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#1 2025-06-23 10:43:08

tahanson43206
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Registered: 2018-04-27
Posts: 21,858

Tangent Launch

This launch system was first discussed in the NewMars forum between 2018 and 2025.

It has come  up again in work done by GW Johnson.

Images are created but not available at the moment.

The concept of the launch method is to accelerate from the surface of the Earth (or any spherical body) in a straight line perpendicular to a line from the center of the Earth. An example of a launch method would be an electric catapult to give a vehicle forward momentum.

The second 'stage' would be an air-breathing phase that would continue until there is insufficient oxygen available to sustain combustion.
The third 'stage' would be a rocket.

Earlier work was done by kbd512, but it will take some effort to find it.

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#2 2025-06-23 10:43:42

tahanson43206
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Re: Tangent Launch

This post is reserved for an index to posts that may be contributed by NewMars members.

Index:

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#3 2025-07-07 12:16:24

tahanson43206
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Re: Tangent Launch

This topic was originally created in response to one of the studies GW Johnson has done on launch topology.

I use that word with care, because we do not often think of that particular word in connection with space launches.

The word itself is (apparently) from the field of mathematics, so I'm hoping NewMars members will provide a better choice.

I'm using the word (temporarily) to differentiate between classes of launches.

Tangent launch is a very particular launch concept.  It applies very well to airless bodies such as the Moon.

It's not as useful on Earth, where the atmosphere would present an obstacle for hundreds of miles it it were used.

In earlier discussions in the forum, members have considered a variety of launch methods from the surface of the Moon.

Electromagnetic launch systems lend themselves admirably to the tangent launch concept if applied on the Moon, because the modest rise of a linear accelerator with respect to the surface implies modest expense for support structures.  Even regolith could be piled up to support a linear accelerator.

I bring this up in light of the arrival of interesting objects to near Earth.  Not too long ago, the arrival of 2024YR4 was in discussion here, and it was determined that a relatively small dV would be required to place a sensor package on the asteroid.  In that case, the asteroid is going to pass close to Earth, and possibly within the Lunar orbit

The interstellar comet (ATLAS) that is approaching is in a VERY different league. It's velocity with respect to the Sun is reported to be on the order of 60 Km/s, and the velocity of Earth in orbit is reported to be on the order of 30 Km/s.  Apparently no human machine exists that can achieve that dV change directly.  That change could be achieved by careful planning of a Solar flyby maneuver, but I understand that such a maneuver would take years to achieve if we depended upon normal Solar gravity to handle most of the flight.

All this leads me to the possibility that humans might be able to build a 30 Km/s magnitude launcher on the Moon.

The first category of such a launcher has been discussed in some depth in the forum.

In this post, I'd like to offer for consideration the "SpinLaunch" concept applied to the entire Lunar sphere.

Humans know how to spin small objects in circles.

Particle accelerators have been in operation on Earth for many decades.

The cyclotron was invented in 1929-1930.  Linear accelerators existed before that.

My suggestion here is to consider using the surface of the Moon as a venue to accelerate a probe to a high velocity by accelerating it slowly in a long track, until it is ready to begin flight to an interesting object.

This would be a kind of "lunar SpinLaunch"

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#4 Yesterday 20:34:32

tahanson43206
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Re: Tangent Launch

In another topic, we have a report of Chinese progress in developing maglev trains.

There is some uncertainty about what they have actually achieved, as compared to the text of the report, which was written for a general audience and is therefore necessarily limited in details.

While we wait for clarification about what has actually been achieved, I think we in NewMars are free to think about the implications of a horizontal launch system to give a space going vehicle a substantial head start.

Since a rail road track necessarily runs along the circumference of the Earth, a vehicle that receives acceleration from such a train would fly on a tangent trajectory unless it is deliberately canted upward, which is not necessary, if the first "stage" of flight consumes atmospheric oxygen.

