp or "mass-specific impulse" is the number that expresses the relationship between thrust and mass flow rate.
Mass specific impulse with units would be Newtons per kg/sec. While that has units of m/s, and may be identical or at least quite close to the average velocity of the exhaust (which will have a distribution), the derivation below is a handy way to either remember how things are related, and/or to get the units to work out.
Force can be equated to change in momentum per unit time.
$$F = fracdpdt$$
Momentum is mass times velocity:
$$p = mv$$
So
$$F = v fracdmdt = v dotm$$
where $dotm$ is the mass rate.
The specific impulse of a Falcon 9 Merlin 1D is about 262 seconds in the atmosphere. Multiply that by standard gravity of about 9.81 m/s^2 to get an exhaust velocity of about 2570 m/s.
$$ 7,607,000 = 2570 dotm$$
Solve for $dotm$.
$$ dotm = frac7,607,0002570 $$
That's one way how to calculate the kg/sec of RP-1 and LOX. If you want to know each one separately, find the the ratio between the two. Search this site for oxidizer fuel ratio or similar terms if you can't find it on the internet.
edited Sep 7 at 1:24
2012rcampion
1,603618
answered Sep 6 at 11:39
uhoh
27.9k1288344
That assumes 100% efficiency and ignores the fuel required for the turbopump, though.
– Hobbes
Sep 6 at 11:41
2
I think uhoh's answer is in the ballpark. Here's another (less precise) approach: First stage has 245,620 L of liquid oxygen and 146,020 L of RP-1 fuel [1] Let's assume oxygen density as 1,1417 [2] and RP-1 density as 0,915 (average of 0.81 and 1.02 in [3]). So we have 280424 Kg of Oxygen and 133608 Kg of RP-1. First stage burn time is 162s [4]. So (280424+133608)/162 = 2555 Kg/s. [1] en.wikipedia.org/wiki/Falcon_9#cite_note-falcon9-2015-3 [2] uigi.com/o2_conv.html [3] en.wikipedia.org/wiki/RP-1 [4] spacex.com/falcon9
– BlueCoder
Sep 6 at 12:19
2
Considering that the engines won't be at their maximum thrust for the whole 162 period (they slow down at least during Max-Q I think) and the uncertainties on these numbers, I think uhoh's answer is correct at the very least in the order of magnitude. By the way, using this calculation we get 1731 Kg/s for the Oxygen and 824 Kg/s for RP-1.
– BlueCoder
Sep 6 at 12:20
1
BlueCoder's approach is the one I had in mind as well, but couldn't find the numbers for on short notice.
– Hobbes
Sep 6 at 12:40
1
@2012rcampion Since (at)BlueCoder's answer chooses to do the numbers, the've already reported a value for this there, so it's not necessary to do here. And while we don't have a specific homework policy as some sites do, I feel that there's a certain comradely cordiality to not over-answering a question that specifically asks only for how to do something rather than "tell me what the answer is."
– uhoh
Sep 7 at 0:43
 |Â
show 4 more comments
up vote
8
down vote
I think uhoh's answer (7607000/2570=2959 Kg/s) is in the ballpark.
Here's another (less precise) approach:
First stage has 245,620 L of liquid oxygen and 146,020 L of RP-1 fuel (1)
Let's assume oxygen density as 1,1417 (2) and RP-1 density as 0,915 (average of 0.81 and 1.02 in (3)).
So we have 245620*1,1417 = 280424 Kg of Oxygen and 146020*0,915 = 133608 Kg of RP-1.
First stage burn time is 162s (4).
So (280424+133608)/162 = 2555 Kg/s.
Considering that the engines won't be at their maximum thrust for the whole 162 period (they slow down at least during Max-Q I think) and the uncertainties on these numbers*, I think uhoh's answer is correct at the very least in the order of magnitude.
By the way, using this calculation we get 1731 Kg/s for the Oxygen and 824 Kg/s for RP-1.
- I just took as good the first sources I found around. To make a better estimate, I would at least verify more carfully the actual RP-1 density and also have a look at the thrust level during the whole 162 seconds.
Also note that some of the first stage fuel is kept for landing.
answered Sep 6 at 12:26
BlueCoder
83415
add a comment |Â
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
11
down vote
accepted
As @RussellBorogove points out in his excellent answer, Isp or "mass-specific impulse" is the number that expresses the relationship between thrust and mass flow rate.
