92 votes
Accepted

Would it be easier to put humans on Venus rather than Mars?

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 ...
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75 votes
Accepted

Is Nibiru real or totally science fiction?

Nibiru is fiction. Nibiru, a purported large object headed toward Earth, simply put - does not exist. There is no credible evidence - telescopic or otherwise - for this object's existence. There ...
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  • 121k
59 votes
Accepted

Assuming a spacecraft is traveling in a constant rate and our Astronaut will exit it to a space walk, will she be "left behind" by the spacecraft?

As long as neither spacecraft nor the astronaut are accelerating or decelerating, the relative speed of the spacecraft and the astronaut remains the same. So the astronaut will hover near the ...
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  • 12.2k
58 votes

Why was Venus rather than Mars targeted for the first interplanetary landings?

The reason is delta-v, which is a crucial concept in Spaceflight. It means change in velocity, and is the primary 'currency' that space mission have to expend in order to reach places in the solar ...
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52 votes

Are there any greater risks of traveling significantly faster to another planet?

The biggest risk on a flight to Mars is cumulative exposure to radiation, so a 1-2 month flight would actually be much healthier for a crew than a 7-8 month flight. I don't know of any risks that ...
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50 votes

Do you need to burn fuel between gravity assists?

Yes, Trajectory Correction Maneuvers (TCMs) are always performed during cruise phases, whether before or after gravity assist flybys. This NASA tutorial serves as a good general reference. One source ...
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  • 17.9k
48 votes

Would it be easier to put humans on Venus rather than Mars?

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'...
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48 votes
Accepted

Why is it so hard to build crewed rockets/spacecraft able to reach escape velocity?

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. ...
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  • 7,365
41 votes
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Why don't we launch spacecraft from the Moon?

First a few terms: Low Earth Orbit (LEO) All spacecraft must first achieve low Earth orbit. This is true whether you're sending stuff to the Moon or Mars. Trans Mars Insertion (TMI) The burn needed ...
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  • 15.1k
41 votes

Is Nibiru real or totally science fiction?

The name Nibiru does appear in science fiction. However, the stuff to which you refer is not science fiction. It's just baloney, malarkey, or "fake news." According to Wikipedia's article Nibiru ...
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  • 148k
37 votes

Why was Venus rather than Mars targeted for the first interplanetary landings?

We didn't know how hostile Venus's surface was, until we had landed there. The atmosphere of Venus makes it easier to land there than Mars. From Wikipedia, we learn: Before radio observations in ...
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  • 118k
37 votes
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Exactly why does Starship need to be this big for interplanetary travel?

A lot of launch costs are independent of rocket size. It's no cheaper to clear the flight path for a smaller rocket, for example. It also takes a lot longer to do 10 launches instead of one large ...
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35 votes
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What uses would the Aldrin-Cycler have?

Imagine a large vehicle that can recycle water and air, has shielding, and contains everything for a trip that would take months. This would be the cycler. The vehicle is heavy and is needed for a ...
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  • 532
35 votes

Assuming a spacecraft is traveling in a constant rate and our Astronaut will exit it to a space walk, will she be "left behind" by the spacecraft?

It turns out that outer space is not a perfect vacuum: there are a few hydrogen atoms per cubic centimeter. (reference) For large X, non-relativistic physics, the astronaut and spacecraft will stay ...
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34 votes
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Why are we interested in visiting the giant planets' icy moons?

The icy moons are of interest for exploration as part of the overall "follow the water" strategy of exploration that NASA (and others) have been exploring for some time. The "where else can water be ...
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  • 2,311
34 votes

Why is it so hard to build crewed rockets/spacecraft able to reach escape velocity?

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 ...
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30 votes

Why haven't telescopes been sent to other planets?

We have sent telescopes to other planets, almost all the optical sensors on probes are in fact telescopes so they can focus on a specific area in detail. These sensors are to explore the planets they ...
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  • 18.7k
29 votes

What uses would the Aldrin-Cycler have?

One good thing about these periodic trajectories / interplanetary orbits, be it Mars Cyclers, Earth-Moon Cyclers (gravity assist UP/DOWN Escalator Orbits), or Resonant Cyclers (fixed VISIT Orbits) is ...
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  • 75.2k
29 votes
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After the loss of Challenger, why weren’t Galileo and Ulysses launched by Centaurs on expendable boosters?

The performance of Shuttle-Centaur would have greatly exceeded that of either the Atlas-Centaur or Titan-Centaur combination. Neither the Atlas nor Titan were able to put a fully fueled Centaur into ...
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27 votes

What is the rarest launch window?

Comet West with its unpredictable but estimated at 558 000 years period is a good contender. Since launch windows can aim for the alignment of N objects, the answer obviously tend to infinity. You ...
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  • 12.2k
23 votes

Is Nibiru real or totally science fiction?

To resonate with @Hobbes general characterization: Nibiru is contrived nonsense. Ignoring the fact that previously announced dates for the Earth cataclysm have come and gone with no such mayhem, some ...
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  • 17.9k
23 votes

Pictures from Mars

Let's compare with 4G, for which I could find some numbers: Your cell phone is transmitting with speeds of up to 50MBps with a maximum of 1 Watt (can be as low as a few µW!), using a tiny antenna ...
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  • 12.2k
22 votes

Elon Musk's ITS Travel Time to Mars Estimate

What is unique about the ITS that would make the travel time so much shorter? Is the propulsion method described in existence today? The current manifestation of the ITS is Starship, and the ...
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21 votes

What is the rarest launch window?

Hohmann launch windows occur each synodic period. Or a more general version of a Hohmann transfer would be a transfer orbit tangent to both departure and destination orbits. This also occurs each ...
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  • 15.1k
21 votes

Assuming a spacecraft is traveling in a constant rate and our Astronaut will exit it to a space walk, will she be "left behind" by the spacecraft?

I feel this sort of question benefits from a series of thought experiments. Imagine instead that you've got two astronauts, side by side, zipping through space at some constant speed. They're kind ...
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  • 1,825
20 votes

Why was Venus rather than Mars targeted for the first interplanetary landings?

One picture is worth all your base to us. Before we sent probes to Venus we had no pictures of its surface. Whether it lands or not you have to penetrate the atmosphere of Venus to take pictures of ...
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  • 536
19 votes
Accepted

What bitrates are currently achievable for communication with interplanetary space probes?

Speed-of-light delay is mostly irrelevant for data transmission rates. Once you get out of Earth orbit, transmissions are generally "fire and forget"; if data gets garbled, you schedule a ...
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  • 11.5k
19 votes

Viability of orbital refueling

This is basically the approach being considered for getting all of the hardware to Mars for a crewed mission. However instead of refueling an upper stage that was used to get you to orbit, it is ...
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  • 57.4k
18 votes

What significance did Pioneer 10 & 11 have?

Yes, Pioneer 10 and 11 each carried a 0.000001 megapixel camera. The single pixel was scanned over the body by the constant spin of the spacecraft in one direction and a slew of the spacecraft in the ...
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  • 57.4k
18 votes
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Traveling through the asteriod belt?

The asteroid belt isn't nearly as dense as popular media makes it out to be. An answer from the Dawn Mission's FAQ, specifically "What is the average distance between individual asteroids? (6/13/10)",...
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