I'd appreciate anyone in the membership who has a few moments to think about how this system might be used, to write a post or two.

Let us assume the article is correct, that the velocity achieved is 800 kilometers/hour, or 220 meters/second.

Is that velocity sufficient to allow ignition of a ramjet, or is this still the province of turbine technology?

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#5 Today 08:22:10

tahanson43206
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Re: Tangent Launch

In this conversation with Gemini, I offered the idea of using maglev trains to accelerate a SSTO hybrid vehicle along a "Tangent" trajectory to LEO.  The proposal would include maglev, rocket, ramjet and rocket finishing acceleration phases.

Conversation with Gemini

Tangent launch discussion - Hi Gemini! Thank you for your assistance with numerous previous requests. Today I am investigating the feasibility of a kind of space launch called "Tangent". This is a (presently hypothetical) launch method that would combine multiple acceleration methods to deliver a space craft to LEO by following a linear path that is tangent to the surface of the Earth or any space object. Today's question arises from news that the Chinese have apparently advanced the state-of-the-art of maglev trains to a velocity capability of 800 km/h or 220 meters per second. The question is: what velocity is needed for a ramjet to achieve ignition in this context?
***
The speed required for a ramjet to achieve ignition and produce significant thrust is generally well above the 800 km/h (220 m/s) capability of the advanced maglev trains.

Here's a breakdown of what the sources indicate:

Minimum Ignition Speed: While some theoretical minimums are as low as 100 knots (approximately 185 km/h or 51 m/s), ramjets do not produce significant thrust at these very low speeds.

Effective Thrust Production: Ramjets typically begin to produce "appreciable thrust" or "significant thrust" at speeds around Mach 0.5 to Mach 1.0 (the speed of sound). This translates to roughly 610 to 1225 km/h (or 170 to 340 m/s) at sea level, as Mach 1 at sea level is approximately 343 m/s or 1235 km/h.

Optimal Operating Speed: Ramjets are most efficient and designed to operate at supersonic speeds, typically in the range of Mach 2.5 to Mach 6, with peak efficiency often around Mach 3. This means speeds between approximately 3,000 km/h to 7,400 km/h (or 830 m/s to 2,050 m/s).

In the context of the Tangent launch and the 800 km/h maglev train:

While 800 km/h (220 m/s) is a very impressive speed for a maglev train, it is still generally below the optimal operating range for most ramjets and might only provide a very small amount of thrust, if any, for ignition. To get a ramjet to effectively accelerate a spacecraft, a much higher initial velocity, typically in the supersonic realm, would be needed. This is why ramjet-powered vehicles usually require a separate booster (like a rocket or turbojet) to get them up to their operational speeds.
Sources
***
A vehicle designed for this flight regime would include ramjets and rockets. As you evaluate the proposal, and taking into account that the fuel and oxidizer on board the vehicle are resources that must be expended with great care, does it seem reasonable to consider a four phase flight plan? This would start with physical acceleration of the fully laden vehicle on a maglev train. The train would accelerate the vehicle to 800 km/h, at which the rocket system would be engaged to accelerate the vehicle to a velocity where it would be possible to sustain acceleration with the ramjet, at which point the rockets would be extinguished. In this scenario, the ramjet would provide acceleration while there is sufficient oxygen available, taking into account that greater velocity provides access to more oxygen, even as the quantity of available oxygen decreases due to altitude. At some point, the ramjet would be discontinued, and the rocket subsystem would return to service. It is noted that drag will be much greater for this flight profile than is the case for vertical launch, but the vehicle envisioned for this scenario would be winged and intended for return to Earth. To clarify for the record, the vehicle shape is envisioned to be a lifting body similar to the X-37b and other similar reusable vehicles.
***

This multi-phase flight plan for a "Tangent" launch vehicle, combining maglev, rocket, and ramjet stages, is quite ambitious but theoretically sound in its general concept for optimizing propellant usage and leveraging the strengths of different propulsion systems. Let's break down the feasibility and challenges of each phase:

Phase 1: Maglev Acceleration (to 800 km/h / 220 m/s)

Feasibility: The news about advanced Chinese maglev trains reaching 800 km/h confirms the technical possibility of achieving this initial velocity on the ground.

