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This illustration in post 150 just above shows the real point to be made here: the launch trajectory has an apogee altitude, where it has gone horizontal before starting downward. At this point, there is some horizontal speed. You make this same point in space your perigee point for a transfer ellipse, with its apogee on the other side of the Earth at your desired circular orbit altitude.
Use the orbits+ course orbit mechanics spreadsheet "orbit basics.xlsx, using the two-endpoints worksheet, set up for Earth. Plug in your perigee altitude and your apogee altitude, and use the average Earth radius value since the inclination is unlikely to be zero. It will give you the transfer ellipse perigee and apogee speeds, and it will also report circular orbit speed at perigee (which you do not need) and at apogee (which you do need).
The difference between transfer ellipse perigee speed and your launch trajectory apogee speed is the ideal dV you need, to get onto the transfer ellipse from your launch trajectory. This might need a little bit of factor-up to cover some small gravity and/or drag losses, more if you do not burn quickly enough to be "impulsive".
You will return to perigee if you do not circularize at apogee. If you do, it is below the entry interface altitude effective for orbital class speeds. That means you will re-enter, unless you raise your transfer ellipse perigee altitude above the entry interface altitude. You do that with a small burn at your transfer orbit apogee.
You avoid that fate and get where you really want to go by burning at apogee to raise your perigee all the way up to that apogee altitude. That IS circularization, exactly per the 1st 3 lessons in the orbits+ course set! The dV there is the difference between circular orbit speed and transfer ellipse apogee speed. It needs no factor-up as long as you do it quickly enough to be "impulsive".
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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The Internet Feed included an item about Spinlaunch today...
https://thespacebucket.com/what-happene … -its-plan/
The news is not good. On the ** other ** hand, the reporter goes into detail about the efforts by the company to find a launch site.
Aside from the technical challenges which would have been severe, it appears that NIMBY won every round.
The company sent a team to Hawaii and to a location in Alaska, and probably other sites.
The founder has stepped down and another gent has bravely picked up the leadership role, but the article writer is not optimistic.
(th)
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This is a follow up to Post #152 above...
I asked ChatGPT4o (the paid version) for advice about alternative designs for SpinLaunch, in light of GW Johnson's attempt to design solid rocket motors that would work with the original sideways rotation design. As often happens, ChatGPT4o surprised me with an idea/suggestion that I had not thought of.
SpinLaunch Variation Questions: Hello Again! Thank you for all the assistance you have provided in the past year and more! I have a scenario to offer for your consideration that I hope you will find interesting. The original SpinLaunch concept was to rotate bullet shaped projectiles inside an evacuated chamber until they had sufficient velocity to be released. A door would open, the bullet shaped projectile would be released from the swing arm, and the projectile would fly into the atmosphere with the pointed nose first, to minimize drag. I have an alternative design under consideration, and thought that your evaluation would be valuable.
ChatGPT said:
ChatGPT
Hello again! It's wonderful to reconnect, and thank you for the kind words about our collaboration. Your alternative take on the SpinLaunch concept sounds intriguing, and I'd be happy to help evaluate it.Please share the details of your alternative design. Is it a variation in the projectile shape, launch mechanism, chamber design, or perhaps the environment (e.g., underwater or in a space setting)? I'd also be curious if you're addressing any specific challenges—like aerodynamic stability, energy efficiency, structural integrity, or material limitations. Let’s dive into your concept!
You said:
Thank you for engaging with me! The original SpinLaunch company has run into numerous problems, and according to news reports, is stalled and may not be able to continue as originally envisioned. The alternative design I have in mind includes changes to the shape of the projectile, to the design of the rotation facility, and most importantly to the design of the solid rocket motors needed to deliver the payload to LEO. I recognize that we are going to be dealing with the strength of materials and other engineering questions, so you will not necessarily be able to assist directly with some of the challenges. However, your knowledge is deep and comprehensive, so I'm confident that where something is outside the scope for this service, you'll be able to suggest tools or resources to help. Let's start at the end, where the solid rocket motor performs it's function. A member of our team is an experienced aerospace engineer with solid rocket motor experience. he has attempted to design a solid rocket motor that would survive the sideways acceleration that the original SpinLaunch design imposed. His experience is with pancake solids, such as those found in artillery shells. These survive acceleration along the axis of acceleration very well, and operate as expected when ignited. The critical factor that comes into play is that solid rocket material flows like water when acceleration is in the elevated levels we are discussing. Therefore, the desire is to find a way to accelerate the SpinLaunch projectile so that it is pointed in line with the rotation arm. This leads to the consequence that the projectile will encounter the air broadside when released. The existing cylindrical design would seem inappropriate for this situation. Can you imagine an airfoil shape for the projectile that would present the least possible air resistance while it makes the transition to nose first flight?ChatGPT said:
ChatGPT
Your alternative design concept and the challenges it addresses are fascinating, especially with the insights into the solid rocket motor dynamics under extreme lateral acceleration. Let’s focus on the airfoil shape for a projectile that transitions from a broadside orientation to a nose-first flight:Key Design Considerations:
Transition to Nose-First Flight:The projectile must have inherent aerodynamic stability to naturally align itself in a nose-first orientation once in the atmosphere.
