# Tag Info

41

From Wikipedia's article on Vostok 1: Path of Gagarin's complete orbit; the landing point is west of the takeoff point because of the eastward rotation of the Earth. The flight was at least one orbit of the Earth (note the latitude of the landing is higher than the launch, see @DavidHammen's answer), and beyond that the mission involved firing ...

29

Using the times of injection and retrofire in this diagram: and the orbit information from NASA, I get that Yuri did about 272° to 273° of a 360° orbit. So about 3/4ths of an orbit. I am not including the ten minutes it took to get from the launch pad to orbit as being in orbit, nor am I including the 30 minutes it took from the deorbit burn to landing as ...

21

So he landed 17 degrees west of the launch site. Sure sounds like a (long) sub-orbital flight. You are looking at the wrong parameter. The Earth rotated underneath the orbiting spacecraft during the 108 minute flight. A better parameter to look at is latitude. He launched to the northeast and landed 5.35 degrees north of the launch site. He passed the ...

20

Gemini 4 was the first unsuccessful try of a rendezvous. They sought at that times it should be possible to rendezvous from a short distance by simply thrusting towards the docking object. They had to learn it the hard way that this strategy works only on very, very short distances and in a short time. The circumference of a low Earth circular orbit with a ...

19

The long comment chain below this answer highlights the mis-conception that NASA astronauts as a whole did not understand the orbital mechanics of docking. As this comment points out, the mechanics was well understood at the time, and at least one astronaut had written a thesis on the topic a few years earlier: ... Aldrins thesis about orbital ...

17

The time dilation of the Moon relative to Earth is dominated by not being as deep in the gravitational field of Earth. Not so much the velocity of the Moon. Though the velocity effect isn't negligible, being about two orders of magnitude down from the gravity effect. Time passes about 0.66 parts per billion faster on the Moon than on Earth, due to not ...

13

First, the Gemini IV maneuver was station-keeping, not rendezvous. Since the target was the just-separated upper stage, the two spacecraft were already rendezvoused, and point-and-burn would have worked if they'd done it properly. According to the Gemini IV mission report, the main causes of station-keeping failure were a mix of procedural mistakes and ...

11

From the telemetry link mentioned by @jkavalik, someone posted an interesting graph: The blue line here is the acceleration of the rocket. It ramps up as fuel is consumed. There's a dip from about 55 to 85 seconds where I believe the engines are throttled back in anticipation of "max Q", the point of highest aerodynamic stress. The acceleration then ...

9

The legal definition of "Weapon of Mass Destruction" in US law is quite broad (see https://www.schneier.com/blog/archives/2009/04/definition_of_w.html ), and an orbital kinetic weapon definitely qualifies if the projectile is big enough to re-enter in one piece. The FBI and/or ATF will want to have a talk with the owner.

9

This is actually a bit tricky, and relates to one of the basic tenants of the space race. The United States made small, accurate weapons, the USSR made large, less accurate weapons. Because the USSRs weapons were larger, and therefore heavier, it required heavier missiles to launch them, and thus they have the mass to achieve orbit if required, while the US'...

7

The periapsis is the point at which the satellite is closest to the central body. The ascending node is where the orbit crosses the equatorial plane of the central body (this can be defined in a number of way but we'll stick with equator at the moment). Now, there's no reason the periapsis can't be at any point in the orbit, so lets discuss a few cases. 1)...

6

As a general rule of thumb, any prograde or retrograde burn establishes a new orbit tangent to the old orbit at the point of the burn. A prograde burn increases the length of the major axis, while a retrograde burn reduces it. To demonstrate, I set up a situation similar to yours in Kerbal Space Program, and had it draw the results of two proposed ...

5

You can pretty easily figure out this kind of thing from a calculator like this one. For your specific answer, using 1 Earth mass, a distance of 6482 km (111 km above Earth), we determine the velocity to be 7.843 km/s. And we have achieved much higher velocities in the past, so we absolutely can achieve that. Lastly, there is actually drag at that altitude. ...

5

I have also been unable to implement PEG and struggled to find an adequate approach in my orbital launch sim. I have tried simply steering proportional to fraction-of-orbital-altitude-reached in the orbital insertion phase. I have tried various forms of quadratic guidance (inspired by the the Apollo LM's landing guidance). None have gotten good results. At ...

4

The technical and organizational causes of the Gemini IV station-keeping failure are discussed in this conference paper. John Goodman, “A Cautionary Tale of a Secret, a Small Team, an Accelerated Schedule, and the Gemini IV Station-Keeping Failure,” 43rd Annual AAS Guidance and Control Conference, Breckenridge, CO, January 30 to February 5, 2020. paywalled ...

