# All Questions

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### GMAT Lambert problem

I would like to plan a mission in GMAT to a certain asteroid, whose orbit and SPK file I have added in GMAT. However, I don't know how to solve the Lambert problem in it to first find the intersection ...
175 views

### What does Paul Birch mean by kg * s^-1 * kg^-1?

In Paul Birch's paper, Terraforming Venus Quickly he mentions a unit kg * s^-1 * kg^-1, which I interpreted as ($\frac{kg}{kg \cdot s} = \frac{1}{s}$). This is a valid unit, representing a rate. ...
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### Is the set of software and hardware of modern attitude control systems exhaustive?

In the book ADCS - Spacecraft Attitude Determination and Control on page 426 there is a diagram of the JWST ACS. Next I attach a reproduction of it from the book. The diagram shows the main soft- and ...
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178 views

### Satellite slew rate with respect to a ground station

For a given satellite orbit and observation time, I have the vectors containing the elevation and azimuth angles of the satellite with respect to a ground station. I know that the elevation slew rate ...
546 views

### Has Blue Origin carried out any flight or landing tests of the New Glenn first stage?

New Glenn is scheduled to launch the EscaPADE probe to Mars in the September launch window. I've read a lot about ground systems testing and prospective BE-4 static fire tests, but can't find ...
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### How do cables and cooling lines transverse the pressure hull of the International Space Station?

The International Space Station (ISS) is notable for having large amount of unpressurized equipments on its Integrated Truss Structure (ITS), including the solar panels and the radiators. The electric ...
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### What caused the LOX leak on Falcon 9?

On July 11, 2024, the second stage of the Falcon 9 had a LOX (Liquid Oxygen) leak in the second stage and it couldn't perform SES-2 (the second upper stage burn), causing the Starlinks onboard to be ...
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### Can Falcon Heavy be used as a temporary replacement for the Falcon 9?

Due to an anomaly with the second relight of the Merlin engine on a Falcon 9 Starlink mission, the FAA has grounded the falcon 9 and will conduct a mishap investigation. Can falcon heavy be used as a ...
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357 views

### Why don't rocket engines use heat tiles on the inside?

I asked in chat about rocket engines not melting @ 3300°C despite steel melting at 1400°C. The two excellent answers were: thermal mass was one answer the propellants are often piped through tiny ...
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### How do satellite trackers work when showing a "satellite"?

There are multiple sat trackers online where you can follow spacecraft orbiting Earth such as the ISS or the HST. I wonder how those trackers actually work when showing something near Earth, as the ...
96 views

### What's the numeral name of the recently launched Starlink satellites and where can I track them?

I'd like to track the recently launched Starlink sats that reached a too low orbit due to the Falcon 9 second stage leak and MVac Engine RUD. For some reason, if I wanna enter "Launch 11 July ...
211 views

### Why did Starship lose an engine on IFT-4?

By T+0:00:06 at the latest, the Super Heavy carrying Starship for Integrated Flight Test 4 appears to have lost an engine (source and image). I know it's not a huge deal, as they can complete missions ...
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### Has a rocket engine ever been reused by a second/third stage

While rockets are basically minimal fuel tanks*, engines are steel monsters that aught to both weight much and be expensive to manufacture**. Has there ever been tried discarding the depleted fuel ...
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### What are the tradeoffs in propellant choices for ion/electric based engines?

I'm under the vague impression that ion engines can use most things for propellant. What are the trade offs that influence selection, with an eye specifically towards oxygen? (Interested in the ...
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191 views

### Would it be possible to create a relatively permanent Kessler syndrome event in interplanetary space between Earth and Venus?

