Questions tagged [design-alternative]

Questions about alternative designs the asker has thought of, such as "why was X built this way and not this way"

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35 votes
6 answers
11k views

Why aren't air breathing engines used as small first stages?

I am wondering why we don't use jet engines as first stages. Most small rockets, like the Electron, can lift off with a small thrust. In the Electron's case, 192 kN. Why can't we replace the 9 ...
29 votes
8 answers
7k views

Would a grinding machine be a simple and workable propulsion system for an interplanetary spacecraft?

I am wondering if any space agency has ever considered using a grinding machine as a propulsion system for an interplanetary spacecraft. This system would not be used to lift the spacecraft off of a ...
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26 votes
3 answers
6k views

Are there any greater risks of traveling significantly faster to another planet?

Earlier I had thought that space ships can strike against space rocks while traveling to another planet. But I've read that space is vastly empty, it's highly unlikely that something will come in the ...
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24 votes
9 answers
10k views

If someone built a vacuum tunnel through the atmosphere, could you have an orbit with a sea level perigee?

This is something I've been thinking about for a while now. My initial estimates for the structure were based on people's estimates for an O'Neil cylinder, but assuming you can make the structure a ...
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23 votes
3 answers
5k views

Why isn't SpaceX constructing the Super Heavy launch mount on top of the water?

With SpaceX creating their launch facility in Boca Chica Texas, right next to the water, why would they bother building a huge launch pad to withstand the blast, as opposed to building it on top of ...
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22 votes
4 answers
3k views

Could an electromagnet be used to raise the apogee of a satellite orbiting Earth?

Suppose we have a satellite orbiting Earth in an elliptical orbit, which has an electromagnet inside it. As the satellite goes from its apogee to its perigee (i.e. losing altitude), it turns on the ...
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22 votes
6 answers
5k views

Why is it not concerning from a cost perspective to have so many engines on Starship?

Starship is meant to imitate (to a degree) the affordability of passenger jets. This applies to Earth-to-Earth travel as well as space travel. Jetliners started with 4 engines, but have since migrated ...
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21 votes
4 answers
4k views

What would be necessary in order for us to achieve a single stage to orbit, reusable rocket?

I have read articles and seen videos explaining why an SSTO (Single Stage To Orbit) rocket* is not possible. But I was wondering... What would be required to achieve this? Answers can be literally ...
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19 votes
3 answers
3k views

Could a spacecraft be made out of wood?

Could a spacecraft use organic materials, like wood or bone or shell or other tissues, as an interface to the vacuum and radiation of space? Would wood outgas and crack up in space? I wonder if life ...
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18 votes
5 answers
11k views

Why doesn’t NASA build its rockets using graphene?

Graphene would be a great material to build a rocket out of. Graphene is extremely thin. One single atom thin layer of graphene can withstand 15 000 000 pascal . A square meter of this material only ...
18 votes
6 answers
9k views

Why can't they just drop a solar winch down from a shuttle and have planes fly up and clip things on?

Why can't they just drop a solar winch down from a shuttle and have planes fly up and clip things on? I know of the idea to have a space lift but the cable necessary is too expensive. Why can't we ...
18 votes
9 answers
5k views

Would it be practical to catch a rocket's exhaust to reuse it as fuel?

It's been some days that i think that would it be possible to make a ship that looks like this? The idea is to catch the fuel as you go. Would this make any sense or the thrust would be canceled by ...
18 votes
5 answers
5k views

Exactly why does Starship need to be this big for interplanetary travel?

As discussed in several answers to Isn't Starship way too big? Starship's unusual size is due to it being intended for missions to the Red Planet. But why? Even a smaller ship could satisfy the ...
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17 votes
6 answers
4k views

Would a higher air pressure on the ISS or elsewhere make it easier to "swim" in microgravity?

What if the atmospheric pressure onboard the ISS was 5 atm, 5 times the pressure on Earth and currently on the ISS, while maintaining the breathable oxygen level, e.g. if the additional atmosphere ...
15 votes
2 answers
1k views

How can cosmic ray muons be used to replace GPS for positioning information in 3D on Earth and underwater?

Task & Purpose's The Navy is testing a GPS-like device that doesn’t require satellites “The future is extremely bright for this line of research." begins: The Navy is researching a new ...
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14 votes
8 answers
9k views

Would a duct tape spacesuit be practical?

Spoilers ahead for season 2 of For All Mankind. Essentially duct tape wrapped around the body, over clothing which looks like standard NASA jumpsuits for pressurized environments onboard spacecraft. ...
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14 votes
3 answers
1k views

A way to overcome fuel limits on JWST and its operational lifetime; "clip-on" propulsion systems in development that might work in the future?

