# All Questions

9,541 questions
18 views

### Help needed with obtaining position vector of Spacecraft in Heliocentric-Ecliptic frame

I have been now using the ephemeris table attached as an image. It gives the orbital elements of all planets on Jan 1 2000 calculated from Heliocentric-Ecliptic frame. The current planetary orbital ...
107 views

### How many Lunar Surface Hasselblad cameras were left on the Moon?

There were six Apollo missions that landed on the Moon. Each mission was equipped with at least two Lunar Surface Hasselblad cameras left on the lunar surface before ascent. But the total number of ...
80 views

### How was the Moon's first telescope used? (Apollo 16)

From Gizmodo's There's Poop on the Moon list of things left on the moon: This gold-plated telescope that was the first tool used to make astronomical observations from the surface of another ...
2k views

### Is it ethical for Chang'e-4 to bring an entire ecosystem to the moon? [closed]

As far as I know, it isn't ethical to contaminate outer space with life from Earth, because then we will never be sure if life can actually grow there. However, I just read reports that the latest ...
41 views

### How to lease a transponder on a GEO satellite?

I have an interesting question. I was thinking about it a year ago when the es'Hailsat 2 was not launched. There was an organization called "Outernet" that promissed to broadcast files (including ham ...
111 views

### How did Chang'e-4 hover, rotate, and then descend so gracefully? (Video)

In this incredible video we can see Chang'e-4 in it's final approach and landing on the moon from the point of view of the spacecraft. The view is horizontal as the spacecraft seems to stop and hover ...
62 views

### Hypergolic Propellant Combination

Is Rocket Grade Hydrogen Peroxide and Liquid Hydrogen a hypergolic propellant combination? I recall, seeing the combination somewhere on the www, however I couldn't retrace the source where I saw it.
29 views

### How to estimate the pose of a dynamic cooperative and known object in space e.g in case of space debris? [closed]

I would like to know some novel approach, method or algorithm. The main purpose of pose estimation is to deal with the robotic capture in space
138 views

### What is a satellite trap?

I keep hearing about satellite traps, which have something to do with receiving and transmitting satellite communications, but I can't seem to find a definition. The securityaffairs.co blogpost Hack ...
6k views

### Why did China land a rover on the moon?

Why did China land the Chang’e-4 rover on the moon? What was it supposed to accomplish or explore?
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### How will JWST maintain its elliptical orbit around L2?

I understand that JWST will have a vertical elliptical orbit around L2, but what I don't understand is how the telescope will actually maintain an orbit if there is no body in L2 to actually orbit ...
168 views

### Use of different fuels for stages of Saturn V

Why were different fuels used for different stages of Saturn V? I read that the first stage used kerosene (RP-1) and LOX combination, but liquid hydrogen and LOX for the second and third stages. With ...
132 views

### Why would the orbit of a satellite in GEO climb by 21 km in altitude over six months by itself?

This answer mentions several effects that tend to move geostationary satellites out of their "box" over time, but one really surprised me. According to the plot below (from there, but uncredited) the ...
99 views

### Why satellite’s solar panel wattage is often listed in specifications?

What is the purpose of listing the power output (Wattage) from solar panel, without the energy/power specification of batteries or other electrical storage devices? Do satellites often use the power ...
90 views

### How often does a geostationary satellite enter into a Lunar shadow?

Is there a chance for the many geostationary satellites to enter into the moon’s shadow? If so, how frequently do such eclipses happen and how long do they typically last? Are such eclipses pre-...
176 views

### Why are the rovers finding the long Lunar night difficult to overcome?

Compared to Martian nights, Lunar nights are long and cold. This has posed a lot of challenges in the past. What specific challenges does long duration night pose? What are the methods to over come? ...
69 views

### Which point in an orbiting body most closely follows its Keplerian trajectory?

Keplerian orbits can describe the motion of a negligible mass around a massive fixed central body, but they also describe the motion of two bodies around their center of motion. But which point ...
46 views

### Understanding shape of DSN's 'kinky uplink protocol' keeping frequency in coherent transponder's optimum bandpass?

This tweet by deep space SDR enthusiast and amateur radio operator Edgar Kaiser @df2mz shows a squiggly tone from MRO. Mars Reconnaiscance Orbiter (MRO) X-band downlink. The signal shows this ...
101 views

### Why does the Apollo-8 Trans-Lunar Injection burn appear to be pulsing in this photo?

This tweet called my attention to The Smithsonian National Air and Space Museum story Photographing Apollo 8's Orbit Toward the Moon. The story is quite an interesting bit of space history and worth a ...
111 views

### What spacecraft components are in the foreground of this image of the Earth and Moon? What is the camera inside of?

This tweet shows the image below, and says: Finally, some images from Queqiao, the relay satellite for the Chang'e-4 far side mission, showing the Earth and Moon! Queqiao is in a halo orbit at a ...
69 views

### Are the ejected first stage Electron rocket batteries really incinerated?

This answer reminded me that the Electron rocket drops one of it's batteries when it is mostly spent. We might call that "micro-staging". This answer quotes Spaceflight 101: With a low auto-...
116 views

### Did Apollo's velocity slow down after TLI due to Earth's gravity?

I assume Apollo's velocity slowed down after it left Earth orbit, for how long was it decelerating. Did it start accelerating as it approached the Moon. What was the rate of deceleration due to ...
238 views

### What is the surface temperature distribution of Venus?

I can find lots of resources stating the average surface temperature. However, I have found conflicting reports concerning the distribution of temperatures on the surface. For example, the Venus ...
69 views

### What fuels would make refueling in space more dangerous/complicated?

I saw the question: Has in-space refueling been done? And was actually beginning to wonder, is refueling and transferring propellant dangerous in space? I understand that this would most likely be ...
4k views