4

The Trident D5 appears to have just enough impulse to reach orbit without its normal payload. This summary, and its daughter pages for each stage provide enough information to determine that whilst the whole missile is 59 tonnes the mass devoted to items other than the three solid stages is nearly 6 tonnes. Whilst the payload is given as 1.6 tonnes I ...

4

@OrganicMarble's answer is correct. An absolutely uniform gravity field would require infinite mass at infinite distance and so realistic gravity fields will usually have local gradients that can be measured with sufficiently sensitive equipment. There might be some pathological situations where higher terms also cancel and gravity appears extremely uniform, ...

3

I was looking for possible answers for an US-sourced engine, and was going to float the RS-27A as a possibility (though it's been out of production for over a decade) -- you'd probably need a cluster of 4 to substitute for a pair of AJ-26. Then I saw this reference to the Aerojet Rocketdyne AR-1 proposal. At 2200 kN, a pair of them would be up in the RD-180 ...

3

In Dec 2014, Orbital selected the Russian Energomash RD-181, which is basically an export version of the RD-191 used in the Angara booster. This is also a LOX/kerosene engine, derived from the RD-170. The RD-170 is a 1.6 MLbs thrust engine used on Zenit boosters (which were initially strap on boosters for Energia) that has 4 thrust chambers. The two ...

3

There have been lots of plans for Lunar built spacecraft. There have been few that have been credible, and all are in the realm of speculation. At present, any such plans are relegated to either distant conceptual plans (NASA, ESA, and ФКА/Roscosmos), fuel processing only (NASA and ESA), or science fiction literature. Distant Conceptual Plans NASA, ESA, and ...

3

With sufficiently precise instruments* you can tell which box you are in because the Earth-based box gravity vectors will point to the center of the earth as you move about in the box (box on the left) whereas the space box will have parallel acceleration vectors (box on the right) * probably not achievable in practice for a reasonably sized box but this ...

2

Sub-orbital space flight as a step on the road makes sense, at least for a commercial space program. You can then scale up your business along with your development process. The most notable disadvantage is that you will not be able to launch satellites, forcing the company to focus more on manned space flight. In contrast, the main focus of the early space-...

2

Yes, Boeing did the HASTOL study and it seems viable with current technology and economy, there is even Wikipedia article about it. Besides of lifting cargo from hypersonic aircraft to orbit, the bolo can also generate power by electrodynamic tethering and there were even several missions testing it.

2

Both gravity fields are not totally equal. In the box on Earth, gravity at top is a little smaller than at the bottom. But in the other box gravity is the same at bottom and top. There are ultra precise atomic clocks that show a very small difference in frequency when mounted at different heights and there are gravimeters with very high sensitivity. The ...

2

I assume you are referring to "Fundamentals of Astrodynamics" by Bate, R. et al. (1971). The author is using non-dimensional units in this example problem. Therefore, as explained on p. 41, $$\mu = 1~DU^3/TU^2$$ And, in this example problem, $$\mathbf{r} = 2~\mathbf{I} DU, \quad \mathbf{v} = 1~\mathbf{J} DU/TU$$ With these, the equation for the ...

2

From the same simulation of the linked question I obtain the following result: The Earth's gravity field is modeled with the SGG-UGM-1 gravity model truncated to the degree and order 15 (for this kind of simulation, J2 + J3 would suffice). No atmosphere.

1

... what are some possible explanations for how [...to] increase the period and semi-major axis of one of the objects? This does not work out for point masses, but only for extended masses: Imagine for example a dumbbell shaped object. Now imagine this object is spinning. One end of this object would be faster than the orbital speed, the other end slower, ...

1

A "classical" fairing is a ballistic object, meaning it has no active controls. You'll find that trying to model its tumbling path through a highly variable atmosphere exceeds our current computational capacity. If you're thinking about the SpaceX fairing recovery techniques, be aware that there are some active controls, as explained in this space.SE ...

1

I know it isn't much, and it's in German, but there is a brief mention of work on the ISS here. The transcript reads "Later, Alexander Gerst finally gets the smelter working. Here, new materials are optimized in that two metals are melted together in weightlessness, and these alloys will be used, for instance, to make vanes for jet engines." It would be ...

1

Can the Oberth effect cause space-time distortions? No, but the mass(es) used for the maneuver might. Note that the velocity of the spacecraft performing the maneuver might cause a slowing of it's time relative to an observer, but: At anything less than extreme speeds (a significant percent of the speed of light) it would be almost immeasurable. As far ...

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