Hiding a spacecraft

 Hmm..., projects, rockets, science, science fiction, spacecraft  No Responses »
Oct 222020
 

A post yesterday linked to a paper on space warfare. Relevant to that discussion is the concept of hiding spacecraft from detection. Space is obviously dark and the background radiation is cold, about 3 Kelvin. Compared to that, any spacecraft in the inner solar system, even one with no active power sources, is going to be something of a lighthouse in infra-red. Put a nuclear reactor or any kind of meaningful active propulsion system on it, and any spacecraft would stick out like a sore thumb. Stealth should be impossible.

But it is, in fact, possible. it’s hard, it’s limited and its often temporary, but hiding a spacecraft, even one with a functional reactor and running engines, should be possible. There are simply some limits to keep in mind.

In order to hide from radar or lidar, all your spacecraft needs to be is dark and preferably angled int he way we’ve come to understand from stealthy aircraft. This is relatively easy. But the real problem is infra red. Being dark makes your spacecraft both absorb and emit electromagnetic radiation; sunlight falling on a dark spacecraft gets absorbed, stepped down, and emitted back out as infra red. In order to hide your spacecraft, you need to either look like a space rock (probably easy to do, but a space rock that suddenly appears on the charts on a suspicious orbit will likely merit further attention), or you need to be roughly as cold as the background. Actually making your spacecraft 3 Kelvin is insanely unreasonable… but you *can* make a balloon filled with helium that cold. And if you put that dark, cold balloon between your ship and the enemies sensors, you shouldn’t show up

Teledyne got a patent in 1994 for sort of that sort of thing:

Satellite signature suppression shield

The invention here is an inflatable fabric cone that a satellite could hide behind. Coated with something reflective like aluminum or gold, you might think that it would be visible; but for the most part all that shiny reflective surface has to reflect is the black of space. Point the cone at the enemy, and all they’ll see is a dark reflection and if they point lasers or radar at it, the beams will reflect off into space and not back at the receiver. The surface will, however, emit IR, so it’ll be visible that way. But if you fill the balloon with helium *and* if you have an active refrigeration system on the far side, cooling the helium to below 3 Kelvin and directing the waste heat out into space the other way… the cone will be dark *and* cold. So from a narrow cone, your spacecraft will be effectively invisible. From every other angle, though, your spacecraft will be a bright hot target. So… pick your targets. A system like this would probably work well for missiles… only need to operate for a short period, and all they really care about is hiding from the target.

 Posted by at 2:43 am

Life/NACA SST

 aircraft, art, history, Monthly Historical Documents Program, Patreon, projects, US Transport Projects  No Responses »
Oct 202020
 

Two years ago I released US Transport Projects #8 that had a piece on an SST designed by staff of the NACA for Life magazine. To make the best possible diagram I did the best job I could of scanning and stitching together several pages from a vintage issue of Life. I’ve finally gotten around to uploading the full-rez version of that to the APR Dropbox, into the 2020-10 APR Extras folder. This is available to any APR Patron or Subscriber at the $4 level and above.

The full-size version is six times wider than this one:

If this sort of thing is of interest, sign up either for the APR Patreon or the APR Monthly Historical Documents Program. If you know of someone who might be interested, be sure to nudge them this way… I could do with an infusion of new patrons/subscribers and as is blisteringly obvious I stink at marketing.



 Posted by at 10:04 pm

SPS Art

 art, history, projects, spacecraft  No Responses »
Oct 192020
 

A late-70’s NASA rendering of the solar power satellite. Not exactly shown to scale… the satellite, approximately the size of Manhattan, would actually reside in geosynchronous orbit some 22,000 miles up. But the size of the receiving station, located outside of a probably fictitious city (gotta love the H-shaped skyscraper), seems about right. Such stations, which would approximate fields of chickenwire suspended atop telephone poles, could be located over farms, fields, lakes and ponds. The wire would intercept the incoming microwaves beamed down from the SPS with the same efficiency as the wire mesh in the door of your microwave oven keeps your face from getting fried while you watch your popcorn or soup getting nuked.

 Posted by at 4:36 pm

Cargo Rockets

 awesomeness, history, Hmm..., news, projects, rockets, spacecraft  No Responses »
Oct 092020
 

Back in the 50’s the idea of lobbing troops and cargo around the world with rockets seemed not altogether unreasonable. US Transport Projects #1 illustrated a battlefield troop transport based on the Redstone missile; US Transport Projects #2 illustrated a scaled-up project for the same sort of thing using a Jupiter missile. In the 1960’s, Douglas scaled up the idea to use a ROMBUS SSTO to launch 1,200 fully equipped Marines halfway across the world (as seen in USTP#4), and Convair studied a similar idea at the same time based on work done on their NEXUS/Post Saturn designs (as seen in Aerospace Projects Review issue V3N3). In the early 21st century, “HOT EAGLE” was a spaceplane concept for hypersonic rocket-launched troop transport (seen in USTP#5 and USTP#6).

It turns out that the idea is still alive, thanks  in no small part to SpaceX.

