# All Questions

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### Cell-Free massive mimo for satellite communication design

I am interested in LEO satellite communication and its integration into a 5g terrestrial network. Cell-free massive mimo (CFmMIMO) is a concept used in 5G design. It looks, CFmMIMO can be used if we ...
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46 views

### What's inside the white round elevated container next to the Falcon 9 starting base? [duplicate]

On images of the Falcon 9 start you see a kind of round elevated container (on the left hand side of the picture). What does it contain and why is it elevated?
• 101
293 views

### At what distance does radio communication become unusable?

How far away from Earth could we reliably communicate using radio? I'm thinking that a primary factor would be how much RF power could be kept in a "tight beam" and accurately pointed. ...
• 2,662
1 vote
63 views

### Is using a variable Isp (constant power & acceleration) more efficient than a constant Isp when launching?

So after I wrote a particularly poorly received answer about variable specific impulse, based on discussion I read here, I realise I may have misinterpreted what was being discussed in that thread. ...
94 views

### How usual is seeing or picturing a space lidar from Earth?

Recently, photographs taken on Earth of the 532 nm beam emitted by the Aerosol and Carbon Detection Lidar have hit the news, perhaps also because of the nice pictures and because Chinese space laser ...
• 11.4k
76 views

### Air-Augmentation on a VTO&L super heavy lift

I'm working on a basic design for an Air-Augmented first stage, which boosts the second, expendable, stage from a near-orbit, to allow for deorbit of the second stage. Essentially it's an SSTO that ...
231 views

### What outdated components of Columbia made it heavier than the other Space Shuttles?

Being the first space-rated orbiter produced, Space Shuttle Columbia was the heaviest and therefore rarely selected for high inclination trajectories like the ISS near the end of the program. Which ...
• 4,992
2k views

### Are fuel cells suitable for missions with high power requirements?

Are fuel cells suited for missions with high power requirements?
1 vote
53 views

### Can the location of gas bubbles in a tank in a spacecraft in zero gravity be influenced? [duplicate]

Can the location of gas bubbles in a tank in a spacecraft in zero gravity be influenced? They for sure cannot be determined, then I guess they also cannot be influenced?
642 views

### Is it wrong to say that the thrust increases with time?

Is it wrong to state that the thrust increases with time? Because it implies that it actually increases over increasing altitude, with time?
1 vote
141 views

### What is the purpose of geosynchronous communications satellites?

This question's sole answer Is it true, that commercial communications satellites account for the largest share of commercially used satellites? explains that: the vast majority of the satellites in ...
• 177
369 views

### Is the launch of a rocket slow because the change in velocity (delta_v) should be as small as possible because of energetic reasons?

Does it make sense to keep the launch of a rocket slow because the change in velocity (a.k.a. delta_v) should be as small as possible because of energetic reasons?
146 views

### Will there be a flame around the capsule from Stoke Space Technologies during reentery?

Stoke Space Technologies (https://www.stokespace.com/) will send fuel through the heat shield of its capsule to keep it from heating up. They actually mentioned that they are more concerned that the ...
• 3,799
1 vote
54 views

### Arctic underwater analogue?

Just want to know if the underneath of the arctic ice sheet is a viable analogue for underwater habitation on the larger moons of the gas giants? (Galilean, large Saturnian) I feel like it would be a ...
56 views

### Does the payload capacity of an interplanetary launch rocket increase with decreasing fuel mass or with increasing escape velocity?

Does the payload capacity of an interplanetary launch rocket increase with decreasing fuel mass or with increasing escape velocity? I was thinking that the escape velocity has nothing to do with it ...
61 views

### Higher nozzle exit velocity generally means higher thrust right?

Higher nozzle exit velocity generally means higher thrust right? If that is the case, then a higher heat capacity could potentially lead to a higher exit velocity, thus higher thrust?
88 views

### Are most launches for science missions?

Are most space missions launched for scientific purposes? I had thought so, but during a group discussion, someone suggested most are actually for commercial purposes. Are they correct? Thanks!
858 views

### Are most commercial satellites communication satellites?

Is it true that commercial communications satellites account for the largest share of commercially used satellites?
5k views

### Would the Space Shuttle have been able to carry the Hubble Space Telescope back to Earth had it been necessary?

The development of the Space Shuttle (STS) and the Hubble Space Telescope (HST) were running in parallel during the 1970s and 1980s. Both plans for STS and HST were announced in the late 1960 and both ...
• 13.6k
427 views

### ESA: Does the ESA initiate the development of necessary new technologies if it is necessary? Does the ESA create new space missions?

