Specific impulse Puns

What improvements would you guys try in order for the Starship to hit the 4% mark Elon was talking about?

I’m doing this homework assignment and I’ve used NASAs CEARUN rocket program to output 3 things. Flame temp, molecular weight of products, and specific impulse. Held constant is the chamber pressure and expansion ratio pe/pa=1.

The independent variable is the equivalence ratio, the fuel/air ratio compared to the stoichiometric ratio. What I don’t understand is why the specific impulse increases with the equivalence ratio? My combustion products are liquid oxygen and liquid hydrogen so increase the equivalence ratio decreases the molecular weight of my products and also decreases the flame temperature. I cannot find a good paper to explain this trend online. If anyone can help me understand why specific impulse increases with the equivalence ratio I would be very thankful.

I'm curious why metallic hydrogen is so good (1700 SI) compared to say methane mix used by SpaceX. Is it mostly a matter of the element or molecule used? And so why? What makes metallic hydrogen so good potentially?

Thanks.

Hello, I've been using Godot for quite a while as a primarily 2D game engine. Recently, I've decided to dive into 3D.

Right now, I'm trying to move a RigidBody to a specific position and rotation using only apply_impulse() and apply_torque_impulse().

I've figured out moving the body to a specific position using apply_impulse():

func _physics_process(delta):
    self.linear_velocity = (self.translation.distance_to(targetPosition)/magnetFriction * linear_velocity * delta)
    apply_impulse(Vector3.ZERO, (targetPosition - self.translation) * delta * moveForce )

(this solution is not perfect but works...)

My problem is that I can't figure out how to move an object to a specific rotation, in the same way, using only apply_torque_impulse().

My target angle is a Vector3, corresponding to an Euler angle.

First I naively thought I could just apply the difference between my current Euler angle and my target Euler angle :

func _physics_process(delta):
    apply_torque_impulse(targetAngle - rotation)

This ended in disaster as it turns out, you can't rotate on two axes at once without your angles going crazy.

Next, I tried to use Quaternions,

I figured out something that sort of works sometimes but will break at other times:

func _physics_process(delta):
    var targetQuat = Quat(targetRotation)
    var currentQuat = Quat(rotation)
    var intermediateQuat = currentQuat.slerp(targetQuat, 1 * delta)
    var intermediateEuler = intermediateQuat.get_euler()
    var targetEuler = intermediateEuler - rotation
        
    apply_torque_impulse(targetEuler * delta * 100)

This solution is really unpredictable and unstable,

The problem is that I'm having a hard time properly understanding Quaternions and how to use them in my problem.

I would really appreciate some help on this seemingly basic problem.

Do you know the specific drive of the Blue Origin engines?

Searching the internet I found nothing. The strange thing is that the lack of this type of information affects almost exclusively the US

Current and upcoming rocket engines (Wikipedia)

Nuclear fission rocket is worst idea. It is polluted

Ion rocket is unsuitable due to its low thrust that may not overcome air resistance.

Is traditional chemical rocket is the only choice to liftoff from earth?

No space elevator

Isp is generally used for describing how efficiently a rocket engine consumes fuel.

https://www.grc.nasa.gov/www/k-12/airplane/specimp.html

So I've read this from NASA. My understanding of specific impulse is, it's the total impulse created by fuel weight carried under 1G ( total_impulse / (mass*g0) ),

or equivalent velocity created under 1G ( Veq / g0 ),

or the amount of thrust created under certain flow rate ( thrust / (mass_flow_rate*g0) )

I wasn't a good student in physics class, so I'm kind of confused by all these units now.

Are impulse and thrust the same? Or thrust is in newtons, while impulse is in newton-second?

If all above is correct, why is "seconds" used as unit for Isp, not something like N*s/kg ?

I’m using imperial units.

So, Impulse_specific=Impulse_total/(m_propellant*g)

Impulse_total has units of lb*sec m_propellant has units of lb g has units of ft/sec^2

After doing dimensional analysis, Impulse_specific has units of s^(3)/(ft). The units of Impulse_specific should be s. What am I doing wrong in terms of unit analysis?

How can i give an impulse only when you have in hand OR when you place it in an item frame a specific item? Like when i have a stick with a specific name, and only when i place it inside the item frame? 1.16.5

I have read it was around 100k to 150k!! Seems just monstruous even compared to metallic hydrogen specific impulse (in the thousand) ... I guess it depends a lot of actual implementation, but in a ball park? Are we talking of 10 thousands, 100 thousands, 500 thousands??

^ |

Hi all,

I'm trying to use the formulas found here: https://www.desmos.com/calculator/ms0zpkjkvp for another project but wondered if there is a way of calculating Isp for a rocket that doesn't change mass (Electric).

My understanding is that Isp is how effective something is at using its fuel, so are electric powered things 0% efficient because the mass doesn't decrease or are they 100% because they can get all their thrust without reducing mass.

I'm trying to avoid re-arranging that equation if I can.

Thanks!

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What is your intended use for this build? The more details the better. Gaming mostly, also probably run a small home entertainment setup. I have a loft condo and I'm thinking I'd like to combine the TV/computer in to one. Please let me know if this is stupid.

If gaming, what kind of performance are you looking for? (Screen resolution, framerate, game settings)

I like playing CIV so lowering turn time would be nice, I think I'll be able to run basically anything else I want to play on the intended build. Probably stuff like Witcher, Far Cry, stereotypical shit.

What is your budget (ballpark is okay)?

I don't have a fucking clue. I think I'd like to keep it under $1500 but I also just spent more on the CPU by a few hundo than what's recommended so here we are.

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US

**Post a draft of your potential build here (specific parts please). This is a super fungible list.

PCPartPicker Part List

Merlin Vacuum Specific Impulse: 311 seconds.

Raptor Vacuum Specific Impulse: 380 seconds.

380-311 = 69.

Elon has been trolling us all along.

Hey guys, I’m writing a paper on different propulsion systems for rockets and had a question about the formula for Specific Impulse. Before saying anything else i’d like to clarify that i’m a freshman engineering student so i’m not too bright lol. But anyways, I’m reading a journal where it compares Chemical, Nuclear Thermal and Electric propulsion and they all list their exhaust speeds. Is the exhaust speed equal to the thrust? or the mass flow rate of the propellant.

Again I’m sorry if this sounds like a retarded question. Thank you all.

I have a bad habit of thinking I need things and ordering them right away and when they come to my house I realise it's not as useful or necessary as I thought it would be and end up returning them... apparently often enough that Amazon became concerned 😬

I know that it's a unit of the efficiency of an engine, but I'd like to know more details, such as how it's calculated, and a sense of scale.

I have been looking at project rho's fusion rocket segments, and there is a large range in which the different designs' performance falls in, going from barely above a gas core NTR, to over a million seconds. I am interested in what a realistic high end estimate (as in we have mastered fusion) for the specific impulse of a fusion drive. I'm also curious about the other specs as well, but I am most curious of the ISP. Thank you!

I believe it could lead to fuel savings as High specific impulse means better fuel efficiency. Please correct me if I am wrong.

because if they turn out to be more efficient than kerosene, loading a Falcon Heavy with stacks and stacks of them could be a cheaper alternative to SLS

I know there are other threads on this but none of them are answered well.