Mass specific impulse with units would be Newtons per kg/sec. While that has units of m/s, and may be identical or at least quite close to the average velocity of the exhaust (which will have a distribution), the derivation below is a handy way to either remember how things are related, and/or to get the units to work out.
Force can be equated to change in momentum per unit time.
$$F = fracdpdt$$
Momentum is mass times velocity:
$$p = mv$$
So
$$F = v fracdmdt = v dotm$$
where $dotm$ is the mass rate.
The specific impulse of a Falcon 9 Merlin 1D is about 262 seconds in the atmosphere. Multiply that by standard gravity of about 9.81 m/s^2 to get an exhaust velocity of about 2570 m/s.
$$ 7,607,000 = 2570 dotm$$
Solve for $dotm$.
$$ dotm = frac7,607,0002570 $$
That's one way how to calculate the kg/sec of RP-1 and LOX. If you want to know each one separately, find the the ratio between the two. Search this site for oxidizer fuel ratio or similar terms if you can't find it on the internet.
edited Sep 7 at 1:24
2012rcampion
1,603618
answered Sep 6 at 11:39
uhoh
27.9k1288344
That assumes 100% efficiency and ignores the fuel required for the turbopump, though.
– Hobbes
Sep 6 at 11:41
2
I think uhoh's answer is in the ballpark. Here's another (less precise) approach: First stage has 245,620 L of liquid oxygen and 146,020 L of RP-1 fuel [1] Let's assume oxygen density as 1,1417 [2] and RP-1 density as 0,915 (average of 0.81 and 1.02 in [3]). So we have 280424 Kg of Oxygen and 133608 Kg of RP-1. First stage burn time is 162s [4]. So (280424+133608)/162 = 2555 Kg/s. [1] en.wikipedia.org/wiki/Falcon_9#cite_note-falcon9-2015-3 [2] uigi.com/o2_conv.html [3] en.wikipedia.org/wiki/RP-1 [4] spacex.com/falcon9
– BlueCoder
Sep 6 at 12:19
2
Considering that the engines won't be at their maximum thrust for the whole 162 period (they slow down at least during Max-Q I think) and the uncertainties on these numbers, I think uhoh's answer is correct at the very least in the order of magnitude. By the way, using this calculation we get 1731 Kg/s for the Oxygen and 824 Kg/s for RP-1.
– BlueCoder
Sep 6 at 12:20
1
BlueCoder's approach is the one I had in mind as well, but couldn't find the numbers for on short notice.
– Hobbes
Sep 6 at 12:40
1
@2012rcampion Since (at)BlueCoder's answer chooses to do the numbers, the've already reported a value for this there, so it's not necessary to do here. And while we don't have a specific homework policy as some sites do, I feel that there's a certain comradely cordiality to not over-answering a question that specifically asks only for how to do something rather than "tell me what the answer is."
– uhoh
Sep 7 at 0:43
 |Â
show 4 more comments
up vote
11
down vote
accepted
As @RussellBorogove points out in his excellent answer, Isp or "mass-specific impulse" is the number that expresses the relationship between thrust and mass flow rate.
Mass specific impulse with units would be Newtons per kg/sec. While that has units of m/s, and may be identical or at least quite close to the average velocity of the exhaust (which will have a distribution), the derivation below is a handy way to either remember how things are related, and/or to get the units to work out.
Force can be equated to change in momentum per unit time.
$$F = fracdpdt$$
Momentum is mass times velocity:
$$p = mv$$
So
$$F = v fracdmdt = v dotm$$
where $dotm$ is the mass rate.
The specific impulse of a Falcon 9 Merlin 1D is about 262 seconds in the atmosphere. Multiply that by standard gravity of about 9.81 m/s^2 to get an exhaust velocity of about 2570 m/s.
$$ 7,607,000 = 2570 dotm$$
Solve for $dotm$.
$$ dotm = frac7,607,0002570 $$
That's one way how to calculate the kg/sec of RP-1 and LOX. If you want to know each one separately, find the the ratio between the two. Search this site for oxidizer fuel ratio or similar terms if you can't find it on the internet.
edited Sep 7 at 1:24
2012rcampion
1,603618
answered Sep 6 at 11:39
uhoh
27.9k1288344
That assumes 100% efficiency and ignores the fuel required for the turbopump, though.