I was wondering: Although it has been widely publicised that the JWST has a lifetime limit. Is it not it possible given current technology regarding drones and the JWST itself as proof of concept to ...
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14 votes
2 answers
1k views

Could one actually make a grain silo rocket?

Watching the recent SpaceX Starship tests got me to thinking: Could you actually make a rocket using grain as the propellant? Image from https://www.teslarati.com/spacex-starship-sn5-second-hop-plans/...
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13 votes
7 answers
9k views

Could a space colony 1g from the sun work?

Let me break down my thoughts and I have no science background so let me know if this could even be possible. Have the colony on an object like a big asteroid or a similar man made construct. Have ...
13 votes
3 answers
5k views

What are the biggest challenges for high altitude rail-gun launch systems?

Use a maglev railgun for initial acceleration - in a new, hyperbolic tunnel facing eastward - this exits from the burrowed -undergrade- track to Equadors' Mt. Chimborazo peak - (a mountaintop both 6 ...
13 votes
2 answers
3k views

Can a rocket refuel on Mars from water?

Can a rocket run only on hydrogen and oxygen? Could a rocket, rover, and electrolysis machine be sent to either of Mars' poles to excavate ice to make hydrogen and oxygen to refuel an unmanned rocket? ...
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13 votes
4 answers
1k views

How does Spinlaunch manage the counterweight right after launch?

Spinlaunch has successfully launched a suborbital test vehicle from a 1/3 scale demonstrator, see for instance aviationweek.com or space.com. While spinning up the arm, perfect balance is achieved ...
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12 votes
3 answers
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 ...
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12 votes
4 answers
2k views

Cyanobacteria as Life Support?

I'm aware that cyanobacteria are responsible for the Great Oxidation Event and are very effective at turning CO2 into oxygen so it stands to reason that with the proper nutrients for the bacteria, you ...
12 votes
1 answer
3k views

Why is an inflatable balloon inside a fuel tank not used to prevent fuel from "sloshing around"?

After seeing all the Starship failures, having something with a membrane keep things in place seems like an obvious solution. Has it been considered or tested - or do we simply lack a material that is ...
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11 votes
2 answers
5k views

Could sheets of stacked graphene be used as part of a heat shield, since its melting point is 3000k to 5000 K

Since graphene material is the strongest manmade material, with "magical" properties, I wonder if it could be considered for use as a heat shield, since its melting point is 3000 to 5000 K ...
10 votes
1 answer
705 views

Does a high staging number have diminishing returns? Is there a way to address that mathematically?

I was reading this question: Help me understand what Farside, a ten "stage" rockoon looked like? How was it configured? Comments link to Highest stage counts in actual launchers? but here ...
10 votes
3 answers
406 views

Would it be possible to alter the orbit of one satellite, with the exhaust plume of a rocket sufficient to deorbit it?

SpaceX plan to launch Starships towards Mars; many of them. This will involve burning hundreds to thousands of tonnes of propellant in low(ish) orbit, since each may require several refueling steps. ...
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10 votes
1 answer
779 views

What's the final word; does the EmDrive drive work or not?

I'd like to know the final verdict on the EmDrive (or EM Drive); does it work or not? Some say yes, others say no, some say the measured effect was not propulsion, but just the energy radiated by the ...
10 votes
1 answer
569 views

Why is the Otto II monopropellant fuel not used in spaceflight applications?

Is anyone familiar with the chemical/thermodynamic properties of Otto II fuel (a monopropellant used in torpedoes)? It is composed of nitrated propylene gycol with a couple additives that make it non-...
9 votes
6 answers
3k views

Using water as a high density storable hydro-lox propellant

Hydro/lox is an excellent fuel choice and has been used in many engine/rockets with high ISP requirements, however, the two biggest drawbacks of the propellant are its density and boil-off. Could this ...
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9 votes
2 answers
1k views

Why can’t cryogenic propellants be storable, at least on the ground, via refrigeration?

Cryogenic fuels (liquid hydrogen, liquid methane)1 and oxidisers (liquid oxygen)2 are the rocket propellants of choice where raw performance is the overriding concern, due to the very high performance ...
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9 votes
3 answers
787 views

What are the deal-breakers with a preheated Hydrogen gas tank orbital rocket?

Consider this thought process: In selecting the propellant for a reaction engine, lower atomic mass is better because equipment is largely temperature limited, and lighter gas will get higher ...
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9 votes
3 answers
370 views

Would this Starship design alternative be viable?