Stability mechanisms, such as tail fins or control surfaces, can assist in this transition.
Minimizing Drag During Broadside Orientation:While broadside, the projectile will experience high drag. A shape that deflects and channels airflow effectively can minimize resistance and turbulence during this phase.
Structural Integrity:The shape must withstand the intense centrifugal forces during spin-up and the shock of atmospheric entry.
Guidance Mechanisms:Passive stability may suffice, but if guidance control is needed for precise alignment, provisions for actuators or control mechanisms must be considered.
Potential Airfoil-Inspired Shapes:
Flattened Oval (Lenticular) Design:A lenticular (lens-shaped) projectile minimizes drag broadside and offers a natural tendency to align with the airflow due to its aerodynamic center being ahead of the center of mass.
This design also distributes forces evenly, reducing stress on materials.
Delta-Winged Body:Incorporating small, integrated delta wings on the broadside profile can reduce drag and provide lift to assist in orienting the projectile nose-first.
Double-Sphere Transition Shape:The projectile can feature a double-sphere shape where the forward sphere acts as a nose cone and the rear sphere contains the motor. Broadside, this shape minimizes drag by splitting the airflow symmetrically, and during transition, the nose sphere leads the alignment.
Disk with a Deployable Nose:A disk-shaped projectile for rotation, with a nose cone that extends or inflates post-launch, could simplify broadside aerodynamics and achieve a smooth transition to a streamlined form for flight.
Rounded Triangular Planform:This shape balances broadside drag and stability, using a tapered rear to naturally align the projectile during deceleration and transition phases.
Simulation Tools:
To refine these designs, computational tools like CFD (Computational Fluid Dynamics) and solid mechanics simulations are essential:OpenFOAM (open-source CFD software): Ideal for airflow simulations.
ANSYS Fluent or COMSOL Multiphysics: For high-precision aerodynamic and structural analysis.
MATLAB/Simulink: Useful for dynamic stability modeling and control design.
NASA's OpenMDAO: A framework for multidisciplinary analysis and optimization, particularly relevant for aerospace problems.
Prototyping and Testing:
Begin with wind tunnel tests or scaled-down versions of the projectile to assess the aerodynamic transition from broadside to nose-first flight.
Use high-speed cameras and smoke visualization to observe airflow and stability.
This exploration should provide a foundation for crafting a projectile that meets the unique demands of your concept. I'd be glad to help refine any of these ideas further!You said:
Thank you for your inspiring reply! I particularly like your interesting suggestion of a disc shaped design. I'll give your reply some exposure to team members and return to let you know what they think. We can discuss changes to the rotation mechanism another day. While I'm away, best wishes for similar success as you attempt to help everyone who stops by to visit.
ChatGPT said:
ChatGPT
Memory updated
Thank you for the thoughtful feedback and kind words! I'm thrilled the disc-shaped design resonated with you, and I look forward to hearing the team's thoughts. Best of luck with your discussions, and I’ll be here whenever you're ready to continue. Wishing you and your team great success in this exciting project!
(th)
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And here is an attempt to illustrate what a projectile might look like, if this image were adapted for the purpose of a SpinLaunch system.
https://images.app.goo.gl/YJaysUGMuBa9aY6q9
Because I have not learned how to use computer drawing tools, I am currently unable to show the simple smooth shape I have in mind.
The flying saucer from a 1950's movie is a hint of what I have in mind.
The shape would be smoothed out so it is aerodynamically clean in cross-section, as seen from any angle around the plane of the "wing".
(th)
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