– Hobbes
Sep 6 at 11:41
2
I think uhoh's answer is in the ballpark. Here's another (less precise) approach: First stage has 245,620 L of liquid oxygen and 146,020 L of RP-1 fuel [1] Let's assume oxygen density as 1,1417 [2] and RP-1 density as 0,915 (average of 0.81 and 1.02 in [3]). So we have 280424 Kg of Oxygen and 133608 Kg of RP-1. First stage burn time is 162s [4]. So (280424+133608)/162 = 2555 Kg/s. [1] en.wikipedia.org/wiki/Falcon_9#cite_note-falcon9-2015-3 [2] uigi.com/o2_conv.html [3] en.wikipedia.org/wiki/RP-1 [4] spacex.com/falcon9
– BlueCoder
Sep 6 at 12:19
2
Considering that the engines won't be at their maximum thrust for the whole 162 period (they slow down at least during Max-Q I think) and the uncertainties on these numbers, I think uhoh's answer is correct at the very least in the order of magnitude. By the way, using this calculation we get 1731 Kg/s for the Oxygen and 824 Kg/s for RP-1.
– BlueCoder
Sep 6 at 12:20
1
BlueCoder's approach is the one I had in mind as well, but couldn't find the numbers for on short notice.
– Hobbes
Sep 6 at 12:40
1
@2012rcampion Since (at)BlueCoder's answer chooses to do the numbers, the've already reported a value for this there, so it's not necessary to do here. And while we don't have a specific homework policy as some sites do, I feel that there's a certain comradely cordiality to not over-answering a question that specifically asks only for how to do something rather than "tell me what the answer is."
– uhoh
Sep 7 at 0:43
 |Â
show 4 more comments
up vote
11
down vote
accepted
up vote
11
down vote
accepted
As @RussellBorogove points out in his excellent answer, Isp or "mass-specific impulse" is the number that expresses the relationship between thrust and mass flow rate.
Mass specific impulse with units would be Newtons per kg/sec. While that has units of m/s, and may be identical or at least quite close to the average velocity of the exhaust (which will have a distribution), the derivation below is a handy way to either remember how things are related, and/or to get the units to work out.
Force can be equated to change in momentum per unit time.
$$F = fracdpdt$$
Momentum is mass times velocity:
$$p = mv$$
So
$$F = v fracdmdt = v dotm$$
where $dotm$ is the mass rate.
The specific impulse of a Falcon 9 Merlin 1D is about 262 seconds in the atmosphere. Multiply that by standard gravity of about 9.81 m/s^2 to get an exhaust velocity of about 2570 m/s.
$$ 7,607,000 = 2570 dotm$$
Solve for $dotm$.
$$ dotm = frac7,607,0002570 $$
That's one way how to calculate the kg/sec of RP-1 and LOX. If you want to know each one separately, find the the ratio between the two. Search this site for oxidizer fuel ratio or similar terms if you can't find it on the internet.
edited Sep 7 at 1:24
2012rcampion
1,603618
answered Sep 6 at 11:39
uhoh
27.9k1288344
As @RussellBorogove points out in his excellent answer, Isp or "mass-specific impulse" is the number that expresses the relationship between thrust and mass flow rate.
Mass specific impulse with units would be Newtons per kg/sec. While that has units of m/s, and may be identical or at least quite close to the average velocity of the exhaust (which will have a distribution), the derivation below is a handy way to either remember how things are related, and/or to get the units to work out.
Force can be equated to change in momentum per unit time.
$$F = fracdpdt$$
Momentum is mass times velocity:
$$p = mv$$
So
$$F = v fracdmdt = v dotm$$
where $dotm$ is the mass rate.