Considering Starship's atmospheric entry, belly dive and "bellyflop", latest iteration displays four aerodynamic surfaces, two aft fins and two canard fins. Soon, this configuration will be ...
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9 votes
0 answers
236 views

Has there ever been a deliberate "Find A Satellite" challenge? Actually, could there be?

Companies often offer rewards for finding security issues in their products or their own IT systems, and hackathons have a long history. I'm just wondering if there has ever been a deliberate ...
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8 votes
6 answers
4k views

Orbital Supercomputer for Martian and Outer Planet Computing

As we know, computing will (and really has) been important to research missions for space science and exploration. I read about the Spacebourne Computer program HPE and NASA used for the ISS as proof ...
8 votes
1 answer
313 views

Has methylsilane (CH₆Si) ever been considered as fuel in rocketry?

Methylsilane CH6Si seems to have some useful properties for rocket fuel: high hydrogen content, 6 atoms per molecule, 13% of overall mass; high combustion energy, -2612 KJ/mol or 56.8 MJ/kg (better ...
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7 votes
5 answers
1k views

Earth Launch System with Water Propellant

Water based thrusters have been proposed (and possibly tested by now) for use in satellites and other in-space vehicles - see this NASA article. The idea is to perform electrolysis on the water to ...
7 votes
4 answers
924 views

Back up plan to use LOX-RP1 for Apollo mission

Today it might seem to be an hypothetical question. I read that Surveyor mission confirmed "re-igniting" a LOX+LH2 engine in space is successful. What if the use of H2 was not successful ? - ...
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7 votes
3 answers
408 views

Fast spinning solar cells to clear Martian dust possible?

I've seen a fast spinning glass wheel used in front of a camera to clear away water, dust or ice. Could Solar panels be made circular and spin to clear dust off of them in the same way may? As ...
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7 votes
6 answers
1k views

Could moon ice be used to fuel a steam powered jetpack for EVA in space or high altitude exploration on the moon?

For long term moon operations, would it be practical to have a jetpack that used steam as a source for EVA on the moon surface and above it in orbit? I imagine a scenario where lunar ice deposits ...
7 votes
2 answers
759 views

Are In-Flight Electrically Heated Steam Rockets Possible?

I wonder if a rocket that uses electricity from internal batteries to heat water in its tanks to high pressure would be able to use that pressure to take off. Is it possible? I've researched here and ...
7 votes
2 answers
265 views

Is there an example of a classic space engineering moment where months of work had to be discarded due to the wrong approach?

Is there any classic aviation/space engineering moment where the engineers had been working on a concept for months and then realised that their approach to the problem wasn't quite right and so had ...
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7 votes
1 answer
1k views

Using coolant as 3rd propellant

Rocket engines often have 2 propelants, one of which is used to cool the engine and after that the hot propellant is injected in the combustion chamber. Would make sense to have a third propellant ...
7 votes
2 answers
887 views

What are the challenges in recovering Falcon 9's second stage this way?

The Falcon 9's second stage is currently disposed of each flight. I know there have been some concepts by SpaceX on making it reusable, but evidently they have not yet done so. From my understanding, ...
7 votes
1 answer
518 views

What would be the challenges for a 50 km long tether to the surface of Venus to get recurrent samples from there?

Basalt fiber would be an excellent material for a tether in the atmosphere of Venus because it could withstand both the acidity and the high temperature near the surface there. From this answer about ...
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7 votes
2 answers
620 views

Is there anything fundamentally wrong with 'autogenous expander cycle`?

This question is a spinoff from here. To set the context, here is my understanding of the expander cycle: Closed expander cycle is very efficient, perhaps more efficient than staged combustion cycle....
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7 votes
2 answers
399 views

Helium balloon as a rocket

This question is not about rockoons, which are rockets using balloons as launch platforms to start from a greater altitude. This question asks about using the balloon itself as the rocket, like a toy ...
6 votes
1 answer
575 views

Why aren't smaller fairings used for smaller payloads?

I saw this picture of the DART spacecraft being encapsulated in its payload fairing. Why doesn't SpaceX manufacture a smaller (shortened or thinned) fairing for the spacecraft? It reduces mass and is ...
6 votes
2 answers
1k views

Can a VASIMR Plasma engine be used to launch a rocket?

When I was in primary school, I spent countless hours designing spaceships that probably wouldn’t work. It’s only now that I’ve stumbled across some of the old drawings and actually thought if it ...
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