# All Questions

10,227 questions
42 views

### Discrepancy between Launch Vehicle Performance website on Atlas V 551 with Juno

I was looking at the Juno space probe which was launched in August 2011 onboard an Atlas V 551. In particular I was looking at https://elvperf.ksc.nasa.gov/Pages/News.aspx and using the performance ...
28 views

### What Methods are Used for Satellite to Site Visibility Calculation?

In the paper, Rapid Satellite-to-Site Visibility Determination Based on Self-Adaptive Interpolation Technique it is claimed that "Satellite-to-site visibility periods are typically determined by the ...
108 views

### Have astronauts lost fingernails on spacewalks before?

Spacewalks can be notoriously taxing on the body - a multi-hour spacewalk is often compared to a marathon in how much the astronaut must exert to overcome the stiffness of the suit. I remember ...
215 views

### What did India's recently tested ASAT vehicle really look like?

Following up to India just shot down a satellite from the ground. At what altitude range is the resulting debris field? which shows the first image below (also seen in video) I also found the second ...
132 views

### How much of the exhaust speed is due to combustion and how much is due to the injection?

The thrust $F$ of a rocket engine is given by $$F=\dot{m}v$$ where $\dot{m}$ is the mass flow and $v$ is the exhaust speed. Now the first factor, $\dot{m}$, is almost entirely due to the turbo pumps (...
103 views

### What is holding SLS back from launching?

I'm kind of confused on this point SLS has engines, a tank, side rocket boosters, a capsule, and seemingly all of the pieces. What is the major technical issue right now that is keeping SLS from ...
198 views

### 99.99% pure iron meteorite [closed]

[![enter image description here][1]][1] I have a 99.99% pure iron meteorite. It is 4,902 grams.
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### Could rockets benefit from Reaction Engine's Air-Breathing Rocket Engine in terms of payload?

While I get that one is a vertically launched rocket and the other is a space plane, is it even wildly possible that there could be a vertical intake version of the SABRE engine? Maybe it can be used ...
47 views

### Is there mineral nitrogen on Martian surface? [closed]

I am aware of the atmospheric composition and pressure. I am looking for research papers which state the mineral content of Martian soil.
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### Who is accountable for damage caused by the debris field of a successful ASAT test

I just saw India just shot down a satellite from the ground. At what altitude range is the resulting debris field? about today's Indian ASAT test... As far as I know an "ASAT Missile" sounds military ...
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### India just shot down a satellite from the ground. At what altitude range is the resulting debris field?

This tweet from India's prime minister Narendra Modi says: मेरे प्यारे देशवासियों, आज सवेरे लगभग 11.45 - 12.00 बजे मैं एक महत्वपूर्ण संदेश लेकर आप के बीच आऊँगा। I would be addressing ...
159 views

### Do owners of reentering spacecraft notify the countries' whose airspace they are likely to violate and seek permission?

@PearsonArtPhoto's answer contemplates: Any object that is below 100 km now is considered an aircraft, and technically needs the permission of the country over which it is flying to enter that air ...
156 views

### Is there a crewed moon lander currently in the works

Recently, the US vice president directed NASA to land astronauts on the moon within the next 5 years [source]. While there are big rockets (SLS, Falcon Heavy, etc.), and crew capsules (Orion, Crew ...
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### Which would be more prone to regolith-ice-melting issues, a rover's wheels or an astronaut's boots?

This answer to Has NASA “gone south”? Why are astronauts needed to explore the Moon's south pole? and the question What would happen if an Apollo astronaut landed on Pluto? both touch on issues of ...
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### Has NASA “gone south”? Why are astronauts needed to explore the Moon's south pole?

Wired: Why America Wants to Send Astronauts to The Moon's South Pole “Before we put boots on the ground at the poles, we urgently need a robotic water ice prospecting mission to the lunar poles,” ...
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### Instantaneous positions of a central body of specified mass that results in an osculating orbit?