The specific impulse of a Falcon 9 Merlin 1D is about 262 seconds in the atmosphere. Multiply that by standard gravity of about 9.81 m/s^2 to get an exhaust velocity of about 2570 m/s.
$$ 7,607,000 = 2570 dotm$$
Solve for $dotm$.
$$ dotm = frac7,607,0002570 $$
That's one way how to calculate the kg/sec of RP-1 and LOX. If you want to know each one separately, find the the ratio between the two. Search this site for oxidizer fuel ratio or similar terms if you can't find it on the internet.
edited Sep 7 at 1:24
2012rcampion
1,603618
answered Sep 6 at 11:39
uhoh
27.9k1288344
edited Sep 7 at 1:24
2012rcampion
1,603618
edited Sep 7 at 1:24
2012rcampion
1,603618
edited Sep 7 at 1:24
2012rcampion
1,603618
1,603618
answered Sep 6 at 11:39
uhoh
27.9k1288344
answered Sep 6 at 11:39
uhoh
27.9k1288344
answered Sep 6 at 11:39
uhoh
27.9k1288344
27.9k1288344
That assumes 100% efficiency and ignores the fuel required for the turbopump, though.
– Hobbes
Sep 6 at 11:41
2
I think uhoh's answer is in the ballpark. Here's another (less precise) approach: First stage has 245,620 L of liquid oxygen and 146,020 L of RP-1 fuel [1] Let's assume oxygen density as 1,1417 [2] and RP-1 density as 0,915 (average of 0.81 and 1.02 in [3]). So we have 280424 Kg of Oxygen and 133608 Kg of RP-1. First stage burn time is 162s [4]. So (280424+133608)/162 = 2555 Kg/s. [1] en.wikipedia.org/wiki/Falcon_9#cite_note-falcon9-2015-3 [2] uigi.com/o2_conv.html [3] en.wikipedia.org/wiki/RP-1 [4] spacex.com/falcon9
– BlueCoder
Sep 6 at 12:19
2
Considering that the engines won't be at their maximum thrust for the whole 162 period (they slow down at least during Max-Q I think) and the uncertainties on these numbers, I think uhoh's answer is correct at the very least in the order of magnitude. By the way, using this calculation we get 1731 Kg/s for the Oxygen and 824 Kg/s for RP-1.
– BlueCoder
Sep 6 at 12:20
1
BlueCoder's approach is the one I had in mind as well, but couldn't find the numbers for on short notice.
– Hobbes
Sep 6 at 12:40
1
@2012rcampion Since (at)BlueCoder's answer chooses to do the numbers, the've already reported a value for this there, so it's not necessary to do here. And while we don't have a specific homework policy as some sites do, I feel that there's a certain comradely cordiality to not over-answering a question that specifically asks only for how to do something rather than "tell me what the answer is."
– uhoh
Sep 7 at 0:43
 |Â
show 4 more comments
That assumes 100% efficiency and ignores the fuel required for the turbopump, though.
– Hobbes
Sep 6 at 11:41
2
I think uhoh's answer is in the ballpark. Here's another (less precise) approach: First stage has 245,620 L of liquid oxygen and 146,020 L of RP-1 fuel [1] Let's assume oxygen density as 1,1417 [2] and RP-1 density as 0,915 (average of 0.81 and 1.02 in [3]). So we have 280424 Kg of Oxygen and 133608 Kg of RP-1. First stage burn time is 162s [4]. So (280424+133608)/162 = 2555 Kg/s. [1] en.wikipedia.org/wiki/Falcon_9#cite_note-falcon9-2015-3 [2] uigi.com/o2_conv.html [3] en.wikipedia.org/wiki/RP-1 [4] spacex.com/falcon9
– BlueCoder
Sep 6 at 12:19
2
Considering that the engines won't be at their maximum thrust for the whole 162 period (they slow down at least during Max-Q I think) and the uncertainties on these numbers, I think uhoh's answer is correct at the very least in the order of magnitude. By the way, using this calculation we get 1731 Kg/s for the Oxygen and 824 Kg/s for RP-1.
– BlueCoder
Sep 6 at 12:20
1
BlueCoder's approach is the one I had in mind as well, but couldn't find the numbers for on short notice.
– Hobbes
Sep 6 at 12:40
1
@2012rcampion Since (at)BlueCoder's answer chooses to do the numbers, the've already reported a value for this there, so it's not necessary to do here. And while we don't have a specific homework policy as some sites do, I feel that there's a certain comradely cordiality to not over-answering a question that specifically asks only for how to do something rather than "tell me what the answer is."
– uhoh
Sep 7 at 0:43
That assumes 100% efficiency and ignores the fuel required for the turbopump, though.