A lot of interplanetary space infrastructure would be focused around Lagrange points, where collision energies would be very low. The threat in this case would come from everything traveling between ...
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1 vote
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### Does the size of a black hole increase with mass? [closed]

I understand that extremely minute black holes can have a lot of mass. For example, A Black hole with a 120 pm radius, like a Hydrogen atom, would have a mass of 3.73x10^67 kg. Is this mass already ...
248 views

### Are there any video/audio recordings of the launch of Sputnik 1?

I've been researching the launch of Sputnik 1, it is often renowned as the event that started the space age though I cannot find any confirmed videos of the launch or even a countdown/audio recording ...
143 views

### What's the theoretical dV of the SNAP-10A satellite?

SNAP-10A, launched in 1965, was the first nuclear reactor tested in orbit. It was intended to produce 500 watts of electricity for a year, but it only lasted 43 days; a voltage regulator in the ...
129 views

### Is it possible to easily change the inclination when using momentum exchange tethers?

Access to space using Momentum exchange tether (like Skyhook, Space elevator,...) is economical, but only to specific orbits. And changing the inclination of the orbit is very uneconomical. Is there ...
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202 views

### Does an interplanetary trajectory exist to escape the Solar System and impact the Sun "simultaneously"?

This question is inspired by Do you need 0 km/s velocity to crash into the sun? which brings up the peculiarity (at least to the layman) of Solar System escape from 1 AU taking less $\Delta V$ than a ...
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### Is perceived weightlessness greater in orbit due to constantly falling?

I'm familiar with $F_{g} = G\frac{m_{1}m_{2}}{r^{2}}$ and I was wondering if that means anyone orbiting the Earth actually experiences greater perceived weightlessness due to orbit itself compared to ...
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### Does it make sense to use a skyhook to launch and deorbit mega-satellite constellations now?

One issue with sky hooks is that to keep them spinning, they need to accelerate and decelerate the same amount of mass; otherwise, they would change their velocity and might even slow down so much ...
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57 views

### Technical Question on Ignition Back Pressure

I am looking for understanding the backpressure or pressure stabilization of the injector inlet of the engines, during ignition (T-0). Are there books or papers that you suggest to check for ...
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### Open air dock to space in a rotating space station?

Suppose you had a very large pipe, say 20 meters in diameter, open to space at the hub of a spinning station, and leading off radially from the hub towards the rim, where the pipe is sealed. After ...
398 views

### TWR of near-term NTR engines

With DRACO aiming for on-orbit demonstration of nuclear thermal rocket propulsion (NTR) in 2027, it seems like a technology that has had on-and-off interest for the last 70 years might finally become ...
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### Could there be a difference to the human body between Low Earth Orbit “zero G” microgravity and midway between planets weak gravitational fields?

Would there be different effects on the human body (physiology, chemistry, psychology, other) over long periods of time if there was very very low gravitational field acting on it instead of being in ...
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### If the Van Allen Radiation Belt reaches temperatures of 35,000C, How is it possible to go through them when the craft has a boiling point of 4000C? [closed]

Van Allen Radiation Belt = 35,000C Boiling point of carbon fiber = 4200C Boiling point of Aluminum = 2470C
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### Are all Starship/Super Heavy "cylinders" 4mm thick?

Source The bodies of both rocket stages are made from stainless steel[18] and are manufactured by stacking and welding stainless steel cylinders.[19] These cylinders have a diameter of 9 m (30 ft) a ...
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### Is Starship monocoqué?

Does Starship have any internal bracing to support it? Or is it a "balloon tank" relying on tank pressure to stand?
135 views

### What is the dark brown gas emission seen during the ascent of Starship?

During the video (see below) of Starship IFT-4 there is a lot of brown smoke or gas in the Superheavy exhaust from near the start for almost 30 seconds. Is this NO2? If so roughly how much is produced?...
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### How much propellent is vaporized to pressurize the Starship and Super Heavy tanks?

We know they use autogenous pressurization. But how much methane and oxygen is vaporised to do this? I would like a figure for each of the 8 individual tanks in the stack. TBH I'm trying to figure out ...
37 views

### Does increased thermal emissivity decrease the effectiveness of a solar sail?

I am aware that increased emissivity in solar sails aids with heat reduction, however, I have done some research and found that the emissivity decreases the trajectory of the solar sail through the ...
1 vote
44 views

### Interpreting phasing maneuver results using electric propulsion in GMAT

I'm trying to simulate an anomaly phasing maneuver in three different scenarios using electric propulsion in GMAT. The idea is to use the altitude difference (of ~7-8km) between two spacecrafts to ...
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### What is the value of air anisotropy?