If I understand correctly, osculating orbital elements such as those posted in JPL's Horizons represent the mathematical osculating (tangential or "kissing") Keplerian orbit about a specified location ...
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### How do scientists determine how big a certain star is? [closed]

I was just wondering, many people say that there are stars that are waay bigger than our sun and in some videos they even try to say the exact diameter of the Sun, but I was wondering: How can ...
31 views

### Suggestions required on radiation tolerance solutions

I wanted to know what methods of increasing radiance tolerance for the microcontroller and memory devices for a Cubesat exist. We have read about methods like having dual CPUs but are there any ...
3k views

### Why not increase contact surface when reentering the atmosphere?

If a craft were to increase the surface area where contact is made with air during reentry, I imagine the heat quantity per area unit would decrease, making the use of (heavy) heat shields less of a ...
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### What is the state of current plans for a permanent moon base?

With all the news regarding SLS/Commercial Crew and the refocus on Moon then Mars, I was curious as to what we will actually be able to do with these upcoming launch capabilities. I'm familiar with ...
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### Will a Cygnus and Dragon be on station at the same time in April 2019?

According to the launch schedule at the moment I looked (which is of course only a snapshot in time) there is a Cygnus mission (NG-11) scheduled for Apr 17, 2019. There is a SpaceX Dragon Cargo ...
202 views

### Could a “nuclear turbo-jet” be built?

Being familiar with jet engines myself, I wonder whether a similar device could be built to provide high $I_{\text{sp}}$ and high thrust in vacuum and space. Using the tried-and-true turbojet formula ...
161 views

### Which company provided communication equipment for Apollo missions in which Neil Armstrong was a part?

In July 1969, the Apollo mission transmitted Neil Armstrong’s first steps on the moon to millions around the world. Which famous company provided the entire communication equipment for the project?
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### How do pressure fed and pump fed systems compare at different scale of rockets

Rocket Design is all about optimising mass, within cost constraints while accepting a certain amount of risk. Both pressure fed and pump fed systems have their pros and cons, but how do they compare ...
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### What is the minimal distance of clearance in the direction of flight path for a rocket?

Usually the rocket launch sites are placed on a coast or a place where there's basically no civilian buildings in the direction of flight path. Is there a standard/regulation on the minimal ...
204 views

### Could a steam Engine outperform other electric producing devices in space? [closed]

What would be the Specific Impulse of a steam-based propulsion system like this model in space? Are there any types of engine that works this way? Could 2 tanks be designed to rotate slowly in space ...
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I'm playing around with optimization of a patched conic approximation for a transit from earth orbit to LLO, and when I take the resulting retrograde trajectory and plug it into an integrator, I get a ...
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### Orion cockpit instrumentation

I'm working on a spaceflight simulator (FSX SpacePort), and currently developing instrumentation for NASA's Orion capsule. I'm using whatever little info is available on line and trying to identify ...
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### Calculation of V1 (orbital speed) during ascent

I am studying instrumentation of NASA's Orion spacecraft, and there is a readout for V1 (I am assuming this is the "first orbital velocity", for circular orbit), and it seems to be in small decimals. ...
94 views

### How does the sunlight affect the height of the atmosphere?

I was reading this question about how high a Mars balloon could go in the mars atmosphere. How much would the sunlight affect how high the atmosphere reaches? Is the atmosphere on Earth elongated on ...
181 views

### For the Starhopper testing, how will SpaceX hold down the vehicle?

SpaceX is testing the Raptor engine on the Starhopper they built in Boca Chica. For static fires of a Falcon 9/Heavy they use the pad itself, the holddowns to the pad, to keep it from taking off. ...
5k views

### Why is delta-v the most useful quantity for planning space travel?

Many of the questions and answers on this site make use of the concept of delta-v. Is there an easy to understand the reason why delta-v, the magnitude of the change of the velocity, $|\mathbf{v}|$, ...
73 views