– Hobbes
Sep 6 at 11:41
That assumes 100% efficiency and ignores the fuel required for the turbopump, though.
– Hobbes
Sep 6 at 11:41
2
2
I think uhoh's answer is in the ballpark. Here's another (less precise) approach: First stage has 245,620 L of liquid oxygen and 146,020 L of RP-1 fuel [1] Let's assume oxygen density as 1,1417 [2] and RP-1 density as 0,915 (average of 0.81 and 1.02 in [3]). So we have 280424 Kg of Oxygen and 133608 Kg of RP-1. First stage burn time is 162s [4]. So (280424+133608)/162 = 2555 Kg/s. [1] en.wikipedia.org/wiki/Falcon_9#cite_note-falcon9-2015-3 [2] uigi.com/o2_conv.html [3] en.wikipedia.org/wiki/RP-1 [4] spacex.com/falcon9
– BlueCoder
Sep 6 at 12:19
I think uhoh's answer is in the ballpark. Here's another (less precise) approach: First stage has 245,620 L of liquid oxygen and 146,020 L of RP-1 fuel [1] Let's assume oxygen density as 1,1417 [2] and RP-1 density as 0,915 (average of 0.81 and 1.02 in [3]). So we have 280424 Kg of Oxygen and 133608 Kg of RP-1. First stage burn time is 162s [4]. So (280424+133608)/162 = 2555 Kg/s. [1] en.wikipedia.org/wiki/Falcon_9#cite_note-falcon9-2015-3 [2] uigi.com/o2_conv.html [3] en.wikipedia.org/wiki/RP-1 [4] spacex.com/falcon9
– BlueCoder
Sep 6 at 12:19
2
2
Considering that the engines won't be at their maximum thrust for the whole 162 period (they slow down at least during Max-Q I think) and the uncertainties on these numbers, I think uhoh's answer is correct at the very least in the order of magnitude. By the way, using this calculation we get 1731 Kg/s for the Oxygen and 824 Kg/s for RP-1.
– BlueCoder
Sep 6 at 12:20
Considering that the engines won't be at their maximum thrust for the whole 162 period (they slow down at least during Max-Q I think) and the uncertainties on these numbers, I think uhoh's answer is correct at the very least in the order of magnitude. By the way, using this calculation we get 1731 Kg/s for the Oxygen and 824 Kg/s for RP-1.
– BlueCoder
Sep 6 at 12:20
1
1
BlueCoder's approach is the one I had in mind as well, but couldn't find the numbers for on short notice.
– Hobbes
Sep 6 at 12:40
BlueCoder's approach is the one I had in mind as well, but couldn't find the numbers for on short notice.
– Hobbes
Sep 6 at 12:40
1
1
@2012rcampion Since (at)BlueCoder's answer chooses to do the numbers, the've already reported a value for this there, so it's not necessary to do here. And while we don't have a specific homework policy as some sites do, I feel that there's a certain comradely cordiality to not over-answering a question that specifically asks only for how to do something rather than "tell me what the answer is."
– uhoh
Sep 7 at 0:43
@2012rcampion Since (at)BlueCoder's answer chooses to do the numbers, the've already reported a value for this there, so it's not necessary to do here. And while we don't have a specific homework policy as some sites do, I feel that there's a certain comradely cordiality to not over-answering a question that specifically asks only for how to do something rather than "tell me what the answer is."
– uhoh
Sep 7 at 0:43
 |Â
show 4 more comments
up vote
8
down vote
I think uhoh's answer (7607000/2570=2959 Kg/s) is in the ballpark.
Here's another (less precise) approach:
First stage has 245,620 L of liquid oxygen and 146,020 L of RP-1 fuel (1)
Let's assume oxygen density as 1,1417 (2) and RP-1 density as 0,915 (average of 0.81 and 1.02 in (3)).
So we have 245620*1,1417 = 280424 Kg of Oxygen and 146020*0,915 = 133608 Kg of RP-1.
First stage burn time is 162s (4).
So (280424+133608)/162 = 2555 Kg/s.
Considering that the engines won't be at their maximum thrust for the whole 162 period (they slow down at least during Max-Q I think) and the uncertainties on these numbers*, I think uhoh's answer is correct at the very least in the order of magnitude.
