# Tag Info

## Hot answers tagged interplanetary

90

Technically, yes, it would be easier to put people on Venus. You need less of a kick for the interplanetary trip and slowing down is trivial with that dense atmosphere...one of the Pioneer Multiprobe sub-probes made a soft landing despite only being designed as atmospheric probes. However, the surface temperature stays close to 464 °C, with over 90 ...

48

As others have already pointed out, getting humans to Venus would be marginally easier than getting them to Mars. Let's consider survival on Venus in a little more detail though. Although there haven't been any manned missions to either Mars or Venus, there have been unmanned missions to both. So let's consider how long those unmanned missions have survived. ...

46

Delta-V to LEO is about 10 km/s. From there to C3 (Earth escape) is another 3.2 km/s. It's just another 30% delta-V. The problem is the Tyranny of the Rocket Equation. More delta-V means more fuel. More fuel means more mass. More mass means more fuel. How much more? Fuel costs scale according to $e^{\frac{\Delta V}{v_e}}$, that is e to the power of the ratio ...

34

It's not hard, it's just expensive. We know exactly how to do it. Compare this to building computer processors with 1nm transistors, or making reliable self-driving cars. Those are both things that we currently don't know how to do, and we don't even know exactly how to get better at doing them. Even going past low Earth orbit to another planet, like Mars, ...

15

From what I've been able to find, the "fluff" is that the Epstein Drive electromagnetically accelerates the exhaust, improving propellant consumption over a "standard" inertially-confined fusion drive. Electromagnetically accelerating plasma is certainly physically plausible...real world ion and plasma thruster designs do just that. The problem is that ...

13

The properties of the fictional Epstein Drive are: Very high ISP with an exhaust velocity at least several percent of the speed of light Very high thrust while achieving that ISP or near to it, enough for 5+ g burns. Fusion powered. Based on the first two parameters, the thrust power is insanely high - this is not a fission sail, NTR, or low-power fusion ...

11

The atmospheric pressure of Venus would crush any human. Mars would therefore be a slight more hospitable. It may be red and dry, but it doesn't rain acid!

8

While Mars is more expensive to reach than Venus (it requires more delta-v, thus your payload-to-fuel ratio is smaller on a Mars mission than a Venus mission, everything else being the same), we have all of the technologies needed to put humans on Mars and sustain them for a substantial period of time. Sure, we have to build the spaceships and refine some ...

8

Return trips are harder The main "problem" with crewed trips is that we generally want those people to return back. This means that we don't just need to accelerate the manned part to the required velocity, but we also need to accelerate a sufficient amount of fuel and engines for the return trip, which is a significant increase - as the other ...

7

Based on clarifying comments by the author of the question, the answer to the question is "no". There have not yet been any secondary interplanetary payloads that are not associated at all with the primary interplanetary payload. All of the secondary payloads mentioned in comments were instead very closely associated with the primary interplanetary ...

6

This sounds like the cycler concept, just using a modified asteroid for the cycler. The idea is that you have the cycler carry lots of heavy life support equipment so you don't have to accelerate and decelerate all this heavy equipment each trip. However, you'd still have to accelerate and decelerate the cargo to rendezvous with the cycler, as others have ...

6

TAI conceptually is time measured by a perfect atomic clock running exactly at the geoid. There are some issues with this concept: A perfect atomic clock does not exist. Older and presumably less accurate atomic clocks are regularly replaced with newer and presumably more accurate atomic clocks. Few, if any, atomic clocks are at sea level. Mean sea level is ...

5

Unlikely The problem with sending a cubesat to Saturn is power. A cubesat isn't large enough to carry a nuclear thermal generator, and almost certainly not large enough to carry enough solar cells to power it in the outer solar system. Consider the Juno probe to Jupiter. Its solar cells weigh 340kg, yet generate only 240W of power at Jupiter, which has ...

4

The polar ice caps of Mars are more challenging for a number of reasons. Mars has a similar tilt to Earth, which means that the polar regions have some of the same problems. The two main problems are extreme cold and very long nights over the winters. These together mean that there is a limited time when such missions could take place. For the last 20 years,...