I am calculating a jet - gas nozzle and to calculate it, I need to know the anisotropy of the air, what is it equal to? In this formula, the desired value is under the letter ...
68 views

### How does a Space-Stabilized Inertial Navigation System actually torque its gimbals?

I've been trying to make a fairly-accurate video (with 3D animations coming soon) about Inertial Navigation Systems (INS), in which I plan to cover all the details from each gyroscopes and ...
232 views

### Does human sensitivity to radiation impose a maximum distance on interstellar voyages regardless of radiation shielding or speed?

The duration of crewed interstellar voyages is potentially limited by exposure to interstellar radiation. radiation dose obtained in a non-relativistic space module moving in interstellar space would ...
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### What's the point of Dream Chaser?

Dream Chaser, a reusable spaceplane launching atop an expendable booster at first, to me at least, seems stupid. There's all the additional development costs, payload penalties, and maintenance ...
156 views

### What is the lift to drag ratio of Starship?

By watching the live feed of IFT-4, its pretty obvious that Starship does not actually re-enter in the "skydiver" position, but rather at an AoA of around 45°. There is no doubt that this is ...
1 vote
187 views

### Electricity used by Falcon 9

How much electricity is used in the entire production and launch process of Falcon 9 (launcher, propellant, etc.)? What about other rockets, like the Ariane 5?
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### Starlink Satellites launching by SpaceX

Starlink Satellites launching by SpaceX Starlink Satellite Launching news 1 Starlink Satellite launching news 2 Theoretically and practically, how many maximum Starlink Satellites can be launched by ...
3k views

### How will the ISS be decommissioned?

According to the latest AP report, it's looking like SpaceX will get the contract to decommision the ISS in 2030. Will parts be saved and reused for a new station? One thing quite objectionable is the ...
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### Could space habitats have large transparent roofs?

This is a question I have regarding the design of space habitats. Basically, a lot of the designs I've seen end up having transparent roofs that are open to space, like this: Or this (technically a ...
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### Is it possible to have a closed(-ish) natural motion circumnavigation around an eccentric target? If so, what parameters define the NMC orbit?

Natural motion circumnavigation (NMC) is when a chaser spacecraft is set in an orbit similar to a target spacecraft's such that the chaser naturally circumnavigates the target spacecraft as a result ...
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### Calculating downrange and crossrange distance and velocity relative to a surface point

I've started to go about implementing a descent guidance algorithm I found in a 1997 paper by D'Souza. However, I've hit a snag. The coordinate system is in terms of downrange position ($x$, relative ...
3k views

### Could Kessler Syndrome be used to control the temperature of the Earth?

Imagine launching a bunch of tiny reflective particles in orbit. This would reflect sun away from earth. Based on the orbit, you could have a swarm only go over certain parts of the earth. Or only ...
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### How would I use SGP4 to simulate the motion of an object in orbit?

Let's assume I wanted to assess the accuracy of SGP4 over time. I have an archived set of orbital ephemerides taken from SpaceTrack for a non-active object over the last year. If I picked an epoch say,...
171 views

### Starship IFT-4: flashes below hypersonic speed

In the camera feed, we see occasional bright flashes well after the ship has ceased being hypersonic. Then at 700km/h the flashes suddenly increase to the point that it looks as if the ship has caught ...
107 views

### What caused the premature loss of Super Heavy Booster 10 on IFT-3?

We are told that engine failures caused the booster to be underpowered during landing. In that case, one would expect the booster to slam into the sea. Instead, telemetry cut our at 463m above sea ...
1 vote
138 views

### What's the highest ISP that a chemical rocket could achieve without using propellants maintained at cryogenic temperatures?

This is related to my earlier question about capturing an asteroid. If you wanted to place an interceptor rocket in space and the purpose of that rocket is to wait for a long time, and then launch to ...
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