# Project Orion-Like Space Vehicle

• Xforce
In summary: How about .01 gram? In summary, the space probe would have to be very small to be effective, and the mass would have to be very small to be useful.
Xforce
TL;DR Summary
The Orion project was available with current technology... however carry thousands of nukes on board might not be a great idea
Nations prohibit the detonation of nukes in space, but I don’t know there is a better way to use these weapons of mass destruction, than propelling a probe on a interstellar travel at relativistic speeds in the near future.

Also, the origin Orion, where all the nukes are carried onboard, will reduce the top speed because of the rocket equations. What about a nuclear mine field?

My idea is, having a probe less than a ton, attached to something like a light sail, tens of kilometers across, but only tens of microns thick, hold together by nanomaterials.

There are around 10,000 nuclear warheads in the world’s arsenal, mostly from America and Russia. We can arrange them into a slightly curved line (curvature decrease as far away from sun) each time when the probe passes a nuke, the nuke detonates nanoseconds after. The thin sail will ablates each time, providing extra thrust than the light pressure, and prevent overheating... when all the nukes have been detonated, the probe should be able to reach relativistic speeds, even sub-light speeds.

In the 70s, someone made a daydream proposal.

Make a light sail, only 1 atom thick, but the size of the Moon. The total mass of the vessel including sail and payload was only one or two grams. It would accelerated by lasers in close orbit around the Sun. He calculated that it could achieve 0.3 c before being out of range for the lasers. I got two takeaways from reading that.
1. The number one thing you can do to improve a space travel idea is not a more powerful engine, it is to reduce the total mass.
2. People are more likely to listen to your idea if you can do the calculations; even back-of-the-envelope calculations.
Can you show us the calculations to back up what you said?
Xforce said:
having a probe less than a ton
...
the probe should be able to reach relativistic speeds, even sub-light speeds.the probe should be able to reach relativistic speeds, even sub-light speeds

The kinetic energy of photons is small indeed. Since they collide with the sail and reflected back, the energy the photon passed to the spacecraft is twice it’s own kinetic energy. So each photon gives E=2*h*c/λ of energy ...
A ton of stuff traveling at .1c will have momentum of Ek=((1/√(1-0.1c2/c2))-1)*mc^2 which at 0.1 c means the kinetic energy of 1% mass converted to energy (interestingly, a bit more than the energy from fusion) or simply 9*10^17 joules. (At this point, I start doubting the nukes are enough)
Let’s suppose each of those nukes yields a megaton, which is 4.18*10^15J . To make calculations easier I’ll use 4*10^15J. Depends on the distance from the detonation, or the strength of the material, but since the energy is randomly emitted in all directions, it will take a infinitely large sail to let 50% photons impact the sail. So let’s say there is a device that directs the radiation, so exactly 50% energy impact the sail on perpendicular direction (this is very unrealistic too), so the total photonic energy onto that huge sail is 2*10^19J The photonic drive have a terrible ratio of power to thrust. At 300Mw per N, if we times this by a second we get 3*10^8J of total energy for 1J of effective energy... this means only 7*10^10J is put onto the spacecraft . In reality the energy is mostly taken up by neutron radiation and alpha radiation... I’m sure they give off more thrust but I still doubt that is enough. Sorry for my clumsy calculations

Xforce said:
9*10^17 joules
You forgot a factor of 2, but pretty close.

Xforce said:
this means only 7*10^10J is put onto the spacecraft .

I didn't check that calculation, but the conclusion is that this scheme is on the order of 107 times too little is the right conclusion. In other words, the mass of the vessel would have to be closer to 1 gram than to 1 ton.

OK, now think the next step. How small could we make the mass of a space probe for it to still be useful? In post #1, you just arbitrarily threw out 1 ton.

## 1. What is a Project Orion-Like Space Vehicle?

A Project Orion-Like Space Vehicle is a type of spacecraft that uses nuclear propulsion to travel through space. It is based on the original Project Orion concept developed in the 1950s, but with modern technology and advancements.

## 2. How does a Project Orion-Like Space Vehicle work?

A Project Orion-Like Space Vehicle works by using nuclear explosions to propel itself forward. This is achieved by detonating small nuclear bombs behind the spacecraft, which push it forward using the force of the explosions.

## 3. What are the advantages of a Project Orion-Like Space Vehicle?

One of the main advantages of a Project Orion-Like Space Vehicle is its high speed and efficiency. It is capable of reaching speeds up to 5% of the speed of light, making it much faster than traditional chemical rockets. It also has a high payload capacity and is able to carry large amounts of cargo or passengers.

## 4. What are the potential risks or concerns with a Project Orion-Like Space Vehicle?

One of the main concerns with a Project Orion-Like Space Vehicle is the use of nuclear explosions as a propulsion method. This raises safety and environmental concerns, as well as potential political and ethical issues. There are also concerns about the cost and feasibility of building and maintaining such a spacecraft.

## 5. Are there any current plans or projects for a Project Orion-Like Space Vehicle?

There are currently no active plans or projects for a Project Orion-Like Space Vehicle. However, there have been proposals and studies conducted by various organizations, including NASA and private companies, to explore the feasibility and potential uses of this type of spacecraft in the future.

• General Discussion
Replies
13
Views
1K
• Nuclear Engineering
Replies
8
Views
2K
• Astronomy and Astrophysics
Replies
5
Views
2K
• Nuclear Engineering
Replies
16
Views
3K
• Aerospace Engineering
Replies
52
Views
18K
• Classical Physics
Replies
2
Views
2K
• Sci-Fi Writing and World Building
Replies
18
Views
5K
• Aerospace Engineering
Replies
10
Views
4K
• Special and General Relativity
Replies
38
Views
7K
• Astronomy and Astrophysics
Replies
3
Views
3K