4

Uneven surfaces are easier to handle for larger landing craft, since the variation is proportionally smaller compared to the vehicle itself. A Falcon 9 booster requires a pretty much flat surface, a Starship should be able to handle as much as a couple meters of variation. If you need to land a vehicle that's less capable, you can land something else first ...

4

The idea is good, but I would argue that the technology isn't there yet. Ignoring the (big) problem of orbital debris, you would need good automated docking technology for small vehicles. Some companies, like Astroscale from Japan, are working on docking technologies for spacecraft refueling. Such technology needs to be mature enough before we can do large ...

3

TINSTAAFL. You still have all the delta-V to deal with at both ends of the trip. The expense of "man-rating" the asteroid would be overwhelming in itself.

3

A dynamic system, with at least 3 massive bodies, will have chaos that can, in theory, be exploited to reach (almost) arbitrary positions within said system at close to zero $\Delta v$ over very long time spans. This is the "Interplanetary Transport Network". This sounds very alluring, but it's easy to be misled into believing this has much ...

3

The big problem with sending supplies and fuel ahead is that there's many ways it could go wrong which would end up with the crew being dead. There's no major advantage to sending supplies ahead of the mission to orbit another body, and a lot of risk. The thought is that you can split the cargoes and launch them in smaller, cheap rockets rather than ...

2

Thank you for posting this interesting question. I learned a little more about navigation than I new before. This Paper from Purdue talks about the method in a little more detail. Although one can graphically follow a set of curves to identify that there is a path at a certain energy level (V-infinity) that takes one from one gravity assist to another, it ...

2

The problem with this is that satellites don't stay where you put them. They orbit. Thus for this to work long term, you would need, say a dozen satellites per orbit to ensure you had one in the right direction. This would be really expensive.

2

According to the Galileo Wikipedia article under Reconsideration-Paragraph 6 (https://en.wikipedia.org/wiki/Galileo_(spacecraft)#Reconsideration), there was consideration that Galileo could of been launched by a Air Force Titan IV-Centaur G in May 1991, but the AirForce could not provide NASA a Titan rocket due to the backlog of Department of Defense Payload....

2

1, Yes, but in an opposite sense. Cosmic rays are densest when the solar cycle is least active, but that corresponds to when there are the fewest sunspots. But the magnetic field reverses when there are the most sunspots, at "solar max." 2, Yes. NASA has published extensively about the risks of cosmic rays to astronauts outside Earth's ...

2

There are some concept missions for manned missions to a high altitude city/research station using balloons. https://ntrs.nasa.gov/citations/20160006329 (Thanks to @eps to finding the reference) At the high altitude the temperatures and pressures are not so crazy. However the difficulty of constructing a site and have rockets landing and taking off is tricky....

2

Based on the following calculations, the departure burn angle is about 53.5° I'm going to be using the following assumptions: The spacecraft is going to depart from Earth moving in the direction of Earth's Travel, to get the maximum benefit from the Earth's path around the sun. Using the following parameters. Earth's Standard Gravitational Parameter: $\... 1 Yes, it is completely possible, in fact the Earth's atmosphere was transformed by simple organisms, albeit over many millions of years. Undoubtedly we will at some point in the near future be able to design bacteria and other life forms that can survive extreme environments and metabolize elements into oxygen and other components that we need to survive. It'... 1 Yes it is not easy, but not impossible. This answer addresses the communications issues mentioned in comments. The MarCO cubesats actually served as communications links between a spacecraft landing on Mars and the Earth. It was a slow link, only 8 kb/s using 5 W of power, and at the time the distance was only about 0.7 AU, whereas Saturn will be 9 or 10 AU ... 1 This answer will be satisfying or unsatisfying depending on each reader's perspective. Impulse This answer to Ratio of low-thrust slow spiral to Hohmann transfer$\Delta V\$? explains that the total impulse for an assymptotically low thrust spiral from one circular orbit to a higher one is higher than that needed for a Hohman two impulse transfer by a ...

1

Would this engine produce any thrust? Yes, but not in the way you envision. Ice in a vacuum sublimates to steam, which will create a tiny bit of pressure (on the order of a few Pascals, barely enough to even measure). As the steam escapes down the tube and out into space, it will produce a slight thrust in the opposite direction. The fact that the sun is ...

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