### Rocket flywheel instead of battery/generator (crazy idea)?

The Electron rocket is launched using a battery instead of generator... I saw some video about research into using flywheels for energy grid buffer storage, I think that they could reach higher ...
29 views

### Total amount of torques and forces in Lunar L2 Halo orbits

I want to design a spacecraft control systems around Earth-Moon L2 Halo orbits but at the first place, I want to have an estimation about the total torques and forces which the control devices should ...
20 views

### spacesuit airconditioning [duplicate]

I read that during the EVA, the astronauts body temp. was maintained by the PLSS, by rejecting the body heat, using porous plate sublimator. In this porus plate, water was made to evaporate into space ...
306 views

### Did anyone piloting a Space Shuttle ever make a significant pilot error?

Did anyone piloting a Space Shuttle ever make a significant pilot error? (I've never heard of any, and I'm curious if that is due to their extensive training, or if it's just that that sort of ...
110 views

### Could you track small particles in space and could you control their position with lasers or reflected light?

If you released a large amount of small but precise particles (the size of glitter or confetti) is space, between a group of cube sats. Could you track the particles with cameras and/or lasers? And ...
29 views

### When were elements on asteroids first identified?

Is there an approximation on when scientists first found out about certain elements on asteroids, more specifically gold?
28 views

### Is OSIRIS-REx's high gain antenna nearly the same as TESS'? If so, why?

These two high gain antennas look very similar superficially, but are not identical. Is this a case of convergent design (a fancy kind of coincidence) or have they evolved from the same source, or ...
28 views

### How exactly will OSIRIS-REx's Navcam be used to navigate?

This remarkable, tweeted OSIRIS-REx image is described in AsteroidMission.org's NavCam Image of Earth, the Moon, and Bennu The particular camera is called a NavCam, and yet it will be used during the ...
63 views

### The fine prints of launching a satellite

I have read about the space law, international and legal responsibility of the companies and countries involved and I must say it is complex, not to say scary. I can't imagine the lawyers' costs prior ...
107 views

### Could inflating while decending for rentry be possible?

Could entry of Mars with balloons work by inflating to equalize with the atmopheric air pressure while establishing buoyancy before meeting the ground? Would a balloon pop if dropped from space? ...
34 views

### Why does the Delta 4 Heavy look burned? [duplicate]

When I was looking at pictures of the Delta 4 Heavy rocket, I noticed that closer to the engines, the rocket looks black instead of the orange color it has right after launch. It looks burned to me. ...
84 views

### Could the $C_L$ of the X-15 be calculated from the flight data near the Kármán line altitude?

The "lift coefficient" $C_L$ can be very different for one specific aircraft at different speeds. According to this article from NASA about the lift coefficient: So it is completely incorrect to ...
97 views

### Docking of CSM with LM

After separation from the SLA (by about 50-100 feet), the CSM "turned around" and docked with the LM to pull it out. This turning around was done by a 180 degree change in orientation. This could have ...
111 views

### Could a spacecraft produce lift using sublimating material?

Following this question, could a spacecraft approaching upper atmosphere from very low circular Earth orbit, produce lift to soar propulsively, bleeding speed at constant apoapsis, by sublimating ...
61 views

### Could ablative material sublimation slow down a spacecraft?

Thought experiment illustrated below: Suppose a weird spacecraft entering Earth's atmosphere from low Earth orbit, payload first. Behind it there is an inverted nozzle shaped structure, attached with ...
136 views

### Looking for Apollo 11 powered descent video

At a science museum I visited on my 2018 fall vacation (I think it was the Chicago MSI), I saw a video loop that looked and sounded very much like part of the moon landing multimedia show at the ...
118 views

### Could a spacecraft be propelled by a 180 degree deflection of two charged particle beams?

I am wondering if the electrostatic deflection of two charged particle beams could create enough thrust, via the Lorentz Force, to propel a spacecraft. Please reference the picture below. This ...
83 views

### What's the minimium velocity for re-entry flames to start?

Considering a space shuttle re-entering Earth, what's the minimum velocity that would cause the vehicle to start burning? Is there an equation to calculate that? I presume it varies according to the ...
77 views

### Can James Webb see Kuiper Belt Objects like 2014 MU69 (Ultima Thule)?

In this paper, we learned that Hubble is the only telescope in the vicinity of Earth that can detect Ultima Thule directly. Hubble will eventually fail, and will be somewhat replaced by James Webb. ...
80 views

### Would Bigelow space stations work if rotated to achieve 1G simulated gravity?

Would Bigelow's proposed space stations work if two of them are connected by a tether and rotated to simulate gravity of 1G (or how much)? Would they hold up structurally? Would there be other ...
128 views

### How to get experiments to space?

How would a person get an experiment done in space? What is the chain of command on something like that? I would like to drop some inflated balloons from space to reenter the atmosphere to see which ...
143 views

### Friendly temperatures at day/night junction in Mercury?

Here's my theory : Since a temperature change is generally smooth when you travel, I was wondering that temperatures would be somewhat decent if you were to stay somewhere in the day/night longitude ...
87 views

### Lunar module on the moon [duplicate]

I understand that a lunar day is about 13 & half earth days, and so also the lunar night. Since there is no atmosphere on moon, the surface temperature during "lunar day" reaches upto +127 degree ...
74 views

### How could tiny nanosatellite Hagoromo with a 4 kg solid propellant rocket inside maintain attitude control?

To the question Hagoromo was a ~36cm nano satellite that was deployed by Hiten while Hiten was in a highly elliptical orbit around the earth, in 1990. From there, Hagoromo was able to enter ...