### How are gravity coefficients calculated?

I was reading Satellite Orbits - Models, Methods, and Applications by Montenbruck & Gill and was trying to use the equations in it to calculate $J_2$ as used in the GEM and JGM gravity models. ...
49 views

### What differences exist between the pressurants and their associated systems between a pressure fed and pump fed liquid rocket engine

There is an apparent need to have pressurants in both pressure fed and pump fed systems. However, since pump fed systems can create the necessary pressure, they can work with less pressurants and ...
6k views

### Why is this part of the Space Shuttle launch pad suspended so high off the ground?

http://science.ksc.nasa.gov/shuttle/missions/sts-107/images/high/KSC-02PD-1894.jpg shows a large part of the launch pad suspended off the ground. What is it for and why is there all that empty space ...
2k views

### What is the smallest body in which a sling shot maneuver can be performed?

This question asks about the smallest sling shot maneuver performed. What was the smallest intentional, acknowledged slingshot maneuver? I'm asking how small of an object be to perform a sling shot ...
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### What types of engines are able to go from Earth orbit to Martian orbit? [closed]

What engine is the most efficient in fuel and/or time to go from Earth orbit to Mars orbit and back again that are not capable of launching from the ground?
116 views

### Is post-X-prize Beresheet better than the X-prize candidate?

As mentioned in this question the total budget of the Lunar X-prize was about US \\$30 million, and that included some other prizes beside the winner. However the budget of Beresheet post-X-prize ...
120 views

### Is there any combustion chamber and nozzle cooled with liquid oxygen instead of fuel?

There are many rocket engines for liquid propellants which use the fuel (rocket petrol or liquid hydrogen for instance) to cool the walls of the combustion chamber and the nozzle. But are there any ...
32 views

### Where can I get design details about spacecrafts and space mission? [closed]

I am doing a project on designing a mission to Mars. I am researching similar missions and I want to find information on the mission details like Delta V, trajectories etc. and details of the ...
134 views

### Why are JPL using this expression to emulate Schwarzschild orbits?

From the documentation ”Formulation for Observed and Computed Values of Deep Space Network Data Types for Navigation ” expression 4-61 on page 4-42 it can be seen that JPL uses the following ...
801 views

### Where did Heinlein say “Once you get to Earth orbit, you're halfway to anywhere in the Solar System”?

I know what it means. I've seen delta-V charts. But I don't know if Robert Heinlein wrote this down, or simply said it off-the-cuff to somebody. Variations include: "Reach low orbit, and your ...
58 views

### How is this engine put together? [duplicate]

I'm going through How to DESIGN, BUILD and TEST SMALL LIQUID-FUEL ROCKET ENGINES and am confused how their sample engine is physically built together. This is a picture of their assembly where the ...
3k views

### How can Trident be so inexpensive? Will it orbit Triton or just do a (slow) flyby?

The recent NY Times article Neptune’s Moon Triton Is Destination of Proposed NASA Mission says (in part): HOUSTON — Is it time to go back to Neptune? Scientists representing NASA’s Jet ...
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### Would a mouse trap snap faster or slower in space than on Earth?

Would a spring loaded mechanism outside a spacecraft activate a lever faster or slower in space with no atmosphere and gravity than on Earth? Basically this is in reference to mechanical instruments ...
60 views

### Why would different Shuttle orbits have different mission directors?

The Wikipedia page for NASA Flight director Holly Ridings contains a portrait with two other STS-117 mission flight directors. The caption there says: Flight directors for the STS-117 mission in ...
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### How are satellites made “demisable” and what else do recent FAA documents tell us about SpaceX's plans for StarLink satellites?

Comments in chat mention that recent FAA documents show that there have been design changes in the StarLink satellites that make future builds "demisable". This sounds interesting but I don't really ...
132 views

### Why would an 8-minute burn result in a 6-month delay?

The Ars Technica article Vice President may tell NASA to accelerate lunar landings ends with: And on Thursday, NASASpaceFlight.com reported that the agency is considering skipping a critical test ...