New Mars Forums

So the idea is, if I get this strait to use beamed energy to push a waverider shaped airplane strait up or away from the transmiter, and then use the lift to change this foce into force acellerating the craft in a forward direction? What is the advantage of this? Since you are staying in the atmosphere the drag is going to be increadable, even with a waverider, unless you are plaining to use some kind of exotic plasma drag reduction device, which would probably interfer with the beamed energy. What you seem to be trying to get around is the fact that it takes 30420 kJ/kg to get to orbit. Since you cannot beam that much power in a short rocket launch period of time, you have to:
a) break the laws of physics
or
b) accellerate slowly
Acelorating slowly will be actually way more ineffect than going quick because you will have to stay in the atmosphere and the drag is going to be too high. Even if you are using some kind of wing to change your direction to horazontal, you are not going to be able to produce extra energy, infact there will probably be a loos due to ineffecencies. 10 megawatts are not enough for 360 pounds, you would need to run it for 18 minutes. With a typical hypersonic Cd of 0.1  you have for drag at 25 km up (probably unrealistically high) and an area of a square meter (very small) =  (0.5) (0.1) (1) (0.04) (7800) (7800) = 121680 newtons of drag. The energy calculations were considering no drag and needed a constant thrust of about 3000 newtons. I don't think this idea will work the way I understand it.

I don't know anything about this hydrogen beaming from solar wind, but it seems to me that the total amount of hydrogen in a resonably sized colector is rather small. Granted, we are talking about terraforming, so I guess reasonalbe isn't a good argument . I would suggest building a gigantic ballon type space craft in Jovian orbit to collect the hydrogen needed from it's atmosphere. It is liquified/slushed and shaded by a sun shade close to the sun. The ship then moves from jupiter to venus with a tether in Jupiter's massive magnetic field. Nuculer or beamed power for electricity. Then the ship slams into venus, helping to throw off some of the atmosphere and cool the planet rapidly since the energy required to bring 10^14 kg of 14K hydrogen venesuian temperatures is quite high. The sun shade that was shadeing the ship, now shades venus. Hmm, now that I've writen this it seems a bit more complex than hydrrogen beaming...  oh well, in case that isn't fesable. [/url]

GCNRevenger - you're probably right about cheap launch before orbital tourism, but I've heard that there is even a waiting list to ride the Soyuz, though there is quite a steep markup. ( if sub orbital costs 200 000 dollars, than multiplied by 36 is only 7.2 million. I know that's a crude calculation, but the Russians are defiantly making some money) I'm willing to wager that a good deal of their success comes from the Soyuz’s proven reliability, it's quite a bit safer than the space shuttle. If Biglow does build his hotel/cruise ship thing and is able to by Soyuz’s to transport passengers, I think you would see a lot more space tourists, right now the Russians obviously have other obligations. Never the less that's unlikely, any I think anything like this will be a long time coming, barring some breakthrough...

I know it was a bit crazy, I'm just fed up with the lack of progress with conventional rockets. Think about the miracles we can do with carbon fiber re-enforced composits and the like, way better than 60's materials for the Satrun V. Yet it was more reliable than the current designs, although I don't know how much composites they use. The space elevator would be very handy, but I distrust the nanothechnology people. How many times have they been claming to have cheap dimond everything? Lots, but we're still a long ways off. I don't think the ballon idea, though absolutly insane, is as bad as you think it is however. I've been thinking, the balloon would's nessiarily have to change focus, if it was set to foucus at, say 1400 km. Then the spacecraft, lifted up above most of the atmosphere with another baloon could accelorate over a long arc. The aiming would still be a problem, but I think a group of propellers could do it (maybe) there's virtually no turbulence at 30 km altitude. As for the massive size, yup, that's a stumper. however, lets just say for the sake of argument we just want to send a tiny capsule up with two or three people. The weight might be around 3000 kg (like the t/space craft) and at a exhast tempurature of 6000 K (got from -http://www.medianet.pl/~andrew/SPBI115.HTM) an exhast velosity of 13200 m/s. so thats 3202 kg of hydrogen if we add another 1000 kg for tank and engine. That means total energy needed is about 279043132162.6148 joules. Over five minutes taht would require 715495.211 square meters of mirror. Over 20 baloons that's a diamiter of about 200 meters, not too much larger than the nasa balloon. I agree however that this is unlikely to work.

Sorry that this is at the end, I just joined, but here's my two cents. Any craft that must use megawatts of stored energy per second is inherently dangerous and ineffecent. Since failure must be kept to a minimum this adds cost and voila- 10,000 dollar per Kg. While conventional ideas like adding an air breathing first stage, reusablitiy, and small workforces can help, they are not going to provide the cost savings looked for. Rockets don't seem too complex at first glance but the exhaust velocities that are limited nessesitate all the smallest effeny increases possible, light weght tanks and so on to keep the rocket a reasonable size. This is what makes small rockets expensive. As for big dumb boosters, they may be a bit of an improvment, but the specail facilities needed to make them and launch them, along with the cost of raw materials and labour drive the cost up. Therefore what is needed is way of providing those raw megawatts safelly and cheap enough so that it can get by with a 20% effentcy. Chemical rockets are not going to provide that kind of power, though not expensive in themselves, the tanks and engines are. The only possiblity I see that is reasonable is beamed power, or accelorating slowly so you don't need megawatts a second. My views on slow acceloration are posted on "airship to orbit" thread, but here I'll discuss beamed power. Microwaves spread out too much and are expensive and inneficent to genorate. Lasers are way too expensive, however there is no reason one has to use a laser to beam light. Given a resonably large reciver, ordinary light from the sun should be able to be focused on spacecraft. I advocate building stationary large variable focus mirrors and using cheap (read free) solar power. How might this be done economically? Baloons, 30 km up with clear tops and reflective bottoms filled with hydrogen could collect large amouts of light given a large enough diamiter and a hard ring. If the baloon material was streachy the foucus could be ajusted by changing the internal pressure. It could be aimed with small electric propellers. Maybe this is radicall enough to be cheap. At least there is low start up costs. The spacecraft it's self could use the light to heat hydrogen to nuculer rocket temperatures.

I have doubts that this thing is going to have enough lift to climb rapidly enough. Unless it has a Cd of 0.001 and can lift it's gross tonage at 1 m/s there is simply not enough energy avalible to punch though all that drag. Maybe those winds disscused earlier would help, but that dosen't seem like it's going to help too too much at 7800 m/s. The massive frontal area of the proposed design is going to goble up all the possible savings from the thin air. I would like to see some numbers about the Cd, or by some one who knows more about these issues than I.