Advantages:

Propellant Savings: This is the primary benefit. By using ground-based electricity to accelerate the fully laden vehicle, you save a significant amount of on-board rocket propellant that would otherwise be used for the initial, most inefficient part of the ascent (overcoming static inertia and dense atmospheric drag at low speeds).

Reduced Stress on Vehicle: A smooth, linear acceleration on a track can reduce structural stress on the vehicle compared to a vertical rocket launch, potentially allowing for lighter vehicle construction.

Challenges:

Track Length: Accelerating a heavy, fully laden space vehicle to 800 km/h would require an extremely long maglev track. Even for much lighter, conventional high-speed trains, tracks are many kilometers long. For a space vehicle, this would be a monumental engineering feat, likely requiring a dedicated, remote launch site.

G-forces: While a linear path helps, the acceleration rate still needs to be carefully managed to avoid excessive G-forces on the vehicle and any sensitive payload.

Sonic Boom/Environmental Impact: Launching at 800 km/h, even horizontally, could generate significant noise and shockwaves at ground level, which would necessitate a very remote location.

Integration: Seamlessly transitioning the vehicle from the maglev track to free flight while engaging rocket engines presents a complex engineering challenge.

Phase 2: Rocket Boost (to Ramjet Sustaining Velocity)

Feasibility: This is a standard rocket operation, albeit starting from a high initial velocity.

Purpose: The rocket phase is crucial because, as discussed, 800 km/h is generally below the effective operating speed for ramjets. The rockets would accelerate the vehicle to Mach 1.5-2.5 or higher, where the ramjet becomes efficient.

Propellant Efficiency: While rockets are less efficient than air-breathing engines, using them for this relatively short, high-thrust burst to get to ramjet operating speeds is a sound strategy to conserve the more efficient ramjet fuel for later.

Challenges:

Engine Transition: The precise timing and smooth transition from rocket power to ramjet power is critical. This involves igniting the ramjets while the rockets are still firing, then shutting down the rockets once the ramjets are stable and producing sufficient thrust.

Aerodynamic Loads: As the vehicle gains speed in the dense lower atmosphere, it will experience significant aerodynamic drag and heating. The "lifting body similar to the X-37B" design helps manage some of this, but the tangent profile means prolonged exposure to dense air.

Phase 3: Ramjet Acceleration (Atmospheric Flight)

Feasibility: This is where the air-breathing advantage comes in.

Advantages:

High Efficiency: Ramjets are significantly more fuel-efficient than rockets at supersonic speeds within the atmosphere because they use atmospheric oxygen as the oxidizer, eliminating the need to carry heavy oxidizer tanks. This is the core propellant-saving aspect of the design.

Sustained Acceleration: Ramjets can provide continuous acceleration as long as there's sufficient air density and speed.

Challenges:

Operating Envelope: Ramjets have a specific operating "corridor" of speed and altitude.

Minimum Speed: As noted, they need to be supersonic to work effectively.

Maximum Altitude: While higher velocity helps ram air into the engine, air density decreases exponentially with altitude. Ramjets typically operate up to 30-40 km (100,000-130,000 ft), with some experimental scramjets pushing higher. The "greater velocity provides access to more oxygen" is true to a point, but eventually, the air becomes too thin regardless of speed.

[color=dark green]Thermal Management: Hypersonic flight within the atmosphere generates extreme heat due to air compression and friction. The vehicle's thermal protection system will be crucial, similar to reentry systems.[/color]

Drag: The "tangent" flight profile, while potentially reducing gravity losses compared to a vertical launch, incurs significantly higher and prolonged aerodynamic drag. This drag penalty will consume a substantial amount of the ramjet's thrust and limit the ultimate altitude and speed achievable with air-breathing engines. This is the fundamental trade-off of this profile.