Pentagon wants SpaceX delivering cargo around the globe — and a live test could come next year

The goal isn’t small… 80 tons delivered anywhere in the globe inside of an hour. Falcon 9 could not do this; this would seem to be a job for Starship/Superheavy. *If* SpaceX can get that system running for their hoped-for cost of only $2 million per flight for an orbital launch, then this would seem entirely practical. $2 million to transport 80 tons seems a bit steep, but given that it would be used for special operations, it might be a bargain. It’s quite possible that the Starship to be used would have to be quite different from the standard Starship, even from a Starship used for point-to-point commercial cargo and passenger service. The landing gear would need to be improved, so the craft could land on uneven and unimproved terrain; it would need defensive systems from ECM to flares to chaff and perhaps even powerful defensive lasers.  Given the likelihood that the Starship would not be recovered, it might make sense to split it into two parts: a stripped down propulsion section and a cargo lander that is basically just a low L/D payload shroud that comes screaming in and lands with chutes and braking rockets, splits apart and spills out all the goodies. Nothing of value left for the enemy to scrounge up, just sheet metal.

 Posted by at 7:05 am

Sikorsky stowed-rotor ad

 aircraft, art, history, projects  No Responses »
Sep 272020
 

A magazine ad from 1967 looking for people wanting to hire on with Sikorsky. The ad shows a stowed-rotor helicopter design for the CARA (Combat Aircrew Recovery Aircraft) role. In the midst of the Viet Nam War, US pilots were being shot down over enemy occupied territory and needed rescue. A helicopter was a perfectly serviceable vehicle for that role… it could hover over the jungle and drop a line down through the canopy that the pilot could latch on to and be pulled up and flown away. The problem was that choppers are relatively slow. You’d much rather get to the ASAP before enemy forces could find them. A stowed-rotor design could theoretically fly at airplane speeds and hover like a helicopter. But as with all hybrid vehicles, being capable of two things means you’re great at neither.

Additional art of this design:

 Posted by at 11:42 am

Colossal Guppy art

 aircraft, art, history, projects, spacecraft  No Responses »
Sep 232020
 

Recently sold on eBay (but not to me, I got beat out) was a piece of concept art of the “Colossal Guppy,” a proposal by Aero Spacelines to convert a B-52 into a Saturn S-II carrier. All of the artwork I’ve seen before has shown a 12-engine design; this eBay art shows only the original 8 engines that were fitted to the B-52. I would assume that this is an earlier iteration of the concept, but can’t say for certain.

 Posted by at 10:47 pm

Venus Balloon

 art, history, projects, science, spacecraft  No Responses »
Sep 192020
 

With the recent news of the possible discovery of the signs of possible life in the upper atmosphere of Venus, there is renewed interest in some quarters in the idea of atmospheric probes to sample the air and clouds directly. The most practical way to do this in something resembling a long term is with a balloon. With Venus’ carbon dioxide atmosphere, something usually useless as a lifting gas like nitrogen or oxygen could be used, but hydrogen or helium would work even better there than above Earth.

Such probes have been proposed for a *long* time. Here is art of Martin Marietta design for a Venus balloon from more than fifty years ago.

Martin studied a Buoyant Venus Station as far back as 1967. Included in the study were the instruments to be carried, including “drop sondes,” expendable instrument packages that would be dropped from the station to radio back data from lower down:

 Posted by at 11:37 pm

“Future Starships”

 art, history, Nuclear Pulse Propulsion, nukes, projects, spacecraft  No Responses »
Aug 312020
 

Late 1970’s depictions of “realistic” starships as understood at the time. These include an Orion vehicle (which, despite claims to the contrary, would make a terrible starship, since the specific impulse of a reasonably conceivable Orion is an order of magnitude or two too low for practical interstellar craft), two Bussard ramjets, and a “golden globe” minimum weight starship proposed by Robert L. Forward, whose operating principles I am currently a bit fuzzy on.

Bussard ramjets would use magnetic fields to collect interstellar hydrogen. The hydrogen would be compressed in a fusion reactor, preferably a steady-state one, and used to provide thrust to the starship. For a number of years this concept promised great things, but in recent decades it has been pretty much discounted. On one hand, the magnetic fields are not very likely going to work well at a reasonable mass, and they tend to not form open-mouthed funnels, but rather closed-mouthed “cups,” thus preventing the hydrogen from getting into the engine. Whoops. Second, thrust is unlikely to exceed drag much above maybe a percent or two of lightspeed, meaning a Bussard ramjet might serve as a decent “anchor” or drag brake, but not as an accelerator to relativistic velocities.

 Posted by at 7:11 pm

Apollo Extension System models

 history, models, projects, rockets, science, spacecraft  No Responses »
Aug 262020
 

This set of models was recently sold on eBay. It depicts a proposed concept for extending the utility of Apollo hardware… in this case, the Command Module and the Ascent Stage of the Lunar Module, by using them in Earth or Lunar orbit in conjunction with a small space laboratory. The Lunar Module would be used as a little space lab of it’s own, with a bolted-on telescope… this idea transformed into the Apollo Telescope Mount on Skylab, which began life as a modified LM. This probably dates from 1965-66. The purpose of the lab was to provide living space for the crew of three, because missions were contemplated lasting several months, providing detailed examination of the Earth or moon. Scientifically useful to be sure, but were the crew packed solely into the CM and LM for that period they’d likely kick the walls out.

 

 Posted by at 7:41 pm
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