I tried to do some research but I couldn’t find any definitive answer to this: Does the ESA initiate the development of necessary new technologies if it is necessary? And does the ESA create new space ...
182 views

### Do Space Shuttle cargo doors carry structural airframe loads, like the lid of a shoebox?

Airframes are usually designed for semi-Monocoque construction. The skin carries the primary stresses to keep the fuselage rigid. https://www.abbottaerospace.com/aa-sb-001/22-aircraft-specific-design-...
• 14.2k
67 views

### Calculate Thrust of Rocket Nozzle - Off Design

I have designed a nozzle for the following input parameters $p_{combustion}=p_c=200*10e5 Pa$ $T_{combustion}=T_c=2800 K$ $F=70 kN$ $\kappa=1,2$ $R = 330 J/kgK$ I assume that all my gas properties ...
153 views

### Could Mars be terraformed by redirecting an asteroid to hit it? [closed]

If so, what kind of asteroid would be best?
841 views

### Upper limit of human comfort in higher atmospheric pressures?

At what atmospheric pressure, assuming an earth-like atmospheric composition, do humans start to feel uncomfortable? I am not asking for the max survivable pressure, but the point where long term ...
• 161
119 views

### How to avoid big nozzle lengths in high altitude?

I am currently designing a serial staged rocket with 3 stages. The first stage brings me up to 10 km. When I do my calculations for the required expansion ratio and nozzle length (Rao Nozzle) for the ...
• 37
312 views

### At some point far from the Sun does the output of solar panels start dropping much faster than inverse square? If so, how fast?

I recall reading somewhere that solar power - already marginal at Jupiter - will cease to produce any power whatsoever at distances much further out than Saturn. Unfortunately I can not now find the ...
55 views

### Difference between Optimum Expansion Ratio and Maximum Thrust

when I look at the equation for thrust of a rocket: $$F=\dot{m}*v_{exit}+(p_{exit}-p_{amb})*A_{exit}$$ In the book "Rocket Propulsion" from Sutton it says on page 33: In the vacuum of ...
• 37
1 vote
114 views

### Do launching states need to seek permission for jettisoning rocket stages over waters not counted as international waters?

Rocket debris such as boosters and payload fairings are often discarded over bodies of water. If the debris is set to be discarded over waters outside the launching state's territory, do they need to ...
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35 views

### Choked Flow: Throat Radius should not change any more below critical pressure ratio?

I am trying to understand some calculations of a student colleague: The pressure inside the combustion chamber is 200 bar. This means, the critical pressure ratio should be p*/p0 with p0=101325 ...
• 37
7k views

### Do astronauts use plumber's bifocals?

Adults steadily loose the ability to see close-up (presbyopia). By the mid-40's, most people have surrendered to the inevitable and switched to bifocals. These provide closer focus when looking down (...
• 14.2k
83 views

### Using orbital construction around another body to build probes

It's what it sounds like: I want to know whether sending a probe builder to orbit a moon or a planet (for this question I'm thinking of Titan or another smallish body in the outer system.), to build ...
655 views

### orbital speed to maintain relative position to the Earth

I note that the orbital speeds of the planets slow down with increasing distance from the Sun. Say we have a space station orbiting the Sun at a distance of about 400 million kilometres (within the ...
1 vote
123 views

### Distance between a satellite and an orbit

I would like to compute the distance between a satellite and a specified orbit. For instance, for an orbit at 897 km altitude, 0 degree eccentricity, 99 degree inclination, and RAAN of 0 degrees on ...
1 vote
97 views