Transition to Scramjet? For really high speeds (above Mach 5-6) and altitudes, a pure ramjet might transition to a scramjet (supersonic combustion ramjet) if designed as a dual-mode ramjet (DMRJ). This would extend the air-breathing phase, but scramjets are even more complex to design and operate. Given the X-37B comparison, which is a re-entry vehicle, not a scramjet-powered one, it suggests a ramjet, or potentially DMRJ, is the focus.

Phase 4: Rocket Boost (to LEO)

Feasibility: Standard rocket operation, but with a significant advantage.

Purpose: Once the ramjet can no longer produce sufficient thrust due to decreasing air density, the rockets take over to accelerate the vehicle the rest of the way to orbital velocity and altitude.

Propellant Efficiency: By starting this phase from a high velocity and altitude (e.g., Mach 5+ and 30-40 km), the rockets are operating in a much thinner atmosphere, reducing drag losses and increasing efficiency (higher effective ISP) compared to a ground-based launch. The majority of the vehicle's "delta-V" (change in velocity) for orbit would still come from this rocket stage, but the initial delta-V provided by the maglev and ramjet significantly reduces the required rocket propellant.

Overall Assessment:

The four-phase flight plan is reasonable in concept for a reusable space launch system aiming to minimize on-board propellant. It effectively plays to the strengths of each propulsion type:

Maglev: Efficient initial acceleration, offloading propellant.

Rockets (initial): Quick boost to ramjet operating speeds.

Ramjet: Highly efficient acceleration through the thickest part of the atmosphere.

Rockets (final): Final push to orbit in the near-vacuum of space.

Key Challenges & Considerations:

Engineering Complexity: The seamless integration and precise control of three distinct propulsion systems, with critical transitions between them, is an immense engineering challenge.

Thermal Management: The prolonged, high-speed atmospheric flight will require advanced thermal protection systems, possibly active cooling, to survive the intense aerodynamic heating.

Structural Integrity: The vehicle must be robust enough to withstand the dynamic pressures of high-speed atmospheric flight, as well as the g-forces from acceleration.

Drag Management: While a lifting body design helps, the drag associated with sustained horizontal acceleration at high speeds and lower altitudes will be a constant battle and will dictate the maximum efficiency and performance of the ramjet phase. The X-37B is designed for re-entry (high lift-to-drag at hypersonic speeds for control), which is beneficial, but its primary purpose is not powered hypersonic flight for ascent.

Noise and Environmental Impact: The sheer scale of such an operation, particularly the maglev track and supersonic atmospheric flight, would necessitate very remote launch locations and careful environmental impact assessments.

Cost: Developing and building such a system would be astronomically expensive, requiring a massive upfront investment in infrastructure (maglev track) and vehicle R&D.

In conclusion, this "Tangent" launch concept is a fascinating and theoretically viable approach to reducing the cost of access to space by leveraging atmospheric oxygen and ground-based infrastructure. However, the engineering challenges, particularly related to thermal management, drag, engine transitions, and the sheer scale of the required ground infrastructure, are formidable. It represents a long-term vision rather than an immediate solution, but the conceptual framework is sound.
***
Thank you for your thoughtful analysis and rephrasing of this proposal. I will share our conversion with a small international forum whose interests include space flight and related topics.
***

You're most welcome! I'm glad I could provide a thoughtful and clear analysis of the "Tangent" launch proposal.

I hope the rephrased information proves valuable for your discussions with the international forum. It's a fascinating concept, and the combination of maglev, ramjet, and rocket technologies presents some truly cutting-edge engineering challenges and opportunities for future space access.

Is there anything else I can help you with today as you prepare for your forum discussion?

This vehicle would be intended for reentry, so the heat shielding for reentry would be called upon to survive acceleration through the atmosphere.