By the way, using this calculation we get 1731 Kg/s for the Oxygen and 824 Kg/s for RP-1.
- I just took as good the first sources I found around. To make a better estimate, I would at least verify more carfully the actual RP-1 density and also have a look at the thrust level during the whole 162 seconds.
Also note that some of the first stage fuel is kept for landing.
answered Sep 6 at 12:26
BlueCoder
83415
add a comment |Â
up vote
8
down vote
I think uhoh's answer (7607000/2570=2959 Kg/s) is in the ballpark.
Here's another (less precise) approach:
First stage has 245,620 L of liquid oxygen and 146,020 L of RP-1 fuel (1)
Let's assume oxygen density as 1,1417 (2) and RP-1 density as 0,915 (average of 0.81 and 1.02 in (3)).
So we have 245620*1,1417 = 280424 Kg of Oxygen and 146020*0,915 = 133608 Kg of RP-1.
First stage burn time is 162s (4).
So (280424+133608)/162 = 2555 Kg/s.
Considering that the engines won't be at their maximum thrust for the whole 162 period (they slow down at least during Max-Q I think) and the uncertainties on these numbers*, I think uhoh's answer is correct at the very least in the order of magnitude.
By the way, using this calculation we get 1731 Kg/s for the Oxygen and 824 Kg/s for RP-1.
- I just took as good the first sources I found around. To make a better estimate, I would at least verify more carfully the actual RP-1 density and also have a look at the thrust level during the whole 162 seconds.
Also note that some of the first stage fuel is kept for landing.
answered Sep 6 at 12:26
BlueCoder
83415
add a comment |Â
up vote
8
down vote
up vote
8
down vote
I think uhoh's answer (7607000/2570=2959 Kg/s) is in the ballpark.
Here's another (less precise) approach:
First stage has 245,620 L of liquid oxygen and 146,020 L of RP-1 fuel (1)
Let's assume oxygen density as 1,1417 (2) and RP-1 density as 0,915 (average of 0.81 and 1.02 in (3)).
So we have 245620*1,1417 = 280424 Kg of Oxygen and 146020*0,915 = 133608 Kg of RP-1.
First stage burn time is 162s (4).
So (280424+133608)/162 = 2555 Kg/s.
Considering that the engines won't be at their maximum thrust for the whole 162 period (they slow down at least during Max-Q I think) and the uncertainties on these numbers*, I think uhoh's answer is correct at the very least in the order of magnitude.
By the way, using this calculation we get 1731 Kg/s for the Oxygen and 824 Kg/s for RP-1.
- I just took as good the first sources I found around. To make a better estimate, I would at least verify more carfully the actual RP-1 density and also have a look at the thrust level during the whole 162 seconds.
Also note that some of the first stage fuel is kept for landing.
answered Sep 6 at 12:26
BlueCoder
83415
I think uhoh's answer (7607000/2570=2959 Kg/s) is in the ballpark.
Here's another (less precise) approach:
First stage has 245,620 L of liquid oxygen and 146,020 L of RP-1 fuel (1)
Let's assume oxygen density as 1,1417 (2) and RP-1 density as 0,915 (average of 0.81 and 1.02 in (3)).
So we have 245620*1,1417 = 280424 Kg of Oxygen and 146020*0,915 = 133608 Kg of RP-1.
First stage burn time is 162s (4).
So (280424+133608)/162 = 2555 Kg/s.
Considering that the engines won't be at their maximum thrust for the whole 162 period (they slow down at least during Max-Q I think) and the uncertainties on these numbers*, I think uhoh's answer is correct at the very least in the order of magnitude.
By the way, using this calculation we get 1731 Kg/s for the Oxygen and 824 Kg/s for RP-1.
- I just took as good the first sources I found around. To make a better estimate, I would at least verify more carfully the actual RP-1 density and also have a look at the thrust level during the whole 162 seconds.
Also note that some of the first stage fuel is kept for landing.
answered Sep 6 at 12:26
BlueCoder
83415
edited Sep 6 at 13:10
answered Sep 6 at 12:26
BlueCoder
83415
answered Sep 6 at 12:26
BlueCoder
83415
answered Sep 6 at 12:26
BlueCoder
83415
83415
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