### SLS Block 2: Original thrust

In older graphics depicting the evolution of the SLS vehicle, it states that the Block 2 upgrade was to produce 11.9 million lbs of thrust. At some point in the last few years, however, this has ...
• 610
803 views

### Propellantless propulsion in gravity field

I have a proposal for a following propellantless maneuver. It is propellantless in sense that no mass is lost from spacecraft. It is not reactionless as spacecraft interacts with planet through ...
135 views

### SLS SRB sound suppression system

The Shuttle, in addition to the water deluge system, used a series of red nylon bags filled with water at the base of each SRB for additional sound suppression. Does the SLS, whose boosters produce ~...
• 610
169 views

### What use (if any) does the "empty focus" of an elliptical orbit have in orbital mechanics?

The 2 bodies in a 2-body system orbit around their common barycenter, which is located at the common primary focus of both their orbits. The empty foci don't seem to have a job in celestial mechanics. ...
• 14.2k
1 vote
54 views

### How is the rocket equation affected by changing the number of engines or boosters? [duplicate]

Specific impulse is not affected by the number of boosters or engines on a rocket, correct? Let's say I take a rocket with two SRBs and add to more for the first stage. The specific impulse of the ...
1 vote
93 views

### How heavy is an orbital pogo stick?

Moving people from a A to B in space often requires a significant change in velocity, requiring propellant eating into the mass budget. But most of this propellant is "wasted" in moving a ...
3k views

### What changes to Voyager could have been made? [closed]

If during the planning and construction of the Voyager missions they knew what we know now, what changes to the missions would have been most helpful in augmenting the science obtained?
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27 views

### Can Tisserand's parameter be modified to correct for perturbing eccentricity?

Tisserand's parameter is an "almost" conserved quantity in the CR3BP, even after flybys (useful for identifying asteroids). $$T_P = \dfrac{a_p}{a}+2\sqrt{\dfrac{a}{a_p}(1-e^2)}\cos(i)$$ It ...
1 vote
61 views

### How would low gravity on Mars be a stress factor on plants?

As a 12 year old doing a science project for my local science fair I have found that many experiments that try to simulate how the environment would be like on Mars while growing plants always forget ...
138 views

### How much of LOX will have to be generated for SpaceX Starship to get back from 16 Psyche?

Mixture ratio for Oxygen/Methane is 3.6 to 1 Liquid oxygen temperature of -183°C 16 Psyche (in shade) -113.15°C (https://simple.wikipedia.org/wiki/16_Psyche) Looks like the idea of bringing enough ...
1 vote
131 views

### Center of gravity changes against the vertical axis of the orbital plane: Help me open some minds with the math on the behavior of objects in orbit [closed]

Edit: Ok, thank you all for your input. I will attempt to clarify the question now based on the additional information I was able to garner from your comments. I believe the math formula I am looking ...
188 views

### Does a space elevator ruin most satellite orbits?

A space elevator would offer a direct connection between the surface of the Earth and geosynchronous orbits. While the concept has several severe problems, according to my understanding of orbital ...
405 views

### What was the available delta v of the Apollo 13 spacecraft, post explosion?

The LM ascent engine wasn't used for direct abort. Presuming no one cares about the crew and just wanted to burn the LM to empty (both stages), what would the delta v have been? If it helps, I'm ok ...
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83 views

### How was SSRMS IROSA IPA disposed

On this video, we can clearly see the payload being disposed, but I fail to understand how it gained so much momentum as the Canadarm appears to not be moving. The video mention a new procedure, can ...
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5k views

### If a sitting President went to space on a USSF spacecraft, would the call sign be Space Force One?

If a sitting US President flew on a spacecraft operated by the US Space Force, would the spacecraft's call sign be Space Force One, analogous to Air Force One, Marine One, etc.? What if he flew on a ...
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1 vote
40 views

### Local space radiation measurement by 1U CubeSat

As far as I know, the general influx of ionizing radiation received by a CubeSat in LEO is mostly trapped protons and electrons, solar protons, galactic cosmic radiation, and neutrons. If the CubeSat ...
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