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#6 Today 09:47:13

tahanson43206
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Registered: 2018-04-27
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Re: Tangent Launch

In this conversation, I asked Google's Gemini to look for more information about a report of research in China to improve performance of their existing maglev trains.

The results found are less impressive than the original (erroneous) report, but still quite an achievement, and definitely promising.

Conversation with Gemini

Chinese Maglev Progress - Hi Gemini! Thank you (again) for your outstanding assistance with numerous previous requests! This one is (hopefully) well within your comfort zone. An article appeared recently about Chinese progress in development of maglev trains. The author appears to be a writer with many interests, and skills translating complex subjects for a general audience. I have written the author for more information, but received an "out of office" reply. My hope is that with your deep search capabilities, you might be able to discover a bit more information. The report described a maglev research project that achieved a velocity of 800 km/h over a distance of 1000 meters. Those details are insufficient to make a reasonable judgement about the research. For example, calculation of the time needed to accelerate from 0 to 800 km/h is 4.5+ seconds, and that yields an acceleration of (something like) 20 g's. This is unlikely, so I'm hoping you can discover information that is more plausible.
***

You're right to be skeptical about 20 G's! That level of acceleration would be completely impractical and dangerous for any form of human transport. It seems there might have been a misunderstanding or misreporting of some details in the article you read.

Here's a breakdown of the latest credible information regarding China's maglev progress, particularly concerning the high-speed tests and acceleration:

Recent Breakthroughs and More Plausible Acceleration Figures:

Several recent reports (from June and July 2025) detail a significant achievement by researchers at the Donghu Laboratory in Hubei Province, China. They have successfully accelerated a 1.1-tonne maglev test vehicle to 650 km/h (approximately 404 mph) in just 7 seconds over a distance of 600 meters.

Let's do a quick calculation for this reported achievement:

Initial velocity (v \0 ): 0 km/h

Final velocity (v f ): 650 km/h = 180.56 m/s (approx)

Time (t): 7 seconds

Distance (d): 600 meters

Using the formula for acceleration (a= tv f −v 0 ):a= 7 s 180.56 m/s−0 m/s  ≈25.79 m/s 2

To convert this to G's (where 1 G ≈9.81 m/s 2 ):a G = 9.81 m/s 2 /G 25.79 m/s 2

≈2.63 G

While still high, 2.63 G's for a brief acceleration test is significantly more plausible than 20 G's, especially for an experimental vehicle that isn't carrying passengers. This is closer to what fighter pilots experience, not typical passenger transport. The goal of these tests is often to push the technological limits of the system itself, not necessarily passenger comfort in that specific instance.

Key Details from the Reports:

Location: Donghu Laboratory, Hubei Province, China.

Test Vehicle: 1.1-tonne (presumably a scaled or specialized test vehicle, not a full passenger train).

Speed Achieved: 650 km/h (404 mph).

Acceleration Time: 7 seconds.

Distance to Achieve Speed: 600 meters (not 1000 meters for the 800 km/h figure).

Track Length: The self-developed high-speed maglev test track is 1,000 meters long, allowing for rapid acceleration and deceleration within a short distance.

Braking: The system is also reported to decelerate from 650 km/h to zero in just 200 meters, indicating powerful and precise control.

Technology: The system uses self-developed electromagnetic propulsion and suspension, virtually eliminating friction and primarily overcoming air resistance. They emphasize ultra-precise speed and positioning measurements (accuracy up to 4 millimeters).

Future Goal: Li Weichao, director of the High-speed Maglev Electromagnetic Propulsion Technology Innovation Center at the lab, stated that the typical operating speed for this test line is 800 km/h, and the entire construction is expected to be completed by the end of 2025, at which point the platform will meet the conditions for acceptance. This suggests that the 800 km/h speed is a design goal for the test platform's capabilities, and future tests may aim to achieve that speed.

Context of Chinese Maglev Development:

Shanghai Maglev: China currently operates the world's first commercial high-speed maglev line in Shanghai, connecting Pudong International Airport to Longyang Road station. It reaches a maximum cruising speed of 431 km/h, though it often operates at 300 km/h.

600 km/h Maglev Train: China has also unveiled a separate 600 km/h maglev train developed by CRRC (China Railway Rolling Stock Corporation). This is intended for future commercial routes and aims to fill the "speed gap" between conventional high-speed rail (around 350 km/h) and air travel (800-900 km/h cruising speed). This train is designed for passenger transport and focuses on factors like passenger comfort, energy efficiency, and reduced maintenance.

Hyperloop/Vacuum Tube Research: There's also ongoing research into "T-Flight" or hyperloop systems that aim for even higher speeds (potentially 1,000+ km/h) by operating in near-vacuum tubes to further reduce air resistance.

It appears the article you read might have conflated the 800 km/h "typical operating speed" goal of the new test platform with a specific 800 km/h test achievement over 1000 meters. The documented achievement is 650 km/h in 7 seconds over 600 meters, which yields a much more reasonable acceleration figure for a test scenario.

I hope this provides the more plausible information you were seeking!
***

Thank you ** very ** much for this helpful research and analysis. I am happy to report your results to a small international forum where I reported the first questionable information. An acceleration of 2 G's is quite acceptable for the first stage of a multi-mode space launch vehicle, such as the one we discussed earlier today. In this context, a horizontal run of multiple kilometers is quite acceptable. The ability to stop the train after it has released it's payload is an important consideration, and I appreciate your including that part of the research.
***

You are most welcome! I'm delighted to hear that this information is helpful and that the more plausible acceleration figures align well with the discussions in your international forum, particularly in the context of multi-mode space launch vehicles.

It's fascinating how advancements in maglev technology, even for high-speed ground transport, can have implications and parallel considerations for other high-velocity applications like space launch systems. The common challenges of managing extreme speeds, rapid acceleration/deceleration, and precise control are definitely shared.

The braking capability from 650 km/h to zero in 200 meters is indeed a significant detail. For a launch vehicle scenario where the "train" component needs to recover after payload release, efficient and reliable deceleration is absolutely critical for reusability and safety. It speaks to the robustness and advanced control systems being developed alongside the raw speed capabilities.

Please feel free to reach out if any other questions or areas for research come up. I'm here to assist!

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#7 Today 11:28:57

tahanson43206
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Registered: 2018-04-27
Posts: 21,858

Re: Tangent Launch

In this conversation with Gemini, I was curious to know how long a maglev track would need to be the accelerate from 0 m/s to 343 m/s at 2 G.

The answer appears to be 3 kilometers.  If the same distance is needed for deceleration, the total track length would be 6 kilometers.

Launch of a tangent flight plan vehicle out over open water would reduce impact of sonic booms on land, but it sure would impact people who are out on the water under the flight path, and it might affect creatures in the ocean under the flight path.

In any case, here is the conversation showing the calculations:

Search Labs | AI Overview
To find the distance needed to reach a desired velocity given acceleration, you can use the following kinematic equation:
v² = u² + 2as
where:

    v = final velocity (343 m/s)
    u = initial velocity (0 m/s)
    a = acceleration (2G)
    s = distance (what needs to be found)

Step 1: Convert acceleration to m/s²
One standard gravity (G) is approximately 9.80665 m/s².
Therefore, 2G = 2 * 9.80665 m/s² = 19.6133 m/s².
Step 2: Plug in the values and solve for distance (s)
343² = 0² + 2 * (19.6133) * s
117649 = 0 + 39.2266s
117649 = 39.2266s
s = 117649 / 39.2266

s ≈ 2999.2 m

The approximate distance needed to reach the desired velocity of 343 meters per second with an acceleration of 2G is 2999.2 meters.

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